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Choosing The Right Additive Manufacturing Technology

Wed, 04/30/2014 - 3:48pm
Mark Barfoot, Managing Director, Hyphen

Where do you start if you’ve been asked to have a part produced using additive manufacturing technology, or you’re exploring whether to invest and bring the technology in-house?

If you go through the additive manufacturing sales process, you’ll find a lot of information about the technologies on the market, with some being touted as all-in-one solutions. Each machine — each additive manufacturing process — is simply a different tool in the toolbox, each used for a different purpose. Our goal is to help guide you through the technology options so that you can feel more confident and educated as you make your technology decisions.

To start, it’s important to understand that all additive manufacturing technologies build parts in a similar manner. The machine takes a computer generated, 3-dimensional design and translates that into layers. Each layer is traced out independently, or “printed.” These collections of layers, one on top of the other, form a stack of layers in the shape of your desired part. How this layering is accomplished varies among the technology categories as follows.

Fused Deposition Modeling (FDM)

You may have heard about this technology since it’s the basis for most home-use systems. The commercial-grade machines are similar, but have additional features that vastly improve surface finish, accuracy, and also allow for processing of a wider range of materials. FDM extrudes a plastic cord through a nozzle that melts the plastic and traces out a pattern. The tray that the pattern is being traced onto is lowered and then the next layer is formed in the same way until the part is fully formed. The result is a strong, native material part (i.e. ABS, PC-ABS, Ultem, etc.), but the layer lines and trace paths are often visible. However, FDM is the easiest process to use and there is a shorter learning curve for being trained on how to use the machine. FDM is often used for end-use parts due to the strength of the parts produced with its native materials.

PolyJet

With the PolyJet process, you can imagine an ink jet printer head spraying out layers of resin that are individually cured with an ultraviolet light. By using a base of two or three materials, you can digitally mix the materials (just like you would with paints to achieve different colors), but the result is a part printed with components that have varying degrees of hardness all in one build. For example, you can build a single part that has both hard and rubbery components at the same time. Add in a third material and you can achieve varying colors. PolyJet parts have a great surface finish, but are not meant for long-term use as they will degrade faster over time compared to other technologies. This technology is also relatively easy to use, but has a higher cost of ownership, given the cost of replacement printer heads and resin.

Stereolithography (SLA)

Stereolithography is the original additive manufacturing technology. A laser traces each layer on the surface of a vat of liquid photopolymers. For each new layer, the tray lowers slightly to coat the previous layer with more liquid before the laser traces the next layer. Wherever the laser makes contact with the liquid, it solidifies the material while everything else remains liquid. The resulting parts have a very smooth surface finish and can be easily sanded.

Laser Sintering

Laser Sintering spreads a thin layer of powder (usually a nylon based material), and a laser traces out the pattern in the powder to form each new layer. The powder acts as support material to hold many parts in place through a build cycle, allowing greater efficiency by stacking parts. Once the build is complete, you need to sift the parts out of the powder — almost like sifting through a sand box — and dig out the parts. Laser Sintering excels in speed, but is the most complicated technology to use. It can also have issues with thin geometry as it is a thermal process and can cause warping. However, the material strength and speed make it one of the technologies most used for end-use parts.

Metal Laser Sintering

This is a newer variation of the Laser Sintering technology, but the powder is metal-based (e.g. titanium, aluminum, stainless steel, etc.). The biggest difference with this technology is that it does need support material to hold the part in place and you cannot stack parts on top of each other. The support structure is built with the base material and can be a challenge to remove. This technology is exciting as a potential option to replace complicated machined parts or die castings for lower-volume applications.

You may come across other technologies, but the ones discussed above are the most popular and widely used that you will want to focus on in your search.

Decision time

After you understand what each additive manufacturing process can offer you, you’ll be better equipped to make a decision about investing in the technology or using a service bureau like Hyphen. It will also be important to consider how often you’ll need to build parts, the size of the parts and whether one technology will meet all of your requirements. Beyond the part build, you should consider your need for facility space and the necessary post-processing tools to make the most out of an investment in additive manufacturing technology. 

Having a machine in-house could potentially expedite your turnaround time and promote the use of the technology in your company. However, you will likely end up working with a service bureau at some point to keep up with the shifts and evolutions in the technology over time. While it may seem like an extra expense to work with a service bureau as opposed to buying your own machine, a service bureau can offer expertise and a broader variety of technologies to give you the part that you need.

It is in your best interest to explore each technology and speak to an objective professional. They will be able to review your requirements and recommend the process that will deliver the best return for your budget — to meet your immediate project goals and to deliver value to your business over the long-term.


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