All manufacturing processes have unique strengths and weaknesses. There are many 3D printing processes, and to choose the correct process for your needs requires an understanding of those processes. To guide you through the options, first we’ll talk about factors to consider (like materials used in that process, cost, speed, size limitations, etc), and then we’ll talk about how each 3D printing process stacks up on those characteristics. So first, here are the factors that you may want to consider when selecting a 3D printing process.

• Material availability: Consider the material properties required for your project, such as flexibility, strength, durability, and heat resistance. Different 3D printing processes use different materials, so choose one that can manufacture parts with the properties that you need. For example, fused deposition modelling (FDM, plastic 3D printing that is commonly done with consumer, desktop 3D printers) is suitable for thermoplastics, SLA (also commonly available) for photopolymers, and SLS for various powder-based materials which include plastics and metals. If you expect your part may be handled roughly or have small features that could easily break off, you need to use processes that produce more durable parts.
• Appearance: Some 3D printing processes (like FDM) produce layer lines or blobs and zits that may be too unsightly if you’re trying to make parts that must look good. Other processes don’t have many color options. 
• Post-processing requirements: Some 3D printing processes require more post-processing, like support removal or surface finishing, and others require post processing to meet particular requirements for the part. Choosing the right 3D printing process can save post-processing time and money.
• Size limitations: Consider the size of the thing you want to print and make sure the technology you choose can print that large. Some 3D printers can cheaply produce larger items, while other 3D printing processes may require you to cut your part into multiple parts and then assemble them or pay for printing time on much larger, more expensive machines.
• Production speed: Evaluate how quickly you need your 3D printed object. Some technologies, like FDM, may be fast enough for small quantities with days of lead time, while SLS or Multi Jet Fusion (MJF) will be more efficient for larger batches and shorter lead times. All 3D printing types can become “faster” simply by using more machines to produce the parts.
• Cost: The cost of 3D printing can vary significantly depending on the technology, requirements, materials, and equipment. Some technologies are simply 10x more expensive straight out of the gate.
• Environmental considerations: Some 3D printing processes produce more waste or require hazardous materials. Polylactic Acid (PLA) filament is bio-based and is industrially compostable, while other 3D printing feed stock is hazardous to your health and to the environment. You may want to consider the environmental impact of your chosen manufacturing process and make an informed decision based on your sustainability goals.

We have gone through the factors that you may want to consider while selecting a 3D printing process that’s right for you. We also provide 3D printing design and manufacturing services at American Filament, so feel free to contact us at sales@americanfilament.us, and we'll help you sort all of this out. Now, let’s get into some 3D printing processes to consider.

Fused Deposition Modeling (FDM):

First, let’s provide a bit of background for FDM. FDM works by heating and push a plastic filament (commonly PLA filament but a variety of filament materials are also available) through a hole to deposit plastic a little bit at a time, layer by layer, to build the part up from the print bed. Imagine a hot glue gun on a robotic arm that pushes the hot glue out at specific places to make something. FDM 3D printing is actually quite like that. Support structures are often required under overhangs (to prevent the nozzle from pushing plastic into midair) and are removed during post-processing.

Now we’ll get into how it FDM stacks up in terms of materials, appearance, post-processing, size limits, production speed, and cost.

Materials: FDM offers a wide range of plastic materials ranging from PLA to carbon fiber composites. These materials can be strong, stiff, tough, and even electrically conductive. FDM offers materials that roughly span what is available in injection molded parts.

Appearance: FDM parts can be printed in a wide range of colors similar to that of injection molded parts. Multicolor 3D prints are also possible and this capability is not common among 3D printing processes. Low cost FDM prints may suffer from visible layer lines or blobs and zits, but high quality 3D printers are able to print parts that are nearly seamless. Many of the appearance issues can be fixed in post-processing, but it will cost you time or money to do that.

Post-processing: FDM parts are made from plastic, so anything you can do to a plastic you can do to FDM parts such as sanding, painting, chemical vapor smoothing, or melting and fusing parts together.

Size Limits: Of the all the 3D printing options, FDM 3D printers can produce large parts the most cheaply. Many inexpensive FDM printers are 12” x 12” x 12” (300 x 300 x 300 mm) in size, numerous industrial FDM printers get to as large as 40” x 40” x 40” (1000 mm x 1000 mm x 1000 mm) in size, and it's quite possible to find machines that are even larger than that. If you want to 3D print large objects, FDM 3D printing is certainly worth considering.

