The Development and Validation of Equipment for Determining Friction and Adhesion Coefficients Under Conditions Comparable to the Injection Moulding Process

Despite extensive research, predicting ejection forces during the injection moulding process remains challenging due to the complex calculation of the coefficient of friction. This coefficient comprises various components that are difficult to isolate, complicating independent predictions. Consequently, using literature-documented coefficient of friction for different material contacts often leads to discrepancies between the experimental data and the predictive models of ejection forces. The adhesion component is a particularly problematic aspect, and is frequently excluded from analyses due to the difficulties associated with measuring it directly. This study aims to present the development of a tool designed to measure both the friction and adhesion forces under conditions that replicate those of the injection moulding process. The measured values were then used to calculate the corresponding coefficients: the static coefficient of friction (COF) and the coefficient of adhesion (COA). The conducted measurements identified the most influential factors in both coefficient values using a Design of Experiments (DoE), revealing that replication temperature was the factor promoting the highest variation across all the tested polymers.