A self-cleaning injection system jointly developed by Spirex Corp. (Youngstown, OH), and Asaclean-Sun Plastech (Parsippany, NJ) is designed to remove resin without disassembling the screw or barrel. The patent-pending PowerPurge system, under license by Community Enterprises LLC, is said to be particularly beneficial for quick color or material changes producing contamination-free product with lower scrap.
The PowerPurge Valve is a three-piece design that consists of a retainer body and check ring with PowerPurge lock made from wear-resistant tool steels. The PowerPurge Valve first works as a standard nonreturn valve, making parts with the check ring at an unlocked lower position. The injection unit is then moved away from the mold and the majority of the remaining resin is pushed out of the injection unit using the Asaclean PowerPurge compound.
The formulation of this compound is designed to attract resin particles to pull them from the injection cylinder, while offering minimal adhesiveness to metal surfaces. A purge plug is put into place, and a precise amount of the compound is fed into the injection unit. The valve ring moves into a locked, open position with rapid extended decompression and the screw is injected forward, exposing the components and screw to abnormally high-pressure backflow. This is said to cause agitated, pressurized scrubbing and cleaning. The ring is pushed into normal operation each time the screw starts to rotate, and the ring moves back into the locked, open position each time the machine uses rapid extended decompression. The machine returns to normal operation when the replacement resin is introduced, and the PowerPurge valve operates like a standard valve.
Spirex reports that in most applications, parts will be 100% acceptable with the first shot. PowerPurge is said to eliminate color streaking and remove tough carbon deposits while reducing scrap rates and the need for chemical compounds. The Power Purge sequence can be programmed for one-touch operation in most molding machines. The system can be used with virtually any commodity or engineering resin including transparent and optical grades.
Demag Plastics Group (Strongsville, OH) is the first OEM to offer this process as an option on its injection molding machines. Spirex is currently negotiating a similar deal with Toshiba Machine Co. (Elk Grove Village, IL).
Spirex Corp., Youngstown, OH
(330) 726-4000; www.spirex.com
Asaclean-Sun Plastech Inc., Parsippany, NJ
(800) 787-4348; www.asaclean.com