Critical rake angle and cutting forces prediction in the orthogonal cutting of polymers

An experimental investigation has been carried out into the machining of polymers which exhibit both anisotropic and normal stress sensitive characteristics. The cutting mechanism is analysed using a modified shear angle relationship based on the mechanical properties of the chosen polymers and the minimum energy criterion. From cutting tests, the material shear stress is estimated and hence cutting forces calculated. The presence of a critical rake angle at which the normal force equals zero has been confirmed. The value of critical rake angle can be estimated from force predictions. The coefficient of friction for polymers was found to decrease with increasing the normal force on the tool rake face.