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SheetMetal MasterSheetMetal Master — Bend allowance, K-factor and unfolding
Start with thickness, inside radius, and bend angle. Bring bending calculations and common unfolding patterns into preparation for fabrication.
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Agree on the dimension convention
Bend allowance is the neutral-axis arc length in the bend. Bend deduction converts the sum of two outside flange dimensions into a flat length. These are different quantities. Confirm whether the drawing gives outside dimensions or straight lengths to the tangent points.
Bends and common unfolding patterns
The catalogue covers bend allowance, K-factor, and patterns such as round-to-rectangular transitions, segmented elbows, and cones. Establish the geometry and seam requirements before applying results to fabrication.
Start with a worked example
The guide below includes a single-bend calculator and a complete example. Use it to understand the neutral axis, outside setback, and flat length. Determine an actual K-factor from the material, tooling, and trial-bend measurements.
Questions before downloading
Can every material use the same K-factor?
No. It depends on material, thickness, radius, and process conditions. Prefer measured or validated values applicable to the actual setup.
Does the web calculator unfold complex parts?
The example handles one uniform-thickness bend. It does not account for multiple bends, hole deformation, springback, or complex seams. Use the appropriate unfolding tools and verify the result.
Can I cut directly from the calculated length?
Check the dimension convention and use parameters appropriate to the equipment and material, with trial bends and inspection where needed. The example does not automatically compensate for production conditions.
Questions or feedback? philonis+support@gmail.com