In this downloadable guide, we’ve compiled eight common DFM considerations that should remain top-of-mind when designing parts for CNC machining. You can save significant time and cost by checking your design against this list before submitting it for manufacturing.

Top 8 Design for Manufacturing Considerations for CNC Machining

1. Are there any deep pockets in the design?

Deep-narrow pockets or slots must be machined by longer tools, and longer tools are more prone to breakage, and can also cause chatter, or machine vibrations. Additionally, it takes several passes to machine a deep pocket, which drives up machining time and manufacturing costs.

Avoid designing parts with deep pockets whenever possible. If a deep pocket cannot be avoided, engineers and designers should decrease its depth as much as possible or increase the cross-section area of the pocket. As a rule, pocket depth shouldn’t exceed 3x the diameter of the tool being used to make it. For example, pockets should be no deeper than 1.5” when using a 0.5” cutter.  Engineers may have to adjust this figure based on the material they are using and the tools that are available to them.

2. Are there any narrow regions?

Narrow regions are difficult to manufacture because the size of the cutter is restricted by the smallest distance between the various faces of the feature. Long and small diameter cutters are prone to breakage and chatter.

Avoid designing features or faces that are too narrow for a cutter to easily pass through. If narrow regions cannot be avoided, however, they must not be too deep. Remember that the depth of any feature should be less than 3x the diameter of the tool.  As a best practice, wall sections should be greater than 0.01 inches thick. A shorter cutter with a larger diameter can also be employed to reduce chatter.

3. Are there any sharp internal corners?

Since all CNC drill bits are circular, it’s difficult to achieve sharp internal corners. Instead, the drill bit will leave behind a pocket of unmachined space called an internal corner radius. It’s possible to machine sharp internal corners using workarounds, like electrical discharge machining, but these methods tend to be expensive.

Avoid sharp inside corners whenever possible. Ideally, a corner radius needs to be slightly larger than the cutter. If a corner radius is the same diameter as the cutter being used to form it, it can cause chatter and premature tool wear.

Increasing the corner radii beyond the standard value by as little as 0.005” can give the tool enough room to move around and follow a more circular path.

4. Are there any inaccessible features?

Inaccessible features like counterbores that open inside another pocket or pockets with negative drafts take longer to machine— if they’re even possible — because the cutting tool cannot easily access them, which in turn drives up costs.

You should ensure a cutting tool has full access to all features within a part without being blocked by another feature.

5. Are there any outside fillets?

Outside fillets, or fillets on the top edges of pockets, bosses, and slots, require an exceptionally sharp cutter and a precise setup. Both of these requirements can be prohibitively expensive for some product teams. To avoid incurring these costs, bevel or chamfer — rather than fillet — the outside edges of features.

6. Are the part’s walls too thin?

When it comes to CNC machining with metal, thin walls increase chatter, which can compromise the accuracy of the machining process and the surface finish of the part. With plastics, thin walls can cause warping and softening. As such, you should do your best to avoid designing parts with thin walls.

The ideal minimum wall thickness for metals is 0.8 mm for metals and 1.5 mm for plastics. You may be able to achieve thinner sections without significant risk, but this needs to be assessed on a case by case basis.

7. Are there any flat-bottomed holes?

Flat-bottomed holes require advanced machining operations and often cause problems down the line for subsequent operations like reaming. Avoid creating blind holes with a flat bottom — especially small holes — and instead use a standard twist drill to create holes with cone-shaped bottoms. Cone angles are commonly 118° or 135°.

8. Can the CNC machine’s drills enter and exit easily?

A drill tip will wander when it comes into contact with the material’s surface if that surface isn’t perpendicular to the drill axis. Also, uneven exit burrs around the exit hole will make removing the burr difficult. To ease entry and exit, avoid designing hole features with start and end faces that are not perpendicular to the drill’s axis.

Recap of All 8 Design Considerations for CNC Machining

1. Avoid designing parts with deep pockets whenever possible because deep-narrow pockets can drive up machining time and cost.
2. Avoid designing features or faces that are too narrow for a cutter to easily pass through to prevent tool breakage and chatter.
3. Radiused corners (middle) or “dog bones” (right) are good alternatives to sharp internal corners.
4. Ensure a cutting tool has full access to all features within a part without being blocked by another feature
5. Avoid outside fillets (shown left) and opt for chamfered edges (right) to save time and cost.
6. Avoid designing thin walls, as they’ll increase chatter in metals and cause warping or softening in plastics.
7. Avoid Flat-bottomed holes that can cause problems for subsequent operations like reaming.
8. Whenever possible, design hole features with start and end faces perpendicular to the drill’s access.

Get Started With a DFM Expert

Designing for manufacturability accelerates the CNC machining process, reduces operating costs, elevates energy efficiency, and helps product teams create clean, functional parts. Refer to this short checklist often to make sure your designs are on the right track, but an experienced manufacturing partner like SyBridge can offer more nuanced insights.

The SyBridge team can help engineers, designers, and product teams ensure they don’t miss the mark when it comes to DFM. We have access to the latest digital design technologies available so our partners can take their designs to the next level, while we provide expert advice on manufacturability and part quality. What’s more, our experts are prepared to assist customers with design and prototyping for a range of manufacturing methods — from CNC machining and injection molding to urethane casting and 3D printing. Let’s create something incredible. Contact us today.

The post The Ultimate CNC Design for Manufacturability (DFM) Checklist appeared first on SyBridge Technologies.

Acrylic, also known as plexiglass or polymethyl methacrylate (PMMA), and polycarbonate are both lightweight, transparent plastics suitable for manufacturing parts via CNC machining. Acrylic is known for its strength and transparency, making it an excellent alternative to standard glass, whereas polycarbonate is incredibly tough and impact resistant, making it ideal for applications that require clarity as well as increased durability, such as safety glass.

While acrylic and polycarbonate are similar in many respects, there are some important differences between these two common materials that can make one better suited for a particular application over the other, or impact the machining process and thus lead time and cost. In this article, we’ll go over what you need to know about machining acrylic and polycarbonate so that you can select the best manufacturing option for your project and create designs that work with the material you choose.

Machining Acrylic and Polycarbonate: What You Need to Know

When it comes to machining acrylic, cast acrylic is often a better choice than extruded acrylic, as the latter is more likely to crack or chip during the machining process. This means that the toolpath strategies sometimes need careful selection to avoid chipping the part. Additionally, since acrylics aren’t very heat resistant, it’s necessary to use a sharp cutting tool in order to obtain a smooth surface finish. Acrylic’s low melting point means that it will also be necessary to use a lower cutting feedrate than other plastics during machining, since higher feedrates will generate more friction and heat, and potentially ruin your part. If necessary, acrylic may be kept in a freezer before machining to ensure that it remains as cool as possible.

With its toughness and impact resistance, polycarbonate is better for machining and is particularly well-suited to CNC milling. However, when machining polycarbonate, the sharpness of the cutting tool is still important, as polycarbonate sheets can melt if too much heat builds up during the machining process. Since polycarbonate is less likely to chip than acrylic, it tends to be easier to machine and allows for more standard toolpath strategies to be used. In addition, because there is a higher temperature working range, more aggressive strategies can be used with a smaller chance of causing issues, potentially saving time and money.

Applications for Acrylic and Polycarbonate

Both acrylic and polycarbonate are lightweight, machinable, and have unique characteristics that make them suitable for an array of applications across industries.

Acrylic is a popular material within the automotive, construction, and aerospace industries, and is often used for things like dry boxes, lenses, radiation shields, and desiccators. Additionally, its transparency, strength, and high impact resistance make it a great alternative to glass, and you can commonly find it used in greenhouses, aquariums, terrariums, security barriers, and more.

Like acrylic, polycarbonate is popular in the automotive, aerospace, and construction industries, but its resistance to heat and strong dimensional stability make it very popular in the medical industry, as polycarbonate parts can withstand limited autoclaves and irradiation sterilization. Among its more common applications, polycarbonate is often used for point-of-purchase retail displays, face shields, architectural features, clear manifolds, bulletproof windows, and much more.

Pros and Cons of Using Acrylic for Your Parts

Acrylic offers a range positive attributes, including:

• Transparency: Acrylic can allow up to 92% of light to pass through it, making it more transparent than some grades of glass and most other thermoplastics. It can also be colored without sacrificing its transparency, though it’s possible to manufacture more opaque acrylic parts, as well.
• Strength: Acrylic is much stronger and more impact resistant than glass. Most grades of acrylic are four to eight times stronger than glass.
• Environmental resistance: Acrylic is naturally resistant to scratches, weathering, and UV radiation, making it ideal for outdoor applications.
• Chemical resistance: Acrylic is resistant to many chemicals, including alkalis, detergents, cleaners, and dilute inorganic acids.
• Moisture absorption: Acrylic has low moisture absorption, which allows it to retain its dimensions when used in outdoor applications.
• Compatibility with coatings: Acrylic parts can be coated with anti-static, hard coat, or non-glare layers in order to improve their surface quality, extend their lifespan, and ensure they meet specific requirements.
• Affordability: Despite its strength, durability, and clarity, acrylic remains relatively inexpensive to manufacture and machine. For comparison, polycarbonate is about 35 – 40% more expensive.
• Color: Acrylic is available in a wide range of colors.

CNC machining acrylic is not without its disadvantages. As previously noted, acrylic is more susceptible to cracking and chipping than polycarbonate, and it’s slightly more difficult to machine, since it will lose structural integrity and begin melting at temperatures over 160°C. When designing acrylic parts for CNC machining, you’ll need to remember that relatively low melting point because it makes the material more susceptible to deformation during the manufacturing process. To avoid the risk of melting, and to achieve a quality surface finish, using a proper feed rate and pass depth is crucial. Similarly, to reduce chatter and achieve quality cuts, acrylic parts should be machined using tools with a short flute length and a cutting depth roughly half the diameter of the bit.

Your product’s intended use will also determine whether acrylic is the best option for your project. For example, acrylic’s extreme biocompatibility makes it a good option for bone implants, dentures, or other skin-contact applications; similarly, its resistance to weather, UV radiation, and scratching make it a good fit for parts which will be used outdoors. On the other hand, acrylic might not be the best choice for food containers that will be exposed to high temperature environments, such as dishwashers or microwaves, since acrylic parts will only maintain their dimensions up to 149°F (65°C), at which point they begin to soften. 

Pros and Cons of Using Polycarbonate for Your Parts

The positives of using polycarbonate include:

• Transparency: Polycarbonate is a naturally transparent thermoplastic that can transmit light just as effectively as glass, making it ideal for lenses, lighting, and bulletproof glass. Like acrylic, polycarbonate can be colored without sacrificing its transparency.
• Variety: There are several formulations of polycarbonate on the market, including glass-filled and FDA-compliant variants, so it’s likely that you’ll be able to find one that meets your project’s needs.
• Strength and impact resistance: Polycarbonate has a tensile strength around 200 times that of glass, and is highly resistant to impact. Accordingly, it’s often used in bullet-resistant glass and protective gear.
• Shrinkage and dimensional stability: Polycarbonate will maintain its dimensions under most conditions, and has a low shrink rate of 0.6 – 0.9%.
• Environmental resistance: Polycarbonate is naturally resistant to UV radiation and can withstand varying moisture levels and fluctuating temperatures, which makes it an excellent material for outdoor applications and eyewear.
• Chemical resistance: Polycarbonate is resistant to many chemicals, including diluted acids, oils, waxes, aliphatic hydrocarbons, alcohols, and greases.
• Moisture absorption: Polycarbonate has slightly lower moisture absorption compared to acrylic.
• Compatibility with coatings: Like acrylic, polycarbonate components can be coated with anti-static, hard coat, and non-glare layers. Polycarbonate is also compatible with UV and anti-fog layers.
• High machinability: Since it’s so durable and tolerant to heat, polycarbonate is easier to machine than acrylic.

