Thin Wall Injection Molding
Thin wall technology refers to the molding objects with wall thicknesses between 0.080 and 0.050 in. (2.0 and 1.2 mm). The most challenging thin wall thickness technology applications are those with wall thicknesses below 0.050 in. (1.2 mm). Benefits include reduction in overall component size and weight as well as reducing costs by reducing material use and processing cycle times. Reduction in wall thickness is translatable to larger parts as well. Typical thin wall applications include: cellular phone components, laptop/notebook computer components, hand held devices and medical devices. GW Plastics Website
Recent US Patents
9/13/2011
8,017,204
Composition suitable for thin-wall injection molded articles
Hensche and Torres of Dow, Michigan, developed resins for thin wall injection molded articles having a minimum wall thickness of from 500 ..µm to 2.0 mm consisting of : (A) 2 to 15% by weight of a propylene-ethylene copolymer having substantially isotactic propylene sequences; (B) 85 to 98% by weight of a random polypropylene copolymer having from 2.5 to 5.0% by weight units derived from ethylene and a melt flow rate of from 25 to 130 grams/10 minutes (g/10 min); and (C) 500 to 2500 ppm by weight of a nucleator/clarifier additive (based on the weight of the random polypropylene copolymer). Typically, the melt flow rate of the compositions is from 20 to 125 g/10 min, and the propylene-ethylene copolymer comprises at least 75% by weight propylene and has a melt flow rate from 4 to 30 g/10 min. (RDC 9/15/2011)
8/10/2010
7,771,190
High pressure injection molding nozzle with low pressure manifold
Jenko of Husky Injection Molding Systems has developed a system for thin wall injection molding based on injecting resin into a hot runner system and the resin is injection into the mold by a separate plunger. (RDC 10/13/2010)
Recent Journal Articles
Effects of mold surface conditions on flow length in injection molding process
(1383–1388) Polymer Engineering & Science 51 #7 (2011)
Otsuka, Oyabe and Ito of the Olympus Corporation and Yamagata University, Japan, studied thin-wall molding and the effect of different mold surface conditions on the flow length and mobility (i.e., ease with, which melted plastics can be filled into the mold) in an injection molding process. Three different coatings were used for the mold surface. Several degrees of roughness were also selected for the mold surface. The results were evaluated by comparing flow length with interfacial tensions, which were derived from Young's formula. Although the interfacial tension exhibited different values, the influence on flow length was generally found to be small. On the other hand, in the mold that gives surface roughness, though the change of interfacial tension was small compared with coatings, the flow length increased linearly with the surface roughness when the roughness exceeded a certain level roughness. (RDC 6/24/2011)