Print-in-place clearance: the gap moving parts need to print free

Parts printed already assembled are held apart only by the gap you model. Make it 0.30 to 0.40 mm per side in X and Y on a 0.4 mm nozzle (0.60 to 0.80 mm across a pin), and a whole number of layers in Z, at least two: 0.4 mm at 0.2 mm layers. Narrower, and the facing walls can weld together.

How much clearance does a print-in-place part need?

A print-in-place part needs 0.30 to 0.40 mm per side in X and Y (0.60 to 0.80 mm across a pin) on a 0.4 mm nozzle, and a Z gap of two whole layers: 0.4 mm at 0.2 mm layers. Ball joints need 0.35 to 0.50 mm per side, and PETG, ABS and ASA up to 0.10 mm more.

Per side means the gap at one face. QIDI gives the reason for its range: the gap has to exceed one layer height in Z and roughly one extrusion width in X and Y, or neighboring walls weld together. That is about twice the 0.15 to 0.25 mm per side a pin fitted after printing needs, because a fused print-in-place joint can’t be sanded apart.

Part printed in place	Per side	Total across	Source
Hinge pin in its knuckle	0.30 to 0.40 mm	0.60 to 0.80 mm	QIDI
Chain or articulated link	0.30 to 0.40 mm	not given	QIDI
Ball in a socket	0.35 to 0.50 mm	0.70 to 1.00 mm	QIDI
Pin fitted after printing, for comparison	0.15 to 0.25 mm	0.30 to 0.50 mm	QIDI

QIDI’s values assume a 0.4 mm nozzle, 0.2 mm layers and PLA or PETG on a calibrated filament (FDM) printer.

Clearance in Z: whole layers, at least two

The slicer cuts a model into whole layers, so a Z gap that isn’t a multiple of the layer height gets rounded. QIDI’s example: a 0.25 mm gap at 0.2 mm layers prints as 0.2 or 0.4 mm. Stratasys’s assembly guide asks for at least twice the layer thickness in Z. QIDI designs 0.4 mm at 0.2 mm layers and 0.36 mm at 0.12 mm layers.

Where a surface prints over air, such as the top of a hinge barrel, QIDI says the first layer droops 0.05 to 0.15 mm into the gap and adds 0.10 mm. Round the sum up to the next whole layer:

Layer height	Z gap, two layers	Z gap under a bridged roof
0.12 mm	0.24 mm	0.36 mm
0.16 mm	0.32 mm	0.48 mm
0.20 mm	0.40 mm	0.60 mm
0.24 mm	0.48 mm	0.72 mm
0.30 mm	0.60 mm	0.90 mm

QIDI slices the mechanism at 0.12 to 0.16 mm, which halves the rounding error, and the body at 0.2 mm with per-object settings.

With a 0.4 mm or a 0.6 mm nozzle

QIDI, Sovol and JLC3DP give their figures for a 0.4 mm nozzle, and none of the sources here publishes one for 0.6 mm. QIDI warns that a 0.6 mm nozzle fuses the joints of a model designed for 0.4 mm.

A 0.6 mm nozzle’s line is about half as wide again: Bambu Studio’s profiles print 0.42 mm lines with a 0.4 mm nozzle and 0.62 mm lines with a 0.6 mm nozzle, at 0.30 mm layers. Start the clearance test below at 0.40 mm per side, the top of the 0.4 mm range, and work up in QIDI’s 0.10 mm steps. Leave a 0.60 mm Z gap (two 0.30 mm layers).

PLA, PETG, ABS and nylon

QIDI adds clearance per side by material. The last column adds it to the 0.30 to 0.40 mm hinge figure:

Material	Add per side	Print-in-place hinge, per side
PLA (polylactic acid)	0	0.30 to 0.40 mm
PETG (glycol-modified polyester)	0 to 0.05 mm	0.30 to 0.45 mm
ABS, ASA (styrene blends), PC (polycarbonate)	0.05 to 0.10 mm	0.35 to 0.50 mm
PA-CF, PET-CF (carbon-fiber nylon and PET)	0.05 mm	0.35 to 0.45 mm
Unfilled nylon (PA)	0.10 to 0.20 mm	0.40 to 0.60 mm
TPU 95A (flexible thermoplastic polyurethane)	0.10 to 0.15 mm	0.40 to 0.55 mm

Sovol adds more for PETG (0.05 to 0.10 mm per side) because it strings, and one strand left in a 0.20 mm gap can weld the parts. Nylon absorbs moisture and grows for days after printing (QIDI), so try the joint again after 24 hours.

