Sheet metal design tips that save money

Design for how the metal behaves

Sheet metal is cut flat and then bent. Most problems, and most extra cost, come from features that ignore how the metal stretches, springs back and cracks. A few habits avoid nearly all of them.

Habits that help

• Use one thickness for the whole part where you can. Every extra thickness means a separate material to buy and handle.
• Keep the inside bend radius at least equal to the sheet thickness for common steels. Tighter bends can crack, and aluminium and stainless steel often need more.
• Keep holes and slots away from bends, roughly at least two and a half times the thickness plus the bend radius. A hole too close to a bend stretches into an oval.
• Keep the flange after a bend long enough for the press brake tool to grip, generally at least four times the thickness.
• Add small relief cuts where a bend meets a flat edge, so the metal does not tear at the corner.
• Avoid very small holes: a hole smaller than the thickness of the sheet is hard to punch cleanly, and laser cutting is the usual answer.

Tolerances in sheet metal

Bending adds error at every bend, so tolerances on bent parts are looser than on machined parts. Give tight tolerances only where parts fit together, and let the fabricator choose the bend sequence.

Tell the workshop the important things

Send a DXF for the flat shape and a drawing with the bends. Mention the material grade, the thickness, the finish, and the quantity. If some edge is visible on the finished product, say so, because it affects how the edges are finished.

Kinds of work

• Die making
• Mold making
• CNC machining
• Casting
• Fabrication