Designing for sheet metal fabrication seems straightforward until prototypes warp, clash, or become uneconomical. Avoidable errors often creep in at the drawing stage, where small oversights multiply on the shop floor. These tips highlight four frequent pitfalls and how to design parts that bend, assemble, and finish cleanly, the first time.
Designing in Isolation
Great parts come from collaboration. Involve your fabricator early to confirm available tooling, minimum radii, grain direction preferences and finishing lines. Standardise holes, fasteners and material grades to shorten lead times.
Overtight Tolerances and Stack Up
Blanking, bending and coating each add variation. Applying ±0.1 mm everywhere drives unnecessary cost and rework. Tolerance features functionally, use GD&T where it clarifies intent, and consider coating thickness and spot-weld growth. Prototype critical interfaces before committing to tooling.
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Ignoring Bend Radii and K Factors
Every material and thickness has a minimum bend radius. Push tighter than that and you risk cracking, wrinkling or misshapen flanges. Account for bend allowance and the K factor when generating flat patterns, and validate with a brake press chart, not guesswork.
Starving Flanges, Slots and Reliefs
Flanges that are too short cannot be held properly, leading to slipping and twisting. A common rule of thumb is at least twice the material’s thickness plus the bend radius. Add corner reliefs where intersecting bends meet to prevent tearing. Keep holes and slots a safe distance from bend lines or they will oval, distort or knife-edge.
