Input: Model the sheet planar faces without fillets and thickness, join them as a manifold polysurface/brep, you can have holes, funny contours, nevermind, do sort of an origami within reasonable fabrication limits reality check. Select material and thickness.
The definition fillets the manifold creases and thickens the sheet as a real plate, the additional component exports the geometry directly from GH as a step file ready for submission to a machining service (laser cut + bending of sheet metal).
K factor is not at play here, as it isn't required by the tested supplier, we give them a step model, not a flatten version of the sheet.
Only tested with Rhino 7.