In a demonstration at NPE2012, Sodick Plustech (Schaumburg, IL), a manufacturer of high-precision injection molding machinery, will mold a medical syringe made of cyclic olefin copolymer (COC) in a mold developed by Nypro (Clinton, MA).
The prototype application demonstrates the use of COCs as a replacement for other plastics and glass in syringe applications. Cyclic olefin copolymer is crystal clear with outstanding moisture barrier and dimensional consistency, according to Topas Advanced Polymers (Florence, KY), which is supplying resin for the part.
|Two-stage injection plunger eliminates check valve.|
Sodick Plustech's injection system uses a two-stage "V-LINE" method for plasticizing and injection. Unlike a conventional in-line reciprocating screw system, the V-LINE plasticizing screw remains stationary during material transfer, minimizing axial wear and ensuring each pellet sees the same heat profile, according to Sodick Plustech.
The injection unit is controlled by a closed-loop system that compares actual speed to set speed and maximum melt pressure. When the exact amount of material is transferred into the injection chamber, the injection plunger that is retracted via the melt is maintained to a set position.
This design eliminates the need for a check valve, which can be a source of material degradation and shot volume inconsistency. Prior to injection, the plasticizing screw is indexed forward creating a positive shut-off (exact dosing). This action prevents any opportunity for backflow of molten material back into the melt stream.
Nypro, one of the largest medical molders globally, also develops proprietary products for the medical market. It has 36 awarded U.S. patents, mostly for medical products, such as valves.
Sodick Plustech, with headquarters in Tsuzuki-ku, Yokohama, Kanagawa, Japan, developed its own design of plunger-style injection molding machines in 1988 based on its experience with Sodick, a major manufacturer of electrical discharge machinery (EDM). Its equipment is designed and built in Kaga, Japan..
Sodick Plustech (Booth 363) and Nypro (Booth 4263) will both be exhibiting in the second level of the West Hall at NPE 2012.