Manufacturing & engineering
Flat pattern
Definition
A flat pattern is the unfolded 2D shape of a sheet metal part, calculated from its bends, radii, and K-factor or bend table. It is what gets cut from the sheet before the part is formed.
Also known as: flat blank, unfolded pattern, sheet metal flat
Updated
Kept in sync with the model#
In sheet metal environments, the flat pattern updates as the folded part changes. Onshape's sheet metal model represents all operations as a flat pattern, lists joints and bends in a sheet metal table, and keeps the folded, flat, and table views updated together.
The flat pattern is usually exported as DXF for laser or punch cutting. A part modeled as a plain solid, including most AI-generated "sheet metal", has no flat pattern and has to be rebuilt with real sheet metal features before it can be fabricated.
Sources
Related terms
K-factor
The K-factor is the ratio of the neutral axis position to the material thickness in a sheet metal bend. CAD programs use it to calculate bend allowance and the size of the flat pattern.
Bend allowance
Bend allowance is the length of material used up by a sheet metal bend, measured along the neutral axis between the bend's tangent points. It depends on thickness, bend radius, bend angle, and K-factor, and it decides whether the flat blank folds up to the right size.
DXF
DXF is Autodesk's documented format for exchanging AutoCAD drawing data, most often 2D geometry. It is the usual handoff for laser cutting, waterjet, and sheet metal flat patterns.