OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 1 2024 Introduction To improve the process effi ciency for items made of modern high-strength, tough-to-machine materials with advanced mechanical and physical properties and performance, it is required both to improve the process itself and the process-related tooling [1–7], and to upgrade the equipment taking into account the new technologies in the fi eld of the mechanical engineering. In this case, the prospective effi ciency improvement can be achieved by process control automation that could reduce considerably the machining and handling time and improve the fi nish quality and productivity. As of today, modern CNC machines are far enough advanced to control the main cutting movements [8–10]. Adaptive control systems that process equipment is usually fi tted with contribute to making the process quality even higher. With advances in new hybrid and mixed technologies [11–20] that combine several types of action on the item to be machined, the issue of timing between the automatic control of process equipment driven elements movement and companion process control of the mixed technologies became critical. One of examples of such technologies is electrochemical diamond grinding with regular dressing of the diamond grinding wheel face by reverse polarity currents [21–24]. To make electrochemical action on the material to be machined possible, an electrical circuit comprising the DC source, the material to be ground and conductive diamond wheel is created. Electrolyte fl uid is fed to the grinding area. For machining, the workpiece is connected with the positive contact of the current source. The surface under machining became softer that contributes to the diamond grinding modes improvement. However, during operation, the effi ciency of the diamond-bearing layer degrades due to fouling. Tool cutting performance restoration is required, and one embodiment is the current source polarity reversing that makes electrochemical dressing of the diamond-bearing layer possible. Thus, to maintain the wheel performance, periodic current pulses are fed to the electrical circuit. Special programmable devices are used to control current polarity and pulse duration [25]. These devices are connected to current switching units. These key element-based units serve to feed direct and reverse polarity currents alternatively to the electrical circuit. CNC machines fi tted with such programmable devices require additional non-interacting automatic control system to be used. In this case, it is challenging to coordinate the driven elements movement control system of the CNC machine and the programmable device that controls current pulses polarity and duration during the mixed processing. In this regard, the purpose is to synchronize the machine’s CNC system and the current polarity switching control system. Methods for studying To investigate the process of automatic control of current polarity during electrochemical grinding and regular dressing of the diamond grinding wheel face using the machine’s CNC system, we used a proprietary test bench. The test bench is based on a three-axis CNC machine, presented in fi g. 1. The machine is equipped with three step motors controlled by the Arduino control board and G codes. For a process sequence programming, a PC SW is used. Fig. 2 shows arduino-based CNC machine control logic. To simulate the mixed processing conditions, the test bench was additionally fi tted with DC circuit comprising the current source, current switching unit, material to be machined, and grinding tool. The spindle was installed horizontally and fi tted with a grinding tool mandrel. The machine components that are the part of the electrical circuit as well as the workpiece holder were insulated by dielectric joints. Overview of the test bench with retrofi ts is shown in fi g. 3. Fig. 1. Three-axis CNC machine
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