While polycarbonate has many positive attributes, there are some disadvantages to using polycarbonate for a CNC machining project, including its high cost and its susceptibility to denting. Additionally, since polycarbonate scratches easily, it’s more likely to require finishing, which is complicated by the fact that only certain finishing processes, such as vapor polishing and coating, work with polycarbonate parts.

Additionally, it’s important to note that polycarbonate parts are also prone to developing sinks or voids in thicker sections. To prevent this, it’s best to break thicker elements down into smaller, thinner sections to be assembled later. It’s easy to remember this tip by keeping costs in mind — machining a thick part out of a single block of polycarbonate will typically be more expensive than working with smaller pieces due to the cost of the raw materials and the machining time.

Finishing Options for Acrylic and Polycarbonate

There are several finishing options available for acrylic and polycarbonate, including some that will help your parts look and feel ready for end-use applications and even improve clarity:

• As-machined finish: The standard and most economical finish, ‘as-machined’ or ‘as-milled’ means that no additional post-processing is applied to the part. As-machined parts have tight dimensional finishes and may represent a faster, more affordable manufacturing option. In some cases, as-machined parts may have small but visible surface tool marks, blemishes, or scratches.
• Bead blasting: An economical finish that creates a uniform appearance, bead blasting tends to leave a dull or satin finish and is effective for removing tool marks and surface blemishes.
• Vapor polishing: This finishing option uses solvent vapor to transform matte or opaque surfaces into smooth, high gloss, or optically clear surfaces. Vapor polishing is often used on parts where rough surfaces are unacceptable or where clarity is paramount. 

With sufficient care during the cutting process, machined surfaces of acrylic and polycarbonate parts will typically be translucent, but can become nearly opaque if the material melts. Should melting occur, it may be possible to address surface opacity with post-processing options such as vapor polishing. However, it’s worth noting that as-machined finishes for acrylic and polycarbonate parts will not be optically clear, although it may be possible to achieve optical clarity if diamond tooling is used, but this must be specifically requested during the quoting process, as it will significantly add to cost.

Bottom line: Comparing Acrylic and Polycarbonate for Machining

Special care should be taken with designs that include machined acrylic due to the increased likelihood of stress cracking. With this in mind, it’s advisable to use razor-sharp cutting tools to avoid melting the acrylic or causing cracking; diamond cutters yield the best surface finish, though carbide cutters are much more affordable. It will also be necessary to use a relatively fast feed rate to prevent the acrylic from melting, but remember that going too fast can cause extreme cutting pressure and breakage.

While polycarbonate is generally better suited to machining thanks to its rigidity, toughness, durability, and higher melting point, the trade-off is that polycarbonate is less transparent than acrylic. However, if you need to create specific-use parts, such as protective gear, fuse boxes, or large, tough components, transparency may not be an issue. On the other hand, if you’re designing a product for which transparency is a top priority, taking the extra effort to machine acrylic may be worth it.

Bringing Your Part Designs to Life with SyBridge

Selecting a suitable material for your manufacturing project can be the difference between success and failure. While we’ve explored the positives and negatives of acrylic and polycarbonate, it’s worth remembering that they’re not your only options. Numerous CNC machining materials may be compatible with your part’s design and intended application, and choosing the right one can be a complicated process. 

Fortunately, a manufacturing partner like SyBridge can reduce that complexity and address the challenges certain materials present. Beyond helping you decide whether acrylic, polycarbonate, or another material will work best for your part, our team can offer access to the tools and expertise you’ll need to ensure production runs as smoothly and cost-efficiently as possible. And getting your project started is simple: just create an account and upload your designs to get a quote for your parts instantly. Or, to learn more about how we can make your project possible, contact us today.

The post Key Differences for Acrylic and Polycarbonate Machining appeared first on SyBridge Technologies.

All post-processing increases part costs and production timelines, but the right surface finish has the potential to bring your design vision to life. Metal finishing for CNC machined parts typically encompasses a variety of mechanical processes, such as tumbling, brushing, and bead blasting, but metal parts may also be treated with chemical finishes such as passivation and zinc plating.

Amongst many useful results, chemical finishing can remove blemishes from a part, alter its conductivity levels, extend its lifespan, and even increase its resistance to wear and corrosion. Chemical finishes have an array of industrial applications: in the aerospace industry, for example, companies use chemical finishes to increase parts’ durability, improve thermal stability, and slow oxidation. In the consumer goods industry, chemical finishes can be found in the production of everything from enclosures and casings to sporting equipment.

While there are plenty of chemical finishes available, they aren’t necessarily interchangeable between materials. In fact, every chemical finish is typically compatible with specific materials and offers its own advantages and disadvantages. In this guide, we’ll explore several common chemical finishing processes so that you can decide which will work best for your CNC manufacturing project.

Choosing Your Chemical Finish

When choosing a chemical finish for your part, you’ll need to think about both compatible materials and end use. This means considering an array of contextual factors, including: 

• The environment your part will be used in
• Whether it requires conductive or insulating properties
• How much weight it will need to bear
• How much wear it will need to withstand
• Tolerance requirements
• Color and transparency requirements
• Surface finish standards
• Any other relevant or desired properties.

To help you evaluate your options, here are some common chemical finishes and their compatible materials:

Let’s take a closer look at these chemical processes, how they work, and how they might benefit your project. 

Anodizing

A popular aluminum finishing option, anodizing thickens the natural oxide layer on part surfaces, creating an anodic oxide film that confers increased protection and improved aesthetics. In the case of aluminum, to form the anodized protective layer, you’ll need to bathe your part in an acid electrolyte bath and then apply a cathode (a negatively charged electrode) to cause the solution to release hydrogen. At the same time, the aluminum part (the positively charged anode) will release oxygen, forming a protective oxide layer on its surface. After a part has been anodized, its surface will have microscopic pores which must be sealed with a chemical solution to prevent corrosion and any build up of contaminants. 

Anodized parts are durable and resistant to corrosion and abrasion, which can reduce maintenance costs down the line. The anodized layer is electrically non-conductive and is fully integrated with the aluminum substrate, so it won’t chip or flake away like plating and paint often do. In fact, in addition to sealing, the porous anodized layer can be painted or dyed, and since anodized finishes are non-toxic and chemically stable, they’re also more environmentally friendly. Anodizing isn’t just a finish for aluminum: the process is also possible for titanium and other non-ferrous metal parts. 

There are three different types of anodization:

• Type I (chromic acid anodizing) results in the thinnest oxide layer, which means it won’t change your part’s dimensions. Type I anodized elements will appear grayer in color and won’t absorb other colors well.
• Type II (boric-sulfuric acid anodizing) has better paint adhesion and is slightly thicker than Type I. With Type II anodizing, you can easily create anodized parts that are blue, red, gold, black, or green.
• Type III (hard sulfuric acid anodizing) is the most common form of anodizing. It has the clearest finish, which means it can be used with more colors. It’s worth noting that Type III anodizing results in a slightly thicker finish than Type II anodizing.

The increased durability, abrasion resistance, and corrosion resistance of anodized parts, and the high level of dimensional control that the process offers, makes anodizing particularly popular in aerospace and construction. Beyond those industries, anodized metal components are found in a wide variety of applications including curtain walls, escalators, laptops, and more.

Despite its broad applications, there are drawbacks to anodization:

• Anodizing metal will change the dimensions of your part, so you’ll need to consider the oxide layer when determining dimensional tolerances or use chemical or physical masks to ensure specific areas of your part remain untreated.
• It can be challenging to achieve a true color match if your anodized components aren’t treated in the same batch. Color fading may also occur.
• Anodizing a metal part will increase its electrical and thermal resistance. In some cases, this might be the intention, but in others, you may need to use a mask to ensure your part retains its full conductivity in certain sections.
• Anodizing will increase your part’s surface hardness.

Passivation

This popular metal finishing process prevents corrosion in stainless steel parts, helping them retain their cleanliness, performance, and appearance. Not only will passivated parts be far more resistant to rust, and thus better suited to use outdoors, they’ll also be less likely to pit, last longer, be more aesthetically pleasing, and more functional. Accordingly, passivation is used across a variety of industries, from the medical industry where sterilization and longevity are key, to the aerospace industry where businesses seek high steel quality and tight dimensional tolerances.

Passivation involves the application of nitric or citric acid to a part. While nitric acid has traditionally been the typical choice for passivation, citric acid has recently increased in popularity because it can produce shorter cycle times, and is safer and more environmentally friendly. During the passivation process, parts are submerged in an acid-based bath to remove any iron and rust from their surfaces without disturbing the chromium. The application of acid to stainless steel removes any free iron or iron compounds from its surface, leaving behind a layer composed of chromium (and sometimes nickel). After exposure to the air, these materials react with oxygen to form a protective oxide layer. 

It’s important to bear in mind that passivation can extend part production time. Before a part can be passivated, it must be cleaned to remove any greases, dirt, or other contaminants, and then rinsed and soaked (or sprayed). While submersion is the most common passivation method because it offers uniform coverage and can be completed quickly, an acidic spray may be used as an alternative. 

Black Oxide Coating

A finish for ferrous metals like steel, stainless steel, and copper, the black oxide coating process involves immersing parts in an oxide bath to form a layer of magnetite (Fe₃O₄), which offers mild corrosion resistance.

There are three types of black oxide coating:

• Hot black oxide: The hot black oxide coating process involves dipping a part into a hot bath of sodium hydroxide, nitrites, and nitrates in order to turn its surface into magnetite. After bathing, parts will need to be submerged in alkaline cleaner, water, and caustic soda, and then coated with oil or wax to achieve the desired aesthetic.
• Mid-temperature black oxide: Mid-temperature black oxide coating is very similar to hot black oxide coating. The main difference is that coated parts will blacken at a lower temperature (90 – 120 °C). Since this is below the boiling point of the sodium and nitrate solution, there’s less need to worry about caustic fumes.
• Cold black oxide: While hot and mid-temperature black oxide coating involves oxide conversion, cold black oxide relies on deposited copper selenium to alter a part. Cold black oxide is easier to apply but rubs off more quickly and provides less abrasion resistance.

Parts that have received black oxide coating will have greater corrosion and rust resistance, be less reflective, and will have much longer life cycles. The oil or wax coating will add water resistance and may also make your parts easier to clean by preventing harmful substances from reaching the metal interior. Black oxide coating will also add thickness, making it ideal for drills, screwdrivers, and other tools that require sharp edges that won’t dull over time.

Chem Film

Chem film, also known as chromate conversion coating, or by its brand name Alodine®, is a thin coating typically used on aluminum (although it can be applied to other metals) to prevent corrosion and improve adherence of adhesives and paints. Chem film finishes often have proprietary formulas, but chromium is the main component in every variety. A chem film finish can be applied via spraying, dipping, or brushing, and, depending on product and formula, may be yellow, tan, gold, or clear in color.

While other finishes reduce thermal and electrical conductivity, chem film finishing allows aluminum to maintain its conductive properties. Chem film is also relatively cheap and, as noted, provides a good base for painting and priming (for additional time-saving benefits). Since it’s prone to scratches, abrasion, and other superficial damage, however, chem film isn’t ideal for projects in which aesthetic appearance is a top priority.

