1. Bending Technical Guide
  2. How to Use and Select Tools (1) R-Bend

How to Use and Select Tools (1) R-Bend

R-Bend by Standard Tools

Multi-Radius Punch
R3 , R4 , R5 , R6 , R8 , R10
Color Radius Punch
R10 - R30 R2.5 incremental
Radius Punch
R10 , R15 , R17.5 , R20 , R25 , R30
Multi-Radius Punch Light Weight Rbend 1V Die AT Pad, Retainer
Acute 1V Die Light-weight R bend 1V Die
Acute 1V Die
AT Retainer (Urethane)
Acute 1V Die
Light-Weight R Bend 1V die

Features

  • 1 process makes easy R bend comparing step-R-Bending
    * Shorter work time
    * Stable accuracy
    * Smoother R surface
  • Several R value can be adapted
  • Cheaper and shorter lead time

Caution for R-Bending -1

Multi-Breakage

Multi-Breakage is typical phenomenon during bending process where the work separates from R-punch surface and the work breaks.
1 the ratio of thickness t and product inner iR (iR/t) too big 2 the work’s tensile strength is low or lower ductility * When the ratio iR/t is more than 30, Multi-breakage occurs.
Multi-breakage

Caution for R-Bending -2

Spring back : Bend angle is larger when the load is off.
1 This spring back value of R-Bend is larger than the value of V-bend.
2 Generally, iR is larger than punch R.

Factor to the spring back

  1. Thickness and iR( inner radius ) iR/t
  2. strength of the Material
  3. tool type ( bending method & structure )
Typical Material and Mechanical Factor
spring back Material Type(%) Tensile Strength N/mm2 Elongation
SS400 410 - 520 17 or more
SPCC 280 or more 38 or more
SPHC 280 or more 29 or more
A5052P 180 or more 19 or more
A1100P 75 or more 30 or more
SUS304 530 or more 40 or more
SUS430 460 or more 22 or more

How to decide punch tip-radius from product inner radius (iR)

iR/t and spring back value

Standard Punch Selection for R Bend

Standard punch selection for R bend

Standard Die selection for R bend

iR(inner radius) chart of SPCC air-bend by various thickness t and various punch R

* Die is selected by punch R
Example: SPCC t=1.0mm bent by R15 punch Chart tells inner radius approx. R16.2

Thickness R10 R15 R17.5 R20 R25 R30
0.8 10.6 16.4 18.9 21.8 28 33.6
1 10.5 16.2 18.6 21.3 27.2 33.2
1.2 10.5 16 18.4 21.2 27 32.7
1.6 10.3 15.7 18.2 20.8 26.3 32
2.3 10.2 15.5 18 20.5 25.8 31.3
3.2 10.2 15.4 17.7 20.2 25.5 30.8

Multi-Breakage Possible Area

iR( inner radius) chart of aluminum air-bend by various thickness t and various punch R

*Test made by A5052-0 and bent parallel to roll direction
*Die selection by punch R
Example : A5052-0 1.0mm thick using R20 punch inner radius becomes R24.4
* t=0.8 punch R30 multi-breakage occurred

Thickness Punch R
R10 R15 R17.5 R20 R25 R30
0.6   12.1 19.5 23.0 27.6 38.0 45.8
18.9 27.0 28.3 34.2 46.8 47.4
0.8   11.3 18.1 21.5 25.5 32.5 42.5
11.7 18.6 20.6 24.8 27.0 37.5
1.0   11.1 17.4 20.8 24.4 30.7 37.4
9.9 14.4 17.0 19.8 20.5 22.2
1.2   10.8 17.0 20.3 23.6 29.7 36.0
7.2 12.0 14.4 16.2 16.9 18.0
1.5   10.6 16.5 19.6 22.8 28.7 34.8
5.4 9.0 10.8 12.6 13.3 14.4
2.0   10.4 15.8 19.0 21.9 27.7 33.5
3.6 4.8 7.7 8.5 9.7 10.5
2.5   10.2 15.6 18.7 21.5 27.4 33.0
1.8 3.6 6.2 6.8 8.6 9.0
3.0   10.1 15.3 18.5 21.2 27.0 32.5
0.9 1.8 5.1 5.4 7.2 7.5

Multi-Breakage Possible Area