Main points of electrical machining control and surface treatment

Modern mold factories cannot lack electric machining. Electric machining can process all kinds of special-shaped and high-hardness parts. It is divided into two types: wire cutting and EDM.

The machining accuracy of slow-moving wire cutting can reach ±0.003mm, and the roughness Rau003d0.2μm. When the processing starts, check the condition of the machine tool, check the deionization degree of the water, the water temperature, the perpendicularity of the silk, the tension and other factors to ensure a good processing state. Wire-cutting processing is to remove processing on a whole piece of material, it destroys the original stress balance of the workpiece, it is easy to cause stress concentration, especially at the corners, so when R<0.2 (especially sharp corners), you should The design department makes suggestions for improvement. The method to deal with stress concentration in processing can use the principle of vector translation. Before finishing, leave a margin of about 1mm, pre-process the rough shape, and then perform heat treatment to release the processing stress before finishing to ensure thermal stability.

When processing the punch, the cutting position of the wire and the selection of the path should be carefully considered. The left end of the workpiece is clamped, the route ① is better than the route ② during processing, because the route ① the workpiece and the clamping part of the material are tightly connected, and the processing is stable. If the route ② is adopted, the workpiece becomes a cantilever after the first pass. The difference in force affects the subsequent processing of several passes. Route ③, using punching and threading processing, the best effect. High-precision wire-cutting processing, usually the number of cutting passes is four, which can guarantee the quality of the parts. When processing taper dies, in a fast and efficient position, the first rough machining straight edge, the second side taper machining, and then finishing the straight edge, so that the X segment vertical finishing is not required, only Finishing the straight edge of the cutting edge section saves time and cost.

Electric discharge machining must first make electrodes. Electrodes can be divided into coarse and fine. The precision machining electrode requires good shape conformity, and it is best to be processed by CNC machine tools. In terms of electrode material selection, copper electrodes are mainly used for general steel processing. The Cu-W alloy electrode has good overall performance, especially the consumption during processing is obviously smaller than that of copper. With a sufficient amount of scouring fluid, it is very suitable for the processing of difficult-to-process materials and the finishing of parts with complex cross-sectional shapes.

Ag-W alloy electrode has better performance than Cu-W alloy electrode, but its price is high and resources are few, so it is generally less used. When making electrodes, it is necessary to calculate the amount of electrode gap and the number of electrodes. When processing large areas or heavy electrodes, the workpiece and electrode should be clamped firmly to ensure sufficient strength to prevent processing looseness. When performing deep step processing, pay attention to the wear of the electrode and the arc discharge caused by poor drainage.

Surface treatment and assembly

The tool marks and wear marks left on the surface of parts during processing are the places where stress is concentrated and the source of crack propagation. Therefore, after processing, the surface of the parts needs to be strengthened and polished by fitter to deal with hidden processing hazards. Some edges, acute angles, and orifices of the workpiece are dulled and rounded. Generally, the electro-processed surface will produce a metamorphic hardened layer of about 6-10μm. The color is off-white, the hardened layer is brittle and contains residual stress. The hardened layer must be fully eliminated before use. The method is surface polishing and grinding to remove the hardened layer.

In the process of electrical machining, the workpiece will be magnetized to a certain extent, with weak magnetic force, it is easy to attract some small things, so before assembling, the workpiece should be demagnetized and the surface should be cleaned with ethyl acetate. During the assembly process, first refer to the assembly drawing, find the parts, and then list the equipment sequence between the parts, list the items that should be noted, and then proceed to assemble the mold. The assembly generally first installs the guide pin and guide sleeve, and then installs the mold After the assembly is completed, the mold inspection should be carried out and the overall situation report should be written. For the problems found, the reverse thinking method can be used, that is, from the back process to the previous process, from finishing to roughing, checking one by one until the crux is found and the problem is solved.