The experience and skills of designers play a crucial role in the design and manufacturing of motor molds. The rationality of the design can only be confirmed through trial molding; The motor mold needs to be tested and modified multiple times before it can be finally completed. In production practice, some motor molds often encounter various problems once they are put into use on the production line, which cannot meet the production or technical requirements of the product, resulting in abnormal shutdown of the production line and bringing many unstable factors. So, how to improve the stability of motor molds has become a practical problem faced by motor mold manufacturing enterprises. 
Stability and influencing factors of motor molds and stamping forming
What is stability? Stability is divided into process stability and production stability. Process stability refers to a process plan that meets the stability requirements for producing qualified products; Production stability refers to the stable production capacity during the production process. 
Due to the fact that most domestic motor mold manufacturing enterprises are small and medium-sized enterprises, and a considerable number of them are still in the traditional workshop style production management stage, they often overlook the stability of motor molds, resulting in long development cycles and high manufacturing costs, which seriously restricts the development pace of enterprises. 
Let's first take a look at the main factors that affect the stability of motor molds and stamping forming, namely: the usage method of motor mold materials; Strength requirements for motor mold structural components; Stability of stamping material performance; The fluctuation characteristics of material thickness; The range of material variation; The resistance of the stretching tendon; Range of variation of edge pressure; Selection of lubricants. How to select materials correctly and provide examples
As is well known, the metal materials used in stamping motor molds involve many types. Due to the different roles played by various parts in motor molds, the requirements and selection principles for their materials are also not the same. Therefore, how to reasonably select motor mold materials has become one of the very important tasks in motor mold design. 
When selecting motor mold materials, in addition to requiring the material to have high strength, high wear resistance, and appropriate toughness, it is also necessary to fully consider the characteristics and production requirements of the processed product material in order to achieve the stability requirements of motor mold forming.
In practical operation, due to the tendency of motor mold designers to choose motor mold materials based on personal experience, unstable motor mold forming often occurs in stamping due to improper material selection of motor mold parts. Here are some examples to illustrate. 
On an iron plate with a material thickness of 1.2mm (shear strength of 64kgf/mm2), process a circular hole with a diameter of 2.8mm. ① Shear force: P=Lt τ. Among them, L: cutting contour length (mm); t: The thickness of the material (mm); τ: The shear strength of the material (kgf/mm2); d: Convex mold diameter (mm); P=3.14 × 2.8 × 1.2 × 64=675kgf ② Stress at the convex die edge: σ S=4t τ/d. That is to say, σ S=4 × 1.2 × 64/2.8=110kgf/mm2
Fatigue characteristics of tool steel
When σ S is 110kgf/mm2 and SKD11 punch material is selected, the punch edge may be damaged when the punch times reach about 9000. If the material is replaced with SKH51, it is expected to increase the punch count to around 40000. From this, it can be seen that in the stage of motor mold design, it is necessary to perform necessary strength verification calculations on the structural components of the motor mold, and there are the following precautions when selecting materials:
① The stress borne by the punch is less than the allowable compressive stress of the punch material
② To improve the bending strength of the convex mold, materials with high elastic coefficients should be selected
③ According to Euler's formula, conduct stability verification and comprehensively weigh various factors that affect stability
It is worth noting that during the stamping process, each stamping sheet has its own chemical composition, mechanical properties, and characteristic values closely related to stamping performance. The unstable properties of stamping materials, fluctuations in stamping material thickness, and changes in stamping materials not only directly affect the accuracy and quality of stamping processing, but may also lead to damage to motor molds. 
Taking stretching ribs as an example, they play a very important role in stamping forming. In the process of stretch forming, the formation of the product requires a certain amount of tensile force that is appropriately distributed along the fixed periphery. This tensile force comes from the force of the stamping equipment, the deformation resistance of the edge material, and the flow resistance on the edge ring surface. If the generation of flow resistance relies solely on the action of edge pressure, the frictional force between the motor mold and the material is not sufficient. 
To this end, it is necessary to install tension bars on the edge pressing ring that can generate significant resistance to increase the resistance of the feed, thereby causing significant plastic deformation of the material to meet the requirements of plastic deformation and plastic flow of the material. At the same time, by changing the magnitude and distribution of the resistance of the stretching ribs, and controlling the speed and feeding amount of the material flowing into the motor mold, effective adjustment of the tension and its distribution in each deformation area of the stretching part can be achieved, thereby preventing quality problems such as product cracking, wrinkling, and deformation during stretching forming. As can be seen from the above, in the process of formulating stamping processes and designing motor molds, the magnitude of tensile resistance must be considered. The stretching ribs should be arranged and the form of the stretching ribs should be determined according to the range of variation of the edge pressure, so that each deformation area can be formed according to the required deformation mode and degree.