Published print-in-place clearances, source by source

Source	Clearance as published	Per side or total
QIDI, interlocking parts guide	hinge 0.30 to 0.40 mm, ball and socket 0.35 to 0.50 mm	per side, with a total column
Sovol, print-in-place guide	PLA 0.25 mm, PETG about 0.30 mm	per side (0.50 mm total for PLA)
Sovol, tolerances guide	about 0.3 to 0.4 mm	total
JLC3DP, articulated animals	0.2 to 0.3 mm (0.4 to 0.6 mm total)	per side
Snapmaker, hinges	0.2 to 0.3 mm between pin and barrel	not stated
Prusa	at least 0.3 mm for movable parts	not stated
Stratasys	at least 0.51 mm (0.020 in) in X/Y on printers without a stated accuracy, twice the layer thickness in Z	a gap between parts

Halve the totals and the hinge figures run from 0.15 to 0.40 mm per side. Snapmaker says a well-calibrated printer gets a tight, smooth hinge at 0.2 mm. The clearance test below shows where your printer sits.

Print-in-place hinge clearance

Model a print-in-place hinge with 0.30 to 0.40 mm per side between the pin and the knuckle’s bore, 0.60 to 0.80 mm on the diameter (QIDI). The tolerance calculator uses 0.35 mm per side for its print-in-place hinge fit, so a 5 mm pin gets a 5.70 mm bore. Between stacked knuckles the gap runs in Z: 0.4 mm at 0.2 mm layers.

Sovol’s tolerances guide lists “about 0.3 to 0.4 mm total” for hinges, half of QIDI’s figure once split over two sides, and its print-in-place guide starts PLA at 0.25 mm per side. If a hinge built to a total figure fuses, check that difference first.

Pin standing up or lying flat

• Pin vertical: pin and bore print as circles in X and Y, the plane Stratasys rates most accurate, with no bridge across the gap (Sovol). The pin is weakest this way: Snapmaker warns that a hinge printed standing up pulls against its layer bonds and snaps.
• Pin flat on the bed: the layers run along the pin, which Snapmaker recommends for strength. The top of each bore is now an overhang over the pin. Sovol draws the bore as a 45° teardrop so its roof supports itself. QIDI adds 0.10 mm where the roof bridges over air.

Keep overhangs inside the joint at 45°

Sovol keeps internal overhangs at 45° or less from vertical, and Prusa gives 45 to 60° as the range a 0.4 mm nozzle prints cleanly without supports. In a vertical hinge the underside of each knuckle prints over the gap below it. A flat underside is a bridge that droops into the gap. A 45° cone on that face supports itself.

Don’t fix a drooping joint with supports. Sovol says support inside a moving gap leaves scars that can lock the joint, and QIDI says it pushes material into an articulated print’s gaps and welds the links.

Gears, chain links and articulated toys

• Chain links: the hinge’s 0.30 to 0.40 mm per side (QIDI), repeated across dozens of joints, where one weld ruins the model.
• Articulated dragons and flexi animals: QIDI’s dragon guide lists what each effective joint gap does. Under 0.15 mm the links weld. At 0.2 mm the joints are stiff and free up after a dozen careful flexes. At 0.25 to 0.3 mm they move straight off the plate, and above 0.4 mm they sag. QIDI doesn’t say whether these are per side. It prints dragons with a 0.4 mm nozzle at 0.15 to 0.2 mm layers, without supports.
• Scaled models: scaling a model scales its gaps. JLC3DP’s example is a 0.6 mm joint gap that becomes 0.3 mm at 50%, and QIDI notes that a dragon scaled to 150% goes loose. Scale the body and keep the joints at size. JLC3DP also checks the gap through the whole range of motion, not only at rest.
• Gears printed in mesh: the shaft in its bore takes the hinge clearance. Sovol’s 0.2 to 0.4 mm of total backlash for printed gears leaves a centered pair only about 0.1 to 0.2 mm at each flank, below the hinge figure. For 0.30 mm normal to each flank at a 20° pressure angle, enter 2 × 0.30 ÷ cos 20° = 0.64 mm of backlash in the gear calculator. Gear faces stacked in Z follow the layer rule above.

How do you 3D print a working bearing?

To 3D print a working bearing, print it with its axis vertical and give each roller 0.30 to 0.40 mm per side to both races and its neighbors (0.35 to 0.50 mm around a ball). Chamfer the bottom edges against elephant’s foot, keep supports out of the gaps, then turn the races by hand until the bearing spins.

• Orientation. With the axis vertical, races and rollers print as circles in X and Y, and no gap needs a bridge (Sovol, Stratasys).
• Rollers or balls. Near its bottom, a sphere’s underside overhangs more than the 45 to 60° Prusa says prints cleanly, and supports can’t go in the gap. Rollers standing on end print as clean circles. A 45° V-groove in each race holds rollers or balls captive with every overhang at 45°.
• Gaps. Use the hinge figure around a roller and the ball-and-socket figure around a ball (QIDI). Leave at least the same gap between neighbors.
• The bottom layer. Elephant’s foot welds rollers to races at the bed first. Chamfer the bottom edge of every race and roller 0.5 to 1.0 mm × 45° and set elephant foot compensation (slicer settings in the last section). If you need a brim, hold it 0.20 to 0.25 mm off the outer race (both Sovol).
• Freeing it. Let it cool to room temperature. Hold the inner race and turn the outer back and forth with gentle, controlled force until it spins (Sovol). QIDI puts dry graphite on rotating pins.

