Prediction of heat transfer process in helical milling

This paper represented a three-dimensional heat transfer model which describes the temperature distribution with the time variation in solid with conduction-convection boundary during the helical milling process. On the basis of the kinematic mechanisms of helical milling, two types of heat sources were presented; one was the first heat source (FTHS) resulting from the peripheral cutting edge, and the other one was the second heat source (STHS) resulting from the bottom cutting edge. Both effects of the FTHS and the STHS on the temperature distribution of the workpiece were investigated. The FTHS was defined as one semicircle which acted on a helical path; the STHS was defined as one straight line and the movements of which consisted of three ways: rotating around the axis of the tool, turning around the center of the hole, and moving along the axial direction. In order to accurately study the heat transfer model, a stationary coordinate established in the hole and a moving coordinate established in the heat source were developed. The transformation of coordinates and the trajectory of the moving coordinate had been illustrated. Under the two coordinates, a nonhomogeneous partial differential equation (PDE) containing heat source term was derived and was solved using the Green function approach. The heat source term was depicted using the Dirac delta function. A series of experimental tails for Ti-6Al-4V were organized. The experimental results agreed well with the data calculated using the model. The effects of different cutting parameters on the temperature rise were also investigated.