Flat pattern: A flat pattern is the unfolded 2D shape of a sheet metal part, cut from flat sheet before it is bent into its final 3D form.
CAD sheet metal tools unfold a bent model into its flat pattern using the bend radius and the K-factor. The flat pattern, usually exported as a DXF, is what the laser or punch cuts, with bend lines marked for the press brake.
What it means for the price
The flat pattern is the starting point of most sheet metal quotes. Its area and bounding box decide the material share in the nest; its cut length and number of pierces decide cutting time; the bend count from the 3D model decides press brake time. A part that unfolds into an awkward shape nests badly and costs more in material than its finished size suggests.
Example: an open box 100 × 100 mm with 50 mm walls unfolds into a cross about 200 mm across. Most of its bounding square is waste unless other parts are nested into the corners. The figures are an example.
Common confusions
A flat pattern made with a CAD default K-factor may not match how the shop bends, so many shops regenerate it from the 3D model with their own values. A flat pattern is also not the same as a 2D drawing of the finished part. Read what drives sheet metal fabrication cost.
Go deeper: Sheet metal fabrication cost: cut, bend, insert, finish