Print-in-place parts: hinges, chains and moving joints

What print-in-place means

A print-in-place model has moving parts that are printed together in one go, already assembled. A hinged box, a chain or a ring that spins inside another ring comes off the bed ready to use, with nothing to glue or screw.

It works because the parts never touch. Between them is a small gap, and the shapes are chosen so each part can be printed without resting on its neighbor.

The gap decides everything

With a gap that is too small, the parts fuse into one block. With one that is too large, the joint rattles. Tools on this site with moving parts have a clearance setting for this gap, and the default suits a well-tuned printer with a 0.4 mm nozzle.

• Parts fused together: raise the clearance by 0.1 mm and print again.
• Joint too loose: lower it by 0.05 mm.
• Print the tolerance test first if you don't know what your printer can do. It shows the smallest gap that still comes free.

Slicer settings

• Do not add supports. The model is designed without them, and supports inside a joint can't be removed.
• Do not scale the model in the slicer. Scaling down shrinks the gaps too. Change the size in the tool instead.
• Set "elephant foot compensation" to 0.1–0.2 mm. A squashed first layer is where joints fuse most often.
• Use 0.2 mm layers or thinner. Thick layers make the sloped faces inside a joint rough.
• PLA is the easiest material for this. PETG strings more and tends to bond across small gaps.

Freeing a stuck joint

A new print-in-place joint is often a little stuck. That is normal: a few thin strands bridge the gap.

• Let the part cool fully first. Warm plastic bends instead of breaking free.
• Work the joint back and forth with small movements, and increase them slowly.
• Slide a thin blade along the gap on the first layer side, where parts fuse most.
• If it takes real force, stop. Raise the clearance and print again.