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Chip evacuation is a critical issue in metal cutting, especially continuous chips that are generated during the machining of ductile materials. The improper evacuation of these kinds of chips can cause scratching of the machined surface of the workpiece and worsen the resultant surface quality. This scenario can be avoided by using a properly designed chip breaker. Despite their relevance, chip breakers are not in wide-spread use in polycrystalline diamond (PCD) cutting tools. This paper presents a systematic methodology to design chip breakers for PCD turning inserts through finite element modelling. The goal is to evacuate the formed chips from the cutting zone controllably and thus, maintain surface quality. Particularly, different scenarios of the chip formation process and chip curling/evacuation were simulated for different tool designs. Then, the chip breaker was produced by laser ablation. Finally, experimental validation tests were conducted to confirm the ability of this chip breaker to evacuate the chips effectively. The machining results revealed superior performance of the insert with chip breaker in terms of the ability to produce curly chips and high surface quality (Ra = 0.51–0.56 µm) when compared with the insert without chip breaker that produced continuous chips and higher surface roughness (Ra = 0.74–1.61 µm).

This paper reports the development of an original design of chip breaker in a metal-matrix polycrystalline diamond (MMPCD) insert brazed into a milling tool. The research entailed finite element (FE) design, laser simulation, laser fabrication, and machining tests. FE analysis was performed to evaluate the effectiveness of different designs of chip breaker, under specified conditions when milling aluminum alloy (Al A356). Then, the ablation performance of an MMPCD workpiece was characterized by ablating single trenches under different conditions. The profiles of the generated trenches were analyzed and fed into a simulation tool to examine the resultant thickness of ablated layers for different process conditions, and to predict the obtainable shape when ablating multilayers. Next, the geometry of the designated chip breaker was sliced into a number of layers to be ablated sequentially. Different ablation scenarios were experimentally investigated to identify the optimum processing conditions. The results showed that an ns laser utilized in a controllable manner successfully produced the necessary three-dimensional feature of an intricate chip breaker with high surface quality (Ra in the submicron range), tight dimensional accuracy (maximum dimensional error was less than 4%), and in an acceptable processing time (≈51 s). Finally, two different inserts brazed in milling tools, with and without the chip breaker, were tested in real milling trials. Superior performance of the insert with chip breaker was demonstrated by the curled chips formed and the significant reduction of obtained surface roughness compared to the surface produced by the insert without chip breaker.

Most of the existing mechanistic (semiempirical) models for turning are orientated towards continuous cut and are applicable neither to nonaxisymmetric parts, nor to the particular case of interrupted turning, so common in real workpieces. Some commercial software packages which simulate machining process by FEM enable to calculate interrupted cut. However, their high computational cost limits the simulations to a very short length of cut, hardly completing one cutting revolution. By contrast, mechanistic models are not as computationally expensive as FEM ones. Despite their limited accuracy, they give approximate estimations of cutting forces during a whole tool path. Consequently, they are extremely useful to detect critical tool path steps, adapt cutting parameters and avoid machine overload. This study presents a mechanistic model to predict orthogonal turning forces in 3 directions (XYZ), torque and power consumption along the machining path of non-axisymmetric parts. The model communicates with CAM software by automatically transferring information about tool path and geometry from the CAM to the mechanistic model in standard format, contained in CL (Cutter Location) and STL (Stereolithography) files, respectively. Thus, the model is suitable to be integrated into any commercial CAM software. The simplicity of the model, the communication with CAM and an easy-to-use interface aim to spread out the applicability of the model among machining companies. The results of the study are validated by comparing simulations to experimental turning tests.

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