The EDM processing method has a certain history and is not the latest technology, but compared with forging and metallurgy, EDM is not old. EDM is to use sparks generated between electrodes and workpieces when electricity is applied ( Because the positive and negative electrodes are in direct contact, resulting in a short circuit), the instantaneous high temperature generated, removes the surface of the workpiece in contact with the electrode layer by layer, so that the material around the electrode is continuously reduced.
The EDM processing technology is usually suitable for the processing of parts with relatively high hardness and the material must have conductivity. The general EDM machine can only approach the workpiece again because the electrode has to be etched off one layer and then lowered. Electric sparks can also be generated, so usually, because of the high precision requirements, the EDM machines used are basically CNC EDM machine tools, which is the best processing method for EDM.
The CNC EDM machine is mainly composed of a main engine, a pulse power supply, an automatic feed control system and a working medium circulation system, etc., involving the mechanical field, PLC control, cooling system, etc., regardless of any type of work, it involves strong professional knowledge. It is obviously different from ordinary equipment, which will be discussed in another article later.
Let’s talk about the characteristics of EDM. The discharge speed set during EDM and the surface quality of the mold are the core factors that affect the machining accuracy and quality. The mold used for EDM (that is, the electrode) In EDM, it is generally divided into several levels, namely coarse, medium, and fine, which can be divided into fine discharge, coarse discharge, and medium discharge.
Coarse EDM is realized by high-power, low-loss discharge method (except for the mold, the power settings of the equipment are different, and the electrode is relatively lossy during medium and fine EDM (the electrode is eroded when the part is etched), and at the same time itself will be consumed, this is like hitting the stick, although there are 10,000 kills, there are also 3,000 self-damages), but in general, during medium and fine EDM, the product margin is less, so the electrode loss It is also extremely small and can be compensated by controlling the processing size during discharge because the loss of discharge is fixed and unchanged. Of course, it can be ignored when the accuracy requirement is not high.
The mutual loss of the electrodes is what we said above, but the EDM machine can be used for a long discharge pulse time, which can effectively reduce the electrode loss, but the EDM machine only uses long discharge pulse waves and high current discharge for rough machining, and the processing speed is fast. The electrode loss is small, but the accuracy cannot be improved. In the finishing discharge operation, a small current discharge must be used, and the discharge pulse time must be reduced. This not only increases the electrode loss, but also greatly reduces the processing speed, but the accuracy can be reduced. Do it.
EDM carbon slag and slag removal are also very important. Carbon slag will be generated during EDM, and it must be carried out at the same time when generating carbon slag and removing carbon slag, and the two can be achieved under the condition of balance. For processing, in actual production, the purpose of removing carbon slag is usually achieved by sacrificing the processing speed, for example: during medium and fine EDM, use a higher voltage, or use a large rest pulse, etc.
Another condition that affects the removal of carbon slag is the complexity of the shape of the processing molding surface, which is easy to make the chip removal path unblocked. This situation is relatively difficult to deal with. In this case, the requirements for folding electrodes are relatively high, because the electrodes are processed by CNC., so folding electrodes is a very important course content when training CNC programming in our school, and it is a must, and it is also a key assessment.