OBRABOTKAMETALLOV Vol. 24 No. 2 2022 TECHNOLOGY EDM sludge particles are subject to destruction. Cracks, dents, as well as zones of crumbling and destruction appear on the surface of spherical particles with an increase in the value of the pulse energy (Figure 2). а b Fig. 2. The surface of spherical sludge particles after destruction: a – at a scale of 5 μm; b – at a scale of 2 μm Local heating of the processed material causes thermal decomposition of the boride phase and the dielectric medium [14, 15]. This dielectric processing medium is in a state of motion and constant circulation. This leads to cooling of the ET and the workpiece material. The fl ow of vapors becomes turbulent and can break up into small fractions. Each part can condense into a liquid, and as a result, into a solid state. The cooling rate of liquid metal drops is reduced by the vapors of the working fl uid that promotes spheroidization and dendritic segregation of particles. The content of the working fl uid and metal vapors decreases at low input energy. This leads to a decrease in the number of particles with a smaller average size. The sludge solidifi es faster if the pulse energies are not high. The fl ow of material vapors and the working fl uid increases along with the values of the input pulsed energy [14, 15]. The movement of sludge particles is turbulent. There is a collision between it. Cracks and dents form on the surface of the particles of this sludge and an inclusion structure also appears. The formation of EDM sludge signifi cantly affects the stability of the EDM process and, as a result, the productivity of processing. Increasing the productivity of the EDM process can be achieved not only by increasing the pulse energy, but also by intensifying the removal of erosion products from the interelectrode gap. Productivity increases with effective fl ushing and intensive removal of eroded particles of PCM and ET from the gap. Flushing brings clean gear oil into the gap and cools the ET and PCM. The deeper the treatment, the more diffi cult it is to ensure proper fl ushing of the zone being processed. This increases processing time and reduces performance. Eroded particles are welded onto a PCM product under certain processing conditions. This leads to uneven processing and reduced performance or even to its stop. Flushing is widely used in EDM of deep holes, including EDM of PCM products. Insuffi cient fl ushing reduces material removal effi ciency. The material that remains in the hole is remelted in the next pulse and welded onto the electrode surface. The intensifi cation of fl ushing during EDM in deep and narrow cavities contributes to an increase in the material removal rate. In [16, 17], it was found that fl ushing maintains the rate of material evacuation after a discharge. In [17], the effect of the ET jump was studied, which is used to evacuate eroded material during immersion under pressure. The electrode movement speed affected the distribution of eroded particles, and the movement amplitude affected the amount of pure dielectric. The work [18] shows the pressure drop of a dielectric liquid at the hole depth, the infl uence of the hole depth on the pressure drop. This was a loss of 15% of the observed 25 mm. Ahigher concentration of eroded material was also established in the corner of the machined hole (Figure 3).
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