Electropolishing

Electropolishing is an electrochemical finishing process commonly used to remove a thin layer of material from steel, stainless steel, and similar alloys. During the electropolishing process, a part is submerged in a chemical bath and an electric current is applied to dissolve its surface layer. Various parameters affect the part’s finish, including the chemical composition of the electrolyte solution, its temperature, and the part’s exposure time.

Electropolishing generally removes between 0.0002 and 0.0003 inches from an object’s surface, leaving smooth, shiny, and clean material behind. Other benefits of electropolishing include improved corrosion resistance, increased part longevity, improved fatigue strength, a lower coefficient of friction, reduced surface roughness, and the elimination of surface defects such as burrs and micro-cracks.

Electropolishing is compatible with steel, stainless steel, copper, titanium, aluminum, brass, bronze, beryllium, and more. It’s worth noting that electropolishing is faster and cheaper than manual polishing, though it still takes time and won’t remove 100% of rough surface defects. 

Electroplating

Electroplating is effectively the reverse of electropolishing. Instead of removing a layer of metal to achieve a finished surface, electroplating deposits an additional outer layer, increasing a part’s thickness. Compatible with cadmium, chrome, copper, gold, nickel, silver, and tin, electroplating creates smooth parts that experience less wear and tear over time thanks to their additional protection from corrosion, tarnishing, shock, and heat. Electroplating can increase adhesion between the base material and its additional outer coating, and, depending on the type of metal used, can make your part magnetic or conductive.

In contrast to other CNC machining finishes, electroplating isn’t particularly eco-friendly since it creates hazardous waste that can seriously pollute the environment if disposed of improperly. Electroplating is also relatively costly, as a result of the metals and chemicals (and other necessary materials and equipment) that it requires, and can be time-consuming, especially if a part requires multiple layers.

Chrome Plating

Chrome plating, or chromium plating, is a type of electroplating that involves adding a thin layer of chromium to a metal part to increase its surface hardness or resistance to corrosion. The addition of a chrome layer can make cleaning a part easier and improve its aesthetics, and nearly all metal parts can be chrome plated, including aluminum, stainless steel, and titanium.

The chrome plating process generally involves the degreasing, manual cleaning, and pretreatment of a part before it is placed in a chrome plating vat. The part must then stay in the vat long enough for the chrome layer to reach a desired thickness. Since the process consumes electricity, and involves multiple steps, chrome plating is a relatively expensive finishing process.

Polytetrafluoroethylene (Teflon™) Coating

Polytetrafluoroethylene (PTFE) coating, commonly known as Teflon™, is available in powder and liquid forms, and is used across the industrial landscape. Some PTFE applications only require one coat, but others need both a primer and a topcoat to ensure maximum protection. The finish can be applied to a range of metals including steel, aluminum, and magnesium.

PTFE-coated parts have non-stick surfaces, a low coefficient of friction, and are highly resistant to abrasions. Since PTFE coating has low porosity and surface energy, coated parts will be resistant to water, oil, and chemicals. PTFE can also withstand temperatures up to 500°F, can be easily cleaned, and offers great electrical insulation and chemical resistance.

Due to its chemical resistance and non-stick properties, PTFE is often used to coat fuel pipes and to insulate circuit boards in computers, microwaves, smartphones, and air conditioners. It is also commonly used to coat medical tools and equipment, and cookware. Although it is popular across industries, the PTFE coating process is relatively expensive and isn’t as long-lasting as other chemical finishing options.

Electroless Nickel Plating

Electroless nickel plating refers to the addition of a protective layer of nickel-alloy to metal parts. In contrast to the electroplating process, which involves an electric current, electroless nickel plating involves the use of a nickel bath and a chemical reducing agent like sodium hypophosphite to deposit a layer of nickel-alloy (often nickel-phosphorus) onto parts. The nickel-alloy deposits uniformly, even on complex parts with holes and slots. 

Parts finished with nickel plating have increased resistance to corrosion from oxygen, carbon dioxide, salt water, and hydrogen sulfide. Nickel-plated parts also have good hardness and wear resistance and, with additional heat treatment, can become even harder. Electroless nickel plating is compatible with a variety of metals, including aluminum, steel, and stainless steel. 

Electroless nickel playing has its challenges. Common problems include the build up of contaminants in nickel baths, rising phosphorus content, and subsequent reductions in plating rates. Additionally, the wrong temperature or pH level can create coating quality issues like pitting, dullness, and roughness. Electroless nickel plating isn’t suitable for rough, uneven, or poorly machined surfaces, and parts will need to be cleaned of soaps, oils, and dirt before the plating process can begin.

Different types of electroless nickel plating coatings are categorized by the percentage of phosphorus in the alloy by weight. Different levels of phosphorus content also offer different levels of corrosion resistance and hardness:

• Low phosphorus nickel (2 – 4% phosphorus): Low phosphorus electroless nickel has an as-plated hardness between 58 and 62 Rc, and is highly resistant to wear. It has a high melting point and good corrosion resistance when exposed to alkaline conditions. Low phosphorus electroless nickel deposits are compressively stressed and are usually more expensive than medium and high phosphorus nickel.
• Medium phosphorus nickel (5 – 9% phosphorus): Medium phosphorus nickel plating offers a middle ground between low and high phosphorus nickel. It is resistant to corrosion in alkaline and acidic environments and has a fast deposition rate (18 to 25 µm per hour). The as-plated hardness of medium phosphorus nickel can be anywhere between 45 and 57 Rc, and the plating can be heat treated to reach 65 to 70 Rc.
• High phosphorus nickel (>10% phosphorus): Since high phosphorus deposits of electroless nickel plating are amorphous, parts won’t end up with phase boundaries or grain, increasing their corrosion resistance and making them ideal for use outdoors or in extreme environments. High phosphorus electroless nickel plating also offers ductility, high thickness, and stain resistance, and will make it easier to polish or solder your final product.

Zinc Plating

Zinc plating, or zinc chromate, is a popular chemical finish that protects steel parts from moisture and corrosion. Zinc-plated products have increased longevity, improved aesthetic appeal, and a more uniform appearance. Zinc plating can also alter a part’s color to silver-blue, yellow, black, or green. Another significant benefit of zinc plating is its potential to protect a part’s surface for years: even if the coating becomes scratched, the zinc will react to the atmosphere and quickly oxidize. Since zinc is chemically susceptible to acids and alkalis, however, zinc plating may not be sufficient for parts destined for wet or extremely humid environments.

There are a few different types of zinc plating. Electro-galvanization requires an electrical current to coat the part in a thin layer of zinc, whereas hot-dip galvanization requires parts to be submerged in a hot zinc bath. Electro-galvanization is the cheaper process, but hot-dip galvanization is better for parts that will be used in aggressive environments or that will experience a lot of wear.

Following the zinc plating process, parts can undergo a secondary procedure for increased protection and improved performance. The ASTM B633 standard, the most widely used standard for zinc plating, includes four types of zinc plating:

• Type I: Type I has no supplementary treatment.
• Type II: Type II involves a colored chromate treatment.
• Type III: Type III uses a colorless chromate treatment.
• Type IV: Type IV uses a phosphate conversion treatment.

Achieving Quality Finishes With SyBridge

Chemical finishing offers numerous ways to achieve the surface quality and performance levels that you need for your part, but not every finishing process will be suitable for every material and end-use. To determine which chemical finish is right for your part, you’ll need to have a strong understanding of critical factors, such as how much corrosion, friction, and wear resistance your final part needs, the environment in which it will be used, and its required conductive or insulative properties. 

Given the importance of those considerations, it’s worth finding a manufacturing partner to help you select a suitable finish, and ensure that it offers the best quality and cost efficiency possible. At SyBridge, our expert team of designers and engineers can offer insight not just into the chemical finishing process, but material selection, tooling, and suitable CNC technologies. If you want to know more about the finishing options available for your next CNC machining project, get in touch with us today. If you’re ready to get started, create your account, upload your designs to get an instant quote, and start making new parts and products in just a few simple steps.

The post A Guide to Chemical Finishes for CNC Machined Parts appeared first on SyBridge Technologies.

In the manufacturing business, more money put into production generally means less profit or higher prices for customers. But careful planning and informed decision making about your design will help save time and money during the CNC machining process.

CNC machining costs can be divided into two main buckets: non-recurring costs and piece costs. Non-recurring costs refer to all of the upfront costs required to get any production run (large or small) off the ground; these costs are amortized over the production quantity. Piece costs are expenses associated with each individual part, and scale with quantity. The bottom line cost to manufacture a single part, taking into account all cost buckets, is often referred to as the fully burdened part cost.

To put this in mathematical terms: 

Fully Burdened Part Cost = Non Recurring Costs / Quantity + Piece Costs

Non recurring costs include:

• Part design 
• Planning (manufacturing process, inspection, etc.)
• CAM programming
• CMM programming 
• Workholding, fixtures, gauges, and tooling identification and sourcing

Piece costs include:

• Machine time
• Labor time (loading and unloading parts)
• Consumable tooling
• Raw material
• Cleaning, deburring, and finishing 
• Manual inspection

Following the equation above, in lower volume runs, non-recurring costs are amortized over fewer parts, which means the expense is higher per part. For example, if the non-recurring costs for a job are $5,000, and the production quantity is 100 parts, then each part will have a burden of $50 for non-recurring expenses. On the other hand, if that same job is ordered for a quantity of 200 parts, this would result in a non-recurring burden of just $25 per part, a potentially significant cost delta. The good news is that you can minimize CNC machining costs for shorter production runs by optimizing your part designs.

Design tips for short production runs

To maximize your time and budget, try these design tips for short production runs:

Use standardized, simple designs

Keep your design as simple and standardized as possible. Overly complicated part designs can require multiple manual rotations and repositions, more expensive CNC systems, or specialized tools. With this in mind, it may be worthwhile to break up a complex piece into simpler components that can be assembled later.

You’ll also want to:

• Design standard-sized holes: The deeper the hole, the more complex the metal chip evacuation process, and the more expensive your part. Try to make each hole’s depth no more than five to six times the drill’s diameter to ensure your machinist can quickly evacuate the metal chips. Also, make sure to use standard drill sizes when designing your holes or you may end up needing to purchase a custom tool, which can drive up costs and overall production time further.
• Use standard threads: As with drill sizes, using standard thread depths and diameters can save time and money. In practice, this means simply using an existing thread class instead of creating a custom thread via CNC machining or 3D printing. Try to use the H2 thread tolerance, since H3 is tighter and more expensive to create. Also, it’s best to keep your thread depth no deeper than required by your part’s functional and structural specifications.
• Design with standard stock sizes in mind: You can also cut costs and machine times by designing your parts to align with standard stock sizes. Instead of ordering a larger piece of material only to have to machine it down, your machinist will be able to buy a standard stock piece and then make few (if any) changes before starting on your part. Beyond choosing standard stock sizes, it’s also a good idea to allow a large enough tolerance so that the outside of the part does not need to be machined.
• Use loose tolerances: Tight tolerances can require specialized manufacturing processes or secondary operations, and can increase set-up, machining, and inspection time and cost. With that in mind, your part’s tolerances should only be as tight as required by functional and structural constraints.

Avoid thin walls, tall walls, and narrow pockets

CNC machining can be a delicate and time-intensive operation, especially if you have thin walls, tall walls, or narrow pockets.

Since they can increase the risk of cutter deflection, deformation, compromised surface finishes, and part failure, and make it difficult to meet specified tolerances, thin walls are generally less stable and more expensive to machine. Beyond those considerations, your machinist may need to take numerous passes over a part to create a thin wall without accidentally fracturing or snapping it with excessive vibrations, which will, of course, further drive up machining times and costs.

