How to use EDM to process kinds of mold

Small gap mold

When the spark gap is less than 0.03mm, the EDM productivity is very low, because the chip removal is also difficult when the spark gap is small. For molds with a matching clearance less than 0.03mm, they cannot be processed by normal methods. The processing methods of such molds mainly include the following two:

1) The electrode and the punch are manufactured separately, and the size of the electrode is made smaller than that of the punch. This method not only increases the machining workload, but also increases the precision requirements for electrodes and punches.

2) Use chemical etching to shrink the whole electrode a bit. However, it is not easy to get a very smooth surface after the cast iron electrode is corroded. In this case, it is better to use steel (such as 15 steel and 30 steel) as the electrode.

Large gap mold

As the spark gap increases, the surface roughness of the workpiece gradually deteriorates. When the spark gap is larger than 0.10mm, the surface roughness cannot reach Ra1.6μm, which cannot meet the requirements for the mold. Therefore, the above-mentioned methods can no longer solve the problem, and other methods must be adopted, mainly including the following three:

1) The electrodes and punches are manufactured separately, and the size of the electrodes is larger than that of the punches. But doing so increases the machining workload, and cannot get a uniform fit clearance.

2) Use the etching method to shrink the punch, or etch the die that has been processed by the normal processing method to a larger size. This method is feasible and simple when the corrosion amount is small (such as 0.02~0.04mm), but if the corrosion amount is too large, it is not easy to be uniform, and the size is difficult to control.

3) Use the translation head to widen the gap. In the case of a translation head, this method is the most simple and reliable, and can improve the average productivity of the machining die and improve the surface roughness; in addition, it can also easily use the CNC wire cutting method to process a large gap mold.

progressive mold

There are two types of progressive multi-station molds: one is that the positioning holes on the die have been processed by other methods, and only need to use EDM to machine the holes, and the positioning size between the holes and the positioning holes has strict requirements ; The other is that the positioning holes and multiple holes on the die need EDM.

For the first category, the positioning size is mainly ensured by precise positioning, and there is no special requirement for EDM.

For the second category, two EDM methods can be used, namely single electrode machining and combined electrode machining. The single-electrode machining method is to machine one hole with one electrode at a time, and then change another electrode to machine the second hole. The distance between the holes is guaranteed by the precise coordinates of the machine tool. The clamping and calibration of the electrode requires special fixtures and measuring tools. . Due to the cumulative error of the coordinate system and the difficulty of clamping and positioning the electrode, this method is not suitable for the processing of progressive molds with many holes. The combined electrode machining method is to pre-assemble the electrodes of the positioning hole and each type of hole as a whole electrode for EDM. The key to this method is to install the combined electrode accurately, and sometimes special fixtures and measuring tools are needed to ensure the accuracy.