processingdetails

Structural Foam Mold Making

Structural Foam Molding is a low pressure injection molding process. It is used to process thermoplastics, such as high density polyethylene (HDPE), in a low pressure environment. The working method of structural foam molding is that it relies on the foaming action caused by an inert gas distributed in the plastic material to facilitate the flow instead of using high pressures to force the molten polymer to fill up the cavity of the mold. Besides that, foaming can also be created by the gases released by the decomposition of a chemical blowing agent added to the resin.

Structural Foam Molding is widely used in the processing application. Compared with injection molding, structural foam molding can use cheaper and lighter molds (aluminum instead of tool steel),is more suitable to produce large structural parts. Structural foam molding allows for the injection molding of thick wall parts through the addition of a foam agent. Any injection moldable thermoplastics can be foam molded. To produce the thicker wall part, a small amount of nitrogen or chemical blow agent is introduced into the plastic material. Under pressure inside the injection screw, the foaming agents do not expand. When the melted plastic enters the mold cavity, foaming occurs. As the foaming plastics fill the mold cavity, the wall of the part solidifies against the cold mold wall. A thin layer of plastic solidifies without foaming along the mold wall. This thin layer forms a skin structure over the foamed inter core. The thin solid wall is supported by the interior cellular foamed structure. A part produced this way results in a heavy cellular structure similar to wood products.