Kang Ru, a wire cutting fluid manufacturer, will tell you the common problems and solutions of CNC wire cutting aluminum parts
Kang Ru, a wire cutting fluid manufacturer, will tell you the common problems and solutions of CNC wire cutting aluminum parts
(1) Bed and column
The bed and column are the basic structure, which ensures the mutual position of the electrode, the worktable and the workpiece. The position accuracy has a direct impact on the processing. If the accuracy of the machine tool is not high, the processing accuracy is difficult to guarantee. Therefore, not only the structure of the bed and column should be reasonable, have high rigidity, and be able to withstand the inertial force of the spindle load and the sudden acceleration of the moving parts, but also reduce the deformation caused by temperature changes. Spray cleaning agent
(2) Workbench
The worktable 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. The workbench is equipped with a working fluid tank to contain the working fluid, so that the electrode and the workpiece are immersed in the working fluid, which plays a role of cooling and chip removal. The workbench is a part that the operator often moves when clamping and aligning. 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, which is composed of three parts: the servo feed mechanism, the guiding and anti-torsion mechanism, and the auxiliary mechanism. Used to control the discharge gap between the workpiece and the tool electrode.
The quality of the spindle head directly affects the processing technology 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) Sufficient feed and pick-up speed;
3) The linearity and anti-torsion performance of the spindle movement are good;
4) High sensitivity and no creeping phenomenon;
5) Possess reasonable ability to carry electrode quality.
As early as the 1960s and 1970s, my country used hydraulic servo-feed spindle heads such as DYT-1 and DYT-2. At present, stepping motors, DC motors or AC servo motors have been widely used as feed-driven spindles. head.
(4) Working fluid and circulating filter system of EDM machine tools
The role of working fluid in EDM has the following aspects:
1) After the discharge is over, the insulation state of the discharge gap (deionization) is restored, so that the next pulse voltage forms a spark discharge again. For this reason, the working fluid is required to have a certain dielectric strength, and its resistivity is between l03~106Ω•cm.
2) It is easier for the electro-corrosion products to be suspended and discharged from the discharge gap, so as to avoid serious pollution of the discharge gap and cause the spark discharge points to not be dispersed and form harmful arc discharge.
3) Cool the tool electrode and reduce the local high temperature generated by instantaneous discharge on the surface of the workpiece, otherwise the surface will cause carbon formation, burns and arc discharge due to local overheating.
4) The working fluid can also compress the spark discharge channel, increase the expansion and explosive force of the compressed gas and plasma in the channel, so as to throw out more melted and vaporized metal and increase the amount of erosion. At present, kerosene is used as the working fluid for EDM, because the electrical resistivity of new kerosene is 106Ω•cm, while in use it is between 105~104Ω•cm, and it is relatively stable, and its viscosity, density, surface tension and other properties are also comprehensive Meet the requirements of EDM. But kerosene is easy to catch fire. Therefore, engine oil or working fluid mixed with engine oil should be used when rough machining is performed.
(5) Pulse power supply of EDM machine The function of the pulse power supply is to convert the power frequency alternating current into the energy needed to supply the spark discharge gap to erode metal. Pulsed power supply has a great influence on technical and economic indicators such as EDM productivity, surface quality, processing speed, processing stability and tool electrode wear.
Now popular (economical) EDM machine tools all use high and low voltage composite transistor pulse power supplies, medium and high-end EDM machine tools all use microcomputer digitally controlled pulse power supplies, and there is an EDM standard database inside. It is possible to set and call various rough, medium and finishing standard parameters through the computer.
(6) Servo-feed EDM of EDM machine tools is different from cutting and belongs to "non-contact machining". During normal EDM, there is a discharge gap S between the tool and the workpiece. If the gap is too large, the pulse voltage will not penetrate the insulating working fluid between the gaps, and spark discharge will not occur. The electrode tool must be fed downwards until the gap S is equal to or less than a certain value (usually S = 0.1~0.01mm , It is related to the processing regulations) in order to break down and produce spark discharge. In normal EDM machining, the workpiece is continuously eroded at the speed of w, and the gap S will gradually expand. The electrode tool must be compensated at the speed d to maintain the required discharge gap. If the feed d is greater than the workpiece's erosion speed w, the gap S will gradually become smaller, or even equal to zero, forming a short circuit. When the gap is too small, the feed speed d must be reduced. If there is a short circuit between the tool and workpiece (S=0), the tool must be reversed quickly at a higher speed d to eliminate the short circuit, and then feed down again to adjust to the required discharge gap. This is a problem that must be solved in normal EDM.