Sloping edges towards the bending line must be avoided, otherwise homogeneous bending along the intended edge is not possible due to the tooling.
Bending is a forming process used to create three-dimensional products from flat sheet metal. Various bending processes allow classically welded or bolted assemblies to be combined into a more cost-effective single part. In industry, bending has become established for both small and large parts.
The smallest possible leg length is a tool-related minimum dimension that must be observed in the part design. If a leg length is too short, the workpiece cannot be bent according to the design.
For a 90° bend, the width W can be used to determine the smallest leg length Smin:
Smin = √2/2 * W
The following table lists the respective guide values for a 90° bend. As the material thickness increases, the minimum leg length Smin changes as a result of the tools used.
Material thickness, 90°-bend
Minimum leg length Smin
1mm
6.5mm
1.25mm
1.25mm
1.5mm
8mm
2mm
9.5mm
2.5mm
12.5mm
3mm
12,5mm
4mm
19mm
5mm
31mm
6mm
31mm
8mm
39mm
10mm
61mm
12mm
76mm
Material thickness, 90°-bend
Minimum leg length Smin
1mm
6.5mm
1.25mm
8mm
1.5mm
8mm
2mm
9.5mm
2.5mm
12.5mm
3mm
19mm
4mm
19mm
5mm
31mm
6mm
31mm
8mm
54mm
10mm
61mm
12mm
76mm
Material thickness, 90°-bend
Minimum leg length Smin
1mm
8mm
1.25mm
8mm
1.5mm
8mm
2mm
9.5mm
2.5mm
12.5mm
3mm
19mm
4mm
19mm
5mm
31mm
6mm
31mm
8mm
54mm
10mm
61mm
12mm
76mm
Workpieces that have a hole or a cut-out near the bending line in the uncoiled state must maintain a minimum distance Lmin. If the distance falls below Lmin, the cut-outs will be deformed during the bending process.
The minimum distance Lmin is calculated with the die width W as follows:
Lmin = 0.75 * W
A quick, workshop-friendly method for determining the minimum distance is to use the smallest leg length. Cut-outs and holes that have a distance to the bending line that is greater than the smallest leg length can be produced without deformations.
In the case of two successive bends, so-called Z-bends, a minimum step dimension Xmin must be maintained due to the bending tool used.
Material thickness, Z-bend
Minimum step size Xmin
1mm
12.5mm
1.25mm
13mm
1.5mm
13.5mm
2mm
16mm
2.5mm
20mm
3mm
20.5mm
4mm
27.5mm
5mm
37.5mm
6mm
39mm
8mm
48mm
10mm
70mm
12mm
85mm
Material thickness, Z-bend
Minimum step size Xmin
1mm
13mm
1.25mm
13mm
1.5mm
13.5mm
2mm
17mm
2.5mm
21mm
3mm
28.5mm
4mm
30mm
5mm
40.5mm
6mm
41.5mm
8mm
62.5mm
10mm
74mm
12mm
90mm
Material thickness, Z-bend
Minimum step size Xmin
1mm
13mm
1.25mm
13mm
1.5mm
12.5mm
2mm
17.5mm
2.5mm
19.5mm
3mm
26mm
4mm
27mm
5mm
38mm
6mm
40mm
8mm
61mm
10mm
72.3mm
12mm
86.6mm
The run-out of the bending lines should not pass directly into the material, otherwise the compression and expansion at the bending zone will be impeded and cause cracks. Attached relief slots minimize the notch effect and thus ensure the desired bending result.
Sloping edges towards the bending line must be avoided, otherwise homogeneous bending along the intended edge is not possible due to the tooling.
This can be remedied by a perpendicular distance to the bending line with the dimension of the minimum leg length or by cutting the slanted edge free.
For process reliability and to avoid unsightly corners when bending edges meet, a corner notch D should be provided at the intersection of the crossing bending lines. Corresponding minimum dimensions are listed in the following table depending on the material thickness.
Material thickness
D ± 0.5
≤ 2mm
3mm
> 2mm ≤ 4mm
5mm
> 4mm - 6mm
7mm
The bending manufacturing process can only be used if the entire sheet metal part can be unwound.
Consequently, if three bending lines intersect, one must be split open. If this edge also has to be closed afterwards, a weld seam or another manufacturing process must be used.