There are options for addressing the increased machining times, higher production costs, and fracture risks associated with thin walls. For example, if you have a metal part, try to design walls that are at least 0.8 mm thick. For plastic parts, try to aim for walls at least 1.5 mm thick. Similarly, you’ll want to avoid including tall walls, deep cavities, and narrow pockets in your part, since these features require longer cutting tools and the removal of more waste material. Like the problems associated with thin walls, these issues can lead to increased cutting tool deflection, chatter, inaccuracies, reduced tool life, and sub-par surface finishes, all of which drive up the final part cost.

Avoid unnecessary text or finishing processes

Adding text to your part will enable you to clearly number components, include a description, or apply a company logo. While machined text looks aesthetically pleasing, and can be functionally useful, it’s an expensive and time-consuming process since you’ll need to trace each character with a small ball end mill or engraving tool. Unfortunately, including raised text on a part is even slower and costlier since even more material will need to be milled away from the part to achieve the effect.

As an alternative to machining, if your part requires text, lettering, or a logo, you may be able to save time and money with a post-production surface finishing method. For example, silk screening, laser marking, rubber ink stamping, and painting will all enable you to add text to your parts faster than direct engraving. Of course, given that adding any CNC finishing process will increase your parts’ turnaround time and overall costs, it’s best to avoid text and other non-critical finishing processes whenever possible.

Choose the proper material

Material selection is important in both long and short production runs since using the wrong metal or plastic for your parts can drastically increase project costs. Some materials are more difficult to machine than others, which means longer turnaround times and higher machining costs. Even if two materials are equally machinable, the chances are that one will be more expensive than the other.

For example, while titanium is ideal for aerospace applications, it’s expensive and difficult to machine. On the other hand, softer, less costly metals, such as aluminum, are easier to machine and strong enough for everything from airplane parts to architectural components. Similarly, if you want to create a plastic part but don’t require the strength or high heat resistance of polyetheretherketone (PEEK), you can save money by using acrylonitrile butadiene styrene (ABS) or another high-performance engineering thermoplastic.

To put it simply, if you don’t really need the properties of an expensive and/or rare material, you should use a less expensive and/or more common material. As an added benefit, using a more readily available material also likely means a reduction in your parts’ overall lead time. It’s worth applying this mentality during the prototyping phase, too; for example, if you only need to create a proof-of-concept model, you should use the least expensive plastic that will still demonstrate the feasibility of your idea.

Additive manufacturing as an alternative for short production runs

While designing with CNC machining lead times in mind can help reduce turnaround and cut costs, depending on your material requirements and the size of your run, additive manufacturing might represent a better option

In contrast to CNC machining, which is a subtractive process that involves cutting away material to shape a final product, the additive manufacturing process builds parts layer by layer. Additive manufacturing is typically far less labor-intensive than CNC machining, sometimes only requiring limited mid-production repositioning and limited post-processing to enhance a part’s functionality, or to achieve a desired finish. Like CNC machining, additive manufacturing can be used to make metal parts, but plastic additive manufacturing is far more common. In fact, many of the plastics used in additive manufacturing are mechanically equivalent to those used in injection molding. 

Generally, additive manufacturing is a better choice for extremely low-volume production runs or for projects in which finished parts or prototypes must be delivered fast, and where tolerance requirements are not tight. By contrast, CNC machining is more appropriate for low-volume production runs with part quantities in the higher double digits or low hundreds, or in projects that have high tolerance requirements.

Working with an experienced manufacturing partner

Each of our design tips for short production runs can help you ensure that your production process is as smooth, cost-efficient, and fast as possible. However, there’s a lot to keep track of when optimizing parts for low-volume production, so working with a trusted manufacturing partner is also a valuable opportunity to take some of the weight off your shoulders.

From design through fulfillment, when you work with SyBridge, our team of experienced engineers will provide you with the support you need to make your project possible. Our cloud-based tools are designed to help you pinpoint design flaws, determine optimal order quantities, and find the right material for your part’s specific application. Simply create an account and upload your part files. We can generate instant quotes for both additive manufacturing and CNC machining projects, which means you can get started making your new parts and products today. Contact us today.

The post Design Tips for Low-Volume CNC Machining Production Runs appeared first on SyBridge Technologies.

In 2021, the global Computer Numerical Control (CNC) machine market size was $56.40 billion. Given how fast, precise, and automated this manufacturing technology is, it’s hardly surprising that the global machine market is expected to grow in the coming years. As the demand for CNC machining grows, the demand for Swiss machining, a manufacturing process that falls under the overall umbrella of CNC machining, will also rise.

As with traditional CNC machining, Swiss machining is used with metal and plastic, offers fast production times, and can produce complex parts with tight tolerances. It’s an incredibly efficient, precise, and repeatable manufacturing process, though it differs in several ways from traditional CNC machining.

In this guide to CNC Swiss machining, we’ll go over what you need to know to decide whether Swiss machining is best for your project.

What is Swiss Machining?

Originally developed to produce intricate watch parts for the Swiss watchmaking industry in the late 19th century, Swiss screw machines required a skilled operator who could turn handles and push levers to form the desired part. However, thanks to today’s CNC technology, Swiss machining is highly automated and can repeatedly produce complex geometries at tight tolerances with extremely fast cycle times.

As a subset of turning machines, also known as lathes, Swiss machines have stationary tools and a workpiece that can turn and move along the Z-axis, allowing for the creation of round and cylindrical parts. However, its sliding headstock and guide bushing set Swiss machines apart from other turning machines. The sliding headstock feeds the bar stock through a guide bushing, which supports and stabilizes the bar stock near the cutting point. This helps prevent workpiece distortion and enables the machine to accurately create different diameters, complex holes, hex edges, slots, and threads without the need for multiple setups or additional equipment.

When it comes to making parts, Swiss machining is the ideal production method for manufacturing high volumes of small components that require complex turning. Swiss machines are also better suited for machining long parts than traditional CNC turning machines, as they are less likely to cause deflections. 

Key Differences Between Traditional CNC Turning and Swiss Machining

The main difference between traditional CNC turning and Swiss machining is that Swiss machines have a moveable headstock that enables the workpiece to spin and move along the Z-axis, whereas the workpiece remains stationary when using conventional lathes.

Additionally, traditional CNC lathes generally have two, three, or four axes, but Swiss machines often have five, seven, or more axes, enabling operators to quickly machine even the most complex parts. Instead of performing multiple operations or using several setups on numerous machines, manufacturers can often do the job with one Swiss machine and fewer setups. It’s also worth noting that many Swiss machines can perform several tooling operations simultaneously, whereas traditional lathes usually complete one operation before moving on to the next, which can help further accelerate production.

By using a Swiss machine, companies can enjoy a reduction of secondary operations and tool changes, reduced labor costs, and faster turnaround times, all without sacrificing part quality. Since the bar stock is firmly supported, tolerances are tight and complex parts with thin walls or delicate features can be repeatedly manufactured.

Industry Applications for Swiss Machining

Swiss machining was initially used to create the tiny, intricate parts used in watches, and it’s still used to create long, small, or slender turned components across various industries. Its speed, accuracy, and relatively low costs have kept Swiss machining popular.

For example, Swiss machining’s high level of accuracy makes it an ideal manufacturing technology for the defense sector, where small, complex geometries with tight tolerances are often required for military hardware. 

Swiss machining also has plenty of applications in the medical industry, where manufacturers can use Swiss machines to produce everything from electrodes to anchors to surgical tools.

In the aerospace industry, Swiss machining can produce components that meet the extreme precision required by the industry’s rigorous demands. The technology can be used to create everything from mechanical components for spacecraft motors to the cockpit controls’ electrical components.

Similarly, Swiss machining’s ability to produce quality and precise parts makes it a popular manufacturing process in the automotive industry. Here, companies use Swiss machines to fabricate bushings, pins, brake system and suspension components, and more.

Essentially, Swiss machining is an excellent production method for manufacturers who need to quickly produce a high volume of small, accurate parts with complex geometries and high-quality finishes for a relatively low cost.

Design Tips for CNC Swiss Machining

While CNC Swiss machining differs from traditional CNC machining, many best practices should still be kept in mind when designing your part to reduce machining time and costs as much as possible. For example, make sure you remember to:

• Ensure your drawings are accurate and clear: You need to have legible and precise drawings to ensure your operator can quickly and correctly understand and machine your part. Include dimensions, tolerances, and material and finish information.
• Use standard-sized holes: Incredibly small or deep holes can make machining more difficult and expensive, so it’s best to use standard-sized holes whenever possible.
• Avoid sharp corners: Whether you’re using a traditional CNC lathe or a Swiss machine, your drill bits will be round, which means it will be incredibly difficult to produce sharp inner corners. While you can achieve sharp inner corners using methods like electrical discharge machining, this can be expensive and time-consuming. Thus, it’s best to always design your parts with rounded corners, as the drill bit will automatically leave an inside corner radius. To avoid chatter and premature tool wear, make sure your corner radius is slightly larger than the common trade sizes of tool diameters, such as 3 mm or ⅛ inch, for example.
• Only include the necessary tolerance: Including unnecessarily tight tolerances can drive up machining time and overall part costs, so it’s best to only assign strict tolerances to areas where they truly matter.
• Pay attention to wall thickness: While it’s possible to machine thinner walls with Swiss machines, it’s still best to avoid designing your parts with thin walls, as they can cause chatter, resulting in less-accurate parts with reduced surface quality. When it comes to plastic parts, thin walls can also result in warping and softening.

CNC Swiss Machining with SyBridge

Swiss machining is a fast, accurate, and cost-effective manufacturing method that’s ideal for creating large quantities of small parts that require complex CNC turning. However, as with any CNC process, it’s best to keep the above tips in mind when designing your parts to ensure your machining time and costs are as low as possible.

Whether Swiss machining is the ideal manufacturing process for your parts or traditional CNC turning is better-suited for your needs, working with an experienced manufacturing partner like SyBridge can help you make the right decisions to get better quality parts faster. Start making the precision-machined parts you need today — contact us to get started.

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Since its development in the mid-20th century, polycarbonate (PC) has been an increasingly popular material in manufacturing. Today, around 2.7 million tons of polycarbonates are produced each year globally. Over the years, various companies have created different formulas for polycarbonate, so there are several industry grades of polycarbonate to choose from. Some forms have more glass fiber reinforcement, while others have additives like ultraviolet stabilizers for protection against long-term sun exposure.

Strong and versatile, this amorphous thermoplastic is resistant to heat, impact, and many chemicals. As such, polycarbonate is ideal for components that need to be tough or repeatedly sterilized and is often used in the automotive and medical industries.

How Polycarbonate is Manufactured

Each company manufactures polycarbonates slightly differently, but polycarbonate materials have traditionally been created via the condensation polymerization of bisphenol A and carbonyl chloride. However, many companies have started to use diphenyl carbonate instead because carbonyl chloride is extremely toxic.

Regardless of whether carbonyl chloride or diphenyl carbonate is used, a bisphenol A solution in sodium hydroxide is required and then mixed with the carbonyl chloride or diphenyl carbonate solution in an organic solvent so polymerization can take place. When the polycarbonate forms, it will initially be in a liquid state. The solution will be evaporated to form granules, or ethanol will need to be introduced to precipitate the solid polymer.

Once created, polycarbonate is often sold in rods, cylinders, or sheets and can be used in various manufacturing processes. Polycarbonate is compatible with thermoforming, extrusion, and blow molding, but it’s most often used with injection molding. After all, as a thermoplastic, polycarbonate can be melted, cooled, and reheated without burning or significant degradation, making it an ideal injection molding material.

