Print in Place Designs: Hinges, Joints, and Mechanisms

James H.

One Print, Done

Print in place designs exploit one of FDM printing's unique capabilities: the ability to print multiple, mechanically separate components simultaneously, in their assembled configuration, without any post print assembly. A hinge prints with the pin already through the barrel. An articulated dragon prints with every joint already connected. A mechanical chain prints as a working chain. The components are printed with deliberately designed gaps that prevent bonding between them, leaving functioning mechanical assemblies that snap into motion the moment you pick them up.

These designs are deeply impressive demonstrations of FDM's capabilities, and they regularly astonish people who haven't encountered 3D printing before, and they're genuinely useful for creating mechanisms that would be difficult or impossible to assemble conventionally. However, they require understanding of clearances, printing orientation, and material selection to produce reliably.

The Science of Print in Place Clearances

The critical variable is the gap between mating surfaces: the pin in its barrel, the ball in its socket, and the chain link through its neighbour. This gap must be large enough that the surfaces don't fuse during printing (FDM prints at elevated temperatures, and adjacent parts can bond if too close), but small enough that the joint has an appropriate range of motion and minimal slop. Typical values: 0.2–0.3mm for a working clearance in PLA. 0.15 mm is possible on well calibrated machines. 0.4mm+ gives a very loose joint with lots of play.

The correct clearance depends entirely on your specific printer's calibration. Print a dedicated clearance test first, a simple pin-and-hole assembly with multiple versions at 0.1 mm clearance increments (0.1, 0.2, 0.3, 0.4 mm). Test each to find which is the loosest that successfully separates after printing and the smallest that moves freely. This calibration is a one time exercise per printer that informs all future print in place designs.

Material Selection

PLA is the most reliable material for the first print in place experiments. Its relatively sharp solidification temperature means it stops being tacky quickly, reducing the risk of adjacent parts fusing. PETG is more likely to string across clearance gaps and bond surfaces together; ensure that you use slightly larger clearances (add 0.1–0.15 mm to your PLA values). TPU creates spectacular flexible print in place designs; imagine a snake-like articulated creature that actually coils and writhes. TPU's flexibility and low inter part bonding risk make it excellent for this application. Start with 95A Shore hardness for reliability. Direct drive is strongly recommended for TPU PiP designs. See our TPU printing guide.

Finding and Evaluating Designs

Printables has a dedicated "Print in Place" category with hundreds of tested designs rated by community success. Start with the classic articulated dragon, as it's widely printed, well documented, and tests all aspects of print in place capability. A successful dragon print confirms your clearance calibration is correct. Then try a ball joint, a chain link, and a working hinge, and eventually design your own mechanisms. The tolerances guide provides the mathematical framework for designing your own clearance values.