A 3D printable 608 bearing

A 608 bearing is 8 mm bore, 22 mm outside diameter and 7 mm wide (SKF 608-2Z). A printed one with the same outside sizes fits a pocket or an 8 mm axle made for the steel part. The rollers sit on the pitch circle, midway between the races, and this many fit:

N = π × Dp ÷ (d + c), rounded down

Dp = pitch circle diameter
d  = roller or ball diameter
c  = gap between neighbors

Worked through at 0.35 mm per side on a 0.4 mm nozzle:

1. Make the races 1.5 mm thick, over the 1.35 mm of three 0.4 mm perimeters (Prusa). The inner race runs from 8 to 11 mm and the outer from 19 to 22 mm.
2. That leaves 4 mm between them, so each roller is 4 - 2 × 0.35 = 3.3 mm across.
3. The pitch circle is 15 mm, or 47.1 mm around: 47.1 ÷ (3.3 + 0.35) = 12.9, so 12 rollers.
4. The 8 mm bore will print small, as printed holes do (QIDI). Test it on the axle and correct it with the hole compensation calculator.

For a bearing under load, press a steel 608 into a printed part instead. The tolerance calculator sizes the pocket.

Print-in-place clearance test

Print your actual joint several times in one job, each copy at a different clearance, and keep the smallest gap that moves freely. One job gives every copy the same thermal history (QIDI). Use the real part’s orientation, layer height, nozzle and material. The result holds only for that combination (Sovol).

Test	Steps	What it tells you
QIDI coupon	0.10, 0.20, 0.30, 0.40, 0.50 mm	the smallest gap that frees on your printer
Sovol coupon	0.15, 0.20, 0.25, 0.30 mm per side	finer steps around its PLA start value
JLC3DP ladder	0.15, 0.20, 0.25, 0.30, 0.40 mm per side	the same, for articulated joints
OrcaSlicer Tolerance Test	six hex holes: 0, 0.05, 0.1, 0.2, 0.3, 0.4 mm	the fit of parts assembled after printing

The OrcaSlicer test isn’t printed in place: you push a 6 mm Allen key or its printed hexagon into each hole, then tune XY hole and contour compensation. Run it first to calibrate the printer. In OrcaSlicer, right-click the plate in Prepare mode and choose “Add Handy Model”.

To read a print-in-place coupon:

• Emboss each step’s value on the part (QIDI).
• Let it cool. Try each joint with gentle force and stop if it won’t release (Sovol).
• Test it warm and again after 24 hours (QIDI).
• Before printing anything, look at the joint in the slicer’s layer preview. If you can’t see daylight between the two bodies, the printer won’t make any (QIDI).

What to do when a print-in-place part fuses

1. Free it once it is cold. QIDI flexes a fused joint once, firmly. Sovol uses gentle, controlled force by hand or with padded pliers. Work an articulated model joint by joint, from the tail toward the head (QIDI). Expect rough faces afterward.
2. Find where it fused. Moving at the top but solid at the base is elephant’s foot. Welded along the whole height means over-extrusion or a gap tighter than the printer can hold (Sovol).
3. Fused at the base: chamfer the bottom edges 0.4 mm × 45° (QIDI) to 0.5 to 1.0 mm × 45° (Sovol), and turn on elephant foot compensation (table below).
4. Fused all the way up: calibrate flow first. Snapmaker says lowering flow by 2 to 5% is often enough to free print-in-place parts. Check that no horizontal expansion is closing the gap from both sides (QIDI). To loosen a downloaded model without editing it, QIDI applies -0.1 to -0.2 mm of XY contour compensation.
5. Widen the gap in the model, 0.05 mm per side at a time (Sovol) or by the next 0.1 mm step of your coupon. Round any Z gap up to the next whole layer.

Elephant foot compensation in each slicer

Each setting shrinks the first layer, which reopens the gap at the bed.

Slicer	Setting	Starting value
PrusaSlicer	Print Settings > Advanced > Elephant foot compensation	about 0.2 mm on a 0.4 mm nozzle, already on in Prusa’s profiles
OrcaSlicer	Quality > Precision > Elephant foot compensation, tapered over a set number of layers	0.15 to 0.25 mm (QIDI), 0.1 to 0.2 mm (Sovol)
Bambu Studio	Quality > Precision > Elephant foot compensation	0.15 mm in the X1C’s 0.20 mm Standard profile; default 0
UltiMaker Cura	Initial Layer Horizontal Expansion	a negative value; default 0