1. Before designing the strip layout, it is necessary to understand the tolerance requirements of the part, material properties, press tonnage, press table, SPM (strokes per minute), feeding direction, feeding height, mold thickness requirements, material utilization, and mold life.
2. When designing the strip layout, CAE analysis should be performed simultaneously, mainly considering the thinning rate of the material, which should generally be below 25%. For particularly deep-drawn stainless steel materials, annealing can be performed after pre-stretching using a high-frequency annealing machine, and the thinning rate can be accepted up to 40%. When designing the strip layout, it is important to communicate more with the customer, and it is best to have the customer provide previous mold photos or structure diagrams for reference. Empty steps are also very important. If the mold length allows, leaving appropriate empty steps is very helpful for mold modification after trial runs.
3. The strip layout design is an analysis of the product molding process, and basically determines whether the mold is successful.
4. In continuous die design, lifter design is very important. If the lifter pin cannot lift the entire strip, automated continuous production will not be possible.
5. In mold design, the selection of mold materials, heat treatment, and surface treatment (such as TD, TiCN, TD time requires 3-4 days) are crucial, especially for drawing parts. Without TD, the mold surface will easily gall and wear.
6. In mold design, for holes or surfaces with small tolerance requirements, adjustable inserts should be made as much as possible to facilitate adjustment during trial molding and production, so as to easily achieve the dimensional requirements of the parts. Adjustable inserts should be made on both the upper and lower molds simultaneously. For date stamps, it is required to be removable on the punch press, without wasting time by disassembling the lower mold again.
7. When designing nitrogen springs, design according to the pressure analyzed by CAE, and do not design excessively large nitrogen springs to prevent product rupture. Generally, small pressure leads to product wrinkling, and large pressure leads to product rupture. To solve product wrinkling, the method of locally increasing draw beads can be adopted. First, use draw beads to fix the sheet, and then stretch it to reduce wrinkling.
8. During the first trial molding, be sure to slowly close the upper mold with the lower mold. For processes with stretching, be sure to use a fuse to test the material thickness at the material position. Trial molding should only be performed after the material position clearance reaches the material thickness, and the cutting edge must be aligned first. Please use active inserts for draw beads to facilitate the adjustment of the draw bead height.
9. During trial molding, the datum holes and datum planes must be matched with the mold before placing the product on the inspection fixture for measurement, or sending it to CMM for a 3D report; otherwise, it is meaningless.
10. Red lead must be properly applied, and the fitting rate must reach over 80% before the cutting edge can be opened and a CMM report can be made. Alternatively, if the datum holes and datum planes have been matched and the product is very stable and tight, the fitting rate can be appropriately reduced. Applying red lead is a very important matter; otherwise, the product will be unstable, and it will be impossible to judge the late-stage mold modification, and the part dimensions will not meet customer requirements.
11. Customer sample requirements: Generally, it starts with laser sample → cut-opening sample → 100% OK sample. In the laser sample stage, red lead should be prepared, feeding adjusted, and issues such as cracking, wrinkling, and dimensional tolerance should be resolved. When opening the cut-opening sample, the main problems are basically corrected, and the subsequent stage involves fine-tuning (local mold improvement).
12. If the customer insists on a cutting edge but the process conditions are not mature, consider opening a soft material cutting edge (that is, directly using 45 steel to open the cutting edge, and directly welding when modifying the cutting edge, and then opening the formal hard material cutting edge after the dimensions are OK).
13. For 3D complex products, 3D laser method can be used for laser engraving. Before 3D laser engraving, be sure to make 3D graphics, use CNC to make benchmark points, and then send them to 3D laser engraving. 3D laser engraving also needs to make positioning sand molds.
14. For high-strength steel plates, the cutting edge material should be A88 or V4 and other hard alloy materials.
15. During die spotting, in order to test the stretching effect, sandpaper can be placed on different positions of the material to test the effect. After confirming the effect, active draw beads or active knurled dot matrix (that is, grinding a plated part into knurled dots) are used at the corresponding positions to create friction to hinder material flow.
16. For parts with more bends, adjust the bending process step by step during mold adjustment.
17. When adjusting the forming angle, you can reduce the R angle during bending or move the reference of the bending line to achieve the purpose of reaching the forming angle.
18. During mold adjustment, shims are mostly used to adjust the height of the forming punch or to move the forming punch left and right, back and forth. Shims are generally made of stainless steel hard sheets. (If the customer does not allow the use of shims, wait until the mold is adjusted before making new workpieces for the customer.)
19. For mold forming parts made of stainless steel, TD cannot be used; (TiCN) or PVD should be used.
22. The slope of the scrap funnel should be no less than 30 degrees. For low-angle scrap boxes (Scope box), pneumatic vibration can be used to solve the problem.
23. For trimming lines affected after forming, trimming should be selected after forming, and transverse cutting can be used to achieve special positions.
24. For multiple datum holes, it is best to use one-time punching to form them to avoid affecting the accuracy after step-by-step punching.
25. For trial mold analysis, it is necessary to analyze the material strip after trial molding step by step, and attach the red lead material strip.
26. For product cracking, multiple methods can be adopted, such as adding a package during the initial stretching, extrusion, increasing the forming area of the sheet bar, and opening holes. CAE analysis should be performed before mold modification.
27. Product materials are divided into two types: coil and sheet. Some coils need to be slit again to the material strip width after arriving at the factory. Usually, the dimension during slitting has a negative tolerance (negative 0.5 mm), and the inner diameter of the coil must meet the size of the feeding rack to avoid being too large, too small, or too heavy.
28. During mold processing, the pin holes cut by wire EDM are usually used as the reference for touching numbers. After CNC programming, the operator needs to provide the coordinates of the two holes to the programmer, who calculates the angle and then rotates the program by an angle before processing. Usually, edge machining is performed during the initial processing of the template, and angle requirements are not necessary. 30.
29. The concept of fine blanking is to leave no blanking clearance (or only leave 0.5%). Generally, the blanking clearance is 10% of the material thickness. The thicker the material, the larger the clearance ratio.
30. If the dimensions of the hardware sample do not meet the requirements, they can be achieved through forming, including using a plum blossom pile, re-flattening, simple punching, and other methods to remove burrs. The above is a summary of experience in actual stamping work. I hope it will be helpful to those who read this article, improve the on-time qualification rate of molds, and reduce the number of trial moldings.
Post time: Jun-25-2025