Sheet Metal Box Flat Pattern Calculator

Inputs

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Finished outside mold-line base length between the length-side bends.
mm
Finished outside mold-line base width between the width-side bends.
mm
Finished outside mold-line side height for all four tray sides.
mm
Sheet thickness.
mm
Inside radius formed by the tooling.
mm
Neutral-axis location as a fraction of material thickness from the inside surface.
Degrees each flange turns from flat. A right-angle tray uses 90 deg bends.
°
Simple square notch size at each corner. Minimum screen is inside radius plus thickness.
mm

Results

Default result
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Flat blank length(Lflat)
394.3mm
Pass

Also computed

Flat blank width(Wflat)Pass294.3mm

Gross blank area(Agross)116,000mm²

Net area after reliefs(Anet)Pass116,000mm²

gross rectangle minus four square relief cuts

Bend line from edge(BLe)Pass48.57mm

distance from blank edge to bend line

Bend allowance per bend(BA)3.134mm

Bend deduction per bend(BD)2.866mm

Sheet metal box flat pattern previewSheet metal box flat pattern previewDashed lines are bend lines; corner relief is shown as square notch locations.Flat blank: 15.522 in x 11.585 inBend line from edge: 1.912 inRelief margin: 0.000 inVerify K-factor, relief and bend sequence with shop tooling.
Method notes 4 notes
  • Dimensions are treated as outside mold-line dimensions.
  • Flat blank length = base length + 2*side height - 2*bend deduction. Flat blank width uses the same relation.
  • Bend line from edge = side height - outside setback + bend allowance/2.
  • Corner relief is a simple square-notch screen. Real boxes may need tabs, miters, hems, weld gaps, bend-sequence changes or shop-specific relief shapes.

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