Change in injection moulded parts shrinkage and weight as a function of processing conditions

Abstract

Results of experiments focused on assessment, in injection moulding, of the effects of independent variables (input parameters) on dependent variables: longitudinal shrinkage ( S ¯ w ), perpendicular shrinkage ( S ¯ p ) and weight ( m) of the mouldings made of semi-crystalline polyoxymethylene (POM) or amorphous polystyrene (PS) were presented. The conditions of injection moulding which were the result of working of many factors connected with injection moulding machine, design of mould, received processing conditions and processed polymer effect on physical state formed moulding. All these decide about mechanical, thermal and useful properties. The results of experiment, which had in view the estimation of influence of parameters of processing on shrinkage (longitudinal and perpendicular) injection moulding parts made from semi-crystalline polymer POM and amorphous PS. The investigations was realized using prepared design of experiment, which consisted with 27 arrangements and five entrance volumes: mould temperature, injection temperature, cooling time, hold pressure and injection speed. Differentiation of perpendicular shrinkage across injection cavity was shown. The analysis of received results hugged the search (estimation) of the equations of regression, which describe the changeability researches volumes in function of processing conditions. Analysis of correlation was done as well, and the results from the data presented in the form of matrix of correlation. It results from the data presented that with the aim to control the shrinkage value and middling weight in the industrial practice it is most advantageous to change the clamping pressure as essential easy to change parameter.