The precision of stamping parts in Dongguan CNC factory is the same as that of panel display media mold. The accuracy of the dimension and position accuracy of the stamping parts depends almost on the blanking accuracy. Therefore, the accuracy of compound stamping of compound die is the most typical and representative of many kinds of common stamping dies with different structures.
Analysis of stamping accuracy of stamping die
Dongguan CNC processing factory analyzes the actual error of stamping parts in each period from die production to failure and scrapping, which shows the increasing period and trend, and analyzes the increasing factors. The so-called initial error is the error of punching parts before the new die is put into production and the first grinding; The stamping error before the die is scrapped after grinding for about 20 times is called conventional error; The maximum allowable error of the last batch of qualified stamping parts before die failure is called limit error. On the spot of Dongguan CNC processing plant, the basis of determining the grinding life of stamping die is the burr height of punching and blanking. Because any forming part has blanking operation (blank blanking or punching), especially for compound die. Therefore, it is very important to check and measure the burr height of stamping parts according to the enterprise standard or jb4129-85 "burr height of stamping parts".
The initial error of the die is usually the smallest in the whole life of the die. Its size mainly depends on the manufacturing accuracy and quality of the die, the size of the stamping part, the material thickness, the size and uniformity of the gap value. The manufacturing accuracy and quality of the die depend on the die making process. For the medium carbon steel composite blanking die with material thickness t ≤ 1 mm, the experimental results and production practice show that the burr height of the blanking die manufactured by WEDM is 25% - 30% higher than that manufactured by forming grinding or NC and CNC continuous path coordinate grinding, that is, precision grinding process. This is because the latter not only has high machining accuracy, but also the roughness Ra value of machined surface is one order of magnitude smaller than the former, which can reach 0.025 μ m。 Therefore, the manufacturing accuracy and quality of the die determine the initial stamping accuracy of the die, and also create the initial error of the stamping part.
The conventional error of stamping parts is the actual error of stamping parts from the first grinding to the last grinding. With the increase of grinding times, the dimension increment caused by the natural wear of the edge increases gradually, and the error of the punch increases. When the error exceeds the limit deviation, the stamping parts will be unqualified, and the die will be invalid and scrapped. The size of the upper hole and inner shape of the punch will gradually decrease due to the wear of the punch; The size of blanking will increase gradually due to die wear. Therefore, the upper hole and inner shape of the stamping part are made according to the one-way positive deviation tolerance and the maximum size close to or almost equal to the limit. In the same way, the blanking tolerance of stamping parts is marked according to the one-way negative deviation, and the die is made according to the minimum size close to or almost equal to the limit. In this way, the conventional error range of the stamping parts is expanded, the grinding times of the stamping die are increased, and the service life of the die is improved.
The limit error of stamping parts is the maximum allowable dimension error of stamping parts with limit deviation. This kind of stamping is usually the last batch of qualified stamping before the die is scrapped.