Snap-fit (cantilever)

A tapered spring arm with a tip barb, plus a catch to latch into.

A cantilever snap-fit is a flexible arm with a barb near its tip. It inserts along the arm’s length: as it slides into a slot the barb is pushed flat, then springs back out sideways once it clears the wall, and the barb’s back face catches the edge of an opening so the arm can’t pull out. The red "Cut window" is a cutting tool, not a finished part — position it on your own mating wall at the latch point and subtract it, so the barb has an opening to snap into. Choose "Mated keeper" instead to get a solid strike-plate already positioned in the latched state, which makes the engagement easy to see. For round parts, use the annular snap instead.

Watch the bending strain read-out. A snap-fit fails by snapping off, and the culprit is almost always an arm that has to flex further than the plastic tolerates. The Properties panel shows the strain at the arm’s root as you change the numbers, from the standard cantilever relation (strain = 1.5 × thickness × barb height ÷ length²). Under about 3% is comfortable in any filament including PLA; 3–6% wants something tough like PETG, ABS or nylon; past that it will break on first assembly. The strongest lever is length, because strain falls with its square — doubling the arm quarters the strain, where thinning it or lowering the barb only helps in proportion. The figure is calculated for an untapered arm, so a tapered one (the default) has a little more headroom than it suggests.

1. Open the Generate panel from the left sidebar and choose Snap-fit (under Enclosures).
2. The arm (and catch) drop in as editable parts. The parameters open in the Properties panel, where you set them.
3. Set the beam length, width, and thickness, plus the barb height, then pick a fit — Tight, Normal or Loose, or Custom to set the latch gap yourself.
4. Pick a catch style — Cut window (a subtract tool for your own wall) or Mated keeper (a ready demo pair).