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How to
Parts that print together and move
Design a hinge, ball joint or chain that comes off the bed in one print and moves, and check it before you print.
A print-in-place mechanism is two or more Bodies printed together, already assembled, that move once they come off the bed: a hinge, a ball joint, a chain. Each moving part is its own Body, and they print where you modelled them, with Z 0 as the bed.
To start from one that works, open Insert › Ready-made and choose Print-in-place hinge, Print-in-place ball joint or Print-in-place chain. Each is ordinary sketches and features in History, so you can open them and change how they are made.
The rule
Every moving part prints from the bed, and never through the part it moves against. For each part, check: how does the printer get from the bed to here? If the only way is across the other part, it will fuse to it, or print on air and sag.
Clearances
For FDM printing with a 0.4 mm nozzle in PLA or PETG:
| Gap | What happens |
|---|---|
| Faces touching | They fuse, every time, even at Z 0 |
| 0.15 mm or less | Almost certainly fuses |
| 0.15 to 0.3 mm | May work on a well-tuned printer |
| 0.3 mm | The standard: use it on every moving face |
| 0.5 mm | A safe first print of a new mechanism |
| More than 0.5 mm | Moves freely, may feel loose |
Between hinge knuckles, leave 0.3 mm a side. Round a pin in its bore, 0.3 mm all round.
Five ways it goes wrong
- A trapped part with nothing to print on. A ball, pin or ring floating inside its socket has no route to the bed. Give it a stem, rod, leg or tab that leaves through an opening in the part around it and reaches Z 0.
- The same gap everywhere. A 0.3 mm gap under the moving part means it prints on air above the other part. Under a part, the route to the bed carries it, not the gap.
- Treating the stem as support to cut off. The rod that carries a ball to the bed is part of the design. Size it from the start, with its own clearance through the opening.
- Flush faces between parts. Two faces of different Bodies that touch or sit exactly level side by side fuse. Leave 0.3 mm.
- Checking the gap but not the path. A part can be 0.3 mm clear and still print on top of the part it moves against. Where one part is over another, slope the upper part's underside at 45° or steeper: cone pins, a 45° roof over a ball, a 45° cap over a ring.
Check it before you print
- Open Make.
- Under Print in place, tap Check moving parts.
- Each row says Pass, Fail, Review or Not measured, with the number it measured,
what it checked and the rule it used:
- On the bed: each separate piece's lowest point is on Z 0.
- Gap: the closest two Bodies come; touching, overlapping or 0.15 mm or less fails, under 0.3 mm needs review.
- Print path: how much of a Body's underside, in mm², prints on another Body.
- Movement: not measured. Whether the part stays in and how far it moves is for you to check by moving it in Assembly, then on the printed part.
Fix every Fail and Review row, then print. Rock the parts gently to free them after printing.
Sources
- The rule, the clearance table and the five mistakes are adapted from the print-in-place design skill's "Print-in-Place Design for FDM" reference (MIT licence).
Last updated 2 November 2026, for MakerSketch 1.0.