Almost every fabricated part is a variation on a small number of shapes, because a press brake bends along straight lines and a laser cuts a flat blank. Designing within that vocabulary produces parts that are cheap, quick and predictable, and designing outside it produces parts that need extra operations for reasons the drawing does not make obvious.
The shapes fabrication makes naturally
The simple bracket, one or two bends in a flat blank. The channel or U section, two parallel bends. The Z section, two bends in opposite directions. The folded box, four bends with corner relief and either open corners, welded corners or tabbed corners. The hemmed edge, folded back on itself for stiffness and to remove a sharp edge. Between them these cover most of what a fabricator makes.
Features that add stiffness without material
A flange along an edge stiffens a panel far more than thickening it would. A hem does the same and removes the sharp edge. Embossed ribs and swages pressed into a face stiffen it locally. A lanced and formed tab makes a locating feature from the material already there. All of these are cheap because they happen at the brake or in the punch rather than as separate parts.
Corners, relief and the tearing problem
Where two bends meet at a corner the material has to go somewhere, so a relief notch at the end of each bend line stops it tearing or bulging. Box corners are either left open, welded closed, or designed with an overlapping tab that is riveted or spot welded. Which one you choose decides whether the box needs a welding fixture, which is usually the largest cost in a small fabricated assembly.
What makes a part expensive without looking it
Bends in more than two directions, which increase the chance of a fold colliding with the tooling. Features close to a bend, which distort. Mixed material thicknesses. A different bend radius on one fold. Tight tolerances across bends. And any shape that nests badly in a sheet, since material is charged by the sheet consumed rather than by the part area.
Questions people ask about sheet metal part
What shapes does sheet metal fabrication make best?
Brackets, channels, Z sections, folded boxes and hemmed panels: shapes made from a flat blank with straight bends and standard tooling.
How do I stiffen a panel without adding thickness?
A flange or hem along the edge, or embossed ribs and swages pressed into the face. All are far more efficient than thickening the material.
Why do box corners need relief?
Because material at the end of a bend has nowhere to go and tears or bulges. A relief notch at each end of the bend line prevents it.
What makes a fabricated part unexpectedly expensive?
Mixed thicknesses, mixed bend radii, features too close to a bend, tolerances across bends, and outlines that nest badly in the sheet.