Gear pump housing requires two holes for high precision machining. In the medium and small batch production, the general use of general-purpose machine tools and special tooling to processing, this processing method is difficult to achieve accuracy requirements. Our factory internship factory production of this part, from the processing methods, cutting tools, fixtures continue to improve, a better solution to this problem, the processing quality is stable and reliable. 1 pump hole accuracy requirements and processing methods Figure 1 gear pump body processing two holes in the process diagram. As can be seen from Fig. 1, the aperture 12.5 is at level 7, and the two apertures have different ultimate sizes. The larger aperture R18.41 is closer to level 8, and the coaxiality, perpendicularity and position tolerances are required, especially the position tolerance is very small. Therefore, the hole is difficult to process. After repeated tests and improvements, the following processing methods are adopted: the two holes are machined on both end faces after the 4-φ9 hole machining process, and the accuracy of a pair of angle holes in 4-φ9 is increased to φ9H8 for positioning. Then three holes are machined with R18.41 and φ12.5. The first process: In the lathe with rotary chuck car indexing R18.41 hole to R18.31 +0.065 + 0.035 (R18.41 with casting bottom hole), drill φ12.5 hole to φ11.5, and then boring to φ12 .4 ± 0.01. The second process: the design of special composite reamers, lathe (due to drilling spindle rotation accuracy is low, can not use drilling) at the same time reaming R18.41 and φ12.5 coaxial hole. Big hole hinge to R18.41 + 0.055 + 0.025, two small holes hinge to φ12.5S7 size. The tool is mounted on the spindle (remove the chuck) and the tail end of the tool is provided with guide bearings on the clamp. Fixture mounted on the carriage (remove the knife holder), with a straight line indexing fixture. The third process: Drilling machine with a floating reamer to one of the small holes hinge φ12.5F7 size requirements. 2 fixture design hole processing as the second process is the key process, here only describes the fixture design process. (1) fixture program and structure: Select the pump body G surface and two φ9 diagonal holes for the positioning of the fixture with two pins on one side of the positioning. Linear indexing form. Clamp the part with two hook clamps. Figure 2 shows the structure of the fixture (Note: the figure shows only the key dimensions and the main part number). Clamp body 1 is an angle iron, with screws, tapered pins mounted on the carriage. Moving indexing block 2 and clamp body 1 through the dovetail guide rail, and with the bolt 3 lock. The indexing block 2 is provided with a cylindrical pin 4 and a chamfered pin 9 by which the part is positioned on the indexing block 2 and is pressed by the two hook- Seat 6 is used to support the rear end of the tool. With hand-drawn cylindrical indexing on the agency. For the convenience of operation, the workpiece is installed on the right side of the fixture, and the fixture body is provided with holes on the indexing block for the tool to enter the workpiece processing. In order to prevent the chips from entering the joining surfaces of the members 1 and 2, the chip holder 10 is fitted in the hole of the clip body 1. 1. Clamping body 2. Moving indexing block 3. Locking nut 4. Cylindrical locating pin 5, 12. Bushing 6. Support seat 7. Cylindrical pin 8. Screw 9. Cutting edge locating pin 10. Anti-chip sleeve Riding Seam 13. Sealing Block 14. Hook Pressing Mechanism 15. Indexing Alignment Mechanism (2) Fixture Operation: Insert the work piece into two positioning pins, tighten the hook-shaped pressure plate nut, and longitudinally move the carriage so that the cylinder of the alignment mechanism 15 The pin is inserted into the pin hole in the first hole. After machining the first hole, loosen the two lock nuts 3, pull out the cylinder pin of the alignment mechanism 15, move the index block 2 so that the cylinder pin of the alignment mechanism 15 is inserted into the second hole Pin hole, and tighten the nut 3, the processing of the second hole. (3) fixture installation requirements: manufacturing, the indexing agencies for the cylinder pin and bushing 12 with the preparation, with the gap of not more than 0.01mm. Installation, to ensure that the fixture center line K and spindle lathe coaxiality, coaxial tolerance of 0.015mm. P positioning and positioning of the lathe spindle axis perpendicular to the tolerance of 0.02mm. When the fixture is installed and adjusted, the horizontal feed must be locked, and the vertical feed should be set as dead stop iron. (4) Fixture features: The principle of reference coincidence, positioning error is small, higher indexing accuracy. Tool support at both ends, beating small, high precision machining hole size. Clamping reliable, easy to operate. The long-term use of proof, can fully guarantee the processing accuracy requirements, the downside is the process of observation is not convenient.
