Veteran screw designed Tim Womer has developed a single-screw micro extruder to improve the cost effectiveness of 3D printing. A U.S. patent application for the technology was published today.
In Womer’s invention, a rotatable screw is attached to a torque drive of the printer, and extends through the feed chamber and conical bore of the barrel. The channel root depth at the exit opening of the extrusion barrel is about 0.025 to 0.075 inches.
Womer said the design uses standard pellets and specifically addresses challenges of 3D printers, which currently use filaments of plastic made from pellets. One immediate advantage is that the plastic won’t have the additional heat history in Womer’s concept.
“With the growth of 3D printing, an opportunity has been created to invent and develop a relatively small extruder, appropriately scaled to size that can deliver a consistently uniform and repeatable flow of molten plastic to a printer head at a rate of 20 lbs per hour or less,” Womer states in the patent application.
In 3D printing, the extruder must be able to operate at screw speeds from 0 to 400 rpm. Different screw designed are used for different plastics.
Womer’s invention overcomes many limitations of the filaments used in 3D printers. First filaments must have uniform composition and dimension or deposit rates will vary from spool to spool. Filaments may also break, slowing production. Spool costs are high and not all thermoplastic resins are available in filament form. Womer sates: “In summary, spool driven 3D printers are slow, failure prone, labor intensive, expensive to operate, and limited to particular polymer resins.”
Womer’s invention is part of a trend to make 3D printing more production friendly. 3D printing was developed as a way to make prototypes rapidly.
A former president of the Society of Plastics Engineers, Womer was the Global Corporate Technical Advisor for Xaloy, and has also served in leadership positions in engineering, research and development at Spirex, Conair, and NRM. He started a consulting business in Edinburg, Pennsylvania in 2011.