During injection molding, polycarbonate needs to be processed at a high temperature and injected into the mold with high pressure because polycarbonate is quite viscous. The melt temperature should be between 280°C and 320°C, and the mold temperature should fall between 80°C and 100°C. However, those numbers can vary depending on the grade of polycarbonate being used. For example, a high-heat polycarbonate will require a melt temperature between 310°C and 340°C and a mold temperature between 100°C and 150°C, whereas a PC-ABS (polycarbonate/acrylonitrile butadiene styrene) blend’s melt temperature only needs to be between 240°C and 280°C and its mold temperature can fall as low as 70°C and up to 100°C.

Properties and Mechanical Specifications of Polycarbonate Material

While there are several grades of polycarbonates, each with their own molecular mass, structure, and properties, all polycarbonates have a few things in common.

For one, they are known for their toughness and high impact resistance. As a result, polycarbonate is often used for applications that require reliability and high performance.

Despite their toughness and strength, polycarbonates are light weight, allowing for extensive design possibilities and relatively easy installation when compared to other materials.

Polycarbonates are also very resistant to heat and flames. A polycarbonate can maintain its toughness in temperatures up to 140°C, which means polycarbonate parts can withstand repeated sterilization. Polycarbonates also have light transmittance rates above 90% and good chemical resistance against diluted acids, oils, greases, aliphatic hydrocarbons, and alcohols.

A polycarbonate’s properties depend on its molecular mass and structure, so each material is slightly different. To give you an idea of what you can expect, here are some typical key characteristics and specifications:

• Specific gravity: 1.21
• Melt temperature: 295 – 315°C
• Mold temperature: 70 – 95°C
• Heat deflection temperature: 137°C at 0.45 MPa
• Tensile strength: 61 MPa
• Flexural strength: 90 MPa
• Shrink rate: 0.5 – 0.7%
• Rockwell hardness: 118R

As you can see, polycarbonate manufacturing has plenty to offer. However, there are a few things you’ll want to be aware of before selecting this material for a project. For example, its mechanical properties can degrade after prolonged exposure to water over 60°C. Polycarbonate is also susceptible to scratching, more costly to manufacture than many other materials, and vulnerable to diluted alkalis and aromatic and halogenated hydrocarbons. Additionally, the polycarbonate formulations without UV stabilizers can sometimes yellow over time when exposed to UV rays.

Common Uses of Polycarbonates in Everyday Life

Polycarbonate’s toughness and high impact resistance make it a popular material choice for automotive industry manufacturers, particularly when it comes to parts that must be clear or translucent and are subject to frequent impact, such as headlight and turn signal lenses.

In the medical industry, polycarbonate can be found in everything from incubators to dialysis machine housings. After all, polycarbonate is tough, resistant to heat, dimensionally stable, and able to withstand sterilization via FDA-approved methods including autoclaves and irradiation. Polycarbonate can be used in blood filters, reservoirs, and oxygenators, as well as surgical instruments. Plus, given its transparency, polycarbonate enables doctors to more easily monitor blood and track the administration of fluids.

Polycarbonate is also a material of choice in many household appliances, such as mixers, hair dryers, refrigerators, and electric razors. Other common uses for polycarbonate include exterior lighting fixtures, machinery guards, protective gear, bullet-proof glass, fuse boxes, television housings, roofing, skylights, greenhouses, suitcases, eyeglasses, and beverage containers, such as baby bottles, sippy cups, and refillable water bottles.

Getting Started With Polycarbonate

Polycarbonate is a strong and impact-resistant thermoplastic that’s used across a variety of industries. However, there are several different kinds of polycarbonate on the market, each with its own characteristics. Working with an experienced manufacturing partner like SyBridge can make all the difference for product teams who are unfamiliar with polycarbonate or are looking to manufacture parts and products with materials that may be more suitable for a specific application. Want to see if polycarbonate is the right material for your next project? Create an account and upload your part files or contact us today to get started.

The post Know Your Materials: Polycarbonate (PC) appeared first on SyBridge Technologies.

The post-processing stage of a CNC machining project is arguably one of the most crucial, as it preps and puts the finishing touches on your part. There are numerous post-processing options available, and determining which is best for your part depends largely on what material it’s made of and the purpose of the part.

Passivation is one of many final treatment options for materials that can significantly improve the quality and performance of a machined part by creating a protective layer that safeguards the part against corrosion.

What is Passivation and How is it Used?

Passivation is a chemical finishing process often applied to materials such as stainless steel, but it may also be used on other alloys and metals, including aluminum. After being thoroughly cleaned to remove debris or other potential impurities, an oxidizing agent, typically nitric acid or citric acid, is applied to the material’s surface, creating a passive oxide film that strengthens its corrosion resistance.

While stainless steel is inherently corrosion-resistant due to its higher chromium content than other alloys, it is still susceptible to rust over time, especially if iron contaminants on its surface are exposed to water. This oxidation can create rouging, which displays as reddish-brown deposits on stainless steel. Etching, pitting, and frosting may also be signs of localized corrosion that should be addressed before they cause operational issues.

Passivation can help deter the development of rouging and rust, and when done correctly, it can even be used as a proactive measure to reduce the need for frequent maintenance.

Practical applications of passivation

The passivation of parts used in highly regulated systems in the aerospace and medical industries is vital due to the critical roles these parts often play. When there is little room for error, components must perform optimally, and passivation has a crucial role in enhancing the lifespan and operation of a part.

For example, the pharmaceutical and medical industries operate under strict regulations to ensure patient and product safety. Maintaining a pristine environment and using precise, high-grade tools are of the utmost importance. Therefore, many components must undergo passivation to decontaminate and to guard against rust and other corrosion.

Below are just a few other practical applications where passivation can be used to discourage corrosion:

• Food processing equipment
• Surgical instruments such as stents, forceps, and implants
• Pharmaceutical products such as inhalers
• Motor vehicle parts such as frames, bushings, and cylinder heads
• Electronic and microelectronic components
• Machine parts such as fittings, housing, and suspension arms

Passivation offers a way to control the quality of your end product so you can have confidence in knowing the parts you’re using will last.

Benefits and Drawbacks of Passivation

Passivation is a practical, precautionary measure that can extend the lifespan of parts and their systems. However, while there are not many, there are a few drawbacks to the passivation process to keep in mind:

• Passivation does not smooth out the metal, so if that is required for the final product, it will need to be addressed prior to treatment.
• Passivation requires a rigorous pre-cleaning process before treatment, which can marginally extend the time to complete the fabrication process.
• Passivation techniques can leave room for error when not applied professionally, rendering the treatment futile.
• If passivating a system regularly as part of a proactive approach to maintenance, downtime must be allotted for treatment application.

The main benefit of passivation is corrosion resistance, but there are a few other additional advantages:

• Passivation offers increased corrosion resistance, leading to longer-lasting machinery that can operate at peak performance for longer periods.
• Passivation reduces the frequency of maintenance as well as the degree of care needed.
• Passivation eliminates surface contamination that can seep into other parts of the system and even contaminate the final product.
• Passivation helps ensure the operating efficiency, quality, and safety of parts and systems over time.

Why Passivate CNC Machined Parts?

Passivation should be considered a post-fabrication best practice for CNC machined parts. While passivation does occur naturally in chromium-rich alloys such as stainless steel, welding, machining, and engraving during the fabrication process can introduce contaminants that compromise the metal. Passivation’s multi-step process involves rigorous cleaning to remove impurities such as free irons that can make the parts susceptible to corrosion.

For heavily regulated industries that require meticulous precision and tighter tolerances, such as the CNC machining of aerospace parts, passivation is not only good practice — it’s essential for increasing the durability, safety, and reliability of components.

Boost Your Parts’ Longevity with Passivation

Passivation can be necessary to ensure the resiliency of your parts, systems, and product quality. Working with a team of specialists who understand the passivation process and are meticulous about their services will ultimately determine the effectiveness of your passivated components.

At SyBridge, we understand that precision and reliability are critical. With our team of experts on your side and advanced digital tools that make manufacturing easier, your parts can go from design to delivery with accuracy and speed. To get started, create an account to put the power of cloud manufacturing at your fingertips or contact us to learn how SyBridge can optimize your manufacturing operations.

The post Passivation: Post-Processing for Rust and Corrosion Prevention appeared first on SyBridge Technologies.

CNC machining is a popular and efficient subtractive manufacturing method capable of producing precision parts from a variety of materials, typically metals or plastics. Regardless of material choice or production volume, performing some key evaluations and adjustments when designing a part can help you streamline your CNC machining process to reduce costs and optimize part quality.

General Advice for Designing for Modern CNC Machines

CNC machines are versatile and capable of producing highly accurate parts. However, there are a few things you’ll need to keep in mind when designing for modern CNC machines to ensure the manufacturing process is as efficient as possible.

You’ll want to:

• Take your drill bit’s diameter or standard drill bit sizes into account as you design your part’s internal corners, edges, holes, and cavities.
• Avoid deep pockets, as the tool’s feed rate must slow when cutting pockets greater than three times the tool’s diameter, increasing cycle time and machining cost.
• Avoid extremely small holes and use standard drill sizes.
• Have a minimum wall thickness of approximately 1.5mm.
• Remember that thicker walls mean shorter machining times.
• Avoid deep-hole tapping or threading where the tapping depth is more than 1.5 times the diameter of the tap.
• Use standard thread forms and sizes.
• Avoid flat-bottomed holes.
• Design rounded internal corners with a depth-to-tool diameter ratio of 3:1 or less.
• Avoid multiple finishes and opt for uniform finishes whenever possible.
• Split up complex parts when necessary.
• Remember that material certifications, non-standard inspection reports, export restrictions, and non-standard finishes can also increase lead time and overall costs.

Streamline CNC Machining via Design

To streamline the CNC machining process as much as possible, you’ll want to make the most of your initial part design. Incorporate the following during the design process:

Design With a Specific CNC Machining Process in Mind

When designing a part for CNC machining, make decisions about your component with a specific CNC machining process in mind. Different machines are better suited for different applications.

Consider whether you’ll use a CNC turning machine or a CNC milling machine. CNC turning uses a rotating workpiece with a stationary tool, while CNC milling involves a rotating tool and a fixed block. CNC turning will generally allow you to produce parts faster than milling, as it typically has shorter setup times. As a result, turning will usually be more affordable than milling.

Whether you use CNC turning or milling, you’ll have to take your cutting tool’s range of motion and working range into account. With a 5-axis CNC machine, you can more easily machine complex designs with fewer adjustments mid-machining. On the other hand, a machining tool with fewer axes may require more repositioning and it may take longer to machine that same complex part. It’s also worth noting that you’ll need specialized tools if your part has any internal geometries.

Consider Machine Tolerances and Size Limitations

You’ll also need to consider tolerances, the amount of acceptable variation from part to part. Tighter tolerances mean more prep time, longer processing times, and a more involved CNC machining process.

Remember that tolerance varies from material to material, as some materials are more machinable than others. For example, CNC machines generally have a +/- 0.005” general tolerance for metals and a +/- 0.010” general tolerance for plastics. To ensure your parts come out as intended and production is as cost-effective as possible, don’t over-tolerance and try to use standard dimensions and tolerances.

You’ll also need to take into account your tool’s capabilities when thinking about the size of your part. After all, if your part has a cut that’s too deep for your tool’s cutting length, you’ll need to resize the product or break it down into smaller pieces for later assembly, which can lengthen the production process. On the other hand, if you design part features that are too small, machining the details may be difficult, if not impossible.

