Gas Assist and Microcellular (MuCell) Molding.Word 文档.doc

Gas Assist and Microcellular (MuCell®) Molding Process Vishu Shah Consultek  What is Gas Assist Injection Molding? Gas Assist injection molding is a process enhancement to conventional injection molding, involving the injection of high pressure nitrogen gas into the resin melt stream immediately after injection of the resin. The intent is not to cause mixture of nitrogen and resin, but for the nitrogen to displace resin in gas channels and thicker sections of the molded product. The process is a high speed, low pressure injection method, enabled by short shooting the tool, and completing the resin filling phase by nitrogen gas, at a much lower pressures as compared to convention injection molding.  Advantages of Gas assist Molding „ Cycle time reduction and lower production costs ¾ ¾ ¾ ¾ Lower clamp tonnage Lower Injection pressures Faster cycle due to hollow sections vs. solid section „ Design Freedom ¾ ¾ Large ribs possible and permissible Long flow lengths without multiple drops „ Quality Improvement ¾ ¾ ¾ ¾ ¾ Lower stress within the part Better dimensional stability and part to part size variations Elimination of sink marks and warpage and voids Greater strength and rigidity Reduced knit lines (No multiple drops necessary) „ Material savings through weight reduction ¾ Hollow parts „ Simplification of Tooling ¾ Elimination of lifters and undercuts  Disadvantages or Limitations „ _Race Tracking of Polymer Through Gas Channels „ _Fingering ( The penetration of the gas from gas channel into the thinner sections of the part) „ _Gas Blow-Through „ _No fully being able to Control where the Gas goes „ _More Expensive than Standard Injection Molding  Gas Assist Process Basics „ Short-shot molding. A process in which certain features such as ribs or thick walls are cored out with gas in an otherwise solid molded part. This process gets its name from the method of only partially filling the ca