Plastics Technology

DEC 2014

Plastics Technology - Dedicated to improving Plastics Processing.

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525 East Stop 18 Road Greenwood, Indiana 46142 Phone: 317-887-6352 Email: sales@TempTek.com For information online www.Temptek.com Factory Phone 317-887-6352 Outdoor Central Chillers • Complete Outdoor Chilling System with Refrigerant Zones and Pumping System • For Use In Most Outdoor Climates • Central Unit for Plant Wide Cooling for Many Processes • Integral Air-Cooled Condenser Indoor Portable & Central Chillers • Use Inside Plant Facility for Single Process or Plant Wide Cooling • Microprocessor Controller and Display • Small Footprint to save floor space • Environment Friendly Refrigerants • Internal Coolant Reservoir And Cirulation Pump Water Chillers with New Product Warranties, industry recognized components for Maximum Reliability, Economically Affordable capital equipment providing perfect bottom-line returns, and a network of factory trained technicians for Unbeatable Service. • Environment Friendly Refrigerants • Microprocessor Instrument Controls • Non-Ferrous Construction • Small Footprint • Other Products: Temperature Control Units, Pump Tanks, Cooling Towers, Material Dryers, Loaders, Granulators pressure to get the machine back into production. Everyone is on the same page on this topic: Put of pulling a screw for cleaning until there is no other alternative. But a clean, well-maintained screw can improve the bottom line via better throughput, shorter screw-recovery time, less contamination, and faster resin and color changes. So, how do we get there with the least cost, efort, and downtime? First, hedge some bets, ask some ques- tions. How has the screw been performing? If you suspect the check ring is leaking, order a replacement. Truth be told, too many molders have to have the faulty part right in their hands to be sure what is needed. Are there any known bolts, thermocouples, wires, heater bands, etc. that need to be replaced? Order them before the teardown begins. Make sure you have the proper tools to do the teardown. With the expected replacement parts and tools on hand, start the teardown. As the screw is being pulled out hot, try to get as much of the molten polymer of the fights as possible. I like to run a high-molec- ular-weight polyethylene through the screw just before pulling it. As the screw comes out—if you have some helpers—use an air knife and brass pliers to peel the PE of. Often the PE is tacky and will pull some of the residual resin and degraded material of the fights. Here are some typical cleaning methods: 1. HAND WORK: Once the screw is out and safely mounted on supports, patiently use tools like copper mesh, brass putty knives, and wire brushes to begin cleaning it. I emphasize patiently because impatient maintenance personnel sometimes go at it with screw drivers, electric- or air-driven wire wheels, and other sharp devices—and before you know it you'll have a screw full of scratches. Getting rid of the caked-on carbon and degraded plastic takes aggressive methods. But the resulting scratches only worsen the situ- ation. Why? In the melting process plastic needs to "slip" on the screw and stick to the barrel wall. Scratches are similar to undercuts; they hold up the plastic and accelerate degradation or formation of black specks. Cleaning takes signifcant time, and, with pressure building to get the machine on line, it's no surprise that folks often bypass Get more insights on Injection Molding from our expert authors: short.ptonline.com/moldingKH Learn more at PTonline.com KNOW HOW INJECTION MOLDING A new method to clean screws uses high-pressure water. The process is clean, can be automated and will do no damage. 26 DECEMBER 2014 Plastics Technology PTonline.com I N J E C T I O N M O L D I N G K now How

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