CALCULATORS / SHEET METAL, FORMING AND WIRE

Bent-part flat-length estimate calculator

Two tangent straight segments plus one neutral-axis bend allowance.

sheet-metal-flat-length.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	bendmm	flatLengthmm
	3.76991	83.7699
	3.76991	73.7699

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

flat length envelope83.77 mm✓ passes

BASELINE INPUTS

legA50 mmlegB30 mmangle90 degradius2 mmthickness1 mmkFactor0.4

CALCULATED

bend3.7699 mm

flatLength83.77 mm

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Bent-part flat-length estimate
# Scope: Two tangent straight segments plus one neutral-axis bend allowance.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

legA = 50 mm
legB = 30 mm
angle = 90 deg
radius = 2 mm
thickness = 1 mm
kFactor = 0.4

bend := angle*(radius+kFactor*thickness) [mm]
flatLength := legA+legB+bend [mm]

check flat length envelope: flatLength <= 90 mm

scenario alternative: legA = 40 mm

Calculated from your source · not saved

Baseline · Baseline

flat length envelope83.77 mm ✓ passes

alternative · alternative

flat length envelope73.77 mm ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

bend: bend = angle*(radius+kFactor*thickness) [mm]
flat length: flatLength = legA+legB+bend [mm]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

leg a: 50 mm
leg b: 30 mm
angle: 90 deg
radius: 2 mm
thickness: 1 mm
k factor: 0.4

Calculated

bend: 3.76991 mm
flat length: 83.7699 mm

Assumptions and limits

Two tangent straight segments plus one neutral-axis bend allowance.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Bent-part flat-length estimate. Inputs: flange dimensions; bend definitions; bend allowance model. Outputs: developed blank length. Model scope: Specified bend geometry and calibrated material/process factors. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: flange dimensions, bend definitions, bend allowance model
Outputs: developed blank length
Modes: calculate, compare, sweep
Drawing: Flat pattern and forming sequence

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS