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Advanced Manufacturing 32 MoldMaking Technology —— AUGUST 2016 This appliance bezel was molded with a high-gloss finish using ball-filled mold technology. As shown in this schematic diagram, a ball-filled-mold system replaces the typical cooling channels with a large recessed area directly under the mold cavity that is packed with hardened steel balls. chemical process requires that chemical blowing agents (CBAs) be mixed into the material, with nucleation happening as the mold fills in an open-loop reaction. Physical foaming makes use of gases, usually nitro- gen or sometimes carbon dioxide, that are mixed directly into the melt stream prior to mold filling. It is a mechanical, closed-loop controlled function between the gas deliv- ery system and molding machine interface. Which method is appropriate depends on several factors, including the functional requirements of the part. In addition to producing a lighter weight part, foaming also results in reduced warp- age and dimensional stability. When a part is going to be highly visual, it is preferable for it to be both flat (with a sink-free surface) and without visible weld lines. The foam- ing process helps achieve this by producing internal pressure through the expansion of cells during cooling. While the foaming pro- cess creates a surface that is flat, the nucle- ation process can also have the unintended effect of creating surface "swirling." This is caused by some of the gases escaping and becoming trapped between the melt and the cavity wall. The resulting appearance may be acceptable in many applications, but parts requiring either glossy or smooth, clean finishes may require additional conditioning after mold- ing, such as painting or covering. However, it is possible to mold foamed parts with high-gloss, smooth surfaces without Oldcastle, Ontario Schaumburg, Illinois Fountain Valley, California Hong Kong Here's our number... call us daily! 1-800-265-4885 www.dmscomponents.com YOUR SOURCE FOR QUALITY MOLD COMPONENTS FOR OVER 40 YEARS Get Locked & Loaded Get Locked & Loaded BZ Hydraulic Locking Cylinder • Saves machining, mold assembly & mold maintenance time & costs • Improves molded part quality & may reduce cycle times • Robust design precision manufactured to ensure longevity & precision • Custom stroke lengths available upon request • Many more features & benefits