Visualization of in-mold shrinkage in injection molding process

This article presents an experimental investigation on the visualization of (material/mold) separation development during the in-mold shrinkage of injection molded parts. The purpose is to correlate the separation times with the shrinkage values. Two cavity designs were studied: (i) a simple rectangular plate (nonconstrained plate) and (ii) a rectangular plate with an obstacle pin (constrained plate). Separation development was recorded using a high speed camera on a designed and manufactured visual mold. The results indicate that although there is a meaningful correlation between shrinkage value and separation time in the nonconstrained mold, this correlation is highly disturbed in the presence of a constraint (here, an obstacle pin).