【China Aluminum Network】 EDM machine tool consists of bed and column, workbench, spindle head, working fluid and working fluid circulation filtration system, pulse power supply, servo feed mechanism, spindle head and table accessories and other parts.
(1) Beds and Columns Beds and columns are basic structures that ensure the mutual position of electrodes and tables and workpieces. The accuracy of the position has a direct influence on the machining. If the accuracy of the machine tool is not high, the machining accuracy is difficult to guarantee. Therefore, not only the structure of the bed and the column should be reasonable, but also have a high rigidity, can withstand the inertial force of the spindle load and sudden acceleration of the moving parts, and should also be able to reduce the deformation caused by temperature changes.
(2) Workbench Workbench is mainly used to support and clamp the workpiece. In actual processing, the relative position of the electrode and the workpiece is changed by rotating the vertical and horizontal screw rods. A working fluid tank is installed on the work table to contain the working fluid so that the electrodes and the workpiece are immersed in the working fluid to perform cooling and chip removal. A workbench is a part that is frequently moved by an operator during the setting of the clamp. By moving the upper and lower slides, the vertical and horizontal positions are changed to achieve the required relative position between the electrode and the tool.
(3) Spindle head The spindle head is a key component of the EDM machine tool. It is composed of three parts: servo feed mechanism, guide and anti-twist mechanism, and auxiliary mechanism. Used to control the discharge gap between the workpiece and the tool electrode.
The quality of the spindle head directly affects the machining process indicators, such as productivity, geometric accuracy and surface roughness, so the spindle head has the following requirements:
1) Have certain axial and lateral stiffness and accuracy;
2) There is sufficient feed and recovery speed;
3) The linearity and anti-rotation performance of the spindle movement are good;
4) High sensitivity, no creeping phenomenon;
5) Have a reasonable ability to carry the quality of the electrode.
In China as early as the 20th century, 60s to 70s, spindle heads such as DYT-l and DYT-2, which were widely used in hydraulic servo feed, have been widely used as feed-driven spindles for stepping motors, DC motors, or AC servo motors. head.
(4) Working fluid of EDM machine and circulating filtration system The working fluid in EDM has the following aspects:
1) After the discharge is completed, the insulation state (deionization) of the discharge gap is restored so that the next pulse voltage again forms a spark discharge. For this purpose, the working fluid is required to have a certain dielectric strength, and its resistivity is between 10<3> and 10<6> [Omega]•cm.
2) The galvanic corrosion products can be easily suspended and discharged from the discharge gap to avoid serious pollution of the discharge gap, resulting in a non-dispersive spark discharge point and the formation of harmful arc discharge.
3) Cool the tool electrode and reduce the local high temperature generated by the instantaneous discharge on the surface of the workpiece. Otherwise, the surface will generate carbon, burn and arc discharge due to local overheating.
4) The working fluid can also compress the spark discharge channel, increase the expansion of the compressed gas, plasma, and explosive force in the channel to throw out more molten and gasified metal and increase the amount of erosion.
At present, kerosene is used as the working fluid for EDM because the new kerosene has a resistivity of 106 Ω•cm, and is between l05~104Ω•cm in use, and is relatively stable. Its viscosity, density, and surface tension are also comprehensive. Meet EDM requirements. However, kerosene can catch fire. Therefore, when the rough standard processing, you should use the engine oil or working fluid mixed with oil.
(5) The pulse power pulse power supply of the EDM machine functions to convert the power frequency AC power into the energy required to supply the spark discharge gap to etch metal. Pulse power has great influence on EDM's productivity, surface quality, processing speed, process stability and tool electrode loss and other technical and economic indicators.
Now, universal (economic) EDM machine tools use high- and low-voltage composite pulsed power supplies. Medium-to-high-end EDM machine tools use microcomputer-controlled pulsed power supplies, and they have internal EDM database. It is possible to set and call the coarse, medium, and fine machining parameters of each file through the microcomputer.
(6) The EDM machining of EDM machines differs from cutting machining in that it is "non-contact machining." In normal EDM, there is a discharge gap S between the tool and the workpiece. If the gap is too large and the pulse voltage does not penetrate the insulating working fluid between the gaps, spark discharge will not occur. The electrode tool must be fed downward until the gap S is equal to or less than a certain value (generally S=0.1~0.01mm). , related to processing standards, can break down and produce spark discharge. In the normal EDM process, the workpiece is continuously etched at the speed of w, and the gap S will gradually expand, and the electrode tool must be fed at a speed d to compensate for the required discharge gap. If the feed rate d is greater than the erosion speed w of the workpiece, the gap S will gradually become smaller, even equal to zero, forming a short circuit. When the gap is too small, the feed rate d must be reduced. If the short-circuit between tool workpieces (S=0), the tool must be made at a higher speed d
Reverse back quickly to eliminate the short circuit condition and then re-adjust it to the desired discharge gap. This is a problem that must be solved in normal EDM.
