What causes fit issues in sheet metal assemblies?

Fit issues in sheet metal assemblies most commonly come from tolerance accumulation across bent features, hole misalignment between mating parts, variation in bend radius from different press brake setups, and underdefined weld or rivet joint locations. Sheet metal bends introduce variation that flat-pattern CAD does not show, and the variation compounds across multiple bends in a single part.

Why this becomes hard

Sheet metal bends are difficult to tolerance correctly in CAD. The nominal bend radius depends on material, thickness, die selection, and the press brake setup—and all of these vary between suppliers and even between runs at the same supplier. Hole positions relative to bent features are the most common source of assembly mismatch.

What teams usually miss

K-factor in the flat pattern CAD is set as a default that may not match the supplier's actual tooling. Teams also commonly omit bend radius callouts on drawings, which means the supplier uses their standard tooling even when the design needs a tighter or looser radius for clearance with adjacent parts.

What KnowYi does

KnowYi reviews sheet metal drawings for hole-to-bend relationship tolerances, flags missing bend radius callouts and K-factor notes, and coordinates with suppliers to verify that critical fit dimensions are checked at first article before the full lot is bent. We require a dimensional report for critical mating features.

What to send us

STEP file, flat-pattern drawing with bend callouts, 2D drawing of the finished part with GD&T, material and finish specification, and batch quantity.

If you already have CAD, drawings, BOM, Gerbers, or even an incomplete file package, send it to KnowYi. We can turn it into a clear manufacturing path with missing inputs identified, quote blockers flagged, supplier routing handled, production records maintained, and delivery evidence returned.

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