Coefficient of friction in the demoulding forces of the injection moulding process—a review

Ejection is the most critical phase in the injection moulding process and depends on several variables that can affect and difficult the demoulding process. Some phenomena in the mould, such as shrinkage, adhesion and friction, can lead to higher ejection forces. Friction, deformation and adhesion mechanisms are components of the coefficient of friction that occurs between the mould and the part surface. An increase in the coefficient of friction will result in higher ejection forces and consequently increase the energy consumption during the demoulding process. Mould and part material, mould surface roughness, coatings and ejection temperature are some of the variables that can affect the coefficient of friction in the injection moulding process. This review paper presents some considerations on the mechanisms, the process and material variables that can affect the coefficient of friction.