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Difficulty solving the thin-walled shell process: four-station flip fixture


Reprinted from: JIAJUXIA
It is difficult to guarantee the technical requirements of the conventional motor clamps of the motor seat shell parts.The pneumatic turning fixture can be used to clamp four workpieces at a time, meeting the concentricity requirements of the front and bottom surfaces, and reducing positioning errors. The design idea is as follows:

Figure 1 Cast aluminum motor base housing

part 01 Process analysis
The part is an anisotropic polyhedron, and the processing surfaces are in a 90 ° relationship.If there is no five axis, consider designing a pneumatic flip fixture on the three axis.

Step 1.Use a vise to clamp on another processing center, and pre-process two a and b points during the processing as the process positioning pins for post-processing (these two places have no effect on the performance and appearance of the product).

Figure 2 bottom surface 3d (process 1)

Steps 2 and 3 (see Figures 3 and 4) are completed at the same time on the pneumatic turning fixture.

Figure 3 Top 3d (Step 2)

Figure 4 3d thread surface (process 3)

part 02 Principle of fixture design
According to the conventional processing, when completing the procedures 2 and 3, it needs to be clamped twice. The pneumatic turning fixture can process four parts at the same time, mainly by the base plate, the movable turning table, the rotary support shaft, the support plate, and the V-shape. It consists of a guide limit support block, a turning cylinder and a steering compression cylinder.

Figure 5 Fixture body

part 03 design of clamping device
3.1 V-shaped guide limit support block design
There are 4 sets of V-shaped guide limit support block assemblies in the left and right groups, which can realize the bidirectional positioning of the horizontal and vertical position limits, and can also play a supporting role to increase the rigidity of its movable flipping table, and It acts as a stroke limit for the cylinder for turning.

Figure 6 V-shaped guide limit support block

3.2 Cylinder design for turning
The movement of the turning cylinder is designed in the lower center of the movable turning table, in addition to the balanced thrust, it serves as an additional support to maintain the rigidity of the movable turning table, while saving working space and shrinking unnecessary processing and avoidance.

Figure 7 Position of the cylinder for turning

3.3 Steering Cylinder Design
The parts are clamped on the movable turning table by two pins on one side, and the clamping of 4 workpieces is completed at the same time by turning and pressing the cylinder. When the workpiece is assembled and disassembled, a total of 10 steering and pressing cylinders on the upper and lower sides are simultaneously clamped. The pressure block is lifted or pushed down, so that there is space for taking parts.The pressure block is roughly located on the symmetrical surface of the workpiece, and the pressing force is balanced to achieve clamping.

Fig. 8 Steering and pressing cylinder before and after pressing

part 04 Use of Fixtures
When the clamp turning cylinder is pushed out, the steering compression cylinder is opened, and the parts are positioned and clamped by two pins on one side.After the steering compression cylinder is closed, the workpiece is compressed and the turning cylinder is pushed out. At this time, the v-shaped guide on the back of the workpiece is limited. The position support block is completely fitted.The cnc is started to perform this surface processing.The state of the fixture in step 2 is shown in Figure 9.

Figure 9

After processing the above surface, the pressing action of the steering compacting cylinder remains unchanged, the turning cylinder shrinks, and the movable turning table is turned 90 °, and the v-shaped guide limit support block functions on the side of the workpiece to ensure its vertical Degrees and displacement errors before and after rotation, so that two steps of one clamping process are realized. The state of the fixture in step 3 is shown in Figure 10.

Figure 10

part 05 other processing details
When the workpiece is processed, the forming knife is used to complete the processing at one time. Because the part itself is an aluminum casting housing, its wall is thin, shaped, the machining margin is small, and there are requirements for roundness. The size of the circle will be more round than the trajectory, and the points on the machining shell circle will be balanced.