Tolerance analysis of cold -formed hole
If the cold-formed profile has punching, botch, embossing and other surface-changing processing, the roll designer must explain the processing sequence. During the forming of the cold bending machine, some parts of the product are under tension, while the rest are under pressure. Before and after forming, the change in length of this part is affected by the roll design. Sometimes, the roll designer can use the final size or pre-estimated size for pre-punching.
However, in most cases, especially for porous molds, it is recommended to use the “test method” to pre-punch to inspect the roll. You can use laser beam, electrical discharge machining, or other methods to make pre-machined holes one by one. According to the measurement of the punching position before and after the cold bending forming, the punching position and pattern are adjusted, and sometimes it needs to be repeated to obtain the required hole size. The test must use the same roll pressure. Excessive pressure will thin the material and extend the product, causing errors in the punching position teat.
Analysis of the position tolerance of the cut in cold-formed forming
The depth of the cut section increases, the number of passes is reduced, the larger the bending radius/thickness ratio, and the increase the length of the product than before forming. If the ratio of the total area of the curved part to the total area of the straight section is large, and the number of passes of section forming is sufficient, the length of the final product is equal to the length of the starting sheet, and occasionally decreases.
The length reduction may be caused by thicker materials and higher portion. If the portion ratio is higher, the reduction in the longitudinal length of the curved part will be slightly higher than the reduction in thickness.