Layer shift: the print steps sideways in X or Y

Symptom

From a certain height, the layers are offset to one side compared with the ones below, like a step. It can happen once or several times (a staircase), along X, Y or diagonally. The rest of the part usually prints fine, just shifted.

Likely causes, from most to least likely

1. A loose or badly positioned motor pulley (its grub screws not tight on the flat of the shaft) or a belt with the wrong tension. This is the most common cause.
2. Something is holding back the print head or bed: filament scraps on the belt or pulley, cables, zip ties or tubes rubbing or pulling, or dirty, scratched or dry rods and rails.
3. The nozzle hits the part: overhangs curling up, warped areas, or very low infill leaving uneven surfaces.
4. Speed too high for a large part, or a quiet mode meant for small prints that leaves the motors with less torque.
5. The plastic parts that hold the belt have come loose over time.

Checks to tell which one it is

• Check which axis the part shifted on to know which belt, pulley and motor to inspect first. On a CoreXY, also move the print head by hand along the diagonals: if one diagonal feels uneven, check the motor and pulley that drive it.
• With the printer off and cold, move the print head and bed by hand from end to end: they should glide without jerks or tight spots.
• Hold the motor shaft by its flat with pliers and try to move the print head or bed: there should be no play. If there is, the belt is loose or the pulley is slipping.
• Pluck the belt like a string: it should sound low and give some resistance when you pinch both sides together.
• In Klipper you can check for lost steps: home, run GET_POSITION, do fast moves or the print, home again and compare the mcu: line. A couple of microsteps of difference is normal.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Remove whatever is holding back the motion

   Turn the printer off. Remove filament scraps from belts and pulleys, and reroute cables, zip ties and tubes so they don't rub on or pull the print head or bed anywhere along the travel.

   Check: The print head and bed move by hand from one end to the other without catching.

   If that does not fix it: Check the motor pulleys.

2. Tighten and align the pulleys

   With the printer off, check the grub screws on each pulley: they must be tight, with one of them on the flat of the shaft. The pulley should line up with the one at the other end and the belt should run straight.

   Check: Holding the motor shaft, you can't move the print head or bed, and the pulley doesn't turn on the shaft.

   If that does not fix it: Adjust the belt tension.

3. Adjust the belt tension

   Tighten or loosen following your printer's manual. If the manufacturer offers a way to measure it (menu, app or reference frequency), use it. Also check that the parts holding the belt are secure.

   Check: The belts sound low and firm, and a printed cylinder comes out round.

   If that does not fix it: Clean and lubricate the rods or rails.

4. Clean and lubricate rods or rails

   Wipe the smooth rods or rails with paper and apply the lubricant your manufacturer recommends. If a rod has deep scratches, it may be damaged: ask your manufacturer.

   Check: Hand movement feels even along the whole travel.

   If that does not fix it: Check whether the nozzle is hitting the part.

5. Stop the nozzle hitting the part

   If overhangs curl up or areas warp, increase part cooling or retraction in the slicer, raise the infill, or split the model into parts.

   Check: You no longer hear the nozzle knocking into the part while printing.

   If that does not fix it: Reduce the speed.

6. Slow down and use normal mode

   For large parts, lower the print speed (many printers let you do it from the menu during the print). If your printer has a quiet mode, use normal mode for large or complex parts.

   Check: The same part prints without shifts.

   If that does not fix it: If it keeps happening with the mechanics in good shape, there may be an issue with a motor, its driver or its configuration: contact your manufacturer's support.

Prevention

• At each maintenance, check belt tension and the pulley screws.
• Keep rods and rails clean and lubricated as the manual says, and clear away filament scraps.
• Route cables and tubes so they don't touch anything along the whole travel.

Still not fixed?

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Printers it applies to

Any FDM (filament) 3D printer, from any brand.

Official sources

This guide summarises the official documentation linked here:

• Layer shifting · Prusa Research
• Adjusting belt tension (MK4/S, MK3.9/S, MK3.5/S, MK3/S/+) · Prusa Research
• Frequently Asked Questions (Can I find out whether the printer has lost steps?) · Klipper