L-Bending
1) Factors that determine the minimum L flexion
Because the middle of the V-groove of the press brake is hollow, during forming, the edge bend must be larger than the hollow section, and the specific size of the seating edge varies in the production of different companies (the lower section of the V-groove is in use for a long time, the R angle increases, which causes the scrap edge distance to increase accordingly, otherwise “sliding” will occur)
2) Reduction formula (empirical): 6 T/2+0.5+(1.8 T/2)
3) As the image below shows, when T = 1, K = 1.8 * 1, the minimum L bending is 3 + 0.5 + 0.9 = 4.4
| V groove/thickness | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 12 | 15 | 16 | 18 |
| 0.5 | 2.5 | 3 | ||||||||||
| 0.8 | 3.2 | 3.7 | 4.2 | |||||||||
| 1 | 3.5 | 4 | 4.5 | 5 | 5.5 | |||||||
| 1.2 | 3.5 | 4 | 4.5 | 5 | 5.5 | |||||||
| 1.5 | 4.8 | 5.2 | 5.8 | 6.2 | 6.8 | |||||||
| two | 7.5 | 8.5 | ||||||||||
| 3 | 11 | 12 | ||||||||||
| 4 | 15 | 16 | ||||||||||
| 5 | ||||||||||||
| 19 | 20 | |||||||||||
| 22 | 24 | 26 | 28 | 30 |
U-fold
1) Types of U-bend
A. Regular forming by bending punch
B. Reverse folding hem with joint (first folding at 30°, placing a suitable gasket in the middle, and then hemming)
2) Factors that determine the minimum U-shaped bending
- Punch shapes (shown in the following image).
Judging from the common punch mold, the best one for U bending is the “gooseneck punch”, which has several types and is specifically subject to the requirements of various companies.
- Fold size (shown in the following image).
The growing relationship between two sizes:
The longer A is, the longer B is.
3 ） Reduction formula (empirical value of gooseneck punch)
◆ 0.5MM Sheet:
Minimum U-bending: A = 7.67, B = 0.5, minimum L-bending = 3.0
Increasing value: Whenever A increases by 1 mm, B increases by 1.87 accordingly.
Formula: When size A is known, then size B = （A-7.67）/T* increasing value + the minimum bending value L of this plate
For example,
when A=15, then B=(15-7.67)/0.5*1.87+3.0=30.4
When size B is known, then size A = （B- the minimum bending value L of this plate）/increasing value *T+7.67
For example,
when B=30.4, then A=（30.4-3）/1.87*0.5+7.67=15
◆ 0.8MM sheet
Minimum U-fold size A = 8.5, size B = 0.8, minimum L-fold = 4.2。
Increasing value: 1.87/0.5*0.8=2.99
◆ 1.0MM sheet
Minimum U-fold size A = 8.94, size B = 1.0, minimum L-fold = 4.5
Increasing value: 1.87/0.5*1.0=3.7
◆ 1.2MM sheet
Minimum U-fold size A = 9.3, B = 1.2, minimum L-fold = 4.5
Increasing value: 1.87/0.5*1.2=4.5
◆ 1.5MM sheet
Minimum U-fold size A = 10.3, B = 1.5, minimum L-fold = 6.2
Increasing value: 1.87/0.5*1.5=5.5
◆ 2.0MM sheet
Minimum U-fold size A = 12.7, B = 2.0, minimum L-fold = 12.0
Increasing value: 1.87/0.5*2=7.4
Grades:
- When size A exceeds 85.0MM and size B exceeds 60.0MM, this formula is not applicable.
- Attached table: A= test value, B= minimum L bending, K= test value
| Thickness | One size (min) | Size B (min) | K |
|---|---|---|---|
| 0.5 | 7.67 | 3 | 1.87 |
| 0.8 | 8.5 | 4.2 | 2.99 |
| 1 | 8.94 | 4.5 | 3.7 |
| 1.2 | 9.3 | 4.5 | 4.5 |
| 1.5 | 10.3 | 6.2 | 5.5 |
| two | 12.7 | 12 | 7.4 |
Related: V and U Shaped Bending Strength Calculator
Z-fold
1) Z-fold types
- When H is greater than or equal to 5T, calculating according to two 90° bends.
- When H is less than 5T, single formation is sufficient
2) The main factors affecting the minimum Z-bending value are the width of the V-groove and the distance from the center of the V-groove to the edge.
3) Formula: 6 T/2+distance from groove edge V+（1.8 T/2）+T（see picture）
For example, in case of 1.0mm plate, up to edge distance = 1.5, then minimum Z bending H = 6 1/2+1.5+（1.8 1/2）+1= 6.4.
Calculation of the minimum bending edge of a bend
The initial state of the L curve is shown in the following illustration:
Reference Table for Internal R Bending and Minimum Bending Height of Cold Rolled Sheet
| No. | Thickness | Slot width | Convex matrix R | Minimum bending height |
| 1 | 0.5 | 4 | 0.2 | 3 |
| two | 0.6 | 4 | 0.2 | 3.2 |
| 3 | 0.8 | 5 | 0.8/0.2 | 3.7 |
| 4 | 1.0 | 6 | 1/0.2 | 4.4 |
| 5 | 1.2 | 8/6 | 1/0.2 | 5.5/4.5 |
| 6 | 1.5 | 8/10 | 1/0.2 | 6.8/5.8 |
| 7 | 2.0 | 12 | 1.5/0.5 | 8.3 |
| 8 | 2.5 | 16/14 | 1.5/0.5 | 10.7/9.7 |
| 9 | 3.0 | 18 | 2/0.5 | 12.1 |
| 10 | 3.5 | 20 | two | 13.5 |
| 11 | 4.0 | 25 | 3 | 16.5 |
The initial state of the Z curve is shown in the following illustration:
The minimum bend size (L) of sheet metal corresponding to Z bend for materials with different thicknesses is shown in the following table:
| No. | Thickness | Slot width | Convex matrix R | Z bending height |
| 1 | 0.5 | 4 | 0.2 | 8.5 |
| two | 0.6 | 4 | 0.2 | 8.8 |
| 3 | 0.8 | 5 | 0.8/0.2 | 9.5 |
| 4 | 1.0 | 6 | 1/0.2 | 10.4 |
| 5 | 1.2 | 8/6 | 1/0.2 | 11.7/10.7 |
| 6 | 1.5 | 8/10 | 1/0.2 | 13.3/12.3 |
| 7 | 2.0 | 12 | 1.5/0.5 | 14.3 |
| 8 | 2.5 | 16/14 | 1.5/0.5 | 18.2/17.2 |
| 9 | 3.0 | 18 | 2/0.5 | 20.1 |
| 10 | 3.5 | 20 | two | 22 |
| 11 | 4.0 | 25 | 3 | 25.5 |
