How Do Tolerances Stack Up on a Part That Is Both Laser Cut and Bent?

They stack in two different units. The laser step gives you a fixed linear tolerance on the flat pattern. The bend step adds an angular tolerance on top, and that angle turns into a growing linear error the farther a feature sits from the bend line.

Two tolerances, two mechanisms

The laser step gives you a flat pattern tolerance that's constant regardless of what happens to the part later. It's a function of kerf consistency and cut accuracy, applied to every hole and edge on the blank before it ever sees a die.

The bending step doesn't add a second linear number. It adds an angular one. A bend angle held to a tight window still produces a growing position error on any feature beyond the bend as leg length increases, because a small angular deviation multiplied by a longer arm is a bigger linear miss. A hole punched right next to the bend line barely moves if the angle is off. That same hole out at the end of a long leg moves a lot more for the identical angular error.

That's the part people miss when they treat sheet metal tolerancing like a single number pulled off a spec sheet. The cut tolerance stays flat across the part. The bend-induced position error does not.

Where this actually bites you

Two features that both sit near the bend line, on either side, don't accumulate much stacked error between each other. They're both close to the pivot, so an angular miss barely moves either one relative to the sheet, and they mostly move together anyway.

The problem case is a feature far out on one formed leg that has to line up with a mating part, or with a feature on the same piece across multiple bends. Chain two or three bends together and each one adds its own angular tolerance on top of a growing leg length. That's how a bracket with three bends in series ends up dead-on near the first bend and visibly off by the third.

What to do about it on the drawing

Dimension critical features from a datum that survives the forming sequence, not from the far edge of the flat pattern. If a hole matters relative to a formed face, call it out that way.

Keep functionally critical holes close to the bend line when the design allows it. Less leg length between the bend and the feature means less amplification of angular error.

Don't stack tolerances you don't need. If a hole's exact position after forming doesn't affect fit or function, don't dimension it as if it does.

For features that must land precisely after multiple bends, consider whether they can be added after forming instead of before. That removes the bend error from the feature entirely, though it's a secondary operation decision.

DigiForge holds ±0.13 mm on the cut and ±0.5° on the bend angle. On a single bend with a modest leg, that's a small, predictable number. On a multi-bend part with long legs, run the geometry math before you lock the drawing, because the angular tolerance is the one that grows.