What You Need to Know When 3D Printing with Thermoplastics
Today, a majority of consumer products and production parts are made from thermoplastics. Thermoplastics are typically used in manufacturing techniques like injection molding, compression molding and machining, but with the invention of 3D printing, they became available for additive extrusion and sintering processes. A new door to advanced manufacturing has opened with 3D printing materials similar to the conventional thermoplastics familiar to engineers and designers.
Thermoplastics are plastic materials, or polymers, that become pliable when heated to a specific temperature and solidify upon cooling. Types of thermoplastics include acrylic, ABS, Nylon, PLA, polycarbonate (PC), polyethylene and other specialty, high performance materials.
If your part requires strength, rigidity or high temperature tolerance, then thermoplastics are a great option to fabricate your production component or prototype. 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: Laser Sintering (LS) and FDM (Fused Deposition Modeling).
Step 1: Laser Sintering Nylons
Laser Sintering’s Nylon 11, 12 and specialty nylons present a range of characteristics, including strength, flexibility and color. Dependent on application, nylons can be used in a variety of environments and industries.
LS 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 dependent on design. The flexibility, high impact strength and high temperature capabilities, make LS materials an excellent option for functional prototyping or production parts including ducting, brackets, clips and flight-certified parts.
LS 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.
LS 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. LS materials are available in white, grey and black without finishing and can be easily dyed to match desired color post-build.
Step 2: FDM Thermoplastics
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.
Step 3: Comparing FDM & LS
Step 4: Familiar & Fast
The ultimate benefit of using LS or FDM to fabricate parts is the familiarity of the materials with the added advantages of 3D printing. LS and FDM offer the ability to build low-volume parts with complicated geometries much faster and usually at lower cost than injection molding.