Adopting the Experimental Pressure Evolution to Monitor Online the Shrinkage in Injection Molding

Abstract

In this work, a procedure is reported which is suitable to analyze online the quality of molded parts in terms of shrinkage. The procedure is based on the evaluation of the average solidification pressure, namely the average along the thickness of the pressure at which each layer solidifies, a parameter which is known to correlate well with shrinkage. The calculation of this parameter normally requires the estimation of the solidification history, information which is currently not reachable experimentally. The procedure reported in this work allows adoption of the pressure evolution measured by a piezoelectric pressure transducer to make an estimation of the solidification profile and thus of the average solidification pressure. The procedure is applied to the data of shrinkage measured on an amorphous PS and a semicrystalline iPP in a wide range of processing conditions.