Sheet metal processing technology - bending

When doing sheet metal processing, the main process is bending, the main machinery is hydraulic press brake. Bending seems simple, but there are many means and tricks in it. The following is to introduce the various bending techniques of sheet metal bending.

Tool
Graphics software CAD

Method and Steps:
1. The general bending 1:(R=0, θ=90°)
L=A+B+K
1. When 0¢T£0.3, K'=0
2. For the iron material:(eg., GI, SGCC, SECC, CRS, SPTE, SUS, etc.)
a. 0.3¢T¢1.5, K'=0.4T
b. 1.5£T¢2.5, K'=0.35T
c. T/2.5, K'=0.3T
3. SUS  T>0.3  K'=0.25T
4. For other nonferrous materials such as AL,CU:
T$0.3,  K'=0.5T

2. The general bending 2: (R≠0   θ=90°)
L=A+B+K’
K is the neutral arc length.
1. T¢1.5,  K'=0.5T
2. T/1.5, K'=0.4T
Note: when using bending knife processing R£2.0, R=0°

3. The general bending 3: (R=0 θ≠90°)
L=A+B+K’
1. T£0.3, K'=0
2. T$0.3, K'=(u/90)*K
Note: K is the amount of compensation when 90° .

4. The general bending 4: (R≠0 θ≠90°)
L=A+B+ K’
1. T¢1.5, K'=0.5T
2. T/1.5, K'=0.4T
K is the neutral arc length.
Note: when R ¢2.0, and processed with knife, is calculated by R = 0, A and B in accordance with the straight length after the zero Angle values

5. Z fold 1 (Straight section length difference).
1. H/5T, When two molding, according to two 90° bend calculation.
2. H¢5T, one time forming, L=A+B+K
K value parameter selection in the attachment.

6. Z fold 2(non-parallel straight edge).
The expansion method is the same as the parallel straight edge Z method (above), and the height H is shown in the illustration.

7. Z fold 3(bevel edge segment difference).
1. H¢2T
j θ≦70∘, According to the calculation of Z fold 1(Straight side difference), the length of expansion = the total length before expansion +K (at this time K'=0.2)
k θ>70, Calculated on Z fold 1 way completely.
2. H/2T, Unfold by two halves bending (R=0 θ≠90°).

8. Z fold 4(The transition section is a two-arc tangent):
1. H≦2T The transition of a segment is a non-linear segment with two circular arc tangent expansion, the perpendicular line is taken at the tangent point of two circles, to ensure that the fixed edge size offset is treated with a material thickness, then unfold in z-fold (straight-side section).
2. H>2T, deal with it after checking.

9. Draw hole
The calculation principle of drawing hole size is the principle of volume invariance, that is, the material volume is invariable before and after the extraction. Generally, the parameters in the formula are calculated according to the following formula.(Set the prepunched hole as X and add the correction coefficient - 0.1.):
1. If the extraction hole is extruded tapped hole (tapping after extraction), then S shall be evaluated according to the following principles:
T≦0.5, S=100%T
0.5 T≧0.8, S=65%T
The prepunched hole is usually used in the attachment;

2. If the hole is used for riveting, take S=50%T, H=T+T'+0.4  (Note: T' is the plate thickness with which it is riveted, and the gap between the hole and the salad hole is unilateral 0.10~0.15);
3. If the hole in the original drawing is not marked, the inner and outer diameters of the hole should be guaranteed;
4. When the calculated value of the prepunched aperture is less than 1.0, all take 1.0.

10. Reverse fold and flatten
L= A+B-0.43T（K'=0.43 T）
1. When it's pressed flat, the actual situation is considered whether the pressing line happen before bending or in the middle of the bending deformation zone.
2. Reverse fold and flatten usually done in two steps.
V fold 30°
Reverse fold and flatten
In a diagram of a bending line, to be prepared in accordance with 30° bend line drawing, as shown in figure:

11. N folding
1. When the N folding machining method is pressed flat, the value of the parameter is calculated by L=A+B+K.
2. When N folds in other ways, expand the algorithm to see "general bending (R≠0 θ≠90°)”.
If the bending is straight (H), the bending is calculated by twice folds forming: L=A+B+H+2K (K=90∘ expansion coefficient) 

END
Matters needing attention:
Value of the dimension tolerance: the median value of the upper and lower limit dimensions shall be taken as the design standard value.
As for square hole and external angle, the straight wall sections unfold by 90° bending, the angle processing approach for further notice.

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WC67K NC Hydraulic Plate Press Brake With E21 Controller
MB8 Automatic Sheet Metal Press Brake Bending Machine With DA56S System