Layer shifting

The head lost its place. Because most desktop printers have no position feedback, once a step is missed the printer never knows — everything above prints perfectly, just in the wrong place. Which axis shifted tells you a lot, so look at that first.

Looks like: The print suddenly steps sideways part-way up and everything above is offset.

Fixes, in the order worth trying

1 · Try this first

Check belt tension

A loose belt lets the pulley skip teeth under acceleration. Plucked like a guitar string, a correctly tensioned belt gives a low musical note, not a dull thud. This is the most common cause by a wide margin.

With the printer off, push the head to the centre and pluck each belt. Both should sound similar and neither should visibly sag. Then check the pulley grub screws — a set screw that is not seated on the flat of the motor shaft will slip under load and mimic a loose belt exactly.

2 · Try this first

Lower acceleration and jerk

Shifts that happen on fast infill or sharp direction changes are inertia beating the motor. Reducing acceleration costs print time but is a definitive test — if the shift disappears, the mechanics cannot keep up with the profile.

Print Acceleration: Cura → Speed (enable Acceleration Control) → −30 %, e.g. 3000 → 2000 mm/s²
Normal printing acceleration: OrcaSlicer → Process → Speed → Acceleration → −30 % as a test
Jerk / Junction deviation: Cura → Speed · OrcaSlicer → Process → Speed → Jerk 8 mm/s · Junction deviation 0.02

3 · Common cause

Stop the nozzle hitting the print

A curled corner or a blob sticking up gets clipped by the nozzle on the next pass, and the impact knocks the head off position. If the shift happens at the same height every time, this is almost certainly it.

Also fix the curling itself — see the warping and over-extrusion pages, since a raised blob is a symptom of one of those.

Z Hop When Retracted: Cura → Travel → Enabled, 0.2–0.4 mm
Z hop height: OrcaSlicer → Process → Quality → Precision → 0.2–0.4 mm

4 · Common cause

Check for mechanical binding

A dry rod, a misaligned linear rail or a wheel tightened too far adds drag that the motor cannot always overcome. With the printer off, push each axis by hand end to end: it should glide with even resistance the whole way.

Clean and lightly oil smooth rods, check that eccentric nuts on V-wheel printers are snug but still let the wheels turn, and confirm nothing (a cable chain, a spool holder, a clip) is catching at the extremes of travel.

5 · Less common

Let the stepper drivers cool

Drivers that overheat go into thermal shutdown for a moment and drop steps, then recover. Classic sign: shifts appear only well into long prints, and only in warm weather or an enclosure.

Confirm the mainboard fan runs, add a heatsink to the driver, and check driver current is not set higher than the motor needs. In an enclosed printer, keep the electronics bay outside the heated volume.

Change one thing at a time. If you adjust temperature, retraction and speed together and the problem goes away, you have learned nothing and you will be back here next month. Re-print the same test object after each single change.

Frequently asked questions

Only the X axis shifted. Does that narrow it down?

Yes — it points at that axis specifically: its belt, its pulley grub screw, its motor, its driver. A shift that affects both X and Y at once is more likely a collision or a firmware/power event than a belt.

Can a bad G-code file cause layer shifts?

It can look like one. A corrupted SD card or a flaky USB connection can drop or garble commands mid-stream, which produces offsets or missing sections that mimic mechanical shifting. Re-slice, copy to a different card, and print again before dismantling anything.

Why does it always shift at the same height?

That is the signature of a collision rather than a random miss. Something at that Z height — a curled edge, a support tip, a stray blob — is being struck. Enable Z-hop and look closely at the layer just below where it happens.