Extrusion printing, sometimes referred to fused filament fabrication (FFF) or fused granulate fabrication (FGM), starts when a thermoplastic feedstock—such as plastic filament or pellets—is forced through a heated nozzle, melting the material and depositing it on a print surface. Either the nozzle, the print bed, or a combination of the two are moved on a gantry in XYZ space, enabling the gradual creation of an object from the bottom up, layer by layer. Extrusion 3D printers, ranging from affordable desktop units to large-format production machines, are widely used across industries due to their versatility, low-cost feedstocks, and user-friendly operation. They find applications in prototyping, jigs and fixtures, tooling and patterns, end-use parts, and more.
Why pellets? The first reason is cost. Thermoplastic pellets are the raw form of most plastics used in industrial forming processes like injection molding and thus cost up to 10x less than traditional 3D printing filament feedstock. Overall, thermoplastic pellets are considered one of the lowest cost 3D printing feedstocks.
Printing directly with pellets also enables faster print speeds. Higher throughput is inherent in the pellet extrusion process. Couple that with large nozzle sizes and 3D Systems' robust CNC motion control system, and print speeds can be 5X -10X faster with EXT Titan Pellet systems than traditional filament extrusion printing. Finally, printing with pellets enables the use of a wide range of materials. There are 100’s of grades of thermoplastic pellets available for printing, including high-performance materials that are not available in filament form including high-percentage glass fiber and carbon fiber-filled plastics and low-shore TPE and TPU.
The thermoplastics used in extrusion printing are available in a wide range of formulations from commodity plastics like PLA, ABS, PETG, ASA, polycarbonate and nylon to aerospace and high-performance polymers for healthcare such as PEEK and Radel® PPSU. Elastomers and carbon-reinforced or glass-filled materials are also available. The open market for extrusion printing materials is expansive, but not every material is printable on every machine. The feedstock format, filaments or pellets, is a primary consideration, as well as maximum nozzle, bed and chamber temperatures.
Thermoplastic pellets are the most affordable 3D printing feedstock available. Pellets also enable high speed printing with larger nozzles, making them the preferred feedstock for large-format extrusion additive manufacturing. Pellet printing also allows the use of highly flexible elastomers as well as high-percentage carbon and glass-filled plastics that are difficult or impossible to print with filament.
Most extrusion-based 3D printers use thermoplastic filament feedstock due to its convenience and availability from various suppliers. Filament is supplied on spools, making it easy to handle and store. Filament is the preferred choice for highly detailed parts and when a clean surface finish is essential.
The printers are typically more affordable than other plastic printers, there are low-cost feedstock options, and the rapid print times help offset costs.
While devising 3D models can be complex, generally the printers themselves are generally user friendly and easy to operate, eliminating the need for extensive technical expertise.
Extrusion printers can process a broad range of thermoplastic materials, enabling a wide array of applications from prototyping to functional parts production.
Extrusion 3D printing enables quick turnaround times, making it an ideal technology for rapid prototyping and final part production. Post-processing is often faster, too.
