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I have an Anet A8 and I currently try to improve the y-axis (with a tensioner and a frame to support the structure). Now after I dis- and reassembled the y-axis, I get a loud rattling noise when homing the y-axis (and also when moving it stepwise from within the firmware). After the rattling goes on for a second or two, the printer halts and asks to reset. During the rattling, the print bed moves much slower. It appears to only rattle at the end of the axis, close to the endstop, however the point at which it starts to rattle appears random.

I tried a tighter and looser belt and aligning the frame. When moving the bed manually, it does require some force, but it does not appear to be tighter at the back side of the axis. Also nothing seems to block the path of movement.

I noticed that with a tighter belt the rattling starts only closer to the end stop, however it appears like I have to overtighten it to work properly. I got it to hit the end stop this way without halting, however it still produced the rattling sound. Also the y-stepper motor made a high pitched humming noise after this operation.

What else could I check or do about it?

This is a video showing the print bed with the rattling sound: https://www.youtube.com/watch?v=H0Xhz2GtUYQ

View from below: https://youtu.be/oTEuZUWD0ZM

This is the motor mount: enter image description here

And this is the tensioner with the support frame: enter image description here

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  • $\begingroup$ I added a video of the setup and the sound. The belt does not appear to rub on the frame. When pulling the belt, I get various sounds, like I said, I tried different belt tensions. $\endgroup$
    – Till B
    Dec 23, 2018 at 13:26
  • $\begingroup$ Added the pictures. Also I noticed that with a tighter belt, I can control the rattling, however it does not disappear. I added a section on this in the question. $\endgroup$
    – Till B
    Dec 23, 2018 at 13:44
  • $\begingroup$ The belt makes noise like a guitar string. Currently it is at around 100Hz. Like I said, I tried various tensions. At this tightness the rattling is less that with a looser belt. $\endgroup$
    – Till B
    Dec 23, 2018 at 13:46
  • $\begingroup$ With the original Anet A8 kit. $\endgroup$
    – Till B
    Dec 23, 2018 at 13:54
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    $\begingroup$ The upper and lower part of the belt need to be parallel to the bed, the standard attachment is a design flaw, see a correct attachment here. $\endgroup$
    – 0scar ♦
    Dec 24, 2018 at 20:33

2 Answers 2

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From your video, it sounds to me as though the stepper motor is fighting against the bed movement. That would indicate to me the bed rails on the X-axis are not square to the bed movement, which would cause binding of the linear bearings on the bed.

To see if this is the issue, loosen the threaded rods in all six places (three placed times two rods). Loosen the belt tensioner so it is not causing any issues. Then see how the bed moves. If the bed is freed up, tighten the nuts on the threaded rods two at a time on the same plane (each plate of the frame). At each tightening, ensure the bed continues to move freely. Measure the distance as accurately as possible to ensure the frame continues to stay square and are parallel to each other. Once you have tightened all of the nuts on the threaded rod, then re-tighten the belt tensioner.

If none of this solves it, it could also be an issue with your linear bearings. If your Anet A8 is a Chinesium clone, the bearings are not what I'd call "top notch". I replaced mine with Igus Drylin bearings and have not regretted the $10 investment. There are other printed options you could go with as well, which you can find on thingiverse.com.

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With the second video and the photos I could identify, that the sound in part stems from the belt:

  • It is too loose and swing sideways as it pulls.

Tighten the belt till it sounds at least like a C3 or D3 (130/146 Hz) and possibly higher. My Ender3 is tuned to something like A3 (220 Hz). It should be tight and show no sideways swinging on using the motor.

It seems also, that the belt is not running parallel but skewed - that would induce sideways swing too. Make sure the axis of the motor and the pully are parallel and the mounting point of the carriage is not sideways of the belt path, as this will rub the belt against the gear.

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  • $\begingroup$ Where at the belt should I pull? I measure and pull on the longer end, i.e. the one directly connecting the tensioner and the motor, not the one where the carriage is mounted. $\endgroup$
    – Till B
    Dec 23, 2018 at 13:55
  • $\begingroup$ I test my long arm, with the carriage at the far side. it is not exact, it is just what I like to hear for my tension: both up and low close to one another and around A3 $\endgroup$
    – Trish
    Dec 23, 2018 at 13:57

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