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Belt Tension & Adjustment

Keep your motion system precise.

Last updated

How tight should the belts be?

There is no frequency target to hit. During calibration the printer runs a frequency sweep and warns you when a belt is loose (HMS 0300-1000-0002-0001 for X, 0300-1100-0002-0001 for Y; the A1 shows a prompt). Then retension as below and run Vibration Compensation again.

Title
Bambu Lab Belt Tension and Adjustment Guide
Section
Guides
Last updated
Page
Status
Not affiliated with Bambu Lab

How to check belt tension

Your printer checks the belts itself: the calibration runs a frequency sweep and warns you when a belt is loose.

PrinterWhere to find it
X1CSettings → Print Calibration → Vibration Compensation (older firmware: Control → Calibrate)
P1S / P1PSettings → Calibration
A1 / A1 miniSettings → Maintenance → Calibration
P2S / X2D / H2 seriesSettings → Calibration → Print Calibration

How to adjust: X1C / P1S / P1P / P2S / H2 series

  1. Power off the printer (P2S: also remove the top glass cover)
  2. Loosen the four belt-tensioner screws at the back 1–2 turns; do not remove them
  3. Move the toolhead back and forth several times, also along Y (P2S: as wide as possible, 3–5 times); X1, P1 and H2: finish at the rear end
  4. Retighten the four screws without over-torquing; the springs set the tension
  5. Power on and run Vibration Compensation
Schematic of a spring-loaded belt tensioner, numbered like the steps on the page: 2 loosen the clamp screws 1 to 2 turns without removing them, so the spring can pull the block with the pulley and take up the belt; 3 move the toolhead back and forth several times; 4 retighten the screws without over-torquing, the spring has set the belt tension2Loosen the screws 1 to 2turns, do not remove them: theblock can slidetensioner screw3Move the toolhead back andforth several timestoolhead4Retighten withoutover-torquing: the springs setthe tensionspringSchematic of a spring-loaded belt tensioner, numbered like the steps on the page: 2 loosen the clamp screws 1 to 2 turns without removing them, so the spring can pull the block with the pulley and take up the belt; 3 move the toolhead back and forth several times; 4 retighten the screws without over-torquing, the spring has set the belt tension2Loosen the screws1 to 2 turns, do notremove them: theblock can slidetensioner screw3Move the toolheadback and forthseveral timestoolhead4Retighten withoutover-torquing: thesprings set thetensionspring
Fig. 1Steps 2 to 4 as a principle: with the screws loosened 1 to 2 turns the spring-loaded block can slide (dashed: where it was), the toolhead moves back and forth, and the retightened screws lock the block where the springs set the tension. Numbers match the steps above; one tensioner drawn, schematic, not Bambu's part geometry.

How to adjust: A1

  1. Raise the X gantry to mid height and power off
  2. X belt: loosen the screw on the back of the toolhead one turn (H2.0), move the toolhead along X three times, retighten
  3. Y belt: remove the small cap at the front of the base, loosen both screws one turn, move the bed back and forth three times, retighten
  4. Z belt: loosen the two screws near the right column one turn, home, move Z up and down once, retighten
  5. Power on and run Vibration Compensation from Settings → Maintenance → Calibration

A1 mini: follow Bambu's A1 mini belt tensioning guide.

Manual check without the printer test

Pluck the belt like a guitar string:

  • Dull thud: Too loose. Tighten.
  • Low twang (bass note): Good.
  • High ping: Too tight. Loosen.

Community rule of thumb, not from Bambu's documentation. Use the built-in check when possible.

When to replace belts entirely

  • Visible cracking, fraying, or missing teeth
  • Belt has been significantly over-tensioned (stretched/delaminated)
  • Tension keeps dropping between checks (belt has stretched past recovery)

Belts are a consumable: replace them when they are broken or worn. Bambu sells model-specific XY belts (P2S: 1444 mm long, 7 mm wide; H2D: 1824 mm, 9 mm wide; H2S: 1836 mm, 9 mm wide), so order the one made for your printer.

Too loose vs too tight: symptoms

Too looseToo tight
Layer shiftingBearing wear
Dimensional errorsMotor strain
Ringing/ghostingExcessive ringing
Inconsistent printsPremature belt wear

Tools for this job

Wera Hex-Plus L-Key Set

Wera Hex-Plus L-Key Set

The only tool this job needs: quality hex keys that loosen and re-torque the tensioner and motor mount screws without stripping them.

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