Statistical approach to determine cutting conditions and cutting geometry for edge trimming of G/PA12 plates

Abstract

The G/PA12 composite used in this study is made of glass-woven reinforcement and semi-crystalline engineering thermoplastic. This type of composite has potential applications, for example, in the automotive industry. The relatively low glass transition temperature and low stiffness of the matrix compared to the high abrasiveness of glass fibres make this type of composite difficult to machine. The workpieces from this type of composite are produced in a near-net-shape, but the free edges of the workpiece must be trimmed in order to achieve the required accuracy and quality of the product. This study recommends cutting conditions and cutting geometry based on statistical evaluation of force, quality and temperature measurements. The double-helix cutter significantly improved the machined surface quality compared to the standard PCD cutter. The PCD cutter was used in this study to identify key control factors for cutting conditions. By selecting the optimal helix inclination and angle, surface quality improved by up to 80%, with only a 12% increase in temperature. Increasing the feed per tooth also contributes to improving surface quality. In addition to improving quality, increasing the feed per tooth significantly affected the cutting forces. A cutting force model was developed specifically for machining this type of composite. The model's accuracy was enhanced by incorporating the effects of face angle and helix. The temperature measurement method during milling was designed to monitor critical temperature limits, such as the glass transition and melting points. An infrared camera was selected and the emissivity of G/PA12 was determined experimentally. The measurements showed that, while the glass transition temperature was exceeded in all cases, the melting temperature remained at least 47°C below the critical limit, even in the worst-case scenario.