Diagram and Calculation Formulas for Bend Allowance

In order to help you master the calculation formula of unfolded length of bending more simply and quickly, we listed four common coefficient tables for you, illustrated sixteen calculation formulas of unfolded length of bending, and we also take some examples for better understanding. I hope that the following contents can help you practically. If you have any questions, Please feel free to contact us.

Diagram and calculation formula for one-bend

A, B--- bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L=A+B-P', which is L=25+65-5.5=84.5

According to Table 1, the plate thickness is 3, the lower die is V25, and the bending coefficient is 5.5

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of two-bend

A(A1), B--- bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L=A+T+B-2*P', which is L=50+2+50-2*3.4=95.2

According to Table 1, the plate thickness is 2, the lower die is V12, and the bending coefficient is 3.4

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of three-bend 

A(A1), B (B1)-bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L=A+T+B+T-3*P', which is L=50+2+90+2-3*3.4=133.8

According to Table 1, the plate thickness is 2, the lower die is V12, and the bending coefficient is 3.4

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of four-bend 

A, B (B1)-bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L=A+A+B+T+T-4*P', which is l = 25+25+100+1.5+1.5-4 * 2.8 = 141.8

According to Table 1, the plate thickness is 1.5, the lower die is V12, and the bending coefficient is 2.8

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of six-bend 

A(A1), B (B1)-bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expand length L=A+T+A+T+B+B1+B1-6*P'

which is l = 50+1.5+50+1.5+150+20+20-6 * 2.8 = 276.2

According to Table 1, the plate thickness is 1.5, the lower die is V12, and the bending coefficient is 2.8

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of bending 180 degrees

A, B--- bending length of workpiece

P'---flattening fillet bending coefficient

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L=A+B-P', which is L=25+65-1=89

According to Table 2, the plate thickness is 2, the lower die is V12, and the bending factor is half of the plate thickness

Note: According to Table 2, the selection of different lower die has different bending coefficients and different plate thicknesses.

Diagram and calculation formula of double-layer bending 

A, B--- bending length of workpiece

P1--- bending coefficient of inner corner

P2--- bending coefficient of external bending angle

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L1=(A-1.5) +(B-1.5)-P1, which is L1= (65-1.5) +(25-1.5)-3.2=83.8

L2=A+B-P2, which is L2=65+25-4.1=85.9

L=L1+L2-T/2, which is L=83.8+85.9-0.75=168.95

According to Table 2, the plate thickness is 1.5, the lower die is V12, the inner corner bending coefficient is 3.2, the outer corner bending coefficient is 4.1, and the 180 bending coefficient is 0.75.

Note: According to Table 2, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of double-layer bending with one edge

A(A1), B1, B2--- bending length of workpiece

P1--- bending coefficient of inner corner

P2--- bending coefficient of external bending angle

P3---90° bending coefficient

R--- bend and fillet (generally plate thickness)

T--- material thickness

P4---180° bending coefficient

The Expanded length L1=A+B1-P2, which is L1=75+29-4.6=99.4

L2=(A1-T) +(B1-T)-P1, which is L2= (37-2) +(29-2)-3.7=58.3

L3=L1+L2-P3 which is L3=99.4+58.3-1=156.7

L=25.5+L3-P1, which is L=25.5+156.7-3.84=178.36

According to Table 2, the plate thickness is 2, the lower die is V12, the inner corner bending coefficient is 3.7, and the outer corner bending coefficient is 4.6.

Note: According to Table 2, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of double-layer bending with two edges

A, A1, A2, B1, B2, L, L1, L2, L3--- bending length of workpiece

P1--- bending coefficient of inner corner

P2--- bending coefficient of external bending angle

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expanded length L1=(A1-T) +(B2-T)-P1 which is L1= (35-2) +(34-2)-3.7=61.3

L2=(B1-T) +(A2-T)-P1, which is L2= (50-2) +(34-2)-3.7=76.3

L3=A+B1+B2-2*P2, which is L3=70+35+50-2*4.6+145.8

L=L1+L2+L3-2*P3, which is L=61.3+75.3+145.8-2*1=280.4

According to Table 2, the plate thickness is 2, the lower die is V12, the inner corner bending coefficient is 3.7, the outer corner bending coefficient is 4.6, and the 90-bending coefficient is 1.

