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Belt tightning

Posted by Nylkos 
Belt tightning
August 27, 2018 12:35PM
I had to rebuilt my CoreXY recently (had a misalignment on the z-axis).
Since then I had some layer shifting and I was hoping to get some info on some test that could indicate if the belt is too tight or too loose.
I am using the single belt setup.
Thanks

Edited 1 time(s). Last edit at 08/27/2018 12:55PM by Nylkos.
Re: Belt tightning
August 27, 2018 01:39PM
Single belt?

Can you post a photo of the top of the machine so the belt paths are visible?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt tightning
August 27, 2018 02:52PM
The path are exactly the same except that you do a single twist at the front (on both side of the belt to avoid contact where the 2 belt crosses).
You still need some height difference but only a few mm...
I am not at home ATM, here is an old image and videothat I got from when I started... I will upload some more later.

Video

Edited 1 time(s). Last edit at 08/27/2018 03:02PM by Nylkos.
Re: Belt tightning
August 27, 2018 02:58PM
OK, not "single belt", but single level- i.e. the belts aren't stacked.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt tightning
August 27, 2018 03:04PM
no, single belt...
only 2 end attached under the carriage, I added a video to my previous post, could provide more info
Re: Belt tightning
August 27, 2018 03:42PM
Is that a steel core belt? They generally don't last long when bent around small pulleys...


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt tightning
August 27, 2018 03:46PM
Yes, it's a steel core belt, I haven't seen any issue yet...
Do you think that this could have been the issue for the layer shifting?
Re: Belt tightning
August 27, 2018 03:55PM
Layer shifting is usually either caused by too much acceleration/jerk, or a mechanical resonance. Belts have to get noticeably loose before you get layer shifts because the belt is slipping. If the corexy mechanism isn't laid out carefully, the belt tension can vary with the extruder carriage position- tight in some places and loose in others, but from what I can see in your video, the layout looks OK. If you manually push around the extruder carriage, does the tension stay more or less the same everywhere?

When steel core belts fail, the steel wires break inside the polyurethane belt, and the belt will start stretching at the break. That causes weird things to happen in prints.

I recently wrote a blog post on layout and tightening belts.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Belt tightning
August 27, 2018 04:17PM
Thanks.
I noticed that when the car changes direction a "deformation" near the pully... would that indicate that it's still too loose?
Re: Belt tightning
August 27, 2018 09:54PM
It definitely indicates there's some alignment issue that could contribute to the problem.

Belts should not connect two pulleys that are at different Z levels. They are intended to work exactly perpendicular to the pulley's axles and can tolerate only a tiny offset.

Edited 1 time(s). Last edit at 08/27/2018 09:58PM by the_digital_dentist.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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