Selection of top punch #
1) The selection of the top punch shall be based on the bending force, and the load of the die shall not exceed the limit.
The punch with hydraulic clamping is also different from the ordinary punch, which needs special customization.
If the user selects special molds, it should be noted that the load of these molds is different from that of normal molds.
Correct selection shall be made to prevent the bending force from exceeding the load limit of the punch, resulting in collapse and cracking of the punch.
2) The shape of the top punch has a great impact on whether the workpiece can be bent and formed. When programming and selecting the punch, you must consider the shape of the punch and whether it interferes in the process of workpiece forming.
3) When the mold is programmed into the mold library of the CNC system, the overall dimension of the mold shall be programmed accurately. When the NC system automatically calculates the bending process, it can accurately calculate whether the mold interferes with the workpiece.
Selection of lower die #
- F0: required bending force per meter when the tensile strength of the material is 450N/mm² (KN/m);
- S: Plate thickness (mm);
- B: Minimum bending width (mm);
- V: Width of lower die opening (mm);
- R: Bending radius (mm);
1) The width of the V-shaped lower die must be determined according to the thickness t of the material according to the following formula.
The general formula is:
- t < 3mm V =(6～8) × t
- t ≥ 3mm V =(8～12) × t
Similarly, the width of the lower die V can be reasonably and scientifically determined according to the change of the minimum bending width b and the fillet radius r of the bending part.
2) The bending force generated in the bending process will gather on the worktable and also act on the die, so the load borne by the die cannot exceed the limit.
The bending force given in the table of the bending force is: when the tensile strength of the material = 45kg/mm² (450N/mm²), the required bending force per meter (T/m) under the condition that the opening of the lower die and the thickness of the plate are determined.
Quick reference table of common bending force
When the materials are different, the tensile strength of the material is σ Kg/mm², the required bending force (T/m) per meter can be calculated by the following formula.
F1 = F0· σ/ 450 （T/m）
Note: if the mold is used for forming, the bending force must be 2 to 3 times the normal bending force.
FP = (2… 3) FB
(FP: forming force FB: free bending force)