Manufacturing & engineering
K-factor
Definition
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.
Also known as: K factor, k-factor sheet metal
Updated
What it represents#
When sheet metal bends, the inside compresses and the outside stretches. Somewhere between them is a neutral axis whose length does not change. Onshape's sheet metal documentation defines the K-factor option as the ratio of the neutral axis to the material thickness, and uses it as the default bend calculation.
A K-factor that does not match the real material, thickness, and tooling produces a flat blank that forms up slightly too long or too short. For parts with tight flange dimensions, use the value your fabricator measures rather than a generic default.
Sources
Related terms
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.
Flat pattern
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.
DFM
DFM is the practice of shaping a part so it can be made reliably and economically with the intended process. It covers choices such as wall thickness, draft, tool access, bend radii, hole sizes, and tolerances the supplier can actually hold.