1 . Minimum bending radius
The minimum bend radius refers to the radius of the inner corner of the bend, as long as the outer fibers of the sheet do not break during the bending process.
It is only necessary to specify the minimum bending radius upon special request, and it should be increased as much as possible under normal conditions.
Table 1 lists the minimum bend radii for various thickness series of commonly used sheet metal materials.
Table 1 Minimum bending radius
| Thickness (mm) | 1 | two | 3 | 4 | 5 | 6 | 8 | 10 | 12 |
|---|---|---|---|---|---|---|---|---|---|
| Materials | |||||||||
| Q195 | two | two | × | × | × | × | × | × | × |
| Q235 | × | × | 5 | 5 | 5 | 10 | 10 | 10 | 15 |
| Q345 | × | × | 5 | 5 | 10 | 10 | 10 | 15 | 15 |
| Commonly Used Aluminum Alloy Sheet | two | two | two | 5 | 5 | 5 | × | × | × |
two . Minimum fold height
2.1 To ensure the quality of the folded part, the straight edge of the folded parts should not be less than the minimum folding height.
When bending to form a right angle, as shown in Figure 1, the minimum bending height is determined by formula (1).
h min = r+2t·····················(1)
Figure 1
2.2 Special bending height requirements:
If the project needs to double the bending height h ≤ r + 2t, the first thing to do is to increase the bending height, then fold it and process it to the required size.
After processing shallow arc grooves in the bending deformation zone, bend again as shown in Figure 2.
Figure 2
2.3 Height of the folded side ruler with chamfered corners.
When folding a folded part with beveled side edges, as shown in Figure 3.
The minimum height of the side edges is as in equation (2).
h min = (2~4) t > 3mm···············(2)
Figure 3
3 . Minimum hole margins
When bending is required after punching, the hole must be positioned outside the bending deformation area to prevent it from deforming during the bending process.
The distance from the edge of the hole to the inner surface of the folded edge is shown in Table 2.
Table 2: Minimum hole margins
 |
 |
||
|---|---|---|---|
| t (mm) | s (mm) | ||
| t (mm) | s (mm) | ≤25 | s≥2t+2 |
| ≤2 | Shit | >25-50 | s≥2.5t+2 |
| >2 | s≥1.5t+r | >50 | s≥3t+r |
4 . Bend line position
4.1 When partially bending a section, the bend line should not be at a location of dimensional abruptness to avoid bending cracks caused by stress concentrations at the sharp corners of the dimensional change.
The mutation distance S must be greater than the radius of curvature r, see Figure 4a.
Or drill holes or slots to separate the deformation zone from the non-deformation zone, see Figure 4b, 4c.
Note the figure size requirements: S ≥ R; groove width k ≥ t; groove depth L ≥ t + R + k / 2.
Figure 4
4.2 When the hole is located in the bending deformation zone, the process measurements to be taken before bending are shown in Figure 5.
Figure 5
5 . Bent parts must be designed to define process positioning holes
To ensure accurate positioning of the sheet in the die and avoid movements during bending that lead to product waste, bent parts must be designed with process positioning holes, as illustrated in Figure 6.
Especially for parts formed through multiple bends, process holes should be used as reference points for positioning to reduce cumulative errors and ensure product quality.
Figure 6
