Key technology experience sharing of progressive die stamping

Progressive die design must reasonably analyze the stamping process, determine the best stamping process plan, calculate the relevant process parameters, reasonably design the layout plan, and select the mold structure type. The key technologies of multi-station progressive die stamping include layout process design, blank calculation, wrinkling, fracture prediction, and springback prediction and control.　　 The following is my key technical experience of progressive die stamping, just for reference.　　(1) Layout process design

Layout is the key to the design of progressive die. Determine the position of the part and the relationship between the stations, the positioning method, the material utilization rate and the mold structure design. The quality of layout has a great influence on mold structure, life, and quality of stamping parts. When nesting, first determine whether to use waste nesting, no waste nesting, mixed nesting or nesting nesting, and whether it is single-row, double-row or multi-row layout according to the shape of the workpiece. The principles that should be followed for layout are: punch first, then blank, first inside and then outside; punch first the parts with high dimensional accuracy, and then punch the parts with low dimensional accuracy; first punch the parts with high coaxiality and symmetry requirements and the inside The center hole is used to guide the positioning and blanking. It should be noted that: for stamping parts with high requirements for shape and position accuracy and size, the number of stations should not be too many during layout to reduce the cumulative error; for stamping parts with small dimensions and complex shapes, when the distance between the stations is small, Vacant stations should be designed to open up the actual punching station spacing.　　(2) Precise calculation of blanks

The design of the blank shape and flanging trimming line directly affects the quality of the die and stamping process design. Reasonable design of the blank shape helps to reduce the required punching force, reduce die wear, and increase die life; it can improve the stress and strain state of the material during stamping, increase the forming limit of the material, reduce the occurrence of forming defects, and improve the forming quality of stamping parts. Accurate design of blanks or flanging trimming lines can reduce workpiece trimming work and reduce mold manufacturing and production costs. For workpieces with complex shapes, it is difficult to obtain a satisfactory blank size. With the development of computational simulation technology, the accuracy of the blank can be improved through simulation calculation.　　(3) Wrinkle and crack prediction

Due to the complex structure of the progressive die workpiece and the influence of factors such as process parameters and lubrication conditions, it is prone to cracking and wrinkling defects, resulting in parts scrap. Before determining the structure of the progressive die, the stress and strain state, thickness change and forming limit of the material during stamping forming are obtained through finite element numerical simulation, and the wrinkle and fracture of each station during the forming of the workpiece are analyzed and the results are predicted. In order to improve the mold structure and modify the forming process parameters, such as optimizing the blank holder force to obtain a reasonable blank holder force value, it can not only suppress wrinkles, but also prevent cracking.　　(4) Rebound prediction and control

The springback after sheet metal forming is an inevitable phenomenon in the process of stamping and forming. There are many progressive die stations, and the prediction and control of springback are more complicated. The presence of springback directly affects the forming accuracy of the workpiece and subsequent assembly. The size of springback is affected by many factors such as material, mold gap, bending radius, blank holder force and drawbead. In order to control the amount of springback within the allowable range, the springback is controlled through continuous process trial and mold repair, resulting in a long mold manufacturing cycle, high cost, and low workpiece accuracy. The design of progressive die must predict and control the springback. Through numerical simulation technology, the sheet metal stamping forming and its springback can be predicted, so as to modify the mold profile of the corresponding station of the progressive die to compensate for the springback. Corresponding countermeasures are used to control the amount of springback so that the workpiece meets the accuracy requirements.