Injection mold making used to be a relatively simple business: machine the cavities and runners, polish, cross-drill for cooling, then shoot resin. Today, however, relentless pressure for lower part cost and higher productivity have led to bigger, faster machines with molds to match.

Multilayer stack molds, gas-assisted molding, overmolding, co-injection, advanced hot-runner systems, and other technologies have collapsed the cost of high-volume commodity resin parts. At the other extreme, a new generation of functional fillers and special-purpose engineering resins are allowing very large, special-purpose part making for industries such as automotive, aerospace, and medicine. In every application, cycle time, dimensional stability, and surface finish are paramount; hiding a sink mark under a trim plate just doesn’t cut it anymore.

Despite all the technical understanding of making injection molds, a surprising number of manufacturing engineers know very little about the complex dynamics that happen inside an injection mold.

 …