Box and Tray Blank Calculator

Along each direction, add the outside dimensions — the base plus two flanges — and take off one bend deduction per bend. For a 300 × 200 × 50 tray in 2 mm with R 2 and K 0.33, each 90° bend deducts about 3.82 mm, so the blank is about 392.36 × 292.36 mm.

Where two bend zones cross, the metal would have to bend in two directions at once; the FAA warns that such a corner can tear or crack (pp. 4-71–4-72). Cutting each corner back 1/32 in past the inner tangent lines of both bends removes that crossing with a small margin for bending error — the margin the FAA gives for relief holes (p. 4-72). The price is an open corner: after folding, each flange ends R + 1/32 in short of its neighbour.

Not yet. The sources disagree on where a relief hole is centred and how big it is — the FAA handbook places it both centred on and touching the intersection of the inside bend tangent lines, and sizes it at about twice the bend radius as well as the bend radius itself — so this version keeps to a plain square notch.

At the middle of each bend zone: the flange leg (height less the outside setback) plus half the bend allowance, from each edge of the blank. They are on the BEND_UP layer of the DXF. For lining the sheet up in the brake, the FAA handbook uses a sight line one radius inside the tangent line, not the middle of the bend (p. 4-66).