Choose Appropriate Materials for Your Project’s Scope

Material can impact motor power, feed rate, and spindle speed, influencing overall cycle times. Plus, material affects the final part’s durability, performance, and overall cost, so you need to consider the function of your component and its end-use environment, as well as various materials’ ease of use, cost, rigidity, and density before making a final material selection.

Soft metals like brass, bronze, and aluminum are less expensive, lighter, and usually easier to machine than hard metals like steel. As a result, it generally costs less to machine soft metals. The drawback is that they can’t take on as much stress as hard metals.

Plastics are typically cheaper and more cost-effective than metals. However, they are more susceptible to warping and don’t have the same weight, rigidity, or structural integrity as metals. As a result, plastics aren’t ideal for parts that will experience extreme stress, wear, or tear. Plus, it’s difficult to achieve tight tolerances when CNC machining plastics.

Streamline CNC Design Files With These Tips

Streamlining your CNC design files before sending them to a manufacturing partner will make the manufacturing process go much smoother, and your parts will come out as you envisioned. The best way to optimize CNC design files for production is to:

• Ensure your CNC vector file has single-line paths and that each line connects to the next line’s endpoint.
• Minimize nodes and intersections if possible.
• Prioritize polylines over arcs and beziers, as CNC machines prefer polylines.

CNC Machining With SyBridge

CNC machining is an efficient, precise form of manufacturing. However, there are always things you can do to streamline the process, from selecting a suitable material to following CNC design best practices to working with an experienced manufacturing partner like SyBridge.

When you work with us, our engineers can help you streamline the entire CNC machining process, and by uploading a part file you can instantly analyze your design to identify potential problems that could arise during production. Create an account or contact us today to see how we can help bring your design to life.

The post Designing With Efficiency in Mind: How to Streamline CNC Machining Processes appeared first on SyBridge Technologies.

To complete your production run on time and on budget, it’s best to have a clear picture of your expected project costs from the very beginning. However, predicting accurate CNC machining project costs is easier said than done for many product teams. You’ll need to consider material costs and machinability, your part’s complexity, post-processing requirements, and the actual CNC machine setups. Let’s explore the effect CNC setups can have on production costs.

Breaking down cost drivers for CNC setups

Depending on the complexity of your design, your CNC operator might need to use multiple CNC machine setups to manufacture parts with features on several sides, planes, or axes. To machine these features, your operator will need to remove your part from the machine and flip it over to work on the other side or move it to a different CNC machine setup to finish the production process. They’ll also need to recalibrate the fixture and tools each time. Plus, the longer it takes to machine a part, the higher your project costs will be.

A part that only needs one setup on a 3-axis milling machine will require only one face to have access for the tool, as seen in the image below.

A part that needs multiple setups on a 3-axis machine will have multiple faces that require access, like the part below.

When identifying if a part will need multiple setups to machine, consider how the tool will access all of the different features in the design.

There are a few additional cost drivers to keep in mind when it comes to any CNC setup, including:

• Fixturing: During machining, the blank must be secured in a fixed orientation or location using a fixture. Fixtures can be required for parts with irregular shapes, when a standard vice can restrict toolpaths, and can be used to help ensure tolerances. Sometimes, all your machinist will need to secure your workpiece is a standard vice, but they may need to design and fabricate a custom fixture for specific projects, which can increase lead time and costs.
• Specialized/non-standard CNC tools: If your design has unique features, your manufacturing partner may need to purchase new CNC machining tools. These tools typically cost between $50 and $500, so they can quickly raise your cost per part, especially if you’re planning a low-volume production run.
• Toolpaths: The toolpath is the pre-set course that the CNC machine’s cutting tool will follow during the machining process. Machinists often optimize toolpaths to minimize or eliminate any inefficient or unnecessary actions and tool travel. Doing so can save time and reduce manufacturing costs, no matter the size of your production run.

Examining the financial impact of CNC setups

Every part and every project is different, so it’s difficult to attach a definite number to how CNC setups increase project costs. However, the more setups you have, the more time your operator will spend resetting the CNC machine, recalibrating tools, and designing new fixtures, all of which can raise the cost of your project.

It’s also important to note that the number of setups isn’t the only driving factor behind setup costs. For example, if you use an exotic or hard-to-machine material, your operator will need to work more slowly with your CNC setup, lengthening machining times and increasing material costs. Using non-standard tooling and running the CNC machine on unoptimized toolpaths can also make your project more expensive.

Product teams looking to maximize their budgets and make CNC machining more cost-effective can make an impact by keeping the above points in mind.

Optimizing CNC machining for cost efficiency

Making a few smart decisions behind the scenes can lower your overall project costs. To reduce CNC machining costs as much as possible, consider:

Opting for a higher production run

One of the easiest ways to drive your cost-per-part down is to order more parts. If your manufacturing partner uses an expensive CNC tool and fabricates a custom fixture to bring a complex design to life but only manufactures a few parts, each part would cost a significant amount of money. Manufacturing a larger number of parts using that same tool and fixture more evenly distributes those costs and allows the manufacturer to purchase raw material in bulk at a lower cost, which together can significantly lower the cost per part.

Selecting materials carefully

Several factors can determine what material you choose for your project, including strength, machinability, cost, and availability. Remember that exotic materials are costly and metals are typically more expensive than plastics. As a general rule, consider using a common aluminum instead of a more expensive metal when possible to lower your overall CNC costs.

You’ll also want to consider material machinability, as less-machinable materials drive up manufacturing costs. Exotic materials often require expensive specialized tooling, and materials that require slower machining speeds mean longer manufacturing times and increased machine operating costs. Whenever possible, opt for materials like low carbon steel and aluminum because they are faster, easier, and cheaper to machine.

Also, look for materials that are already similar in size and shape to your part. This ensures you aren’t wasting money machining away a lot of excess material, and it also reduces machining time.

Using standard tooling, blanks, jigs, and fixtures

As with most things, customization costs more. Tooling, blanks, and other objects typically come in standard sizes such as whole numbers and fractions in multiples of two (i.e. ¼, ⅛, etc.). If you design a feature that requires a drill with a 0.265-inch diameter, your manufacturer will need to acquire a custom drill bit to meet your requirements. However, if you opt for a more standard tool size, such as 0.25 inches, the standardized tooling your manufacturing partner has on hand will suffice. Similarly, using standard raw material blanks, jigs, fixtures, and other components instead of custom elements can help cut costs and accelerate production.

If using a standard fixture would block tool access, however, creating a custom fixture to avoid multiple setups makes sense. Fortunately, you can use additive manufacturing technology to quickly and cost-effectively create custom fixtures.

Not over-tolerancing

Tight tolerances can also drive up manufacturing costs and turnaround times, as your operator will need to machine at a slower pace. They will also need to regularly remove and inspect your part to ensure tolerances are correct, which prolongs the production process and increases overall costs.

Don’t over-tolerance and make sure that the tolerances you set are compatible with what your part actually requires. If you’re creating a consumer product, don’t use the extremely tight tolerances necessary for aerospace parts. Or, if you’re manufacturing a prototype, you should use a looser tolerance than you might for your final product.

Performing design for manufacturing (DFM) checks early

Performing design for manufacturing (DFM) checks to identify and correct potential problems before manufacturing can also help keep costs low. Pay particular attention to:

• Deep pockets or slots: If your part has deep regions, your machinist will need to use longer tools that are more expensive and more likely to break.
• Sharp internal corners: CNC drill bits are circular and leave behind internal corner radii, making achieving sharp internal corners tricky.
• Narrow regions: Narrow regions require cutters with small diameters, but long tools with small diameters are more susceptible to chatter and breakage, increasing costs and lowering part quality.

If you notice any of these flaws, you might want to consider redesigning your part. You can also easily check for common DFM errors like those mentioned above by uploading your part to your SyBridge dashboard.

CNC machining with SyBridge

CNC machine setups can significantly impact your overall production costs, but sometimes using multiple CNC setups can’t be helped. The good news is that you can make your project more cost-effective — even if multiple setups are required — by setting reasonable tolerances, designing for manufacturability, and thoughtfully choosing CNC materials. Working with an experienced manufacturing partner like SyBridge can help.

Get started on your next CNC machining project today by uploading your part to for an instant quote or by contacting our team.

The post How CNC Setups Affect Project Costs appeared first on SyBridge Technologies.

Computer Numerical Control (CNC) machining is a modern, efficient, and automated subtractive manufacturing process that allows manufacturers to make repeatable parts of consistent quality from a wide range of materials, including plastics, metals, and composites. Today, CNC-machined parts can be found in a variety of different industries, from aerospace to automotive to medical.

The beginnings of CNC technologies can be traced back to a few different points in history. The first modern machining tools appeared in 1775 when industrialists developed a boring tool that allowed manufacturers to produce steam engine cylinders with more consistent degrees of accuracy and precision.

The technological forebears of modern computing appeared earlier in the century, however, emerging from the textiles industry. In 1725, Basile Bouchon began using a system of punched holes in paper tape to encode data. Decades later in 1805, Joseph Marie Jacquard refined the process, swapping out the paper tape for sturdy punch cards. When tied in a sequence, the punch cards directed how the fabric was added to the loom, simplifying the process and providing one of the first examples of programming. This machine, the Jacquard loom, is in a way the forebear of our modern computing and automation solutions.

This guide to all things related to CNC machining will walk through how modern CNC machining processes work, including material options, design considerations, cost drivers, and more. Keep reading or click here to download the PDF.

Types of CNC Machining

Today, there are several technical processes included underneath the CNC machining umbrella.

3-Axis Machining: Milling and Turning

Once the operator enters the machining instructions, 3-axis CNC machines will carry out the input operations by using cutting tools to cut along three axes: X (left to right), Y (front to back), and Z (up-and-down). CNC milling and CNC turning are two common examples of 3-axis machining.

3-axis CNC milling involves fixing the block of material — also called the workpiece or “blank” — with a vice or machine bed. This holds the workpiece stationary as cutting tools and rotating drills, attached to a central spindle, make cuts to remove material and shape the final component. The 3-axis CNC milling machines are easy to program and operate and can be used to create most parts with simple geometric designs.

Since the cutting tools and drills are limited to three axes, some design features or areas of the blank may be difficult to complete or reach (e.g., unconventional shapes or deep, narrow cavities). However, multiple setups can help orient the workpiece for the machines to reach these features. While almost every 3-axis machining job has more than one setup per part, too many setups per part can quickly increase production costs. Processing geometrically complex parts can, for instance, require operators to manually reposition workpieces, which can impact processing speed, increase labor-related costs, and create more opportunities for human error.

The CNC turning process operates a little differently. The blank is fixed to a rotating spindle, and a lathe then shapes the piece’s inner and outer perimeters or bores holes around the workpiece’s center axis. The most significant design restriction with CNC lathes is that they always produce rotationally symmetrical parts. The process is ideal, therefore, for the manufacturing of parts such as screws, bowls, or chair legs. For these types of rounded parts, lathes can produce pieces faster and at lower costs than CNC milling machines, especially when producing parts in high volumes.

5-Axis or Multi-Axis Machining

Multi-axis machining processes allow the cutting implements greater freedom of movement while the workpiece is milled or turned. 3-axis processes allow either the blank or the cutting tool to rotate, but not both. In contrast, 5-axis processes allow both the workpiece and the tool to rotate and move along the X, Y, and Z axes simultaneously. 5-axis CNC machining saves time and is ideal for creating complex and precise parts like those found in the medical, oil and gas, and aerospace industries.

