Low-volume production is often overlooked by high-volume projects. Low-volume is rarely catered to or even acknowledged by suppliers or customers. In this three part series, I would like to discuss today’s methods of manufacturing for low-volume production plastic parts. Times are changing and engineers and buyers are slow to make the adjustment.
It is necessary to maintain a uniform wall thickness in the areas of the substrate that will be filled or covered by the second shot. The same design principles that apply to plastic parts apply to the voids in the substrate to be filled by the 2nd shot. These would include ribs being 60% of the thickness of intersecting walls, and generous radii and fillets for flow. Typically there is no shrinkage applied to the 2nd shot mold since the substrate will not shrink after the over-molding process.