Sheet metal design guidelines are followed to design quality sheet metal enclosures. This helps in delivering the product at low cost and time. All design guidelines can not followed in one part. Therefore exceptions can be there for complex features design. In this article we will discuss sheet metal design guidelines for manufacturing parts using sheet metal press bending.
Sheetmetal are available in standard thickness. Sheet manufacturer provide sheets thickness in gauge. But designers design sheet metal parts considering sheet thickness in mm. You can use this guide to convert sheet thickness from gauge to mm.
Sheet Metal Material Selection
Material selection is very important part of product design. It also affect the sheet metal enclosure design. Sheet thickness and material can be selected using:
- Simulation Studies
- Past Experience
- Study existing products
- Experimental Studies
Inside Bend Radius
Sharp inside bend radius are not recommended in sheet metal design. 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.
Recommended inside bend radius shall be equal to material thickness. But for harder materials ( e.g. CRCA) it can be kept 0.65 times of sheet thickness.
Bend radius throughout the sheet metal design is kept constant to take the advantage of using same tool during manufacturing.
Minimum Bend/Flange Length Guidelines
Minimum Hole Diameter Guidelines
Hole/Slot Distance from Bend Edge
Center to Center Distance Between Two Holes
Minimum center to center hole distance is maintained to avoid metal distortion, deformation and fracturing.
Minimum distance between two hole center during sheet metal design should be equal to sum of hole radius plus two times the sheet thickness.
Recommended Distance = Radius of Hole1 + Radius of Hole2 + Sheet Thickness
Effect Of Grain Direction in Sheet Metal Bending
During sheet metal processing ( rolling operation), sheet metal grains are arranged in the direction of rolling.
When Sheetmetal is bend perpendicular to rolling direction grain rearranges. That has negligible effect on part strength.
But bending parallel to rolling direction can lead to cracks because of destruction in grain structure.
Extrude Hole Size & Position Guidelines
Creating extruded hole using punching process requires extreme pressure/Force. Extruded hole close to the part edge can lead to sheet metal deformation or tearing. Therefore minimum distance between extruded hole to edge if maintained.
Round Emboss Design Guidelines
Creating Emboss feature using sheet metal punching requires extreme pressure. Very close emboss to the part edge, can lead to deformation in the sheet metal part.
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
Minimum distance between louver feature and bending 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
Minimum distance between knockout feature and bending 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. We suggest you to check electronics enclosure design guidelines. This will give you an overview of complete enclosure design process.
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