Forming
 
Forming Practice
  
  Forming Radius (R) /
Plate Thickness (t)
@ 60º & 90º
Die Opening (W) /
Plate Thickness (t)
@ 60º
Die Opening (W) /
Plate Thickness (t)
@ 90º
GRADE Transverse
to the rolling
direction R/t
Parallel to
the rolling
direction R/t
Transverse
W/t
Parallel
W/t
Transverse
W/t
Parallel
W/t
A36/44W 2.0 2.5 7.0 8.5 12.0 12.5
50W/572-50 2.5 3.0 7.5 8.5 12.5 13.5
HS 100 2.0 3.0 7.0 8.5 13.0 13.5
HS 400 3.0 4.0 8.5 10.0 13.5 14.0
HS 500 10.0 12.0 16.0 18.0    
For bending to 90º  in V-die die opening should "match" top tool radius to prevent impression in the plate.
Bending Force

V-die and rollerbending are almost equivalent from a forming point of view. Increasing the die opening decreases the required bending force, but increases the springback. When forming to a 90º angle in a V-die, the value of the formula W/t - (1.4 x R/t) should be greater than 9 to prevent impression in the plate.

An example:
Bending a typical 3/8" thick HS 100 plate with a W/t of 12.0 for forming transverse to the rolling direction, and an R/t recommended at 2 for a 90º bend, the formula shows.
Required bending force for rollerbending and V-die is calculated according to the following formula:
Bending Forces Needed in a Press Brake - Tons
THICKNESS WIDTH HS 100 HS 400 HS 500
1/2" 96" 420 540 560
1/2" 48" 210 270 280
3/4" 96" 625 800 840
3/4" 48" 310 400 420
Bending force may vary due to die and shoulder design, surface condition and lubrication.
The springback for different steel grades are illustrated in the table below. To compensate, overbending is necessary.
Typical Springback for Minimum Recommended Die Width Opening
GRADE RM P.S.I. SPRINGBACK
A572-50 80,000 3 - 5º
HS 100 125,000 6 - 10º
HS 400 181,000 9 - 13º
HS 500 225,000 13 - 16º
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