Effect of Indirect Cryogenic Cooling on the Machining Accuracy and Tool Vibration in the Turning of Polysulfone

Abstract

Abstract Cutting deformation and cracks are common problems during the machining of precise polymer parts. This paper aims to explore the effects of different conditions on the contour profile of machined surfaces and tool vibration. Turning experiments of polysulfone (PSU) were performed under three conditions: dry, conventional flood cooling, and indirect cryogenic cooling. Then, the formation mechanism of machined surfaces' contour profile under different cutting conditions was clarified by the Eyring equation from the perspective of molecular chains relaxation time. Furthermore, extension models of crazing and cracks were proposed through the microscopic morphology of machined surfaces and the discriminant formula of crazing generation to explain the differences in tool vibration. The results indicated that the indirect cryogenic cooling condition with the internally cooled cutting tool could significantly improve the machinability of polysulfone, which has an excellent performance on the contour profile of machined surfaces with and the inhibition of crazing. Compared with dry and conventional flood cooling, indirect cryogenic cooling could reduce the mean of the Contour profile (Ra) by 40.3% and 30.1% and the machining accuracy error by 41% and 83%. The indirect cryogenic cooling method proposed in this work provides a reference for the cryogenic machining for polymers.