The multi-axis CNC machining family includes three processes:

• Indexed 5-axis CNC milling: During indexed 5-axis milling operations, not only can the cutting tools move along the three linear axes, but between operations, the machining table and tool head can swivel in two directions. The most noteworthy benefit of 5-axis milling is that the blanks no longer need to be manually adjusted between cutting operations, which makes it possible to create components with complex geometries more accurately and with greater efficiency. Indexed 5-axis machining is great for fabricating components like housings, jigs, and fixtures. The process falls somewhere between 3-axis CNC milling and continuous 5-axis CNC machining (see below) in terms of speed, precision, and the ability to handle complex geometries.
• Continuous 5-axis CNC milling: Continuous 5-axis CNC milling machines can move and rotate both the cutting tool and the workpiece simultaneously during each operation, allowing for the manufacture of parts with extremely intricate geometries and smooth surfaces. While this is the most expensive form of CNC machining on a per-part basis, the cost of continuous 5-axis CNC milling is typically offset by improved surface finish, speed, and dimensional stability.
• Mill-turning machining with live tooling: Mill-turning combines elements of CNC lathe machines with milling tools. The workpiece is affixed to a rotating spindle while cutting tools remove material from the blank. By combining the elements of CNC lathe machines with milling tools, mill-turning CNC offers high levels of accuracy and geometric versatility, making it great for creating parts with loose rotational symmetries, such as camshafts or centrifugal compressors.

Choosing the Right Type of CNC Machining

When selecting a manufacturing process for your part, you’ll need to evaluate if it’s a better fit for 3-axis or 5-axis machining. Generally, parts with simpler designs can be made quickly and affordably using 3-axis machines, while 5-axis machines are better for creating geometrically complex pieces with increased speed and accuracy.

If you’re on a budget or only need to cut a flat surface, 3-axis machines are the way to go. In addition to being more affordable, 3-axis machines are simpler to program, so you won’t have to incur the cost of working with expensive 5-axis programmers and operators. Plus, prep time is shorter with 3-axis machining.

If you need to produce a deeper part or one with complex geometry, you’ll want to use 5-axis machining. Using 5-axis machines lets you machine the workpiece from all sides with no manual rotation required. With 5-axis machining, you’ll have higher yields, greater accuracy, and increased freedom of movement, as well as the ability to manufacture larger parts faster.

Common CNC Materials

One of the advantages of CNC machining is that the process is compatible with many different materials, plastics and metals being the two most common material families. Here are some of the plastics and metals you’re likely to encounter.

High-Performance Polymers

• Acrylonitrile butadiene styrene (ABS): ABS is an impact-resistant engineering thermoplastic with excellent mechanical properties. Strong and rigid while retaining a degree of flexibility, ABS is noteworthy for being mechanically strong, providing good insulation, and being resistant to abrasion and strain.
• High-density polyethylene (HDPE): One of the most versatile thermoplastic polymers around, HDPE is a flexible and easy-to-process material that is highly resistant to stress cracking, chemicals, and corrosives — even at low temperatures. It also offers excellent impact strength. HDPE is commonly used to make plastic bottles, plugs, seals, insulators, piping, and many other goods.
• Low-density polyethylene (LDPE): Primarily used to create orthotics and prosthetics, this tough, flexible plastic is easy to weld and heat seal. While providing good chemical resistance, LDPE is not ideal for applications that require stiffness, high structural strength, or high-temperature resistance.
• Polyamide (PA) or Nylon: Nylons are a family of low-friction plastics that are well-suited for replacing metal components, like bearings or bushings, due to its unique combination of elasticity, rigidity, and stiffness. Nylons can be reinforced with a range of additives to create specific material and chemical properties or combined with other plastics for increased performance and material characteristics.
• Polyamide (PA) or Nylon 30% GF: Glass fibers, one of the most common additives for engineering plastics, dramatically increase the strength and rigidity of nylon parts. Unfortunately, these fibers also increase the brittleness of the material and are therefore recommended only for applications that do not involve high-impact stress or deflection.
• Polycarbonate (PC): This plastic is widely used for a number of reasons — it’s tough while still being lightweight, it’s a good electrical insulator, and it’s naturally heat resistant. PC is inherently transparent and translucent and takes on pigment well. In addition, PC is resistant to diluted acids, oils, and greases, but is susceptible to hydrocarbon wear and UV rays.
• Polyetheretherketone (PEEK): A high-performance polymer with a unique combination of mechanical properties, PEEK is chemical-, wear-, creep-, fatigue-, liquid-, and temperature-resistant. In addition to being recyclable and biocompatible, this material is also lightweight, strong, and insoluble in all common solvents. Similar to nylon, PEEK can replace metal in CNC machining. Common applications for this material include piston units, critical airplane engine parts, and dental syringes. Notably, it is one of the more expensive CNC machining plastics on the market.

• Polyetherimide (PEI): Commonly known as ULTEM®, PEI is a high-performance plastic and manufacturing staple. Not only is PEI strong and easy to use, but it’s also resistant to chemicals and flame, and can withstand extremely high temperatures without losing its stable electrical properties. For this reason, PEI is typically used to create products like circuit boards, eyeglasses, food preparation and sterilization equipment, and aircraft parts. It’s one of the few commercially available amorphous thermoplastic polymers that keeps its mechanical integrity at high temperatures.
• Polymethyl methacrylate (PMMA): PMMA is a rigid thermoplastic polymer often called acrylic or acrylic glass. Extremely shatter-resistant, this tough and lightweight material is translucent and resistant to weathering and UV light, making it ideal for low-stress applications like greenhouses, the covers of car lights and turning signals, or solar panels. However, it’s important to note that PMMA is susceptible to high heat, impact, wear, and abrasion, and it’s prone to cracking under heavy loads.

• Polyoxymethylene (POM): Commonly known as Acetal or by its branded name, Delrin®, this semi-crystalline engineering-grade thermoplastic offers excellent dimensional stability, stiffness, and low friction. Due to these properties, acetal is often used to create highly precise parts used in applications where high strength, durability, and wide operating temperature range (-40°C to 120°C) are required.
• Polypropylene (PP): This cost-effective plastic is lightweight, highly resistant to chemicals in corrosive environments, and resistant to most organic solvents, degreasing agents, and electrolytes. Compared to LDPE and HDPE, PP has a lower impact strength but offers better tensile strength.
• Polytetrafluoroethylene (PTFE): PTFE, commonly known as Teflon®, is a versatile polymer favored for its mechanical properties. Resistant to chemicals, temperature, light, UV rays, water, weathering, fatigue, and adhesion, PTFE is commonly found in the coatings of nonstick pans but is also used in semiconductors, gaskets, and even some medical applications. Although PTFE is one of the most corrosion-resistant plastics, it’s sensitive to creep and abrasion.
• Polyvinyl Chloride (PVC): PVC is one of the world’s oldest plastics. Stark white and rigid, PVC is an affordable rubber alternative that has been in high demand for decades. Boasting strong resistance to light, chemicals, and corrosion, PVC is a popular material in the healthcare, IT, transportation, textiles, and construction sectors.
• Ultra-high molecular weight polyethylene (UHMW): A tough, versatile, and highly machinable plastic, UHMW can be used to create parts with high abrasion and wear resistance, durability, and low friction coefficients. UHMW isn’t typically suited for high load-bearing applications or conditions exceeding 80 to 100°C.

Metals

Steels and stainless steels, aluminums, and soft metals like brass, bronze, titanium, and copper are among the most popular machinable metals. While steels and aluminums are the most commonly machined, each family of metals offers a different set of physical properties and price points.

• Aluminums: Aluminums are soft, low-density, non-magnetic metals that are much easier to machine than steel. Due to their low tensile strength, these metals are often alloyed with other materials in order to accentuate desired physical properties. Aluminums are generally around 1/3 the weight of steel, meaning that they offer a better strength-to-weight ratio. This can be useful in lightweighting parts. They are also much better thermal and electrical conductors than steels.
• Steels: Steels are iron-based metals that have been alloyed with carbon and other metals, typically including manganese, phosphorus, or sulfur. Steels tend to be stronger and more durable than aluminums. However, they are also heavier and harder to machine without the use of carbide or other specialty tools, which can increase production costs.
• Stainless steels: The primary difference between steels and stainless steels is that the latter is alloyed with chromium rather than carbon. While standard steels are susceptible to rust and corrosion when exposed to moisture and oxygen, the chromium content in stainless steels creates a passive chromium-oxide layer on the surface of the metal, preventing the iron within from oxidizing further. This also inhibits steels’ ability to conduct electricity. Stainless steels can be alloyed with other metals (including molybdenum, nickel, or titanium) to increase a part’s resistance to corrosion and heat.
• Soft metals: Soft metals like brass, bronze, titanium, and copper offer a wide range of physical characteristics that are attractive for specific applications. However, soft metals — especially those with high copper content — may actually be more difficult to machine due to copper’s high ductility. Machining soft metals can contribute to increased heat build-up at the cutting site, greater tool wear, and galling (a gummy build-up on the tool’s cutting edge). Titanium, specifically, is also less rigid than other metals and therefore requires a tight grip on the workpiece to ensure precision and accuracy. All of these factors can contribute to higher machining costs for soft metals.

CNC Surface Finishes and Post-Processing

After a part or component has been machined, it may need to undergo one or more finishing processes. These processes can be used to remove aesthetic flaws, improve a product’s appearance, provide additional strength and resistance, adjust electrical conductivity, and more. Common finishing processes for machined parts are anodizing, powder coating, and bead blasting. However, it is also common to leave parts as-machined or as-milled when other finishes are not necessary.

Common CNC Finishing Options

• Anodizing (aluminum): Anodizing is an electrochemical process in which aluminum or titanium alloys are submerged in an electrolytic bath in order to thicken a machined part’s natural oxide layer to make it denser, electrically non-conductive, and more durable. Anodized finishes also promise good dimensional control, which makes them best used in high-performance engineering applications, particularly for internal cavities and small parts. Anodizing offers one of the most aesthetically pleasing finishes for CNC machined parts, but it comes at a higher price.

• Bead blasting (metal or plastic): Bead blasting uses a pressurized air system to fire millions of glass beads at the part, which effectively removes tool marks and imperfections, and can be used to create a consistent grainy, matte, or satin surface finish. Bead blasting adds no chemical or mechanical properties and, unlike powder coating which adds material to a part, it’s a reductive finish, meaning that the process removes material from the part. This is an important consideration if your part has strict tolerances. Bead blasting is one of the most affordable surface finishes but must be executed manually. Bead size and grade will also affect the final finish.

• Black oxide (steel, stainless steel, copper): This electrochemical or chemical treatment process creates black iron oxide on the surface of ferrous metals. Also called blackening, oxidizing, or black passivating, this process does not simply deposit a black oxide layer on the surface of the metal. Rather, the chemical reaction between the iron in the metal and the oxidizing salt solution creates an iron oxide called magnetite, which has a matte black appearance. This process improves the part’s dimensional stability and aesthetic appearance while reducing the surface’s light reflection, which is important for parts used in applications involving radiation. Black oxidizing steel can also help sharpen tools like screwdriver tips and drill bits.

• Powder coating (all metals): Powder coating is similar to spray painting. The machined part receives a primer coat to protect it against corrosion. Then, the part is “painted” with a dry powder coating from an electrostatic spray gun and cured in an oven heated to at least 200°C. Multiple layers can be applied to increase the thickness of the finish, which creates a thin protective layer on the part that is strong, wear-resistant, and aesthetically pleasing. This process can be combined with bead blasting to increase the part’s corrosion resistance and create greater uniformity in texture and appearance. Unlike anodizing, a powder-coated finish is compatible with all metals, is less brittle, and offers greater impact resistance. However, powder coating generally yields less dimensional control than an anodic finish and is not recommended for use in small components or internal surfaces. Powder coating’s higher price point can also make larger production runs expensive.