Production Speed: A single FDM 3D printer is relatively slow. Small parts may be printed in 30 minutes while larger, highly detailed parts may take several days. FDM printing can be fast for large batch production if your supplier uses many 3D printers simultaneously. It is possible for 3D print farms to contain hundreds of even thousands of 3D printers which makes FDM 3D printing capable of producing thousands of parts in a single week.

Cost: FDM 3D printing provides the lowest cost on the low end, but some high end processes within FDM (such as printing in engineering grade materials) can cost as much as the alternative 3D printing processes.

Environmental Considerations: FDM 3D printing uses plastic and therefore produces plastic waste. Some plastics can be recycled while others cannot.

FDM printing is the most popular type of 3D printing among 3D printing hobbyists, because of its affordability and accessibility. FDM also has many uses in industrial applications for the same reasons, and because it is very good at producing large, structural or functional parts. You probably want to baseline FDM 3D printing as the process for you, and only eliminate it as the right process if its shortcomings (parts are made with plastic and may have surface imperfections like layer lines or blobs and zits) disqualify it based on your needs.

Stereolithography (SLA)

SLA uses a photopolymer resin that solidifies when exposed to ultraviolet (UV) light. A build platform is submerged in the resin vat, and a laser or projector selectively cures the resin layer by layer to create the desired shape. After printing, the part is cleaned, support structures are removed, and it is post-cured using UV light to further solidify it and improve mechanical properties. SLA is known for its smooth surface finish and ability to produce parts with very small details. Now let’s talk about the pluses and minuses of SLA 3D printing.

Materials: SLA offers relatively few materials (all of which are thermoset plastic), because the process by which the resin is polymerized does not work for any material. Within the plastics available, there is a decent range of material properties though, so you can select varying ranges of toughness, strength, and heat resistance.

Appearance: SLA parts are known for their smooth and aesthetically pleasing finish. The SLA process is great for tabletop game miniatures or artistic pieces. SLA parts are generally gray, but you can add pigments to the part to make it a different color. Because of the process used to make SLA prints, you won’t get to have multiple colors on a single layer of the SLA print.

Post-processing: The SLA process itself has more steps that could be called post-processing, and these steps add time for every print that is done in SLA, but because SLA has limited multicolor capabilities, you will need to have a part painted if you want it to have multiple colors.

Size Limits: Generally speaking, SLA 3D printers have a small build volume, so it is more expensive to produce large SLA 3D prints. A typical, consumer-grade desktop SLA 3D printer has a build volume of just 5 x 3 x 6 inches (130 x 82 x 160 mm), but it is possible to find large industrial resin 3D printers that are 60 x 30 x 22 inches (1500 x 750 x 550 mm) or even larger.

Production Speed: SLA 3D printers are relatively fast, because the printer is able to solidify multiple places in a layer all at the same time. The time it takes to produce a part is approximately 2-3x faster than FDM 3D printing, and many 3D printers can be used in parallel to produce lots of parts rapidly.

Cost: SLA 3D printing is the second cheapest 3D printing process (generally speaking) behind FDM 3D printing.

Environmental Considerations: SLA 3D printing uses some dirty chemicals that are dangerous to your personal health as well as the environment. These can be safely handled, but ultimately, SLA 3D printing is not a very environmentally friendly option.

SLA 3D printing is the most popular method of 3D printing small, highly detailed parts that need to look good. Its main drawbacks are that it requires a painting step if you want to get multicolor parts, and the process itself is relatively dirty compared to FDM 3D printing. It is a relatively cheap process and certainly worth considering for your artistic or aesthetically pleasing prints!

Digital Light Processing (DLP)

DLP is similar to SLA but uses a digital light projector instead of a laser to cure the photopolymer resin. The entire layer is exposed at once, making it faster than SLA, but the build size is often smaller. DLP produces parts with high resolution and smooth surfaces, comparable to SLA. Overall, DLP is very similar to SLA (from the perspective of someone who is looking for the right process to make a part), so please reference SLA to get an idea of whether DLP fits with your needs.

Multi Jet Fusion (MJF)

MJF is a powder-based 3D printing technology that uses a fine-grain material and a fusing agent. An inkjet array selectively applies the fusing agent onto a layer of powder, and a heating element fuses the material together. This process is repeated layer by layer similar to other 3D printing processes. MJF produces parts with high detail, good mechanical properties, and relatively fast production times. No support structures are needed because it is simply held up by the powder underneath, and any remaining powder is removed and can be reused after printing.

