Small knowledge of drawing parts-selection and design

Stretching is a stamping process in which flat blanks or hollow parts of a certain shape are molded into various open hollow parts by stretching. Thin-walled parts with cylindrical, stepped, box, spherical, cone and other complex shapes can be made by stretching. Therefore, stretching occupies a very important position in the stamping production of various industrial sectors such as automobiles, tractors, electrical appliances, instruments, electronics, aviation, aerospace, and daily necessities. Analysis of the selection and design problems of drawing parts: 1. The standard mold base should be used as far as possible for the manufacture of drawing parts, and the type and specifications of the standard mold base determine the type and specifications of the upper and lower mold bases. If you need to design the mold base yourself, the diameter of the circular mold base should be 30~70mm larger than the diameter of the concave template, and the length of the rectangular mold base should be 40~70mm larger than the length of the concave template, and its width can be slightly larger or equal to the width of the concave template . The thickness of the mold base can be determined with reference to the standard mold base, generally 1.0 to 1.5 times the thickness of the concave template to ensure sufficient strength and rigidity. For large non-standard mold bases, it must be designed according to actual needs, casting process requirements and casting structure design specifications. 2. The selected or designed mold base must be compatible with the relevant dimensions of the worktable and slider of the selected press, and must be checked. For example, the small outline size of the lower mold base should be at least 40-50mm larger on each side than the size of the leakage hole on the press table. 3. Generally, HT200 and HT250 are used as mold base materials, and Q235 and Q255 structural steels can also be used. For mold bases of large precision molds, cast steel ZG35 and ZG45 are used. 4. The parallelism of the upper and lower surfaces of the mold base should meet the requirements, and the parallelism tolerance is generally level 4. 5. The center distance of the guide sleeve and guide post mounting hole of the upper and lower mold bases must be consistent, and the accuracy is generally required to be below ±0.02mm; the axis of the guide post and guide sleeve mounting hole of the mold base should be aligned with the upper and lower planes of the mold base Vertical, when installing the sliding guide post and guide sleeve, the perpendicularity tolerance is generally 4 levels. 6. The upper and lower surface roughness of the mold base is Ra1.6~0.8μm. Under the premise of ensuring the parallelism, it can be allowed to be reduced to Ra3.2~1.6μm. Backing plate: The function of the backing plate is to directly bear and diffuse the pressure transmitted by the convex mold to reduce the unit pressure of the mold base and prevent the mold base from being partially compressed. The shape of the backing plate is the same as that of the concave mold, and its fixing method It is also fixed with screws and pins. The principles to be followed in the design process of drawing parts: First, ensure the normal use of the product, and then try to reduce the dimensional accuracy level and surface roughness level of the drawing parts under this premise, which is not only conducive to production, but also reject rate It will be reduced a lot accordingly, and the quality of the product will tend to be stable. Each stretch-part manufacturer has limited mechanical equipment, so when we design product solutions, we must make full use of these equipment as much as possible. In fact, in the final analysis, the quality and performance of the stretched parts are the key, and compliance with the later use is also a basic principle. Of course, in the process of processing and production, products will inevitably have defects. What we have to do is to reduce these unqualified rates to a small amount, so as to improve the production efficiency of stretched parts. Recommended article: There are coups for extending the service life of drawing stamping parts. Previous article: Analysis of common problems and solutions in bending forming