How to check and tighten a loose belt
A loose belt is often confused with a loose pulley. Please check for a loose pulley first.
When to check and tighten a belt
You should check for a loose belt if your prints have slanted, staggered or shifted layers, or if you've noticed one your printers axes not moving correctly.
Inspection takes just a few moments, maintenance may take up to 15 minutes as and when required.
We recommend checking belt tension each month as part of a regular check up.
What do I need?
- 1.5mm hex key (included in your printers maintenance kit).
- Set of cutters (included in your printers maintenance kit).
- Spare zip ties (included in your printers maintenance kit).
- 10mm spanner (included in your printers maintenance kit).
- A paperclip or this 3D printed clip:
How to check belt tension
Step 1 - Determine which axis is affected
- The easiest way to identify which axis is causing problems is by looking at the prints the printer is producing. The slanted, staggered or shifted layers will occur along the affected axis.
- Print a Cali-cat from 'Featured Models' in BuildBee and pay observe which direction the fault occurs.
Step 2 - Check the belt tension
- With the printer in the home position, make sure you are able to access the affected axis.
- For the Y (print bed) axis and Z (vertical) axis, test tension by carefully sliding the 10mm spanner between the belt and the axis. If the spanner is held in place by the belt the tension is good, but if the spanner slides or falls, the belt may need to be tightened a bit.
- For the X (extruder) axis, test tension by seeing if you can get your finger between the belt and the axis. If you can't easily get a finger underneath the belt then the belt tension should be good, but if you can easily get a finger under the belt it may need to be tightened. You may also compare the tension of the X axis belt to either the Y or Z axis to get an idea of how tight it should be.
The belt should be aligned with the centre of the pulley.
How to tighten a belt
X and Y axis
- Make sure your printer is in the home position.
- Remove the two screws from the endcap on the right side of the axis. Place them somewhere safe so they don't get lost.
- Carefully clip the existing cable tie away from the belt. Be careful not to cut the belt.
Be careful not to twist the belt whilst making adjustments
- With the belt threaded through the endcap, line up the corner of the endcap with the corner of the axis as shown in the pictures below:
- Carefully pinch the end of the belt around the endcap so you don't lose your position on the belt and interlock the 'teeth' of the belt together.
- Hold the two sides of the belt together with a paperclip or the 3D printed clip linked above.
- Test the tension by carefully pulling the endcap back around to align it with the screw holes and perform the spanner grip test. If the spanner stays suspended you have good tension If the spanner slips (too loose) or you can't return the endcap back to its original position (too tight), you will need to adjust it further.
- To make further adjustments, remove the paperclip or the 3D printed clip while pinching the belt to save your place. Move the end of the belt around the endcap by one 'tooth' at a time to tighten or loosen to perfect tension.
- Once you are happy with the tension of the belt, hold the two sides of the belt together with the paperclip or the 3D printed clip and place a new zip tie around the two sides of belt close to the endcap and with the 'knob' of the zip tie facing in towards the axis. Tighten as far as you can go.
- Cut the excess off the zip tie and remove the paperclip or the 3D printed clip.
- Carefully pull the endcap back around to the end of the axis and replace the two screws, making sure the 'knob' of the zip tie is inside the groove of the axis:
- Print the Cali-cat from 'Featured Models' in BuildBee to see if the fault has been fixed.
Z axis
- With the printer turned off, prop up the X (extruder) axis with a box (filament box works well) so that it is almost at the top of the Z (vertical) axis.
- Loosen, but don't remove the screw at the base of the Z (vertical) axis a little bit.
If you loosen the screw too much, it may come out of the T-nut that attaches the tension-holding tab to the axis.
- Put the 10mm spanner between the belt and the axis and pull the the tab down to tighten the belt and hold the spanner in position.
- Whilst continuing to hold the tab down, re-tighten the screw to lock the belt in position.
- Remove the spanner and return the X (extruder) axis to the home position.
- Print the Cali-cat from 'Featured Models' in BuildBee to see if the fault has been fixed.
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