Materials: MJF offers a wide range of material options similar to the materials available in FDM 3D printing. The MJF process itself typically produces relatively homogenous, isotropic parts that are able to reach their maximum strength and durability.

Appearance: MJF parts can have fine details, but have a surface roughness similar to sand paper or a cast part, and this gives the parts a matte appearance. Some MJF machines can print parts in multiple colors.

Post-processing: MJF parts can be smoothed by sanding, tumbling, and chemical polishing. They can be further finished with coatings like dyes or paints.

Size Limits: MJF printers exist in a wide range of sizes. Desktop, consumer grade MJF printers do not exist, and a typical industrial MJF printer would be around 11 x 15 x 15 inch (284 x 380 x380 mm), but you should contact a supplier to see what capabilities they have.

Production Speed: MJF 3D printers are very fast, because each layer is rapidly melted in a matter of seconds. The time it takes to produce a part is typically 100-1000x faster than FDM 3D printing, and many 3D printers can be used in parallel to produce lots of parts rapidly.

Cost: MJF 3D printing is a relatively expensive process. MJF patents are still valid, so there are not hobbyist level MJF printers on the market today. An “entry level” MJF printer costs more than $100,000, and that has to be recouped by the 3D printing company. Because MJF printers are so fast, the amortization of the printer cost on each part produced is lower than it would otherwise be, but entry level MJF parts are in most cases more expensive than entry level FDM or SLA parts.

Environmental Considerations: MJF 3D printing uses plastics. Some plastics can be recycled and others cannot. Because MJF uses powder and doesn’t require supports, MJF efficiently uses the materials and the production process itself produces relatively little waste.

MJF is the first purely industrial grade process that we have talked about so far. FDM and SLA both have industrial grade options, but also have lower cost consumer grade alternatives. MJF printers are incredibly fast, so an individual part can be shipped to you faster than even a print farm of FDM printers could achieve. MJF parts are relatively strong because the process lends itself to more isotropic and homogenous end part.

Selective Laser Sintering (SLS)

SLS uses a high-powered laser to sinter powdered material (such as nylon, polyamide, or metals) layer by layer. Since the unsintered powder provides support, no additional support structures are needed. After the process is complete, the part is removed from the powder bed, and any excess material is brushed or blown off. SLS is known for its ability to produce complex, functional parts with good mechanical properties.

Materials: SLS offers the widest range of materials including plastics and metals. The material properties obtained in SLS printing can be very good if the part is processed correctly. Rocket engines have been made and successfully tested with this process.

Appearance: SLS parts generally have a slightly rough surface. SLS parts are typically monochromic (one color), but recent research and development has produced multicolor SLS parts, so there is the possibility of multicolor SLS parts in the future!

Post-processing: SLS parts can be smoothed by sanding, tumbling, and chemical polishing. The can be further finished with coatings like dyes or paints. Additionally, metal SLS parts are often post processed by machine, anodization, or other metal finishing processes.

Size Limits: SLS printers exist in a wide range of sizes. Some SLS printers are the size of a small car, but often the build volume for these printers is around 12 x 12 x 12 in (300 x 300 x 300 mm).

Production Speed: SLS printers can be very fast, but their speed depends upon the material you’re printing with. Metal parts require more energy to melt and are therefore more difficult to print rapidly.

Cost: SLS metal printing is the most expensive type of 3D printing that we have covered. On the other end, SLS plastic printing is fairly competitive with some of the other plastic 3D printing options that we’ve already discussed.

Environmental Considerations: SLS printers require a lot of energy and floor space. Some SLS printers require entire buildings to facilitate the power and ventilation needs. The environmental impact depends somewhat on the material that you’re using as well.

SLS 3D printing is the most versatile and the highest-end of the 3D printing options that we’ve discussed so far. If you want to print metal in a complex shape that is hard to create through traditional machine, casting, or other metalworking processes, then this is the way to go. If you want to print a plastic part, you probably want to consider one of the other options above first.

In Conclusion

Each of these 3D printing processes has its unique advantages, and disadvantages. The best process for your needs depends on several factors and the requirements of your parts including materials, appearance, post-processing, size limits, production speed, and cost. If you need help deciding, then please email us at sales@americanfilament.us and we will guide you through the process of making your parts whether you need 1 of them or 100,000!