Key principles.
Pre-bend
Sheet metal layout before bending operations.
Material flow
Material stretches during bending. Add to flat dimension.
Negative allowance
Subtract from flat for outside dimension.
Material constant
Material-specific neutral axis position.
Cardboard / packaging
Dieline for cardboard packaging. Different from sheet metal.
Automatic
CAD software generates flat patterns automatically.
FAQ
Material stretches/compresses during bend. Bend allowance corrects.
Position of neutral (unstretched) axis. K=0.5 means middle. Material-dependent.
Allowance: amount to add. Deduction: amount to subtract from outside dimension. Different math.
Solidworks, Inventor automatically calculate K-factor + bend allowance.
Different K-factor per material/thickness. 5052 vs 6061 different. Stainless different.
Flat layout ±0.1 mm. Bent assembly ±0.5 mm. Per specification.
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