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Z-Axis Banding

The Problem

Z-Banding manifests as a pattern of protruding or indented horizontal lines on the surface of the print. Unlike normal layer lines, these bands are inconsistent or have a visible repeating pattern.

A close-up of a print's vertical surface showing Z-axis banding A close-up of a print's vertical surface showing Z-axis banding

A close-up of a print's vertical surface showing a pattern of inconsistent, repeating horizontal lines, which is characteristic of Z-axis banding.

Common Causes and How to Fix Them

Z-Banding can be frustrating because the causes can be mechanical or extrusion-related.

1. Mechanical Issues in the Z-Axis

Any imperfection in your printer's vertical movement will be "printed" onto the walls of your part.

  • Dirty or Bent Lead Screw:
    • Solution: Clean the Z-axis lead screw with a cloth and isopropyl alcohol to remove dust and old lubricant. Then, apply a thin layer of appropriate lubricant (like white lithium grease or Super Lube). To check if it's bent, remove it and roll it on a flat surface. If it wobbles, it's bent and should be replaced.
  • Loose or Misaligned Coupler: The coupler that connects the Z-motor to the lead screw may be loose.
    • Solution: Ensure all grub screws on the coupler are tight.
  • Z-Wobble: The lead screw may not be perfectly parallel to the frame, causing a wobbling motion as it rises.
    • Solution: Ensure the Z-motor mount and top bearing (if present) are not over-constraining the lead screw, allowing it a small amount of lateral movement to self-align.

2. Extrusion Inconsistency

If the amount of extruded plastic varies slightly from layer to layer, it will create thicker and thinner lines.

  • Unstable PID Tuning: The nozzle temperature fluctuates during printing. Temperature variations change the plastic's viscosity, changing how it extrudes.
    • Solution: Perform a "PID Tune" calibration for your hotend. This process, done via a terminal like Pronterface or OctoPrint (command M303 E0 S210 C8), calibrates the heating algorithm to maintain a much more stable temperature.
  • Poor Quality Filament: Variations in filament diameter along the spool cause inconsistent extrusion.
    • Solution: Measure the filament diameter at several points with calipers. If it varies more than +/- 0.05mm, the filament is low quality. Try using a more reputable brand.

3. Bed Temperature Issues

On some printers, the bed heater cycling on and off can cause minute expansion and contraction that reflects on the part.

  • Solution: Perform a "PID Tune" calibration for your bed (command M303 E-1 S60 C8). This stabilizes the bed temperature, minimizing this effect.

Quick Checklist

  • Clean and lubricate the Z-axis lead screw(s).
  • Check if the lead screw is bent.
  • Perform a "PID Tune" for the hotend.
  • Perform a "PID Tune" for the bed.
  • Test with a high-quality roll of filament.