Polarity effect
The so-called polarity effect is that in lathe processing, due to the different positive and negative polarities. The phenomenon that the amount of electrolytic corrosion is different from each other is generated. Practice proves. In the process of lathe machining, both the positive and negative poles are subject to electro-erosion, but their respective electro-erosion amounts are different, which is the result of the polarity effect. Before studying the polarity effect, it is necessary to understand that the direct cause of the polarity effect between the pulsed power supply and the workpiece and tool is due to the difference in the energy distributed to the surfaces of the two electrodes. The energy between the electrodes is the result of the interaction between the positively charged ions and the negatively charged electrons. The electrons have small mass, small inertia, and flexible movement. A large number of electrons run towards the positive electrode and bombard the positive electrode surface, causing the positive electrode surface of the lathe to melt and melt rapidly. Vaporization: while positive ions have large inertia and slow motion, only a small part can reach the surface of the negative electrode, while a large number of positive ions cannot. Therefore, when a narrow pulse (that is, a long discharge duration) is used for processing, the positive ions with large mass and inertia will have enough time to reach the surface of the negative electrode. stronger than electrons. At the same time, the positive ions reaching the negative electrode will restrain the movement of electrons, so the amount of electrolytic corrosion of the negative electrode will be greater than that of the positive electrode. At this time, the workpiece should be connected to the negative electrode. It can be seen from this that the "negative polarity" method is used when using narrow pulse processing, and the "positive polarity" method is used when using long pulses.
In order to make full use of the polarity effect and minimize the loss of tool electrodes, the polarity wiring method should be correctly selected, so that the removal speed of the workpiece is the highest and the tool loss is minimized.
Influence of metal materials on the amount of galvanic corrosion
The uneven distribution of galvanic corrosion on the surface of positive and negative electrodes is not only related to the polarity of the electrodes, but also has a great relationship with the materials of the electrodes. When the pulse discharge energy is the same, the higher the melting point, boiling point, specific heat capacity, latent heat of vaporization, etc. of the metal workpiece, the less electrolytic corrosion will be, and the more difficult it will be to process. The larger the thermal conductivity of the metal, the more heat can be conducted and dissipated to other parts, which reduces the amount of corrosion. Therefore, the amount of electrode erosion is closely related to the thermal conductivity and other thermal constants of the electrode material.