Layer shifts and surface ringing: belts and axes

Layer shifts on one axis and ringing near the model’s corners usually point to a motion problem. The good news: on the X1 and P1 series belt tension is restored with a standard procedure, and you usually don’t need a new belt.

First — check for obstructions

Before adjusting anything, check that nothing is blocking the head’s movement on the X and Y axes. A filament offcut, a piece of plastic from a failed print or a cable in the way gives exactly the same symptoms.

For the X1 and P1 the manufacturer also recommends cleaning the carbon rods — it reduces the risk of layer shifts.

Adjusting belt tension on the X1 and P1

The procedure needs no measuring tools:

1. Turn the printer off.
2. Loosen the 4 belt tensioner screws — loosen them, don’t remove them.
3. Gently move the print head back and forth a few times.
4. Move the head to the back of the printer.
5. Tighten the 4 screws again.

The spring-loaded tensioner sets the correct tension by itself. Don’t overtighten the tension screws — too much force does as much harm as slack.

How the printer checks tension itself

The X1 measures belt tension through resonance: during calibration the motors create vibrations at different frequencies and look for the one where resonance occurs. It’s related to tension by f = √(k/m). That’s why the printer may report that the X-axis resonance frequency is low — a clear hint that the belt is slack.

After any work on the mechanics, run a calibration: on the X1 you can do it right from the screen, and for the P1 and X1 calibration is also available in Bambu Studio.

When the belt really should be replaced

• the belt shows cracks, delamination or worn teeth;
• it goes slack again a few prints after tensioning;
• the belt was mechanically damaged — pinched, frayed or melted.

Don’t forget the rollers

Idler rollers and bearings affect print geometry as much as the belt, but they get less attention. Signs of wear: humming or crunching during movement, a roller that turns jerkily, a belt that drifts sideways, or play at the mounting point.

What you may need: belts and bearings, printer diagram.