The boom of commercial 3D printing has given rise to a number of common misconceptions about the process. For instance, many believe that additive manufacturing processes can only use plastics. In reality, engineers can also create 3D printed parts using metals.

For projects involving metals, engineers should familiarize themselves with the advantages and disadvantages of both metal injection molding (MIM) and metal 3D printing. A closer look at the two processes shows that metal 3D printing offers a surprising range of benefits. Here are the key differences — plus key considerations — for engineers.

Metal Injection Molding (MIM)

Metal injection molding (MIM) combines plastic injection molding with powder metallurgy and requires four stages — feedstock preparation, molding, debinding, and sintering.

First, fine metal powders are combined with thermoplastic material and wax binders and then granulated into small pellets. These pellets are then heated and injected into a mold cavity. After molding, the binder is removed from the metal powder, resulting in a “brown part,” which moves onto the sintering stage. The furnace cycle typically involves a number of stages. The brown part is heated to a relatively low temperature to burn out any remaining binder, then it is sintered at a temperature near the melting point of the metal. The metal powder densifies to produce the final product.

Applications

Engineers turn to MIM when they need to produce parts — particularly small or complex ones — that cannot be efficiently manufactured with any other process. Since only one mold is required to make a part with MIM, this process is also highly repeatable and yields parts that are uniform in size, shape, and strength.

MIM parts have a wide range of applications in major commercial and industrial sectors, from automotive to aerospace. Common applications include hinges on eyeglasses components, watch cases, laptop hinges, and precision medical instruments.

Benefits

MIM is an efficient method by which to produce a high volume of small, complex parts. Finished parts have a smooth surface finish and are relatively strong for their size, often yielding above 95% density. MIM is compatible with a wide variety of materials that can be broken down into a powder form and are suitable for sintering. These are mostly steels.

Limitations

Unfortunately, metal injection molding comes with numerous limitations, primarily due to the molds required to produce MIM parts. MIM molds can cost anywhere from $50,000 to $100,000, which could be prohibitively expensive for low-volume production runs. Often, MIM makes financial sense for annual volumes over 50 thousand with a long production lifecycle.

Further, metal injection molding poses considerable design challenges for engineers. Mold designs aren’t easily changed and there are still significant limitations in regard to shape. For instance, the part cannot have large overhangs, as it has to be ejected out of the cavity. Wall thickness presents another design challenge due to debinding. If the part walls are too thick, it may be impossible to extract the wax from the middle. Designers and project managers must keep these considerations in mind if they plan to use metal injection molding for their project. If not, they might be forced to make costly adjustments later on in the manufacturing process.

Metal 3D Printing

Metal 3D printing offers many advantages that other processes, including MIM, cannot match. One kind of metal 3D printing is laser-powder bed fusion (L-PBF), sometimes known as DMLS, which is a printing process that produces parts from metal powder.

During this process, a chamber is prepped with an inert gas like argon to minimize oxidation. A thin layer of metal powder is spread on the top of the build platform and then a laser melts the powder together in small sections; the process repeats until the part is fully built. Excess powder is removed after the part cools. From there, the part is stress-relieved, detached from the build plate, and then heat-treated if necessary.

Applications

Parts made from the L-PBF process are ideal for industrial applications and high-performance end-use engineering parts. Common use cases include jet engines, turbine blades, medical equipment, and power generators. This process is compatible with a growing list of metal alloys and even some precious metals like gold and platinum. There are also other metal 3D printing processes that are better suited for applications with fewer regulation and critical performance requirements, such as metal binder jetting and metal extrusion.

Benefits

Engineers turn to metal 3D printing when they need to create specialized parts that require high strength and durability, chemical resistance, and access to unique design features. Unlike metal injection molding, metal 3D printing offers engineers a great amount of design freedom. Metal 3D printing does not use molds, so engineers are not beholden to certain shape limitations, and changing the design of a part is as simple as updating the design on a computer. Making a design more complex won’t contribute to additional production costs.

Limitations

That said, metal 3D printing does have its own set of challenges. Build size is limited due to the strict manufacturing conditions and process controls required. Also, metal 3D printing startup costs for an industrial-grade machine can soar into the millions — before factoring in the cost of materials. However, the high price tag can be a worthy investment for engineers who want unmatched design flexibility and great mechanical strength.

Get Started With Metal 3D Printing

Metal injection molding is well-suited for creating small, complex parts that are surprisingly strong for their size. However, metal 3D printing outpaces this process in many key areas. Metal 3D printing offers more design versatility and parts made with this process can be optimized for high strength, durability, and chemical resistance.

At SyBridge, we’re well-versed in additive manufacturing with a variety of different materials. Whether your parts require plastic or metal, our team of experts will help you get started and guide you every step of the way. It’s never too early to start working toward your vision — contact us today.

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Metal additive manufacturing has proven to be an excellent option for the right applications; the aerospace, tooling, medical device, and automotive industries have embraced metal additive in recent years to build specialized parts that traditional processes are still not able to create.

Although the market is growing rapidly, the substantial investment and learning curve associated with metal additive is enough to deter some engineers and manufacturers from exploring this new technology. Many continue to rely on tried-and-true traditional metal manufacturing, like molding, casting, and subtractive processes, as they are more affordable and familiar. However, depending on the application, metal additive prototypes and finished products could prove to be invaluable to your project.

Here we clear up four common misconceptions about metal additive so you can better understand how to use it for your parts.

Misconception 1: Metal Additive is Just Like Polymer Additive

Though certain metal and polymer 3D printing processes are based on the same general principles—powder bed fusion, material jetting, material extrusion— designing for metal-based additive has different set of design rules than designing for polymer-based additive. Material properties, design constraints, and post-processing considerations differ significantly between metal and polymer technologies, and even between types of metal 3D printing processes.

