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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.

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