Sheet Metal Design Guidelines

Sheet metal design guidelines are followed to achieve better quality and reduced cost sheet metal parts. Turnaround time for good designed parts is also less.

You can use this guide to design sheet metal parts for manufacturing. All  guidelines does not fit into one product. Therefore exceptions can be there for the design of complex features.

Sheet Metal inside Bend Radius

Sharp inside bend radius are not recommended in sheet metal parts.
Minimum inside bend Radius shall be equal to material thickness. But for harder materials ( e.g. CRCA) minimum inside radius can be kept 0.65 times of thickness.

Why Minimum Bend Radius is Required

  • Small inside bend radius can cause material flow problems in soft material and fracturing in hard material. Which results in localized necking or fracture.
  • It is most economical to keep same bend radius throughout the design because of the advantage of using same tool during manufacturing.

Minimum Bend/Flange Length

Minimum Flange or bend length shall be equal to three times of sheet thickness plus bend radius.

Min. flange Bend length = 3X Sheet Thickness + Bend Radius

Why minimum Flange Length is Required?

Minimum flange Bend length is maintained to avoid cracks in bending area.

Minimum Hole Diameter

For softer materials, recommended hole minimum diameter should be equal to sheet thickness but for more harder materials it should be equal to two times of sheet thickness.

Why minimum hole diameter is required?

Small sizes punches are more prone to failure during punching operation.

Hole/Slot Distance from Bend Edge

Recommended minimum distance between hole /slot edge to bend shall be equal to three times the sheet thickness plus bend radius.

Why minimum distance from hole edge is required ?

Minimum distance between hole/slot edge to bend edge is maintained to avoid metal distortion, deformation and fracturing.

Center to Center Distance Between Two Holes

Recommended minimum center to center distance between two holes is equal to sum of hole radius plus two times the sheet thickness.

Why it is required? 

Minimum center to center hole distance is maintained to avoid metal distortion, deformation and fracturing.

Effect Of Grain Direction in Sheet Metal Bending

During sheet metal processing operation, sheet metal grains are arranged in the direction of rolling.

When Sheet metal is bend perpendicular to rolling direction grain rearranges. That has negligible effect on part strength. 

But bending parallel to rolling direction can leads to cracks because of destruction in grain structure.

Bend Relief

Bend relief is provided at the end of bending edge to avoid any crack tearing at the corner.

Height of the relief is generally kept greater than two times of sheet thickness plus bend radius.

Extrude Hole Size & Position Recommendation

Making Extruding hole with sheet metal punching requires extreme pressure/Force. Extruded hole too close to the part edge, lead to sheet metal deformation or tearing. Therefore minimum distance between extruded hole to edge if maintained.

Extruded hole to part edge (B)  = 3T + D/2

Center of extruded Holes (A) =  (5 + Hole Dia + 2T)

Extruded Hole and bend edge (C) = 3T + R + D/2

Round Emboss Design Guidelines

Making Emboss using sheet metal punching requires extreme pressure . Very close emboss to the part edge, can lead to deformation of the metal.

A – Distance From Emboss To part Edge = 3T + D/2

B- Distance Between Two Emboss =  (5 + D)

C- Distance between Emboss and Sheet Metal bend = 3T + R + D/2

Dimple Feature Design Guidelines

Louver Feature Design Guide

Distance between lower features and from bed edge is maintained to avoid metal deformation.

(P1) Distance Between Two lowers on Shorter Edge = 5 mm

(P2) Distance Between Two lowers on Longer Edge = 8 mm

Round Knockout Design Recommendation

Distance between knockout feature and from bend edge is maintained to avoid metal deformation.

(P1) Distance Between Two knockout  = (5 + D) mm

Conclusion :

To sum up, sheet metal design guidelines are followed to make parts manufacturable, reduce risks and save cost.

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