Knowledge that must be understood by the luggage hardware industry
When analyzing the relationship between the die edge shape and the punching force, shear behavior plays a key role. Regardless of how much the relief die wears, the initial clearance remains largely unchanged. As wear increases, the fillet radius of the punch and die becomes larger, which in turn increases the shear force required for the cutting process.
However, as both the punch and die experience wear, the actual clearance between them gradually increases. This leads to a reduction in the shearing force needed to cut the material, since the increased gap allows for more deformation before fracture occurs. In reality, even though the edge may appear rounded, the effective clearance still influences the cutting process. It's important to note that the imaginary clearance is different from the real one, and this difference significantly affects the punching force.
Moreover, the cutting edge formed by the relief angle β on the concave die tends to be more easily pressed into the material compared to a straight edge. This results in a more localized shear deformation, with higher squeezing forces concentrated near the tip. Consequently, the resistance to rupture is lower than that of a straight edge. The presence of a back angle on the die edge makes it weaker during the punching process. It’s also worth mentioning that the punch typically wears out faster than the die, and many die failures are initiated by damage to the punch. Therefore, to maintain balance, the design of the concave die edge should incorporate a back angle to compensate for the uneven wear between the punch and die.
In summary, a straight-edged die offers greater resistance to material shearing, while a die edge with a back angle reduces the punching force due to its weaker structure. This relationship between the die edge form and punching force is crucial in determining the performance and longevity of the tooling.
DIN 975 Thread Rods
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