Metal and polymer processes also come with different risks and infrastructure needs. Metal powder bed fusion, for example, uses laser or electron beams and metal powder to build components; manufacturers who use this method need to carefully consider the health and explosion risks and the high energy demands that come with this process.

Misconception 2: All Metal Additive Processes can Produce the Same Parts

Your part’s applications will determine which metal additive process will work best. For example, powder bed fusion could produce the high density and fatigue strength required for a specialized medical implant. A small automotive part that doesn’t need the same level of performance could be made with binder jetting, which produces parts economically in medium to large production runs.

Misconception 3: Metal Additive is Too Expensive

Although metal additive isn’t usually financially feasible for mass production today, there are some instances where the upfront cost leads to longer term savings, such as increased fuel efficiency, a more cost-effective supply chain, and material reduction. A standout example comes from GE Aviation, who used metal 3D printing to create the fuel nozzle tip for their best-selling LEAP engine. The original fuel nozzle tip was welded together from 20 separate pieces, so it was labor-intensive to make, and it was heavy. The new additively made version of the nozzle tip consolidates those 20 parts into a single piece, and reduces the weight by 25 percent, improving fuel efficiency.

Rather than focusing solely on the cost of materials, consider the value today’s metal 3D printing technology adds by creating parts that are impossible to make any other way. As each manufacturing project comes with its own pros and cons, it is best to speak with an expert about your application to see if metal additive is a good fit.

Misconception 4: Metal Additive Isn’t Ready for Production Parts

Metal additive is commonly used as a tool prototyping, but it can also create finished products that are ready for end-use. Relativity Space, for example, uses the largest 3D metal printer in the world to build a ready-to-fly rocket in just 60 days. The world of medicine is also embracing metal 3D printing, creating custom-built joint replacements and implants. Additionally, additive manufacturing makes it easier and more cost-effective to create custom parts; rather than investing in multiple machines and molds for customization, a CAD file can be adjusted to print the exact designs needed for each customer.

There are still limitations to metal additive manufacturing, but the rapid rate of technological improvements make it an important process to get acquainted with. Even if it isn’t the best option for your product today, metal additive might be able to save your company significant time, money, and resources in the future. Reach out to SyBridge to learn more about metal additive and whether its right for your next project.

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Metal additive manufacturing is exciting for the new things it makes possible. It’s already helped create lighter parts for more fuel-efficient aircrafts and improved the lives of patients with custom medical implants. The market is growing too, with analysts predicting that metal additive will produce $228 billion worth of components in the next decade.

The promise of metal additive is clear but not necessarily easy to realize, in part because designing for metal additive has a steep learning curve. The manufacturing industry hasn’t accumulated decades of functional knowledge like we have for subtractive legacy processes.  Plus, designing for metal additive has a different set of rules than designing for polymer-based additive.

Getting familiar with metal additive design takes time and effort. Our team of application engineers at SyBridge has extensive first-hand knowledge on the subject. We compiled our top four design rules for metal additive to help get you started.

1. Understand the Material Set

Metal additive processes fall into two categories based on the densification process they use: melting / solidifying with fusion or solid-state densification. Fusion-based processes resemble traditional welding in the way they bond materials, while solid-state processes resemble traditional sintering.  The materials used for each additive process are similar to those used in their traditional analogs, and they’re generally good for the same types of applications. There’s a lot of overlap; both methods use the same family of stainless steels, for example. It’s important to note, however, that materials will behave differently depending on the technology you use.

When choosing the right method for your project, you need to evaluate not only the types of materials available, but also how the printing process with affect the properties of your final part. The good news is that in some cases you might be able to leverage additive design—perhaps by consolidating elements or creating complex geometries—to make your part with a material that wouldn’t meet your requirements in traditional processes.

2. Plan and Design for Post-Processing

Metal additive can be tricky. Even if it looks like your part will print perfectly, it could end up failing if you neglect to design for post processing, so you need to take special precautions. Many metal additive processes involve powder, so you need to design for powder removal or risk failure when powder agglomerates during heat treatment. In some cases, especially when creating hollow parts, you might have to facilitate powder drainage by adding holes to your design.

With powder bed metal additive technology, your part forms a strong bond to the build plate and must be removed, which can pose design challenges. For example, wire EDM can be a good option for separating part from plate, but you might need to design a fixture to keep the part from get damaged when it’s detached. Parts made with metal additive usually require adjustment to meet final requirements after they come off the printer, so make sure your design takes post processing into account.

3. Try to Make Your Design Self-Supporting

Generally speaking, you should always aim to minimize overhangs and reliance on support structures when designing for additive. This recommendation is even more crucial for metal. Because of the way metal additive processes fuse layers on top of one another, overhangs may come out misshapen or poorly finished if the angle to the build plate is too small. Support structures aren’t always an ideal solution to overhang issues because they waste material and their removal can compromise the stability and finish of your part.

There isn’t a general rule of thumb to determine when an overhang requires support. Each metal additive technology is different and can support overhangs at different angles. The overhangs supported by each method should be a key determining factor in choosing a process for your design.

4. Prepare Your Skillset for Metal Additive

Metal additive is still in the relatively early stages of adoption, but the market is maturing rapidly. Building expertise now will future-proof your business and give you a competitive advantage as the technology becomes more accessible.

But expertise doesn’t come easy. As we’ve outlined here, designing for metal additive takes a different skill set than designing for traditional manufacturing or even polymer-based additive. An experienced manufacturing partner like SyBridge can help you choose the right technology for your application, get your metal additive designs ready for production, and manufacture parts accurately. Once you’ve been through the process, you’ll start to see how metal additive can improve existing products and create totally new ones.

Ready to try metal additive? Contact us today to get started.

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