Vacuum jig design principle and key points
I . In the workpiece deformation is the main problem of thin plate parts in the processing of parts affecting the machining accuracy
[1] The use of high-speed milling can better avoid the deformation of the workpiece due to cutting force, cutting heat, cutting vibration and other factors to ensure the machining accuracy and surface roughness of the parts
[2]. The use of vacuum clamping fixture to clamp the workpiece to a uniformly distributed load clamping force
The deformation of the workpiece caused by the clamping force is greatly reduced and the machining accuracy of the part is improved.
This paper introduces the design and application of a general-purpose vacuum clamping milling fixture.
Second, the structure design and working principle of vacuum adsorption fixture
The structural design of the vacuum adsorption fixture for high-speed milling of thin plate parts As shown in Figure 1, the clamping principle is to form a closed cavity through the workpiece 1, positioning element 3, seal 4, sealing plate 5 The vacuum port of the vacuum generator is connected to the closed cavity Ⅰ through the vacuum tube When the compressed gas flows from the supply port of the vacuum generator to the exhaust port, the closed cavity of the fixture generates a vacuum and presses the workpiece by atmospheric pressure. The clamping force is evenly distributed, reducing the deformation of the workpiece. After the workpiece is finished, the workpiece can be loosened by connecting the closed chamber II to the atmosphere.
III. Design points
The depth of the sealing groove is adjusted according to the type of parts to be processed, and the height of the sealing strip projection is about 0.15. To eliminate the impact of the flatness of the blank material itself. In order to let the seal better fixed in the sealing groove, we usually will seal the groove processing a dovetail shape can be firmly fixed seal
The seal can be made of soft materials, such as nitrile rubber, foam seal, silicone, etc. In the use of oil occasions need to choose oil-resistant seals. Or regularly check whether the seal has hardened and other phenomena. The design can choose the standard seal and then calculate the perimeter of the sealing groove, which is conducive to sealing effect
IV. Positioning datum selection principles
1. When the drawing specifies the benchmark, comply with the drawing requirements.
2. Select the surface that is not machined as a rough reference.
3. Select the surface that requires uniform machining allowance as the rough reference.
4. For all surfaces to be machined parts, the surface with the smallest allowance and tolerance should be selected as the rough datum.
5. In order to make the workpiece positioning stable, reliable clamping, the rough benchmark selected as flat and smooth as possible, does not allow forging flying edge, casting gate cut marks or other defects, and sufficient support area.
6. In the same dimensional direction of the rough benchmark is usually allowed to use only once.