Quick diagnosis
Z-banding shows up as horizontal ripples or rings that repeat at a consistent height up the print, coming from uneven vertical motion rather than the model’s own layer lines. It is a Z-axis problem, distinct from ghosting, where wavy artifacts trail sideways from vibration on the X and Y axes instead of stacking evenly up the Z axis.
1. Confirm the interval is fixed, not random
Measure the distance between bands on a tall test print. A repeating interval that stays the same for the whole height points to a mechanical Z-axis cause such as a bent leadscrew or a loose coupler. Bands that appear at random heights or only on one side of the part suggest a different cause, such as vibration from the X or Y axis or an inconsistent layer time. Confirming a fixed interval first saves time chasing the wrong system.
2. Check the leadscrew or rod for bend and misalignment
Remove the leadscrew and roll it across a flat surface. Any visible wobble means the rod is bent and should be straightened or replaced before anything else is adjusted. With the screw reinstalled, move the gantry to the middle of its travel and check that it slides up and down freely by hand with the motor disconnected. Binding at any point means the leadscrew is not parallel to the smooth rods, and the mounting brackets need to be loosened and realigned.
3. Inspect the motor coupler
A loose grub screw on the coupler lets the motor shaft spin slightly before the leadscrew catches up, which shows as inconsistent Z movement rather than a perfectly repeating band. Check that both grub screws are tight and seated on the flat part of each shaft, not just against the round section. A rigid coupler also transmits any runout in the motor shaft directly into the leadscrew, so swapping in a flexible coupler can remove wobble that alignment alone cannot fix.
4. Remove backlash at the nut
Backlash is the small amount of play between the leadscrew threads and the nut riding on them, and it lets the gantry sit slightly differently each time the axis changes direction. An anti-backlash nut, which uses spring tension to take up that play, is a common fix on printers that ship with a simple brass nut. Check for play by holding the gantry still and gently rocking the leadscrew; noticeable movement without the screw itself turning points to backlash rather than a bent rod.
5. Adjust layer height or check dual-Z synchronization
On printers with two leadscrews driving the Z axis, bands that appear on only one side of the part often mean the two motors have drifted out of sync, which calls for a homing or synchronization routine rather than a mechanical fix. On single-leadscrew printers, changing the layer height slightly can shift where the banding lands or make it less visible, though it does not remove the underlying mechanical cause. Treat a layer height change as a workaround while the real fix, alignment or a coupler swap, gets scheduled.
Z-banding checklist
- Band interval is fixed and repeats at the same height.
- Leadscrew rolls flat with no visible bend.
- Gantry slides freely by hand with the motor disconnected.
- Coupler grub screws are tight on the shaft flats.
- No play at the leadscrew nut.
- Dual-Z motors are synchronized, if applicable.
This is a Z-axis problem, distinct from ghosting, where wavy artifacts trail sideways from X/Y vibration instead of stacking up the Z axis. Loose belts and frame vibration can also cause stringing. A Z axis that skips a layer’s height entirely, rather than rippling unevenly, is covered in fixing skipping layers.