Compression spring

A helical coil spring, wound to a length and coil count that will actually print.

A helical compression spring: round wire wound into a coil, built as one swept solid rather than a stack of rings, so it comes out as a single connected body every time.

Four numbers describe it — wire diameter, outside diameter, free length and coils — and the one that decides whether it works is not among them. The coil gap is what is left over after the coils are spread across the length, and it is the whole game: too small and the turns fuse into a rod on the plate, and there is no way to see the difference in the viewport at any realistic zoom. So the panel reports it rather than leaving you to find out.

Free length is the parameter that gives. Wire, diameter and coil count are what a spring *is*; the length is a consequence of how tightly it was wound. Ask for a length that cannot hold that many coils apart and it is raised to the shortest one that can, and the panel says so. Pulling the slider lower will feel stuck — that is the honest answer, because the shorter spring does not exist at that coil count. Want it shorter? Use fewer coils or thinner wire.

Three end treatments. *Open* winds at one pitch throughout and ends mid-rise, so the spring does not stand square. *Closed* winds the last turn at each end as tightly as it can print, which flattens it. *Closed & ground* additionally cuts both ends off flat — the way a real spring is finished — and it is the only setting whose height is exact: the others come up a few microns short, because the wire section sits perpendicular to the helix and so does not quite reach the full radius at the very end.

Read the rows. *Wind* gives the spring index (the ratio of coil to wire — real springs run 4 to 12), the pitch, and that all-important gap. *Travel* gives the useful stroke and the solid height — the point where every coil is touching and no load compresses it further, which is the hard limit a spring specified for more travel will simply not meet. A third row appears only when something binds: wire thinner than two extrusion widths, a wind tight enough that the diameter had to be raised, a length that was raised, or a gap sitting on its floor.

Hand only matters when one spring has to nest inside another.

Prints upright without supports — each turn lands on the one below it. Pairs with the ball bearing and pulley families for mechanisms; stays editable in the property panel.

1. Open the Generate panel from the left sidebar and choose Compression spring (under Gears & drives).
2. The spring drops in as one editable body. The parameters open in the Properties panel, where you set them.
3. Set the wire diameter and the outside diameter — the outside diameter is measured across the coils, the way a caliper reads it.
4. Set the free length and the coil count, then read the Wind and Travel rows before you print.
5. Pick the ends: Closed stands square, and Closed & ground is the only setting that lands the height exactly.