What is Bending
The plastic forming process of metal sheet materials
Bending - Under the pressure of the upper or lower die in the bending process, the metal sheet first undergoes elastic deformation and then enters plastic deformation. At the beginning of the plastic bending stage, the sheet is freely bent. As the upper or lower die applies pressure to the sheet, the inner surface of the V-shaped groove of the lower die gradually tightens, and at the same time, the radius of curvature and the bending force arm gradually decrease. Continue to apply pressure until the stroke ends. When the upper and lower dies are in full contact with the sheet metal at three points, a V-shaped bend is completed, which is commonly known as bending.
1. Process principle
The plastic deformation of metal sheet between the upper and lower molds involves three stages:
Recoverable deformation occurs during the elastic deformation stage.
During the plastic deformation stage, the lattice slip of the material forms permanent deformation.
During the correction stage, the rebound amount is reduced through overtravel pressure.
During the forming process, the sheet metal and the V-shaped groove of the lower die form a three-point full contact, ensuring that the bending axis coincides with the center line of the die.
2. Process parameter matching
The processing parameters should follow the following matching rules:
The ratio of V-groove width to plate thickness is 6:1 to 12:1 (for stainless steel, the upper limit is taken).
The minimum bending edge L≥(V/2)+1.5T (T is the material thickness). For example, when a 1.5mm plate is matched with a V6 groove, the minimum length on one side is 6.0mm
The pressure calculation adopts the approximate formula P=650s²L/(1000V), where s is the plate thickness (mm) and L is the bending length (mm).
3. Quality Control
The quality control system includes:
Four-stage inspection: full-size measurement of the first piece, key recheck of the second piece, batch inspection, and archiving of the last piece
Angle tolerance: ±1° (Precision grade), ±1.5° (Commercial grade), ±3° (Industrial grade)
Dimensional tolerance: ±0.3mm when the short side length is ≤10mm, ±0.5mm when it is > 10mm
4. Mold design
Easy mold design follows special specifications:
The forming height of the bridge needs to be compensated by an additional 0.2mm
For plates with a thickness of no more than 0.8mm, an additional 5° Angle compensation is required
The width of the segment difference forming is limited to within 30mm, and the N-side positioning method is preferred
R-angle grinding can improve bending fracture, and the stepwise forming strategy can solve the problem of material pulling
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