When machining narrow grooves, corners, and other complex cavities with trochoidal milling, the irrationally large trochoidal step usually leads to chatter, while the conservative trochoidal step constrains the machining efficiency. In this paper, a stability prediction model of trochoidal milling is established to solve these problems. An approach considering trochoidal steps and spindle speeds is presented to predict stability boundary of trochoidal milling. With considering the varying cutter-workpiece engagements, the stability of trochoidal milling process is predicted by obtaining the stability lobes of different cutter location (CL) points along the trochoidal milling tool paths. Based on the proposed stability model, a trochoidal step optimization strategy is developed to improve the machining efficiency of trochoidal milling under other parameters in a given situation. Cutting experiments are performed on the machining center GMC 1600H/2 to show the effectiveness of the proposed trochoidal milling stability model. Finally, simulations are adopted to illustrate the optimization strategy.
The white layer formed in machining has significant impacts on the friction property, fatigue resistance, and service life of products. This paper presents an analytical model for white layer prediction in orthogonal cutting based on phase transformation mechanism. The effects of stress, elastic, and plastic strain on phase transformation temperature are taken into consideration. A function related to cutting temperature and phase transformation temperature is defined to determine the white layer thickness. The theoretical model is validated by machining AerMet100 steel under different cutting conditions. Optical microscope and X-ray diffraction (XRD) are employed to analyze the microstructures of the white layer. A phase transformation is detected in the white layer region, and the predicted white layer thicknesses are in good agreement with the measured values. In addition, the plastic strain is found to be the major factor that causes a reduction in phase transformation temperature. This work can be further applied to optimize cutting conditions to improve machined surface integrity.
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