The CNC electric discharge machine is a high-precision machining machine tool, which is suitable for the production and manufacture of various molds. It uses the high temperature ablation of the workpiece surface material generated by the instantaneous spark discharge between the tool electrode and the workpiece electrode to realize the processing.
When the tool electrode and the workpiece are close to each other in the working fluid under the driving of the feed mechanism, the voltage between the electrodes breaks down the gap and generates spark discharge, releasing a large amount of heat. The surface layer of the workpiece reaches a very high temperature (above 10000°C) after absorbing heat, and the local material is eroded away due to melting or even vaporization, forming a tiny pit. The working fluid circulating filter system forces the clean working fluid to pass through the gap between the tool electrode and the workpiece at a certain pressure, to remove the electrical corrosion products in time, and filter the electrical corrosion products out of the working fluid.
The rectangular shape with sharp edges and corners adopts the flat-bottomed square side trimming plan, and the round or multi-curved ellipse adopts the flat-bottomed round side trimming plan. During the side trim process, the tool electrode moves and feeds to the workpiece at an angle. At this time, the tool electrode moves from the center to the outside (X direction and Y direction), from top to bottom (Z direction), with the CNC automatic control, that is, three-axis linkage. This type of movement is not easy to accumulate carbon, easy to remove chips and exhaust, and does not cause arcing. It has high production efficiency and uniform roughness on the side and bottom surfaces. Compared with the single-axis translational head electrical discharge machining(EDM) method, it reduces the labor intensity.
The CNC electric discharge machine that conducts X-axis lateral machining of split chase molds has unique advantages. The mold clamping accuracy is high, and the productivity can be increased by 20% compared with Z-axis downward machining.
The erosion introduced in the basic principles of electrical machining must be eliminated in time to achieve a balance between generation and elimination, otherwise it will not work normally and stably, which will affect the processing efficiency. Generally, cutter lifting on time is to raise the cutter according to the length of time regardless of whether there is erosion in the cavity. The so-called self-suitable cutter lifting means that if the production of erosion in the cavity is less than the elimination and the discharge is stable, the cutter is not lifted; While if the production of erosion in the cavity is larger than the elimination, the balance is broken, and the machine tool automatically lifts the cutter at this time. The liquid suction discharges the excess eroded material, and stops lifting the cutter when the balance is reached or the elimination is greater than the production, and the efficiency is improved.
When there is an arc or a false short circuit in the row cavity, resistance is generated between the electrode and the workpiece, and it is in a state of neither short circuit nor open circuit. The energy of the power supply continues to release heat energy in the electrode and the workpiece, and the temperature of the tool electrode is getting higher and higher. It may even ignite the kerosene to cause a fire. For safety, this machine has added special control in the control circuit. When an arc or false short circuit occurs, the pulse power is immediately cut off, and the energy supply to the cavity is stopped. The electrode temperature will not continue to rise, reducing the risk of fire.
The CNC EDM machine reduces the low-voltage circuit current-limiting resistance in the circuit, that is, reduces the heat generated by a nearly 2KW current-limiting resistance of a 50A power supply, reduces energy consumption, and saves more than 20% of power compared with similar power supplies.
The general pulse power supply of CNC electric discharge machine in cavity processing is to send a series of pulses to the gap. Due to the complex conditions in the gap, the breakdown doesn't happen at the initial of each pulse, but after a period of time, which causes a narrowing of the effective pulse width of the spark, and the narrowing of nearly 30% pulse at random. The unstable pulse of the effective pulse width will increase the wear of the electrode of the tool. This machine tool adopts a complete low-voltage pulse method after high-voltage breakdown. The pulse width is equal. And practice has proved that this pulse method further reduces the loss of the tool electrode, the processing surface is rough and uniform, and the end surface loss of the tool electrode is almost zero.
The CNC electric discharge machine uses one electrode for rough and fine machining, which saves the manufacturing time and cost of the double electrode, saves the trouble caused by the correction of the fine machining electrode, and shortens the time for mold manufacturing.