Fused Deposition Modeling (FDM) technology was developed by S. Scott Crump in the late 1980s and was commercialized in 1990. The build material is usually a filament or wire of thermoplastic material but can also be plastic pellets fed from a hopper. Many materials for FDM are industrial grade thermoplastics, which suit today’s consumer and commercial products.
If the material is in filament/wire form, it is unwound from a coil and fed to the nozzles. The nozzles contain heaters that keep the material at a temperature just above melting for easy flow. The nozzle moves horizontally, depositing a layer of the material. Once the material leaves the nozzle, it usually hardens immediately and bonds to the layer below. Then, the build platform lowers by the depth of a layer and the nozzle moves horizontally again to deposit another layer.
The extruder die diameter determines the layer thickness and vertical dimensional accuracy, which ranges from 0.013 to 0.005 in. Resolution in the X-Y plane is 0.001 in. A water-soluble material may be used to create temporary support structures while the part is built. Usually, no post processing is needed.
The early material used in FDM technology was known as ABS (acrylonitrile butadiene styrene). But materials for FDM have advanced and evolved. Today, there are four versions of ABS, each tougher than the original formulation. And the FDM material family has expanded to include a number of options, including engineered thermoplastics.
ABS is the most widely used material in FDM machines. These materials are an excellent choice for models, prototypes, patterns, tools and end-use parts. The newer versions are 40 to 70% stronger than the FDM materials of just a few years ago. They also offer greater tensile, impact, and flexural strength.
Another type of material suitable for FDM is polycarbonate (PC). This material produces accurate, stable, and very durable parts. It has excellent mechanical properties and heat resistance and is suitable for tough applications—functional testing, tooling, or production.
The first engineered thermoplastic available for FDM was PPSF (also called PPSU). This super material meets the needs for “under-the-hood” and other advanced applications involving high heat of more than 189° C. It is mechanically superior to most other FDM materials. More specific information on FDM materials is available in the Materials portion of this handbook under Stratasys.
Fused Deposition Modeling and FDM are registered trademarks of Stratasys. Members of the RepRap project created an exactly equivalent term to avoid legal issues. That term is fused filament fabrication (FFF). Click here for a closer look at available FDM machines.