The drawing is a simplified diagram of a split-shear gear box. It is a welded part with a complex shape and a forged welded structure. It is heavy in weight, large in size, and has strict dimensional accuracy and dimensional tolerance requirements. The entire cabinet consists of a box cover, a middle case and a lower case with a total weight of 88 900k g. Therefore, in the processing of each box, not only the processing method must be considered, but also the lifting capacity of the appropriate machine tool and the workshop crane should be considered. In order to ensure the lifting and processing accuracy of the box to meet the design requirements.
1. Main technical requirements
The dimensional accuracy and shape accuracy of the shaft hole have a great relationship with the mating quality of each bearing, and thus have a significant influence on the rotation accuracy, transmission stability, noise, and bearing life of each shaft and crankshaft. The dimensional accuracy of each shaft hole is IT7, and the shape accuracy of the shaft hole is within the dimensional tolerance range. The distance between the two crankshaft shaft holes and the input shaft shaft hole is 1 200mm, the tolerance is ±0.052mm, and the parallelism tolerance of the shaft hole axis and the box joint surface A is 0.025mm. The flatness tolerance of the joint surface between the respective casings was 0.04 mm, and the surface roughness value R a was 3.2 μm. The two positioning keyways between the middle box and the lower box are 2 495 mm from the center of the box, the tolerance is 0.1 mm, and the parallelism tolerance to the reference B is 0.05 mm. There are two positioning pin holes with a large spacing between the middle box and the lower box, the hole spacing is 3 240mm, and the pin hole size is φ 215H7.
2. Cutting and cutting gear box processing
In order to reduce the deformation of the gear box after machining, and to ensure its shape and position tolerance, coarse and fine machining is applied to each main machining plane and each shaft hole. In addition, in order to improve the machining accuracy of the gear box, in addition to the machining of the middle and lower casings and the cover of the gearbox on the boring and milling machine, the joint faces of the middle and lower casings and the positioning pin holes and positioning Important processing surfaces such as keyways are machined on 17m CNC gantry milling and boring machines. When roughing the box, firstly machine the plane B of the machining plane of the box, and use this surface as the processing reference plane and measuring base surface for the subsequent processing. Each shaft hole is finished after the joint surface between the boxes is finished.
In order to reduce the occupation time of the 17m CNC gantry milling machine, the gear box body is firstly carried out in the boring and milling machine during rough machining. The shaft holes are left in the diameter direction with a machining allowance of 8mm. The joint surface of each box and the cover is 2mm on each side. Machining allowance. The joint surface of each box and cover and the finishing of the four φ 215H7 locating pin holes are all carried out on a 17m CNC gantry milling machine. After the joint surface of the middle and lower tanks and the lid are processed, the middle and lower tanks and the lid are bolted together, and then the shaft holes are finished.
(1) Finishing of shaft hole When finishing the shaft hole, the middle and lower boxes and the cover are required according to the drawings, bolted, clamped on the workbench, and the workpiece is close to the bed box as much as possible to shorten the boring machine. The overhang of the spindle. The front and rear axle holes are machined on the W200HA boring and milling machine using a carbide tool to machine the front and rear axle holes from one end at a high speed. The part that cooperates with the front part of the split-shear gear box is the front panel. The front panel has a large shape and is difficult to process, and it is difficult to ensure the accuracy of the shaft hole, and the front panel and the shaft of the gear box are the same shaft. The diameter is matched, so the front panel should be machined with the crankshaft shaft hole. However, since the shaft hole is relatively deep, if it is completed in one process, the spindle length of the machine tool is long, and it is difficult to ensure the accuracy of the shaft hole. In view of the above situation, when the front panel and the gear box are combined to machine the shaft hole on the front panel, the shaft hole on the gear box body is processed to a section of 150 mm deep, which is processed as the shaft hole of the box after the front panel is disassembled. Find the datum. Therefore, after the front panel is disassembled from the gear box body, the aligned shaft hole on the gear box body is accurately aligned, and then the shaft hole on the gear box body is processed.
(2) Processing of locating pin holes Due to the large size of the locating pin holes between the boxes, if the appropriate matching margin is left, the working strength of the fitter is large and difficult, and it is difficult to ensure the accuracy; Therefore, it is decided that the positioning pin hole is separately processed by the 17m numerically controlled gantry milling machine, and no longer is reserved for the margin. However, in order to ensure the positioning size, when processing the pin hole on one of the boxes, the positioning size should be strictly controlled, and the actual positioning size value should be recorded; when another box is to be processed, the box is strictly processed. The positioning dimension recorded in the body is used to machine the positioning pin hole on the box, thereby ensuring the correctness of the positioning pin hole after the assembly of the box, eliminating the fitter assembly work and reducing the working intensity of the worker.
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