Welding puts heat into one side of a joint. As the seam cools it shrinks, and the frame moves. You cannot remove distortion, but you can plan for it.

Balance the heat

Seams placed evenly around the neutral axis pull against each other. A frame welded all on one face will bow toward that face every time.

Sequence

Tack the whole frame first, then weld in short runs that alternate from side to side. A robot cell repeats the same sequence on every frame, which is why robot-welded parts are more consistent than their seams alone would suggest.

Fixtures and pre-set

A stiff fixture holds the parts while they cool. Where movement is predictable, we set the joint slightly off so it pulls into position.

Machine after welding

• Leave stock on mounting faces and bores
• Stress-relieve the frame if tolerances are tight
• Machine the datum features last, in one setup

A welded frame is accurate where it has been machined, and close everywhere else.

Design choices that help

Use fewer, smaller seams. A 4 mm fillet carries more than most designers assume, and doubling its size quadruples the heat. Bent corners instead of welded ones remove the seam altogether.