Overview of the stability of die and stamping forming

The stability of the mold is a practical problem faced by mold manufacturing companies. Since most of the domestic mold manufacturing companies are small and medium-sized enterprises, and a considerable number of these companies are still in the traditional workshop-style production management stage, they often ignore the stability of the mold. , Resulting in a long mold development cycle, high manufacturing costs and other issues, seriously restricting the pace of development of the enterprise.

So what is stability? Stability is divided into process stability and production stability. Process stability refers to a stable process plan for producing qualified products; production stability refers to a stable production capacity during the production process.

First of all, we must understand the main factors that affect the stability of molds and stamping forming. They are: the use of mold materials; the strength requirements of mold structural parts; the stability of stamping material performance; the fluctuation characteristics of material thickness; the range of material changes ; The resistance of the tensile ribs; the range of the blank holder force; the choice of lubricants.

How to select materials correctly and examples

As we all know, the metal materials used in stamping dies involve many types. Due to the different roles of various parts in the dies, the requirements and selection principles for their materials are also different. Therefore, how to select mold materials reasonably has become one of the most important tasks in mold design.

When selecting mold materials, in addition to the requirements that the material must have high strength, high wear resistance and appropriate toughness, it must also fully consider the characteristics and output requirements of the processed product material, so as to achieve the stability of mold forming Claim.

In actual operation, because mold designers tend to choose mold materials based on personal experience, the problem of instability of mold forming due to improper selection of mold parts often occurs in stamping. .

Fatigue characteristics of tool steel

When σS is 110kgf/mm2, the punch material is SKD11, and the punching frequency reaches about 9000 times, the punch cutting edge may be damaged. However, if the material is replaced with SKH51, the stroke rate can be increased to about 40,000 strokes. It can be seen that in the mold design stage, it is necessary to carry out the necessary strength check calculations for the mold structural parts, and the following precautions should be taken when selecting materials:

1. Stress on the punch

2. In order to improve the bending strength of the punch, a material with a large elastic coefficient should be selected

3. According to Euler's formula, check the stability ability

Comprehensive weighing of various factors affecting stability

It is worth noting that in the stamping process, because each stamping sheet has its own chemical composition, mechanical properties and characteristic values u200bu200bclosely related to the stamping performance, the performance of the stamping material is unstable and the thickness of the stamping material is unstable. Fluctuations and changes in stamping materials not only directly affect the accuracy and quality of stamping processing, but may also cause damage to the mold.

Take stretch ribs as an example, which occupies a very important position in stamping forming. In the stretch forming process, the forming of the product requires a certain amount of tension that is appropriately distributed along the fixed periphery. This tension comes from the force of the stamping equipment, the deformation resistance of the material at the edge, and the flow resistance on the blank holder surface. . If the flow resistance only depends on the blank holder force, the friction between the mold and the material is not enough.

For this reason, it is also necessary to install a tensile rib that can produce greater resistance on the blank holder to increase the resistance of the feed, so that the material produces greater plastic deformation to meet the plastic deformation and plastic flow of the material Requirements. At the same time, by changing the size and distribution of the resistance of the stretched ribs, and controlling the speed of the material flowing into the mold and the amount of feed, the effective adjustment of the tensile force and its distribution in each deformation zone of the stretched part is realized, thereby preventing stretching. Product quality problems such as cracks, wrinkles, and deformation during forming. It can be seen from the above that in the process of formulating the stamping process and mold design, the size of the tensile resistance must be considered, and the tensile ribs are arranged according to the change range of the blank holder force and the form of the tensile ribs are determined, so that each deformation area is deformed as required. The way and the degree of deformation are completed.

In order to solve the problem of mold stability, it is necessary to strictly check the following aspects:

In the process development stage, through the analysis of the product, the defects that may occur in the product are predicted, so as to formulate a stable manufacturing process plan; implement the standardization of the production process and the standardization of the production process; establish a database, and Continuously summarize and optimize it; with the aid of CAE analysis software system, get the most optimized solution.