The Sheet Metal DFM Checks That Matter

Bend Radius Validation

Minimum bend radius for sheet metal is a function of material, temper, thickness, and the bend direction relative to the grain of the sheet. Inside bend radius below the minimum for the specified material and thickness causes cracking at the outer surface of the bend. The minimums are published by material suppliers and covered in standards.

AI inspection reads the modeled inside radius on every bend feature and compares it against the minimum for the specified material and thickness. It flags violations with the specific radius, the minimum required, and the source standard or internal guideline cited.

This is straightforward to check manually on a part with three bends. It is not straightforward on a complex enclosure with 40 bend features across six faces.

K-Factor Accuracy

K-factor describes where the neutral axis sits within the material during bending, as a ratio of the neutral axis position to the material thickness. It directly affects flat pattern dimensions: use the wrong k-factor and your flat pattern is wrong, which means your part does not conform to the 3D model after forming.

The correct k-factor depends on material, thickness, bend radius, and your specific tooling setup. Most CAD tools use a default k-factor that is approximately correct for common mild steel at typical thicknesses. For aluminum, stainless, high-strength steel, or non-standard thicknesses, the default is often wrong.

AI tools connected to your fabricator's process data or your internal manufacturing guidelines can apply the correct k-factor for the specified material, flag when the CAD default is being used for a material where it is not accurate, and calculate the correct flat pattern length.

Hole-to-Bend Clearance

Holes too close to a bend distort during forming. The minimum clearance is typically expressed as a multiple of material thickness plus bend radius. A hole at 1.5 times material thickness from the bend tangent line in 3mm steel is going to distort. The rule is calculable. AI checks every hole on every part against the applicable clearance rule.

Flat Pattern Interference and Grain Direction

Flat pattern interference occurs when a feature in the flat pattern overlaps or conflicts with another feature, which only becomes visible when the 3D model is unfolded. AI tools that read the geometry can unfold the flat pattern computationally and check for interference before the file goes out.

Grain direction matters for bending performance in aluminum and some stainless alloys. AI inspection can flag bends oriented parallel to the rolling direction on materials where perpendicular orientation is required for crack-free bending.

Feature-Specific Checks

Relief cuts at bend terminations. Minimum flange lengths for press brake tooling access. Tab and slot alignment for welded assemblies. Countersink depth versus material thickness. Each of these is a geometric check that AI handles the same way: compare the modeled geometry against the rule, flag violations with citations.