2. Specific operation method
In the rough machining of precision parts, 0.3mm finishing allowance is reserved for each dimension, and 0.2mm allowance is reserved for semi finishing of inner hole; The rough machined parts are vacuum quenched to 60-64hrc; Process the inner hole and end face of the part to meet the size requirements of the drawing; In order to ensure the accuracy of the parts, Guangdong machining factory used the spindle (Fig. 2) to locate the inner hole of the workpiece, and used the magnetic dial indicator to check the runout of the machined spindle to ensure that the runout was within 0.005mm, Then, the grinding parts are matched with the spindle, the nut on the spindle is locked, the center hole of the spindle is positioned by the center, the outer circle is machined with 90 ° cylindrical turning tool to the size required in the drawing, and the micrometer is used for inspection; Then install 3 WEDM tools at the same time. Due to the strict requirements of groove distance of parts, the outer diameter and end face of the tool are adjusted with the help of 1:100 magnifying glass before processing, and the error value is within 0.01mm. Refer to the process parameter table 1 in the following table, use the CNC machine tool grooving cycle program for grooving, pay attention to the direction of cutting chip removal, and fully cool the tool with cutting fluid. As shown in Figure 2


3. Problems encountered in processing groove
When machining the first part on the CNC horizontal lathe, the spindle speed is set at 120r / min and the radial feed rate is 0.1 mm / min. the first tool program runs normally, and the second tool ignores the modification of the cutting edge. When machining 45 slots, the iron filings become noodles. The machine stops for inspection, and it is found that the cutting edge collapses seriously and the tool squeezes, As a result, the groove of the parts is extruded and the parts are scrapped. When machining the second part, the spindle speed and radial feed rate are reduced after the tool is corrected. When machining the first tool and the second tool, the cutting sound and chip removal are normal. After cutting the second tool, the program pauses to check whether the surface roughness of the part meets the requirements, and continues to run the program. After finishing the part with the third tool, the surface quality of the part is excellent, It is found that the depth of the groove is asymmetric during the measurement, and the reason is carefully found out. When the forming tool stays at the bottom of the groove for a short time in the finishing process, every time a groove is cut, the program runs and the tool is withdrawn quickly, resulting in the different depth of the groove.
The solution of Guangdong mechanical processing plant: reduce the spindle speed and radial feed rate, polish the cutting edge when grinding the tool, and extend the residence time at the bottom of the groove by 1s when the program is running. Learn from the previous failure, set the spindle speed of 80 R / min, radial feed rate of 0.07 mm / min, 3 tools in sufficient coolant, cycle the grooving program, and finally finish the groove perfectly after 5 hours, and use the wire cutting inspection template for light gap inspection. After processing, the parts obtain excellent surface quality, which can meet the drawing size and tolerance requirements. The processing parameters are shown in the attached table. All the tools used in the table are Zhuzhou Diamond yt05 cemented carbide welding tools.
4. Conclusion
Guangdong mechanical processing plant processes according to the processing parameters in the table. After many failures, it has made use of the advantages of yt05 cemented carbide and the successful case of wire cutting tool in NC horizontal lathe. It has successfully replaced the precedent of machining high hardness parts on NC grinder and accumulated experience for machining high hardness parts with ordinary cemented carbide, And the worn cemented carbide tool can be cut by wire again for grinding. At the same time, it reduces the processing cost, shortens the processing time, improves the production efficiency, and successfully completes the product delivery plan.