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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 bushing or hot runner with temperatures over 450 F, the locating ring can actually expand to the point where you will have a problem removing the mold from the platen until it cools down. To compensate for this problem, some hot-runner manufacturers reduce the diameter of their locating rings to as little as 3.985 in. for high-heat materials (see table on p. 36). The combination of all of these factors can create a minimum misalignment stack-up tolerance of 0.008 in. or more. That may not seem like a lot, but it is enough to cause damage to the sprue- bushing seat, especially if sprue break is used. Now let's consider the importance of the steel type and hardness value. A molding machine's platen is made of cast iron, which is relatively soft. I measured the hardness of several platens and found they ranged from 140 to 220 BHN (Brinnell Hardness Number, more commonly referred to as HB). Similarly, two leading magnetic-platen manufacturers report that their magnetic platens have a hardness value between 105 and 126 HB. Then I measured the hardness of several locating rings from various domestic suppliers and found they ranged from 120 to 195 HB, which is about the same hardness as the platen. I also found some locating rings made offshore with a hardness value as high as 300 HB. Since locating rings are cheaper to repair or replace, they should be softer than the platen of the machine. Some molding machines have an alignment-ring insert in the platen. You can remove these rings for repair or replacement. I 0.008 Shown above is a damaged sprue bushing seat caused by misalignment. 38 APRIL 2017 Plastics Technology PTonline.com K now How