Abstract : In view of the deficiency of V-shaped block clamping device, a new type of multi-piece milling arc clamping fixture was designed.
Key words: V-shaped block clamping device; arc surface clamping device; positioning block; fixture
1 Introduction
When milling flat files and straight slots on a milling machine, most fixtures use V-block clamping devices, but for some parts with special shapes and sizes, as shown in Fig. 1, V-block clamping will give milling. Processing brings difficulties.
When the two sides of the milling part are clamped with V-shaped blocks, the clamping is performed with 10 outer circles. Since the length is too short, only 5 mm, although it can be clamped, the clamping force is not enough from the center of the clamping point. The workpiece is easily driven by the milling cutter during milling. If you increase the clamping force, it is easy to scrape the clamping surface into a triangular shape. If the external machining surface of 18 is clamped into the V-shaped block, the end surface of the workpiece cannot be positioned, resulting in machining errors.
For this purpose, we designed a multi-piece milling fixture that is clamped with an arc surface. It not only meets the requirement of workpiece clamping and positioning, but also simplifies the manufacturing process of the fixture. Using this fixture not only reduces the reject rate, but also greatly increases the productivity.
1. Special-shaped plug 2. Cylinder head screw 3. Special positioning block 4. Positioning block 5. Clip concrete 6. Clamping block 7. Clamping screw 8. Directional key 9. Countersunk head screw 10. Left and right cover plate 11 .Cylinder pin
2. Structure and technical requirements of multi-piece milling fixtures
2.1, multi-piece milling fixture structure shown in Figure 2. It is composed of a special plug 1, a positioning block 3, 4, a clamp 5, a clamping block 6, a clamping screw 7 and an orientation key 8. The fixture orientation key 8 is mounted on the work surface of the X62W milling machine, and the A surface is parallel to its work surface. After installation, the clamping screw 7 can be tightened.
2.2, the technical requirements of multi-piece milling fixture
(1) Ensure that each positioning block is in a straight line.
(2) Ensure that each positioning block can move flexibly within the slot.
(3) The center hole of the positioning block and the outer circle 18 of the part select the 18H/J56 transition fit.
(4) The center hole of each positioning block needs to be cut longitudinally along the center of the center hole after being processed.
2.3, multi-piece milling fixture positioning and clamping method
A group of parts to be machined are positioned in the center hole between the positioning blocks. Since each positioning block can be freely moved in the groove, the clamping screws are tightened after positioning, so that the positioning blocks are pressed to achieve the purpose of clamping. .
2.4, the choice of milling cutter
In the multi-piece milling jig, the machining of the end face, the side surface and the symmetry plane can be performed. After the machining surface is determined, different types of tools can be selected according to the corresponding plane. Figure 2 shows the milling of two planes of symmetry on a X62W milling machine using a combination cutter.
3, the conclusion
Multi-piece milling fixtures have the following features:
(1) A set of parts can be processed to significantly increase productivity.
(2) The three-point clamping method using V-blocks instead of V-blocks is ensured by the arc surface clamping, which ensures the product quality and reduces the reject rate.
(3) Milling of large feeds can be performed, and the workpiece is stable like "Tarzan". To ensure the accuracy of the position when processing.
(4) In actual production, if the number of positioning blocks of a multi-piece milling jig is increased, the productivity can be further improved.
(5) The fixture manufacturing process is simple and the actual operation is also more convenient.
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