(2) Process of valve body parts
Due to the special processability of the five eccentric holes on the valve body part, the difficulty of the machining process is determined. For example, the No. 1 hole, the No. 3 hole, and the No. 4 hole are deep holes, and the size is (100 mm ± 0.1 mm). The No. 2 hole and the No. 5 hole are small diameter deep holes. At the same time, the internal structure of each piece of eccentric hole is complicated. Including the tapered groove, internal thread and radial tolerance, plus the surface roughness of each inner hole surface is also low, most of which requires R a = 1.6μm. ② Number hole section reaches R a = 0.4μm. Through the above analysis of the structure of the part and adding 1. positioning pin 2. positioning screw 3. fixing flange precision and surface roughness 4. movable flange 5. locking screw 6. understanding of the workpiece, combined with existing processing experience and Technically, the holes of the valve body parts are machined (the cutting parameters selected for each hole are roughly the same):
1 Drill the center hole and drill the pre-hole with the center.
2 Drill holes on the lathe to the depth dimension with a drill bit, R a up to 12.5 μm.
3 Using a special boring tool made of high-speed tool steel to drill the hole → semi-fine 镗 → fine boring. According to the valve body part material (1Cr17 Ni12) and tool material (high speed tool steel), the spindle speed is v=165r/min during machining, the rough feed is 0.12~0.2mm/r, and the semi-precision feed is 0.08. ~0.12mm / r, fine feed rate is 0.03 ~ 0.05mm / r. Using the above process method and cutting parameters, the machining accuracy of the inner hole is calculated from IT7 to I T8, and the surface roughness R a is 0.8 to 1.6 μm. Therefore, the accuracy can be fully achieved. When there is R a =0.4μm at the No. 2 hole: 8.5mm, it must be treated by special processing methods, polished or super-finished after the fine boring process to meet the surface roughness requirements. .
4. Conclusion
For the processing of the eccentric hole of the valve body parts, the above eccentric indexing rotary jig is used to better improve the machining precision and processing efficiency, greatly reducing the requirements on the skill level of the operator, and the fixture meets the positioning and clamping requirements of the machining. The structure is simple and compact, and has good processing technology and economy. For the structure and processing characteristics of similar valve body parts, general lathe machining with common machining precision, whether it is single-piece production or mass production, designing such fixtures can greatly improve the processability and economy of machining.
For more exciting articles, please refer to "Mechanical Workers" Cold Processing 2007 No. 1
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