Molded Part Design for the Gas Injection Technique

Abstract

The gas injection technique (GIT) is a multicomponent process that involves different raw materials being successively injected into the mold, leading to a layered molding structure. The hollow spaces are created in areas of the molded part with higher wall thicknesses by injecting inert gas into the molten plastic. The use of this process can be motivated either on purely process engineering grounds or for design reasons. In many cases, design requirements are placed on parts that only permit cost-efficient production by the gas injection technique. The different variants of the gas injection technique can be distinguished on the basis of the nature of the gas introduction or the type of melt injection. The gas can be introduced either via the machine nozzle or via a mold injector. To form the hollow spaces, melt is pushed out of the liquid center of the molded part and replaced by gas and hence it is necessary for a similar-sized volume to be available or to be created in the molded part to receive this displaced material. The mold cavity is only filled by the short-shot process and the residual filling with gas conducted in such a way that melt is conveyed by the gas guidance geometry as unfilled volume.