Bending sheet / Useful knowledge / Our knowledges & what we worked on

A bent plate, regardless of its angle, always has a rounding, the inside radius of which is at least equal to the thickness of the bent plate.

When folding, the outer fibers stretch and the inner fibers compress.

Only a so-called neutral fiber located in the middle of the thickness practically does not vary.

All calculations must be made from this fiber for thin sheets.

For thick sheets (> 4mm), the neutral fiber is generally located:

• At ⅓ of e if Ri ≤ 3 × e

• In the middle of e if Ri > 3 × e

Thin sheets up to 4mm thick

• It is necessary to proceed with the layout by taking the external dimensions (we do not hold the neutral fiber)

Developed length:

(20 – e) + (40 – e)

Developed lenght :

(20 – e) + 45 – (2 x e) + (15 – e)

Thin sheets greater than 4mm thick

For the development, take into account the rounding, calculate its development by taking the length developed at ⅓ of the thickness.

R = Ri + ⅓ × e if Ri ≤ 4 × e

R = Ri + ½ × e if Ri > 4 × e

The unique and valid formula for calculating a developed is:

(pi * R (Ri + neutral fiber) * unfolding angle) / 180

Internal bending radii depending on the material :

• Commonly used steel: r = e

• Commonly used stainless steel: r = 2.5 × e

• Annealed aluminium: r = e

• Hardened aluminium: r = 3 × e

• Annealed copper: r = e

• Hardened copper: r = 2.5 × e

The chart below shows the minimum radii to be respected as well as the height(s) according to the thickness of the sheet.