Discussion on the process plan of machining large

2022-08-23
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Discussion on the process scheme of NC milling processing large shroud arc section

1 machine tool selection

according to the processing capacity of small and medium-sized parts processing workshop, XK715F small NC milling machine tool is selected as the processing machine tool, and the parameters are as follows:

worktable: 500 × 2000(mm × mm);

longitudinal stroke: 1400mm

transverse stroke: 500mm

equivalent displacement: X · y · Z 0.001mm/pulse

2 difficulties in the test process

how to ensure the selection of the coordinate system of each pre drilling position, ensure the dimensional accuracy of the inner and outer circles of the arc segment, and ensure the fitting of the positioning surface during clamping and moving

principle: as shown in Figure 1, the total weight of plastic on the initial vehicle only accounts for 10% of the vehicle weight. The origin of the machine tool will be located at the intersection P0 (x0, Y0, Z0) of the inner circle of the finishing dimension and the vertical centerline of the two alignment pins. At the same time, the alignment pins are used to locate, so that the arc segment has no impact on the dimensional accuracy when the outer circle moves along the circumference of the arc segment. After the NC milling determines and records the origin position of the machine tool, calculate the coordinates of the center of the arc segment relative to P0, and divide the arc segment into two segments for milling. After the inner and outer circle processing is completed, the pre drilling coordinate system is selected, and the arc segment guide is listed. Another 6 test pieces should be taken to recheck the wire cutting pre drilling center coordinates of the blade hole, and then the pre drilling is drilled according to the coordinates of each point

Figure 1 original coordinate system

process: take the product shown in Figure 2 as an example. In order to solve the above difficulties, two F50 H7 alignment pins, one auxiliary pin and one F8 H7 positioning pin are used. First clamp the sector blank on the workbench of the machine tool, mill out part of the arc of the excircle according to the maximum stroke of the machine tool, and then pad it with Q235-A · f steel plate 30 × eight hundred × 200. Clamp it on the workbench, drill and ream 3-f50h7 pin holes on the process steel plate, including 2 alignment pin holes and 1 auxiliary pin hole. The auxiliary pin hole is on the right side of the alignment pin. The relative spacing of the three pin holes is 260mm, and the pin hole is circumscribed with the outer circle of the arc section. Drive the alignment pin. Place the milled outer circle against the alignment pin and press it with a pressing plate. According to the alignment pin and figure 1, determine the origin of the machine tool at the position of the inner circle of the arc segment after finishing, and calculate the coordinates of the circle center of the sector segment relative to the origin of the machine tool. Mill the remaining excircles by moving the workpiece. Use the method of moving the workpiece when milling the outer circle to mill all the inner circles and the left radial end face. Drive the auxiliary pin and move the workpiece

Figure 2 product schematic diagram

place the left radial end face on the vertical centerline of the center of the alignment pin and clamp it. The purpose of this step is to establish the x2oy2 coordinate system with the intersection of the radial end face and the outer circle as the origin of the positioning hole coordinate system, so as to determine the center coordinates of each positioning hole. As shown in Figure 2

the calculation method of relative coordinates of each pre drilling position is discussed below

Figure 3 contour line and pre drilling location figure

Figure 3 is the contour line diagram of the shroud hole, which gives the selection of the original coordinates and the coordinate system after the corner and the location of the pre drilling. In order to ensure that the radiation end face is on the vertical centerline of the center line of the two alignment pins, according to the coordinate system shown in Figure 2, through the point coordinate query, list the coordinate values of the 10 positioning points to the right, as listed in Table 1. Move the origin of the machine tool to the intersection of the excircle and the left radial end face, drill 10 pre drilled holes to the right on the shroud as shown in Figure 3 according to the coordinates given in Table 1, drill and ream f8h7 locating pin holes near the pre drilled position at the left end, and drill and ream on the process steel plate at the same time. Move the sector. Insert the F8 locating pin. Follow the above steps to complete the processing of the remaining pre drilling. The guide vane hole profile is fitted by an arc, and the 11 point coordinates of the key points are given by the profile diagram as shown in Figure 3. At the same time, the converted coordinate points are listed in Table 2. Table 1 positioning point coordinates

serial number coordinates x2149.395246.907344.086440.800536.919632.314726.854820.414912 086y2107.218114.499125.358139.779157.744179.227204.201232.630364.477299.699

Table 2 3.5047/e line original and installation angle 35 ° coordinates

serial number original coordinates (x1oy1) installation angle 35 ° coordinates (xoy) x1y1xy10.0015 04388.029228.65139.837130.15043.638369.23137.56795.60722.. 5831.4180.8610.. 9930.04650.5581.471678.08120.01278.28831.52679.0531.191124.03886.. Most of the value consists of materials 14425.88661.12812 2414.0040... 5912.8870... 8720.33000.735

3 conclusion

by shifting the conical shroud sector, the processing load of gantry milling can be relieved, and the parts can be processed with xk715 F. by setting the alignment pin and auxiliary pin and their mutual positions, the positioning and alignment of the sector on the machine tool can be solved; Through coordinate transformation, the problem of determining the center of the locating hole after the part moves can be solved

in a word, according to the above method, the small equipment can solve big problems, ensure the drawing requirements, and the state after assembly is very good, meeting the assembly and processing requirements. According to the above method, the processing cost is saved, and the gap in the processing method of similar parts from large gantry milling to small CNC vertical milling is filled, and the main environmental problems are considered; It provides experience for processing similar parts in the future. (end)

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