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

Looking for the ultimate guide to bending limit dimensions calculation? Look no further!

Our comprehensive blog post covers everything you need to know about determining the minimum flange size, middle height of Z-shaped hem, maximum Z-shaped folded edge reverse size, U-shaped bending width, and maximum height of four-side folding.

Whether you’re a seasoned professional or a beginner in the field, this article is a must-read for anyone looking to master the art of bending limit dimensions calculation.

So, grab a cup of coffee and settle in for an informative and engaging read!

1. Minimum flange size

Lmin =(V/2)+ 2 + t ………(7)

The minimum flange size, “lmin“, for various material thicknesses is listed in Table 5.

Table 5 minimum hem size Lmin

LminMaterial thickness t
Width of lower mold groove877.27.5     
12  9.510    
16    12.513  
25     17.518.519.5

2. Minimum middle height of Z-shaped hem

The height of the center of a Z-shaped flange is influenced by the distance from the center of the V-shaped groove to the bottom edge of the die.

The minimum flanging height is formula (8):

Hmin =(V/2)+ 2.5+ 2t  ………(8)

Refer to Table 6 for the minimum middle height, “Hmin“, of a Z-shaped hem for various material thicknesses.

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Table 6 Minimum Z-shaped hem middle height Hmin

HminMaterial thickness t
Width of lower die groove V88.58.99.5

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 features a Z-shaped fold, and its size on the reverse side is influenced by the height of the lower mold and the mold base.

The maximum reverse side height is formula (9):

Lmax = 59 + t …………(9)

3.2 When the center height of the Z-fold is less than 30, Table 7 displays the maximum reverse side size of the Z-fold for various material thicknesses.

When the center height of the Z-fold is significant, it may be impacted by various components of the lower die base of the bending machine. In such cases, the maximum size of the reverse side should be determined on site.

Table 7maximum reverse side size of Z-type hem

Material thickness t1.

4. U-shaped bending

4.1 As depicted in Fig. 7, the width (H1) of the U-shaped hem should not be excessively narrow, and the height (H2) should not be overly large due to the impact of the machine tools and molds.

When the height (H2) reaches the minimum hem size specified in Table 5, the minimum value for the width (H1) can be calculated using formula (10).

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H1 = 12 + 2t …………………(10)


41.1 the value of H1 is shown in Table 8

Material thickness t1.
H1 min141515161718

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

4.2 Maximum height of four side folding H

The maximum height of the four-side fold (Hmax) is limited to less than 175 due to the influence of the mold, as shown in Fig. 8.


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