Replication capability of micro injection moulding process for polymeric parts manufacturing

Micro injection moulding process represents a key technology for realizing micro components and micro devices used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this work, the authors investigate the process parameters on the overall quality of a miniaturised dog-bone-shaped specimen in order to determine the process constraints. The factors affecting parts aspects and mass are studied by experimentation designed using DoE methodology and then discussed. Two polymer materials (polyoxymethylene and liquid crystal polymer), particularly suitable for injection moulding applications due to their flowability and stability, are tested and evaluated in relation to the process replication capability. It has been found that the holding pressure and holding time for POM and holding pressure and injection velocity for LCP have the highest influence on achieving high part mass. Differently, melt temperature has the highest influence on minimising the process variability for both tested polymers. A further investigation has been carried out on the relationship between the holding pressure and the part mass and dimensions demonstrating the existence of a linear correlation between specimens mass and dimensions.