What happens when unleveled sheet parts are processed?

chamfering:

Enclosed tensions in the sheet metal are unleashed by chamfering. As a result defects in angularity occur, which enhance  scrap and the expense on refinishing works.

bending:

Enclosed tensions and unevenness of sheet metal parts result in shape distortion and thereby affect the dimensional accuracy of the bending process.

welding:

Selective thermal treatment leads to the release of internal stress, what in turn causes deformation of the material. Unflat sheet metal parts extend the through-put times in different ways. Prearrangements for welding grow with unleveled material. Further more, processing uneven sheet metal parts elevates refinishing works. Besides, process stability of robot welding declines by using unleveled material.