Sheet metal bending radius is a value required in sheet metal drawing, which is difficult to determine in actual processing.

In fact, the sheet metal bending radius is related to the material thickness, the pressure of the press brake machine and the width of the lower die groove of the bending die.

What’s the specific relationship? Let’s study it today:

The bending radius of sheet metal processing is related to the material thickness and the width of the bending notch. The simple, convenient and rough method is:

- Generally, when the plate thickness is not more than 6mm, the bending radius in the plate can directly take the plate thickness as the radius during bending;
- When the plate thickness is greater than 6mm and less than 12mm, the bending radius in the plate is generally 1.25 to 1.5 times of the plate thickness;
- When the plate thickness is not less than 12mm, the bending radius in the plate is generally 2 to 3 times the plate thickness.

Experience in actual sheet metal processing shows that when the plate thickness is generally no more than 6mm, the inner radius of sheet metal bending can directly use the plate thickness as the radius.

When the bending radius is r = 0.5, the general sheet metal thickness t is equal to 0.5mm.

If the radius size larger or smaller than the plate thickness is required, it needs to be processed with a special die.

When the sheet metal drawing requires the sheet metal to be bent by 90 ° and the bending radius is particularly small, the sheet metal should be grooved first and then bent.

It can also use special press brake toolings, punches and dies.

The bending radius of sheet metal has a certain relationship with the width of the lower die groove of the bending die.

Through a large number of experiments in sheet metal processing, it is found that there is a certain relationship between the lower die groove width of the bending die and the bending radius.

For example, 1.0mm plate is bent with 8mm groove width, so the bending radius pressed out is R1 ideally.

If the groove width of 20mm is used for bending, because the upper die moves downward during bending, the depth of the stretched plate reaches a certain angle.

Then we know that the area of a 20 mm wide groove is larger than that of an 8 mm wide groove. When bending with a 20 mm wide groove, the tensile area becomes larger and the R angle increases.

Therefore, in the case of requiring the bending radius of the plate without damaging the press brake die, try to bend with a narrow groove.

Under normal circumstances, it is recommended to operate according to the standard ratio of plate thickness to groove width of 1:8.

The minimum thickness shall not be less than the ratio of 1:6 between plate thickness and groove width.

The sheet metal bending can be properly smaller and can not be operated less than the ratio of plate thickness to groove width of 1:4.

**Suggestion:** if the strength allows, the method of grooving first and then bending is preferred to make small sheet metal bending radius.

The following figure is the corresponding table of bending radius, pressure and minimum bending height provided by the press brake manufacturer.

- V – bend notch width
- R – bend radius
- B – minimum bending height
- S – sheet thickness

Note: the data with gray scale in the table is the pressure P (KN / M) required for bending, and the maximum bending force of the press brake is 1700kn. The existing bending knife edge V = 12, 16, 25, 40 and 50.

Please refer to the existing knife edge and bending length to determine the bending radius, so as to calculate the accurate unfolding material length.

The above description refers to the pressure parameters and bending notch width of a press brake. The actual application is calculated according to the press brake pressure and bending notch of your own sheet metal processing plant.