Plastics Technology

FEB 2013

Plastics Technology - Dedicated to improving Plastics Processing.

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close up liquid silicone molding ...Continued from p. 13 which do not bond chemically. This required a mechanical lock for the LSR on both sides of the PP, analagous to a rivet shape. Prototypes were molded on a 1+1 tool with a cold-runner valve gate for the LSR, using robotic transfer of the part from the PP to the LSR cavity and demolding the fnished vial at the same time. A 4+4 production mold is planned when volumes increase. The mold runs in a two-shot, 160-ton Engel victory combi press. Engel enlisted Pro Systems of Churubusco, Ind. (pro-systems.com), to supply custom automation with a six-axis robot to perform post-mold assembly operations, including placing a water-soluble pouch containing bacterial growth media inside each water-test vial. HEATING LSR MOLDS WITH WATER Hot oil is an established method of heating molds above the boiling point of water, but risks of contamination of the molding environment are undesirable for medical and other clean-room molding. The alternative is electrical cartridge heaters, which are vulnerable to burnout and to uneven heating (hot spots) along their length. Another "clean" alternative that has been gaining attention is pressurized hot water, which can operate at up to 437 F/225 C. On its own initiative, Roembke is experimenting with such WHY USE THIS MUCH OF PURGING COMPOUND... WHEN YOU CAN USE MUCH LESS WITH ULTRA PURGE? ULTRA PURGE CUSTOMERS TYPICALLY USE 2-3 TIMES LESS MATERIAL COMPARED TO OTHER PURGING COMPOUNDS. 1.877.884.3129 • www.ultrapurge.com 48 february 2013 Plastics technology Roembke is unusual for a moldmaker in having six Arburg and Engel LSR injection presses permanently on site, one a two-shot model and one with X-melt capability, plus two other presses on temporary consignment. a unit from Single Temperature Controls, Charlotte, N.C. (single-temp.us), capable of heating up to 392 F/200 C, which is suffcient for LSR jobs. Roembke is gathering data on the performance of this mold-heating system. Matthew H. Naitove, Executive Editor

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