Living Hinge Pattern Generator (laser flex)
Laser-cut living hinge (flex) patterns sized from the bend angle and radius — SVG, DXF and PDF.
How it works
Generate a living hinge (kerf bending, flex pattern) for plywood, MDF or acrylic: straight, wave or zigzag rows of staggered cuts across a bend zone. The zone length follows from the bend angle and the inside radius on the neutral axis; you also get the number of rows, the twist each strip has to take, the size of the torsion links and the total cut length.
- Bend length on the neutral axis = bend angle (radians) × (inside radius + thickness ÷ 2). The zone gets round(length ÷ row spacing) + 1 rows, so the zone is (rows − 1) × spacing and sits in the middle of the panel.
- Each row has cuts of the given length separated by bridges; neighbouring rows are shifted by half a period, so the material between two rows forms torsion links of length (cut − bridge) ÷ 2 and width row spacing − kerf. Every link row takes bend angle ÷ (rows − 1) of twist.
- Cuts keep one bridge length from the top and bottom edges. Wave and zigzag rows follow the same function, so neighbouring rows never touch. Only the outline is kerf-compensated; the hinge cuts stay on their lines. SVG files use millimetres (width/height in mm, 1 user unit = 1 mm) with one group per layer: cut (red #e4002b), score (blue #0067c5), engrave (black) and labels (grey). DXF R12 uses the same layers, millimetres, y up.
How far a hinge bends depends on the material, the grain, the glue in plywood and the laser settings — cut a short sample first. Laser cutters and CNC routers can start fires and release harmful fumes: never leave the machine unattended, use extraction, and never cut PVC, vinyl or other chlorine-containing plastics. Sizes, kerf and fit are starting points — check them with a test cut and follow your machine maker's safety rules.
Sources
- Scalable Vector Graphics (SVG) 1.1, Second Edition — paths and units (W3C)
- AutoCAD DXF Reference — R12 entities POLYLINE, VERTEX, TEXT and the LAYER table (Autodesk)
- ISO 32000-1:2008 Document management — Portable document format (PDF 1.7) (Adobe / ISO)
Part of Kerfwise
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Kerfwise Cabinet & furniture CAD
Design cabinets and furniture, get cut lists, optimised sheet layouts, costs and drawings.
How to use the Living Hinge Pattern Generator
Size a laser-cut living hinge from the bend angle and radius, choose straight, wave or zigzag cuts and read how much each strip has to twist.
What it is for
A living hinge (also called kerf bending or a flex pattern) makes stiff sheet material bendable. Rows of staggered cuts turn the panel into many thin strips that twist like torsion bars, so 3 mm plywood can wrap around a rounded box corner or form a book cover spine. The difficult part is choosing how long the cut zone must be and how many rows it needs.
This generator works that out from the bend: you enter the bend angle, the inside radius and the material thickness, and it places the rows across a zone of the right length in the middle of your panel. You can choose straight, wave or zigzag cuts and tune the cut length, the bridge between cuts and the row spacing. It gives geometry, not a strength calculation; how far a hinge really bends depends on the material and your laser.
Worked example
The first example bends 3 mm plywood by 90° around a 15 mm inside radius on a 140 × 60 mm panel, with 18 mm cuts, 3 mm bridges and 1.6 mm row spacing. The tool reports:
Living hinge: 17 rows of straight cuts over a 25.6 mm zone bend 90° around a 15 mm inside radius in 3 mm material; each strip twists about 5.63°.
The bend length on the neutral axis is 25.92 mm: the quarter circle measured through the middle of the material, π/2 × (15 + 1.5). Seventeen rows 1.6 mm apart cover 25.6 mm. The strips between the rows form torsion links 7.5 mm long and 1.45 mm wide, and the panel has 79.2 cm of cuts in total.
The wave example bends 180° around 20 mm with 2 mm spacing: 35 rows over 68 mm, 5.29° of twist per row and 261.85 cm of cuts, which takes noticeably longer on the laser.
How to read the result
- Bend length on the neutral axis is the arc your hinge must cover.
- Bend zone is the real width of the cut area: a whole number of row spacings.
- Rows of cuts and Twist per row tell you how hard each strip works. Fewer degrees per row is gentler.
- Torsion link is the length and width of the material between two neighbouring rows.
- Total cut length helps you estimate cutting time.
Tips and common mistakes
- Keep the twist per row low for plywood and MDF; the tool warns above 6°.
- Run the hinge rows across the grain of the face veneer where you can.
- Thin links burn easily: if the row spacing is close to twice the kerf, the tool refuses the settings.
- Only the outline is kerf-compensated; the hinge cuts themselves stay on their lines.
- Cut a short sample with the same settings before you cut the real part.
FAQ
Which pattern bends best?
Straight cuts are the most common and the easiest to cut. Wave and zigzag cuts spread the twist over a longer path and can feel softer, but they take longer to cut.
Can I use it for acrylic?
Acrylic is brittle and cracks easily in thin links. Use wide spacing, a gentle bend and test first.
How do I attach the hinge to the rest of the box?
Leave plain material on both sides of the zone; the panel width sets how much. Glue or finger-joint those plain parts to the neighbouring panels.
Does the tool check if the hinge will break?
No. It gives the geometry and the twist per row; material strength, glue lines in plywood and burn marks are not modelled.
Guide last updated:
For scripts and AI agents
- JSON API:
POST https://kerfwiselivinghinge.usefulweb.app/api/v1/calculate(same calculation as this page) - Interface description: OpenAPI 3.1 · AI guide: llms.txt
- MCP server (Streamable HTTP):
https://kerfwiselivinghinge.usefulweb.app/mcp· tool namekerfwise_living_hinge
Example request
curl -s -X POST https://kerfwiselivinghinge.usefulweb.app/api/v1/calculate \
-H 'content-type: application/json' \
-d '{"width":140,"height":60,"thickness":3,"angle":90,"radius":15}'