• As-machined (metal or plastic): Not applying finishing processes to machined parts is referred to as an “as-machined” or “as-milled” finish. The part will have small but visible tool marks and blemishes. As-machined parts have the tightest dimensional tolerances and are extremely affordable to produce because post-processing isn’t necessary. This is ideal for applications in which dimensional integrity matters more than aesthetics. However, it’s important to note that without additional finishing or protective coating, the surface hardness of as-machined makes them susceptible to nicking, scuffing, and scratching.

Choosing the Right Materials and Finish

Selecting materials and post-processing options for your part relies heavily on how and where your part will be used. Key end-use considerations for selecting your part material and surface finish include:

• Environmental factors: The environmental conditions of a given part’s end-use application play a significant role in determining which materials and treatments are ideal. Factors like heat, cold, flame, UV radiation, exposure to chemicals or autoclaving, and more must be taken into account in order to ensure the viability of the part.
• Electrical factors: Whether a part requires conductive or insulating properties is another critical consideration. Knowing your part should conduct electricity, you may select a conductive material like copper, whereas a material like Nylon 66 would be appropriate when searching for a good insulator.
• Mechanical factors: Parts intended to endure heavy loads, wear, or other external forces need to be made from materials that can withstand those forces. Identifying the most desirable or necessary properties for a part — such as flexibility, impact resistance, tensile or compressive strength — can help teams pinpoint which materials make the best fit.
• Cosmetic considerations: While aesthetics can be of secondary priority for some parts, this is not the case for many consumer products. Some parts or applications may require materials with particular cosmetic options when it comes to color, transparency, or surface finish.
• Tolerances: Some degree of variation between parts is expected in manufacturing, and dimensional tolerances refer to the range of acceptable variation that viable parts must fall within. Tighter tolerances are more labor-intensive and costly to achieve repeatedly but may be necessary based on how a component is used.

Designing for CNC Machining

Designing a high-quality part that will perform as expected is only half the challenge. You must also be able to machine the part in an efficient and cost-effective way. Design for manufacturability (DFM) is the process framework that helps integrate how a part will be made with the part design. DFM is critical to manufacturing and affects everything from production timelines and costs to operational efficiency and the quality of the part itself. The most common design considerations for CNC machining include:

Deep Pockets:

Features like deep or narrow pockets and slots require longer tools to machine properly. However, longer cutting tools are more prone to breaking and are often less precise due to machining vibrations, or chatter. Deep features also typically require several cuts to machine properly, which increases both machining time and production costs — especially since smaller tools will likely be necessary to complete the finishing passes. If slots or deep pockets must be machined, aim to either reduce the depth of the feature as much as possible or increase the area of the pocket’s cross-section. The depth of a pocket or slot should be no more than 3x the diameter of the smallest tool needed.

Narrow Regions:

Narrow features limit the size of viable cutting tools. This can present a challenge for manufacturers because of how susceptible long, small-diameter tools are to chatter and breakage. Just as with deep features, narrow regions should be no less than 3x the diameter of the smallest cutting tool. Minimizing the depth of these features allows you to use shorter, larger-diameter cutting tools, which helps to reduce machine chatter.

Sharp Internal Corners:

CNC end mills are circular, which makes it difficult to machine sharp internal corners because the bits will leave behind a corner radius. While there are methods of machining sharp internal corners, these processes tend to be costly. In general, sharp internal corners should be avoided for machined parts. Internal corner radii should also be larger than the radius of the intended cutting tool. By designing internal radii to be larger than the cutting tool, the machine can create a smooth transition between walls. In contrast, an internal radius that is the same size as the cutting tool will force the machine to make a sudden change in direction, resulting in a less smooth finish.

Inaccessible Features:

Features like counterbores — those that open inside another pocket or pockets with negative drafts — can pose a significant challenge for production teams. These design features take considerably more time to machine because of how difficult it can be to allow the cutting tool access. It’s critical to ensure that cutting tools can freely access all of a part’s features without being blocked by any other feature.

Outside Fillets:

Outside fillets, or rounded corners along the top edge of pockets, bosses, slots, and other features, require custom cutting tools supported by a precise machining setup — a pairing that can quickly become expensive. Beveling or chamfering the outside edges can help avoid these costs.

Wall Thickness:

Thin walls can create issues for metal and plastic parts alike and should be avoided wherever possible. Thin metal walls are more prone to chatter, for instance, which negatively impacts the accuracy of the part and its surface finish. Plastic parts with thin walls are also more likely to warp or soften. The minimum wall thickness for metal parts should be 0.03” (0.762mm) and 0.06” (1.524mm) for plastic parts.

Flat-Bottomed Holes:

Holes with flat bottoms are not only difficult to machine, but they also tend to create difficulties for any subsequent operations. In general, product teams should avoid blind holes with flat bottoms in favor of standard twist drills, which create holes with cone-shaped bottoms.

Threaded Parts:

When machining internal or external threads, there are a few different design considerations.

For internal threads:

• Include a countersink at the end of internal threads.
• Reduce the number of threads whenever possible. Most of a part’s stress actually falls on the first three threads, so increasing the number
• of threads produces diminishing returns.
• Use standard forms and sizes.
• Opt for coarse threads to keep costs low.

For external threads:

• Include a chamfer in all screw designs.
• Avoid terminating near the shoulder of areas with large diameters.
• Turned external threads should have a relief groove.
• Use shorter external threads unless the part specifically calls for high thread strength.

Drill Entrances and Exits:

If the surface of a workpiece is not perpendicular to the axis of a drill, the drill tip will wander when it comes into contact with the material. To minimize uneven exit burrs and streamline the burr-removal process, ensure that hole features have start and end faces that are perpendicular to the drill axis.

A Checklist for Reducing Costs

1. Keep parts simple
Parts with complex designs or manufacturing processes can have a number of downstream effects. Complexity can increase machining time and cost, introduce opportunities for error, and make it difficult for end-users to understand the exact use of components or parts. Separating which characteristics and design features are vital to the viability of the part from those that are desirable yet non-critical helps remove unnecessary complexity from a part’s design and machining operations.

2. Design with tool geometry and setup orientation in mind

While most CNC machining jobs require more than one setup orientation, you’ll want to keep the number of orientations per part to a minimum. For example, if you need to flip a workpiece three times for the cutting tools to be able to access all of the features, this is going to increase costs because each setup requires re-mounting the part, zero-ing the machine to establish the correct axes, and running a new G-code program. 5-axis machines are going to be more capable in this aspect as they can reach more features without requiring multiple setups, though this is dependent on the geometry of a particular part.

Minimizing the number of cutting tools required is another way to reduce costs. As much as possible, try to keep radii consistent so that fewer tools are needed to machine internal corners. Likewise, avoid very small details where possible. Smaller cutting tools aren’t able to cut as deep into the workpiece and are also more prone to breaking. Typically, the smallest internal features that can be machined are 0.0394” (1mm), though holes can go as small as 0.0197” (0.5mm).

3. Balance your tolerances

Choose your critical dimensions thoughtfully. Not every dimension requires inspection or is critical to the viability of the part, so focus your attention on those that are most essential. Determining how precise specific features need to be will allow you to adjust tolerances accordingly, reduce costs, and streamline the manufacturing process. Make sure that tolerances are still within machineable limits, adhere to given standards, and account for tolerance stacking.

Avoid over-dimensioning your part, as well. Unclear part drawings defeat the purpose of geometric dimensioning and tolerancing, which is to clarify and streamline communication. At SyBridge, we recommend that you align drawing datums with the CNC coordinate system, as using consistent datum reference frames between machining and measurement systems is more likely to ensure parts are accurately located.

If possible, ensure all datums — points, surfaces, or axes used as references for measurement — reference the same setup. If a datum was machined in a previous setup, it becomes more difficult to hold tight tolerances after a setup change. Finally, be conscious about your datums. Choosing reference datums that are easy to measure from will ease manufacturing.

4. Tailor inspection levels

Similar to balancing your tolerances, strategically applying the right inspection levels can help reduce costs and optimize the production processes. Typical inspection options may include a visual inspection of the part, checking part dimensions using hand tools, or a first article inspection (FAI) where the first manufactured part is checked to ensure all requirements have been met. More in-depth inspections require more time and labor, which increases manufacturing costs.

Increasing the number of parts that you inspect will also increase the cost of production, so it’s important that you select the right sampling plan to ensure confidence across the entire order. At SyBridge, our default sampling rate is based on ANSI ASQ Z1.4 Level 2.

5. Design to common stock sizes

Designing parts to common stock sizes can help streamline the manufacturing process by minimizing the amount of material that needs to be removed from the workpiece. For example: if it’s acceptable for a part surface to retain its stock finish — that is, if the surface can be rougher than 125 μin Ra — and it does not need to be machined, you have an opportunity to reduce machining time without sacrificing part quality.

This is why knowing the common stock sizes for various materials is important. Metals, for instance, are typically available in a number of stock forms, including sheets, rods, bars, or tubes, which can be purchased according to dimensions like length, width, thickness, and diameter.

Keep in mind that metric sizes are more commonly available in Asia, while imperial sizes are more commonly available in the U.S.

6. Minimize deformation risk

Removing a large amount of material from a workpiece can cause the material to deform. This requires additional processing during machining to prevent deformation, leading to higher costs. Plastics have a higher risk of deformation than metals.

7. Choose your material carefully

The material you pick has a significant impact on the overall cost of your part. For example, metals are generally more expensive than plastics. Avoid over-engineering your parts and consider whether a specific grade or material certificate is required for the part. If a generic material can fulfill the part’s requirements or multiple materials can be accepted, select the less expensive material to keep costs low.

The machinability of the material should also be taken into consideration. Steels, for example, are typically more difficult to machine, which leads to higher costs because steel parts take longer to machine and increase wear-and-tear on cutting tools.

Common Applications for CNC Machining

Many industries rely on CNC machining processes to produce reliable, accurate parts that meet precise specifications and regulatory requirements, including the aerospace, automotive, medical device, electronics, and commercial parts manufacturing sectors.

Aerospace parts are held to high quality, testing, and regulatory standards in order to ensure proper function, fit, and safety. CNC machining is an excellent fit for creating plastic and metal parts with extremely tight tolerances that satisfy the aerospace manufacturer’s need for an incredible degree of precision and a range of highly specialized parts. The same is true for automotive components.

CNC machining can also be used to create a variety of medical devices, from implants to surgical implements to components for medical electronics.

Care and precision are critical when producing these sorts of devices and tools, as they are held to additional safety standards and requirements. Semiconductors and electronics components also have incredibly stringent precision requirements and tolerance standards, given their size and complexity. As a process, CNC machining has few material limitations, allowing it to be used with conductive materials like silicon. Many commercial parts — from aluminum castings and extrusions to steel and plastic parts — can also be machined.

Another common application for CNC machining is tooling, or the process of creating the various components, tools, machinery, and master patterns that will be used in production. Tooling is an integral part of every manufacturing and molding process and encompasses items like molds, jigs, and fixtures.

Starting Your CNC Machining Project With SyBridge

At SyBridge, we make it simple and straightforward to get quality parts through our CNC machining service. To get started, visit os.fastradius.com, upload your part designs, and you’ll receive instant DFM feedback. The site also allows you to manage designs and orders from a single intuitive interface.

When you choose SyBridge, you’re choosing to work with a seasoned group of experts. You’ll receive the full support of our team of engineers, customer success managers, account executives, and others across the business. We’ll also leverage options for domestic and international CNC machining to ensure that your project is carried out as efficiently as possible, without sacrificing quality.

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