Note: According to Table 2, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of step bending

A, B--- bending length of workpiece

R--- bend and fillet (generally plate thickness)

T--- material thickness

Unfolded length L=A+1

Note: When the step is equal to the thickness of two plates, add 0.5 for each step and 1 for each step.

Diagram and calculation formula of bending special angle 1

A(A1), B (B1)-bending length of workpiece

P'---bending coefficient of edge bending (bending factor: one factor minus one bend)

R---bend and fillet (generally plate thickness)

T--- material thickness

The Expand length L=(A-T) +(B-T)-P', which is L= (66-1) +(26-1)-2=65+25-2=88

According to Table 3, the plate thickness is 2, the lower die is V12, and the 60 bending coefficient is 2

Note: According to Table 3, the neutral layer is selected as the bending length and width.

Diagram and calculation formula of bending special angle 2

A (A1, A2, A3, A4), B--- bending length of workpiece

P--- bending factor of 135 bending angles

R--- bend and fillet (generally plate thickness)

T--- material thickness

The Expand length L = A1+A2+A3+A2+A4-P-P.

Note: the same pressure step bending only needs to reduce two coefficients

According to Table 3: the plate thickness is 2, the lower die is V12, and the bending coefficient at 135 is 1.1.

Diagram and calculation formula of bending special angle 3

A (A1, A2), B (B1, B2)-bending length of workpiece

P1---120° bending coefficient

P2---145° bending coefficient

P3---90° bending coefficient

R--- bend and fillet (generally plate thickness)

T--- material thickness

Note: if the graphic size is marked on the shape, the shape size should Be converted to the neutral layer size when calculating the unfolding length;

The Expand length L=A11+B11+B21+A21-P1-P2-P3, which is l = 80+50+103+70-1.7-0.7-3.4 = 297.2

According to Table 3: the plate thickness is 2, the lower die is V12, the 120 bending coefficient is 1.7, the 145 bending coefficient is 0.7, and the 90-bending coefficient is 3.4

Note: According to Table 3, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of common binding 1

A, B, C--- length, width and height of workpiece bending edge

P--- bending coefficient

R--- bend and fillet (generally plate thickness)

H(H1), l (L1)-the unfolded length of each side

T--- material thickness

D--- bending process clearance (generally 0~0.5)

The Expanded length L1=A, which is L1=27

L=A+C-P, which is L=27+9-3.4=32.6

H1=B-T-D, which is H1=22-2-0.2=19.8. Note: D is 0.2.

H=B+C-P, which is H=22+9-3.4=27.6

According to Table 1: the plate thickness is 2, the lower die is V12 and the bending coefficient is 3.4

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of common binding 2

A, B, C--- length, width and height of workpiece bending edge

H(H1), L (L1)-the unfolded length of each side

P---90° bending coefficient P1---30° bending coefficient

R--- bend and fillet (generally plate thickness)

T--- material thickness

D--- bending process clearance (generally 0~0.5)

The Expanded length L1=B-T-D, which is L1=20-1.5-0.2=18.3

L=B+C1+C2-P-P1, which is L=20+12+8.9-2.8-0.5=37.6

H1=C1+A-P-D, which is H1=12+35-2.8-0.2=44. Note: D is 0.2.

H=A+C-P, which is H=35+20-2.8=52.2

According to Table 1: the plate thickness is 1.5, the lower die is V12, the bending coefficient is 2.8, and the 30-bending coefficient is 0.5

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.

Diagram and calculation formula of common binding 3

A, B, C--- length, width and height of workpiece bending edge

H(H1), L (L1)-the unfolded length of each side

P--- bending coefficient

R--- bend and fillet (generally plate thickness)

T--- material thickness

D--- bending process clearance (generally 0~0.5)

The Expanded length H1=B-B1-D, which is H1=50-12-0.3=37.7. Note: D is 0.2.

H2=B-T-D which is H2=50-2.5-0.3=47.2

H=B+C+B1-2*P, which is H=50+47+12-2*4.5=100

L1=A+C-T-D-P, which is L1=55+47-2.5-0.3-4.5=94.7

L=A+C+B2-2*P, which is L=55+47+12-2*4.5=105

According to Table 1: the plate thickness is 1.5, the lower die is V16 and the bending coefficient is 4.5

Note: According to Table 1, different bending coefficients of lower dies and different plate thicknesses are different.