Belt Tension
Proper belt tension is crucial for the coreXY motion system. Loose belts or insufficient tension can cause many printing issues, such as circles being printed as ellipses.
The belts and gantry form a mass-spring system, where the belt acts as the spring (k) and the gantry as the mass (m). The system’s natural frequency is f = √(k/m). Loose belts lower both k and f, thereby affecting vibration compensation.
The H2C monitors belt tension using this equation f = √(k/m). During calibration, the motor generates vibrations at different frequencies and looks for resonance, which occurs when the input frequency equals the natural frequency. We call this process a frequency sweep, which produces noticeable noise as the pitch rises.
When the natural frequency of the H2C changes, the belts need to be tightened. This can be done with a simple adjustment.
Belt tensioning steps
Important reminder: Disconnect your printer from the power source before proceeding.
Core XY Belt Tensioning
Step 1. Prepare the machine
Before tensioning the belts, please turn off the printer and remove the top glass cover.
Step 2. Loosen the belts
Use an H2.0 hex key to slightly loosen (only 1–2 turns, do not remove the screws) the four tensioning screws to release the XY belts.
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Step 3. Ensure the belts are fully seated
Manually move the toolhead back and forth along the XY directions as widely as possible, 3–5 times. Finally dock the toolhead at the center rear.
Step 4. Tension the belts
After completion, tighten the four screws on the back again to fix the tensioners in place and complete the tensioning.
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Note: Do not overtighten the screws to avoid stripping the threads.
Z-Axis Belt Tensioning
Step 1. Prepare the machine
Remove the top glass cover, tilt the printer, and use an H2.0 screwdriver to loosen the tensioner screw. (Do not remove this screw.)
Step 2. Tension the belt
Pull the Z-axis belt back and forth 3-5 times by hand to confirm that the movement is smooth, and then use an H2.0 Allen wrench to tighten the Z-axis tensioner slider fixing screw (M3x6).
Step 3. Install the top glass cover
Place the printer back on a stable surface and install the top glass cover.
The printer is quite heavy, it is recommended that two people operate it together to avoid damage or injury.
Induction Hotend Rack Belt Tensioning
Step 1. Remove the protective cover
Use an H2.0 screwdriver to unscrew the two retaining screws and remove the protective cover.
Step 2. Loosen the motor
Locate the three fixing screws of the motor and loosen them with an H2.0 screwdriver
Note: Only loosen the screws, do not completely remove the screws to avoid the motor falling off.
Step 3. Ensure the belt is fully seated
After loosening the screws, gently shake the motor to ensure it can move freely, leaving room for subsequent tension adjustments.
Step 4. Tension the belt
Next, adjust the bottom tension screw. While tightening the screw, you need to press the belt gently and continuously to judge the tension by touch, and ensure that the tension is even and moderate.
Excessive belt tension may cause the components to wear quicker.
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Step 5. Evaluate the belt tension
After the tension adjustment is completed, press the belt gently. If you can clearly feel that the belt is tight and there is no looseness or rebound, it is ready.
As shown in the image below, if the belt still feels loose and not taut when pressed, it indicates insufficient belt tension and the tension screw needs to be readjusted.
Step 6. Secure the motor in place
Tighten the three fixing screws on the motor to secure its position.
Step 7. Reinstall the protective cover
Reinstall the protective cover, align it with the mounting holes, and tighten the two fixing screws to complete the tensioning operation.
Calibrate the machine
After completing the belt tensioning operation, the resonant frequency identification needs to be recalibrated to record the new resonant characteristics of the equipment.
On the screen, tap “Calibration - Print Calibration,” check only Vibration Compensation, and complete the calibration.
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The H2C can also be calibrated via the machine screen or Bambu Studio.