What are the characteristics of the structure of hard alloy wire drawing molds
The structure of the hard alloy wire drawing die is basically the same as that of steel. It can be made into single process molds, as well as composite and continuous molds. However, due to its brittleness, it is not recommended to use it during punching, as the cutting edge is subjected to force on one side. The mold structures used in mass production are mostly continuous mold structures.
Regardless of the construction method used, compared to ordinary steel, hard alloy wire drawing molds have the following structural characteristics:
1. Most hard alloy wire drawing dies adopt a floating die handle structure to prevent the influence of press accuracy on the stamping process during stamping.
2. The mold frame has sufficient rigidity. The template should be 5-10mm thicker than the regular steel mold template, and 45 grade steel should be used more often.
3. The movement of the guiding mechanism mold should be stable and reliable, with high precision requirements. Generally, a ball guide column type mold frame is used, and a four guide column guiding structure is often used.
4. To avoid cracking of hard alloy during stamping, both concave and convex pads should be equipped with hardened pads.
5. The discharge and ejection device should adopt a fixed discharge plate structure as much as possible to avoid impact on the mold during stamping. When using an elastic discharge plate, it is necessary to install a small guide pillar to guide the discharge plate. To prevent impact force, the height h of the unloading plate pressure step should be one material thickness smaller than the thickness H of the guide plate, h=H-t-0.05
6. The gap between convex and concave molds is larger than that of steel molds, usually 0.15 times the thickness of the material or 1.5 times the gap between ordinary molds.
7. The guide plate, positioning pin, and guide pin should be heat-treated and hardened.
8. The structure should be relatively stable after the combination of the mold insert and the fixing plate.
Hard alloy wire drawing molds will experience shrinkage during the sintering process, and different batch numbers may have significant differences in shrinkage due to differences in composition, pressing, and sintering processes; Due to different shrinkage amounts, various parts of the mold often form a "saddle" or "bell mouth" shape. The fluctuation of the external dimensions of the mold blank, although in compliance with the mold blank standards, far exceeds the interference requirements during installation, resulting in severe unevenness in the bearing of pre-stress and a significant reduction in service life. Therefore, the mold blank needs to be ground with an outer circle, and a special fixture needs to be used on the grinding machine to grind with a diamond grinding wheel.
