raw materials graphite electrode
Raw materials graphite electrode requirements for discharge conditions
Raw materials graphite electrode requirements for discharge conditions 1. Requirements for pulse current (IP): The characteristics of pulse current are: the larger the value, the faster the discharge machining speed, the larger the discharge gap, and the rougher the surface roughness. The lower the electrode loss.
1. The pulse current is affected by the discharge area, that is, the current density. The principle of selecting the pulse current of raw materials graphite electrode is based on the average current. When the raw materials graphite electrode is large, the current density is usually set to 10-12A/cm2; raw materials For graphite electrode, the current density is usually set to 6～8A/cm2.2) The pulse current is affected by the size reduction (spark position) of the raw materials graphite electrode. It is suitable for normal electric discharge machining of raw materials graphite electrode. The selection of current must be determined by the size of raw materials graphite electrode, which is the most reasonable method. When the average current of raw materials graphite electrode reaches 10A～120A, the loss of raw materials graphite electrode Minimal. With the increase of current, the loss of raw materials graphite electrode also increases.
2. Requirements for pulse width (ON TIME, discharge pulse width): characteristics of pulse width: the larger the value, the longer the discharge time, the faster the processing speed, the smaller the loss of raw materials graphite electrode, the larger the discharge gap, and the rougher surface The coarser the degree, the worse the processing stability. The pulse width of raw materials graphite electrode ranges from 0 to 1000 us. When the pulse width is large, the processing speed increases with the pulse width, the processing is unstable, and the processing time increases. The processing speed slows down and the surface of the workpiece is ablated; its value generally does not exceed 420 us. When the pulse width is 100～300us, the raw materials graphite electrode has the least loss. The selection of the pulse width should be determined according to the current size and the requirements of electrical discharge machining If the discharge area is large or used for rough machining, in order to increase the processing speed, the pulse width should be larger; when the surface roughness is taken into account for small areas or fine machining, the pulse width should be smaller. The workpiece material is different, the processing With different polarity, the pulse width has different effects on the processing effect. Different manufacturers, different grades, and different batches of graphite materials have different effects on the pulse width. The same pulse width, the smaller the graphite particles, the more the raw materials graphite electrode loss Small.
3. Requirements for pulse interval (OFF TIME discharge pause): The function of pulse interval is to make the discharge disappear automatically, eliminate ionization, allow the working fluid medium to remove impurities, and prepare for the next discharge. The characteristics of pulse interval: only Affects the electrical discharge machining speed and processing stability, but has little effect on others. When the value is larger, the processing stability is better, the processing speed is relatively slow, but the discharge stability is faster than the instability; the value of the pulse interval The range is much wider than the pulse width, which can be between 0～2500 us. When the pulse interval is 100us, it reaches the minimum value. If the pulse interval is increased, the loss of raw materials graphite electrode will increase instead. The pulse interval is often used in electric discharge machining of raw materials graphite electrode. (OFF)=Pulse width (ON), and adjust to 1/3～2/3 of the pulse width according to the stability of the processing. When the pulse interval is appropriate, with the increase of the pulse interval, the deionization of the inter-electrode medium is compared It is sufficient, which is beneficial to the formation of a covering layer (the carbon content of the erosion product and the decomposition of the medium adheres to the surface of the raw materials graphite electrode during the electrical processing), so the loss of the raw materials graphite electrode is reduced, but when the pulse interval is greater than 100us, the raw materials The cooling time of the materials graphite electrode and the workpiece surface is too long, the next pulse requires more energy to form the discharge channel, and it is not conducive to the formation of the cover layer, and the loss of the raw materials graphite electrode increases instead. If the pulse interval is too small, the deionization between the raw materials graphite electrode and the workpiece may be insufficient, and ablation may occur on the surface of the raw materials graphite electrode and the workpiece. The rest time generally only affects the speed of electrical discharge machining, but has no obvious effect on the loss of raw materials graphite electrode and the surface roughness of the processing.