X axis belt tension  

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dkoemans
(@dkoemans)
New Member

TL/DR - My mk3 X axis belt test reads between 185 - 199, too tight. I've loosened the belt (moved the teeth on the extruder) to the where it is floppy and nearly jumps teeth on the gear, still reads 185-199 on multiple test, there is no way it is too tight. What is going on?

I'll try and keep this brief but the problem I describe above is just one of many symptoms. I'm describing the rest here in case it is relevant. I bought and built the printer in April 2018 and it worked great for about a year.

In summer 2019 I installed a pi nano with octoprint so I could monitor and print remotely. Worked great. About a month or two later I sent a big 24 hour job and when I woke up the next day the printer software had crashed mid print, it just stopped printing. The display screen had garbled characters. I had just updated the firmware the day before. Rebooted and was prompted to recalibrate. I removed the Pi board thinking that may have had something to do with it. Couldn't pass self test, x axis wasn't hitting limit. Fixed it, then wouldn't bed level without hot end hitting the bed, adjusted probe. Worked, kind of.

I've had some luck printing since then but only small stuff and not all the time, roughly an 80% fail rate for lots of reason, none the same as the first. Usually bed adhesion or the print head clips the print. I have video.

So I'm trying to rebuild the printer from scratch making sure everything works like it did when I first got it but I'm still seeing weird stuff like the belt tension testing giving crazy readings. I can't find anyone that has reported similar problems so it has been difficult to narrow down. Any help is greatly appreciated.

Posted : 14/02/2021 11:50 pm
Peter M
(@peter-m)
Prominent Member

Bets test number is not precise.

Adjust belt so it is tight, but not to much, it needs to have a little play, if to tight you will see this in your walls of your print.

The use the printer and do not look at the number.

Posted : 15/02/2021 11:24 am
Dan Rogers
(@dan-rogers)
Honorable Member

Download the tool that Prusa posted in the prints section for adjusting belt tension.  The sensors are not very accurate, and the little tool lets you zero the right tension right in.

Posted : 15/02/2021 2:29 pm
Diem
 Diem
(@diem)
Honorable Member

Unplug and reinsert all the electrical connections.  Noise from a loose or corroded connection can cause all sorts of issues.

Adhesion problems arising after a long period of success are often accumulated oxides that are not soluble in the usual cleaners. So a thorough wash and scrub with a new dish sponge first and if that isn't enough you could risk the acetone treatment.

The belt reading is not tension but resistance, check the idler end as well.

Hth, Cheerio,

Posted : 15/02/2021 3:52 pm
dkoemans
(@dkoemans)
New Member

@dan-rogers

I'll give this a go and report back.

Posted : 15/02/2021 8:07 pm
dkoemans
(@dkoemans)
New Member

@diem

Plate adhesion I'm guessing is related to nozzle height in this case. I'm not able to calibrate accurately due to other issues. I tried cleaning the build plate conventionally using alcohol (91%) and then later, acetone. Neither improved adhesion even after a live Z adjustment. I also tried the powder coated steel plate but that was a total failure but I didn't recalibrate for the thickness change so that is on me.

I did reseat all my connection when I took apart the rambo board to remove the raspberry pi. I can try that again.

Posted : 15/02/2021 8:10 pm
Diem
 Diem
(@diem)
Honorable Member

@dkoemans

Try a full reset followed by reinstalling the latest firmware.

Plate adhesion I'm guessing is related to nozzle height in this case. I'm not able to calibrate accurately due to other issues.

After a full reset you will need to calibrate again.  Take a photo of the calibration square in case problems persist in which case post it here.

Also clean the sheet with dishwashing detergent (Dawn/Fairy) and plenty of HOT water, rinse well and dry with a fresh paper towel. Handle by the edges only.

The nozzle clipping the print is often due to poor adhesion, one end lifts off the bed into the path of danger.

The belt readings are proportional to the mechanical resistance felt by the stepper motors.  In a well set up machine this is an approximate tension metric; BUT it is also affected by dirty axis rods: (clean and lubricate) damaged or clogged idler bearings, damaged or clogged belts, slipping drive-end grub screws, distorted axes and a few other rare occurences.

You may be able to feel some of these causes if you slide the axis by hand.

Hth, Cheerio,

Posted : 16/02/2021 3:00 am
Dan Rogers
(@dan-rogers)
Honorable Member

@diem

Do Do Do this if your printer sat unused for a while.  

Posted : 16/02/2021 3:06 am
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