For reusable wire-cut EDM machines, there are many factors affecting the surface finish of cut pieces proceed by wire-cut EDM, among them, the two most important reasons. One is the size of pits in single discharge erosion, and its RZ is usually between 0.05 ~1.5μm, which is secondary to the sinker EDM surface finish of the cutting. The second reason is the convexity and concave stripes caused by the direction change of the wire drum.
The RZ of these stripes is usually between 1 ~ 50μm and may be larger than 0.1mm at some worst situations, which is the most important reason that affects the surface finish of the CNC EDM wire cut machine. At the same time, it is accompanied by a reversal of the black and white stripes, the visual impact is very bad.
Controlling the pit size caused by a single discharging is easier by reducing the energy of a single high-frequency pulse. But when single pulse energy is getting smaller to a certain range, it would be difficult to cut the high workpiece, and appears short circuit and interrupt stable discharging.
Moreover, the RZ caused by discharging pits and the RZ caused by wire drum direction change is not in the same magnitude range, so it is most important to control the RZ caused by the direction change of the wire drum.
1. appropriately reduce the pulse width and peak current, that is, reduce the size of the pit.
2.guide wheels and bearings to maintain good accuracy and smooth operation, reduce shaking of the electrode wire, wire jump so that the vibration of feeding wire can maintain in a very small and acceptable range.
3. Keep proper tension for the feeding wire in both forward and backward directions, nowadays, double direction wire tension control devices are used in the industry to minimize the issue caused by wire tension. King's latest PLC servo control system has very good performance in keeping proper tension and has simplified the mechanical structure and improved the performance, increased the cut accuracy and surface finish of the jobs. Please video of how it works here.
4. Wire should not be too tight, working liquid should not be too new, the new working liquid is beneficial for the cutting efficiency, but the cut surface finish is not the best with new working liquid.
5. If the workpiece is too thin, add at the plates to the upper and lower sides of the material, so that the wire drum direction change stripes would be better on the needed cut piece.
6. XY movement stability, accuracy, follow-up fidelity is good, no crawling is also extremely important.
7. Sampling of the cutting is also particularly important, Kingred's reusable wire cutting EDM machine has a high fidelity sampling system which is helpful for getting a better surface finish.