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Research on the Problem of Surface Strain of Stretching Die and Preventive Measures

by:Fortuna     2021-03-05
In the stamping process, molds such as stretching, bending, flanging, sheet roll forming, etc. all have a common feature. The contact surface of the mold and the processed material during the forming process of the stamping part must be relatively sliding, stretching the mold and the stamping part The surface is prone to strain, which is also called napping and scratching. The consequence of the strain is to affect the appearance and product quality of the product, and normal production cannot be carried out. The strain is particularly serious when the working pressure of forming is relatively large or when the austenitic stainless steel material is stretched and formed. Combining years of scientific research and practical experience, the stamping parts factory analyzes this problem and discusses its solution. There are two main reasons for the strain of the metal drawing mold: One is due to the macroscopic mechanical unevenness of the mold convex and concave mold surface, or the inclusion of other hard particles between the molded material and the mold convex and concave mold surface. The surface of the stamping part or the surface of the convex and concave molds causes mechanical wear. The solution is to carefully polish the convex and concave surfaces of the mold and strengthen the management of the production environment. The second is the strain caused by the adhesion and wear between the surface of the stamping part and the surface of the convex and concave molds of the drawing die, which is also the most common and difficult to solve in production. To solve the problem of strain in the forming process of drawing dies and stamping parts, the starting point should be to change the nature of the contact pair in accordance with the basic principle of reducing adhesive wear. The three parties that constitute the pair of contact pairs are analyzed below, namely, the raw material of the stamped part, the relationship between the stamping part and the mold, and the drawing mold. 1. Through surface treatment of raw materials, such as phosphating, spraying or other surface treatments on raw materials, a non-metal film layer is formed on the surface of the formed material, which can greatly reduce or eliminate the strain on the workpiece. This method is often The cost is high, and additional production equipment and production processes need to be added. Although this method is sometimes effective, it is rarely used in actual production. 2. Adding a layer of PVC or other film between the drawing mold and the forming material can sometimes solve the problem of straining on the stamping parts. For the production line, the continuous supply of film can be achieved through the mechanism, and for the periodic production of stamping equipment, a film needs to be added for each stamping part produced, which affects the production efficiency. This method is generally costly and generates a lot of waste. It is advisable to use this method for the production of small batches of large workpieces. In some occasions where the forming load is very small, sometimes by adding lubricating oil or adding EP (extreme pressure) additive lubricating oil can solve the problem of stamping parts strain. 3. In the aspect of drawing mold, by changing the material of the convex and concave mold of the mold or performing surface treatment on the convex and concave mold of the mold, the contact pair properties of the material to be formed and the convex and concave molds are changed. Practice has shown that this is an economical and effective method to solve the strain problem, and it is also a widely used method at present. In summary, there are many ways to solve the problem of surface strain on the convex and concave molds of drawing dies and stamping parts. For specific cases, the application method should be selected according to the size of the workpiece and the load, the production batch, and the type of material to be processed. In all methods to solve the strain problem, it is better to use cemented carbide as the mold material, chemical vapor deposition and TD coating treatment on the convex and concave mold surfaces, and TD coating treatment is cost-effective. Recommended article: Several structural forms of commonly used bending dies and their respective characteristics Previous article: Several precautions to be kept in mind in the processing of stamping elbows
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