Overmolding

Overmolding is a molding process that combines two different plastic materials to produce a unique part. The first material is used to mold a rigid plastic substrate. The second plastic material, usually a rubber-like plastic elastomer, like our Polylastomer® compounds, is molded over the substrate. The overmolding process allows designers and engineers to create a strong structural product with excellent ergonomic comfort for the end user. Overmolded parts can add further appeal by being molded in two different colors.

PPI has used the overmolding process to produce parts for many customers and is now a leading expert in the field. In a recent order PPI was asked by a manufacturer of water filters to mold parts used in series of filter spacers, part of the ionization and filtration process. This overmoldng process was different from the norm in that the substrate (the three layers of mesh) was flexible. The part (called a C spacer) was a thin plastic housing surround that seals three fibre mesh filters. The challenge was to overmold the mesh with the thin housing surround while maintaining the surface integrity of the mesh. Too much mold closing pressure and the mesh is crushed and cut away, too little pressure and the mesh fails to remain taut and effective. The critical compromise was achieved and the customer was satisfied, another job well done!

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