Summary of Calculation Formulas for Bending Limit Dimensions of Various Sheet Metals

1. Minimum flange size

Lmin =（V/2）+ 2 + t ………（7）

The minimum flange size lmin for different material thicknesses (see Table 5).

Table 5 minimum hem size Lmin

2. Minimum middle height of Z-shaped hem

The middle height of Z-shaped flanging is affected by the distance from the center of V-shaped groove to the lower die edge.

The minimum flanging height is formula (8):

Hmin =（V/2）+ 2.5+ 2t  ………（8）

See Table 6 for the minimum Z-shaped hem middle height Hmin of different material thicknesses.

Table 6 minimum Z-shaped hem middle height Hmin

3. Maximum Z-shaped folded edge reverse size

3.1 The maximum reverse side size of Z-shaped folding (as shown in Fig. 6).

The left door of the general switch cabinet is Z-shaped folding, and its reverse side size is affected by the height of the lower mold and mold base.

The maximum reverse side height is formula (9):

Lmax = 59 + t …………（9）

3.2 When the middle height of Z-fold is less than 30, the maximum reverse side size of Z-fold with different material thickness is shown in Table 7.

When the middle height of Z-fold is large, affected by different parts of the lower die base of the bending machine, the maximum reverse side size should be determined on site.

Table 7maximum reverse side size of Z-type hem

4. U-shaped bending

4.1 (as shown in Fig. 7) due to the influence of machine tools and molds, the width H1 of U-shaped hem should not be too small and the height H2 should not be too large;

When H2 meets the minimum hem size in Table 5, the formula for the minimum value of H1 is (10):

H1 = 12 + 2t …………………（10）

41.1 the value of H1 is shown in Table 8

4.1.2 When H1 value is large, it should meet: H2 ＜ H1- 35.

4.2 Maximum height of four side folding H

Affected by the mold, the maximum height of four side folding Hmax ＜ 175 (as shown in Fig. 8).