An investigation of workpiece temperature variation of helical milling for carbon fiber reinforced plastics (CFRP)

Better prediction about the temperature distribution of workpiece has a great significance for improving performance of cutting process, especially relating to the workpiece of carbon fiber reinforced plastics (CFRP). In this paper, a heat transfer model is developed to investigate the temperature distribution of CFRP workpiece in helical milling process. Depending on characteristics of helical milling, two kinds of heat sources have been presented, the geometrical shapes of which are modeled as semicircle arc and line. The complex trajectory of each heat source relative to the stable workpiece has been studied. Based on the analysis, unsteady state three-dimensional governing equation of heat transfer in CFRP workpiece with adiabatic boundary condition is proposed. The solution procedure of this nonhomogeneous heat transfer equation consists of two steps: it is transformed into homogeneous equation according to the heat transfer theory firstly; and then the homogeneous equation is solved using the separation of variables. Basing on the solution of the homogeneous equation, the temperature distribution resulting from the moving semicircle arc heat source and the line heat source has been studied detailedly. In order to calculate the heat generation in the helical milling process, a cutting force model is presented and the heat partition transferring into the CFRP workpiece is solved using the Conjugate Gradient Method. A series of tests of helical milling for CFRP are conducted, and the experiment results agree well with the results calculated by the predicted model. This model can be extended to optimize the cutting condition and restrain the thermal damage of the CFRP workpiece.