A cooperative effort between Thermwood Corporation, Applied Composite Engineering (ACE), Techmer PM and Purdue University’s Composites Manufacturing and Simulation Center has produced a composite helicopter part using a 3-D Printed Polysulfone (PSU) mold.
The PSU mold and resulting part were displayed at the recent AM2017 Additive Manufacturing Conference in Knoxville, Tenn. According to a recent blog post from Thermwood, despite Polysulfone’s ideal properties for this application, the participants believe this is the first time PSU has been 3-D printed since it processes at temperatures and requires torque levels above those needed for normal polymer extrusion.
The mold was printed from Techmer supplied carbon fiber reinforced material and trimmed on Thermwood’s Large Scale Additive Manufacturing (LSAM®) machine. The extruder and print head on Thermwood’s LSAM machine has been specially designed for ultra-high temperature, high-torque operation. ACE produced a production part from the tool in an autoclave using normal production processes.
The part, an oil drip pan for a Chinook Helicopter, was molded in an autoclave at 275 F and 90 PSI. The printed mold held vacuum without the need for special coatings other than normal mold prep and release. With a Tg (glass transition temperature) of 372 F, the participants believe that this particular PSU formulation may be able to process parts at up to 350 F which is adequate for about 95 percent of composite parts processed today. Additional tests will be performed to determine the suitability and durability of this material at this temperature. They also plan to evaluate Polyethersulfone (PES) which processes and operates at even higher temperatures.
Thermwood says its additive manufacturing material cost was 34 percent less and it required 69 percent fewer labor hours. Build time for the additive tool was three days versus eight days for the conventional tool. If the part was larger, a support structure would be needed for the conventional tool which would add two days and more labor hours to the conventional process. A larger additive tool would not require a support structure.
“The goal of this collaborative effort, according to Thermwood, is to develop materials and processes to efficiently and reliably 3-D print production composite tooling, capable of operating at elevated temperatures in an autoclave,” Thermwood wrote. “These first successful results may indicate that they are very near reaching that goal.”