Cantilever snap-fit generator
Generate a parametric cantilever snap-fit (arm + catch)
A cantilever arm with a barb near its tip: it flexes as it enters a slot, then springs back so the barb catches the far side of an opening. The panel shows the bending strain at the arm’s root as you type — 1.5 × thickness × barb height ÷ length² — and under 3% is comfortable in any filament, 3–6% wants PETG or nylon, past that it breaks on first assembly. Download a print-ready STL or 3MF.
How the Cantilever snap-fit generator works
What you can adjust
- Length
- Width
- Thickness
- Tip taper — 0.2–1
- Barb height
- Fit — Tight · Normal · Loose · Custom
- Latch gap
- Generate a catch
- Catch style — Cut window · Mated keeper
Snap-fit strain chart
Root strain from the same relation the generator’s read-out uses (strain = 1.5 × thickness × barb height ÷ length²), for a 1 mm barb. Up to 3% suits any filament, PLA included; up to 6% wants PETG, ABS or nylon; above that, lengthen the arm.
| Arm length | 1.5 mm thick | 2 mm thick | 3 mm thick |
|---|---|---|---|
| 6 mm | 6.25% · too high | 8.33% · too high | 12.5% · too high |
| 8 mm | 3.52% · PETG, ABS or nylon | 4.69% · PETG, ABS or nylon | 7.03% · too high |
| 10 mm | 2.25% · any filament | 3% · any filament | 4.5% · PETG, ABS or nylon |
| 12 mm | 1.56% · any filament | 2.08% · any filament | 3.13% · PETG, ABS or nylon |
| 16 mm | 0.88% · any filament | 1.17% · any filament | 1.76% · any filament |
| 20 mm | 0.56% · any filament | 0.75% · any filament | 1.13% · any filament |
Designing a snap-fit that does not break
- Length is the strongest lever. Strain falls with the square of the length: doubling the arm quarters it, where thinning the arm or lowering the barb only helps in proportion.
- Watch the strain read-out. Bending strain at the root shows in the Properties panel as you change the numbers. Up to 3% is fine in any filament; up to 6% wants a tough one. These are filament rules of thumb, not a material model, so a test print still decides.
- Print the arm lying flat. The layers then run along the arm. An arm printed standing up bends across its layer lines, which is exactly where printed parts split.
- The taper buys headroom. The read-out is calculated for an untapered arm, the cautious case. An arm that tapers toward its tip, as the default does, has a little more headroom than it shows.
- Choose how it latches. Cut window is a cutting tool you subtract from your own wall so the barb has an opening to snap into. Mated keeper gives a solid part already in place. Fit (Tight, Normal, Loose) sets the latch gap.
Snap-fit questions
How do you design a snap-fit joint for 3D printing?
A flexible arm with a barb near its tip: going in, the barb is pushed flat, then springs back behind an edge. Choose the length, thickness and barb height so the strain at the root stays under 3% for PLA. This generator works it out as you adjust.
What is the formula for a cantilever snap-fit?
Root strain = 1.5 × thickness × barb height ÷ length². With an arm 2 mm thick and 16 mm long and a 0.8 mm barb, that is 0.94%.
Which filament is best for snap-fits?
As a rule of thumb, PLA tolerates about 3% strain and a tough filament such as PETG, ABS or nylon about 6%. Past that, nothing survives repeated assembly: lengthen or thin the arm.
How do I add the catch to my own part?
Turn on Generate a catch. With Cut window, place the red tool in your own wall at the latch point and subtract it. Mated keeper gives you a solid part already in position. To build the arm into a lid, use Attach to in the Properties panel.