Multi-Bend Flat Pattern (Developed Length)

flat = mold-line - n_bends x BD, the sum of the outside (mold-line) flange dimensions minus the bend deduction per bend (from bend-allowance). A U-channel of 2 + 4 + 2 = 8 in mold-line with 2 bends at 0.1355 in BD develops to 7.73 in; a hat section of 12 in mold-line over 4 bends develops to 11.46 in -- more bends pull more material out of the blank. A layout aid; confirm the first part against a test bend, since the real BD shifts with tooling, material, and grain.

flat = mold_line - n_bends x BD; the per-bend bend deduction BD = 2 x OSSB - BA comes from the bend-allowance geometry.

Machinery's Handbook (sheet-metal bend geometry) by name; SME Sheet Metal Forming by name; press-brake developed-length practice.

Older Machinery's Handbook editions free at archive.org; the flat = mold_line - n x BD arithmetic is public geometry.

Estimate. AHJ and licensed professional govern.

Field names used by the API: mold_line_in, n_bends, bd_in, flat_in, total_deduction_in

• Developed length flat = mold_line - n_bends x BD, mold-line measured to sharp outside cornerssheet-metal layout practice
• BD source the per-bend bend deduction comes from the bend-allowance geometry (BD = 2 OSSB - BA)Machinery's Handbook
• Test bend governs the real BD depends on tooling, material, and grain; confirm on a test partshop practice