Using 3D printing, engineers can make parts with the most commonly used thermoplastics, such as ABS, polycarbonate, a variety of blends, as well as thermoplastics engineered for aerospace, medical, automotive and other specialty applications. There are two additive technologies at Stratasys Direct Manufacturing that utilize thermoplastics: Selective Laser Sintering (SLS) and FDM (Fused Deposition Modeling).
Selective Laser Sintering’s Nylon 11, Nylon 12 and specialty nylons present a range of characteristics, including strength, flexibility and color. Depending on application, nylons can be used in a variety of environments and industries.
SLS builds with powdered nylons and a CO² laser that melts layers of material. The cake bed that envelopes the parts allows for complicated geometries with interior features, undercuts and negative draft. Parts can be thin and flexible or strong and thick depending on design. The flexibility, high impact strength and high temperature capabilities make SLS materials an excellent option for functional prototyping or production parts; including ducting, brackets, clips and flight-certified parts.
SLS nylons differ from injection-molded nylon in areas like elongation at break and impact resistance, but Stratasys Direct has developed materials specifically formulated to counter these differences. Nylon 11 EX for example, was developed as a high-elongation polyamide-based material. Durable polyamide nylons, like Nylon PA and Nylon GF plastic, exhibit impact resistant properties, and FR 106 is flame retardant.
SLS nylons have an average surface finish of 125-250 RMS finish, but parts can be hand sanded smoother. They accept most coatings, textures, printing or other special finishes. SLS materials are available in white, grey and black without finishing and can be easily dyed to match desired color post-build.
FDM offers a wider variety of polymers, from ABS to polyphenylsulfone (PPSF), in order to provide engineering-grade materials in a 3D printing process. FDM thermoplastics offer special qualities, such as electrostatic dissipation, translucence, biocompatibility, VO flammability and FST ratings. These robust materials make FDM a viable option for functional prototyping and production parts in aerospace, automotive and medical industries.
FDM builds by extruding molten thermoplastic layer by layer until a part is produced. Since FDM adds small amounts of molten material in a heated environment, warp and the deformation of vertical walls is best avoided by adding ribs to thin-walled sections of a part, similar to injection molding.
FDM materials differ from injection-molded thermoplastics since they are non-isotropic due to the build style of the technology at certain orientations. FDM can also affect a part’s elastic modulus, elongation at break and flexural strength. With careful design considerations, these differences may not be significant for some applications.
Each FDM material is dimensionally stable and durable enough for demanding applications. The easiest way to identify the right FDM thermoplastic would be to consider the part’s characteristics, support material type and color. Similar to conventional thermoplastics, finishing FDM parts depends on the chosen material. Some FDM thermoplastics have soluble supports and offer up to ten color choices.
The ultimate benefit of using SLS or FDM to fabricate parts is the familiarity of the materials with the added advantages of 3D printing. SLS and FDM offer the ability to build low-volume parts with complicated geometries much faster and usually at lower cost than injection molding.
