Theoretical simulation of the process interelectrode space flushing during copy-piercing EDM of products made of polymer composite materials

Abstract

Introduction. Polymer composite materials (PCM) are used to improve the mechanical properties and increase the working period of products. For the processing of products made of PCM, the use of electrophysical processing methods is standard. One of these methods is copy-piercing electrical discharge machining (EDM). The use of such methods for processing PCM is due to its high physical and mechanical characteristics and the complexity of processing by blade methods. Considering the fact that the PCM element is a binder – epoxy resin, which is destroyed at the edges of the resulting holes and grooves during EDM, PCM can be considered difficult to process. During the EDM of holes in PCM products, the temperature rises, and inefficient cooling often occurs in the processing zone. The paper is devoted to theoretical simulation in the Ansys package, which makes it possible to evaluate the impact of flushing method on the efficiency of the EDM of PCM products based on numerical simulation in finite element analysis software systems. The aim of the work is to increase the productivity of the processes of EDM for PCM products. Methods. Experimental studies were carried out according to the method of a classical experiment on a copy-piercing electrical discharge Smart CNC machine. The workpiece was processed at a constant voltage U = 50 V, pulse on-time Ton = 100 µs and current: I = 10 A. For theoretical simulation of the flow, the ANSYS CFX 20.1 software was used. Flow distribution simulation was carried out at three processing depths (2 mm, 10 mm, 15 mm), as well as at three nozzle inclination angles (15°, 45°, 75°). Results And Discussion. The analysis of the data obtained showed that in the case of the EDM of PCM, the angle of the location of the flushing nozzles should be taken into account in order to increase the productivity of processing deep, blind holes. It is established that the highest performance value is achieved when the nozzles are located at an angle of 15˚. The laminar motion prevails. With this arrangement of the nozzles, the value of the liquid pressure and the removal of the sludge are stable both with the EDM of PCM to a depth of 2 mm, and when processing to a depth of 15 mm. It is noted that for processing holes with a depth of 10 mm or more, it is worth considering the angle of inclination of the flushing nozzle for effective processing, it is necessary to remove eroded particles from the gap. In the process of conducting an experimental study, when processing holes with a depth of 15 mm, sticking of sludge to the electrode-tool was observed, as well as the closure of the EDM process, the occurrence of secondary discharges in the processing zone, which caused the processing to stop.