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 design guidelines can not followed in one part. Therefore exceptions can be there for complex features design.
Sheet metals are available in various thickness. If we go to manufacturer, They provide sheets in gauge thickness. But During design designers use sheet thickness in mm. You can use this guide to convert sheet thickness from gauge to mm.
Value of sheet thickness depends on part structural requirements. It can be calculated using simulation studies.
Inside Bend Radius
Sharp inside bend radius are not recommended in sheet metal parts. Because Small inside bend radius can cause material flow problems in soft material and fracturing in hard material. Which results in localized necking or fracture.
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.
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 Hole Diameter
Hole/Slot Distance from Bend Edge
Center to Center Distance Between Two Holes
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.
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.
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
To sum up, sheet metal design guidelines are followed to ensure good quality, reduced cost and robust design. All design guidelines can not followed in one part. Therefore exceptions can be there for complex features design.
You suggest you to check electronics enclosure design guidelines as well. This will give you overview about complete design process.
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