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Metal Stamping and Design Considerations, Part 2: Forming

A progressive die can control an inside radius but cannot control an outside radius. Similarly, the die can control dimensions to the inside of a bend but not to the outside.

Metal stamping guide 2A

 

Metal stamping guide 2B

 

Metal stamping guide 2C

 

Metal stamping guide 2D

 

To avoid hole deformation, leave at least three times the material thickness from the form tangency to the edge of the hole.
Metal stamping guide 2E

 

Forming an undercut can eliminate the need for a formed sharp corner. The tooling cost is the same; however, the undercut die will hold up better than the sharp corner die, thereby reducing downtime.

Metal stamping guide 2F

An improperly designed bend radius can cause fractures in the bend area.

Metal stamping guide 2G

General Rule #3:
The radius of a bend should be a minimum of 1.5 x the material thickness.

Angular Form Tolerances:

Metal stamping guide 2H

 

90°  ± 2°
1 Form Station
Not many tool adjustments

90°  ± 1°
1 Form Station
1 form qualifier or cam (50 tooling hours) and some tool adjustments.

90°  ± ½°
1 Form Station
1 form qualifier or cam (50 tooling hours) and many tool adjustments.

To form beyond 90° in one station, add a gusset:

Metal stamping guide 2I

It is preferred to eliminate lancing by blanking around a tab before forming. The cutout should extend a minimum of .030 beyond the bend line.

Metal stamping guide 2J