When it comes to Additive Manufacturing, or more commonly 3D Printing, there are a few that have become quite commonplace: FDM, SLA, and SLS. They stand for Fused Deposition Modeling, Stereolithography Apparatus, and Selective Laser Sintering respectively. But what are they and what are the main differences?
FDM: Fused Deposition Modeling
In a nut shell, in FDM, you are Fusing Deposited layers of plastic together to create a Model. You can think of a robot controlled hot glue gun, but instead of glue, it is liquid hot plastic. As the plastic extrudes and comes out of the nozzle it is cooled in place, and the process repeats for the next layer, until you have your finished part.
This is by far the most inexpensive kind of 3D Printing available today and many people have these kinds of printers as a hobby. If you are at all interested in picking this up as a hobby yourself, I highly recommend starting with an FDM printer and playing around with it to get your bearings.
The plastic used in FDM printing can range from common plastics to chocolate, glass, cement, you name it. The most common type of plastics used are PLA or Poly Lactic Acid and ABS or Acrylonitrile Butadiene Styrene. Both are everyday plastics that you come into contact with on a daily basis. PLA is becoming more popular in recent years as it can be easily infused with other materials like wood and metal. PLA+ is an advanced version of PLA which has similar mechanical properties to ABS, and is far easier to work with. ABS has a tendency to warp and curl as it cools, and much care needs to be put into the environmental controls. ABS is also quite toxic and harsh on the environment.
SLA: Stereolithography Apparatus
Simply put, SLA printing uses lasers to cure UV Photopolymer Resin in layers that are built up to create your model. Instead of extruding hot material to extrude into place, the build platform is inverted and dipped into a bath of resin, the laser then cures layers upon layers in a pattern onto the buildplate, to create your model. There are several advantages of SLA printing over FDM printing. Accuracy is the foremost advantage. SLA printing is highly accurate with resolutions of up to 25 microns. To give you an idea, each layer printed would be 4x thinner than the width of a human hair. When printing “organic” type models with many curves, this is your best options to preserve the fidelity of you model. The main drawback to SLA printing is cost, on the range of 8-10x the prices of the same part printed with FDM.
There is a range of materials that you can print with SLA printing. Formlabs produces Standard resin in Black, Grey, White, and Clear. They also produce Tough, Durable, Flexible, and High Temp Resins, each with their own specialized characteristics.
SLS: Selective Laser Sintering
SLS is an incredibly interesting process that provides strong and durable parts that function like finished products. The technology uses a high powered laser to Sinter Nylon Polymer Powder layer after layer. What is interesting about this process is that because each layer of powder is added and sintered to the last, there is no need for any support material. This is because all of the unsintered powder acts like a giant support structure, and when the parts are finished, the powder is brushed away and lightly sandblasted.
This leaves you with intricate parts that are strong, heat resistant, biocompatible, and ready for action.
