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X-axis belt tension problems: very confused  

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Bill
 Bill
(@bill-2)
Active Member
X-axis belt tension problems: very confused

I'm very confused about what I read and what I see about the x-axis belt test.  I've read the assembly guide, I've read some excellent posts here (such as: Prusa i3 X/Y-Axis Belt Adjustment Guide) and have learned:

  • That the Belt Test number I get, in the range of 221-231, is too low.
  • That the number indicates my belts are too tight, which seems crazy. I'm able to deflect them easily to touch.
  • That I can adjust the tension by loosening the stepper motor, adjusting that little stop-screw, and then tightening the motor back.  Done that, the stop screw is almost completely removed.

This saga began about two weeks ago, where I had some ringing(?) in the X direction of my prints, with layers near the bottom (Z distance of about 1cm above the build plate) were distorted and sometimes shifted.  I finally had a major failure which prompted me to investigate further.

I ran the belt test, loosened the belt, and things improved.  If I recall correctly, the belt test number had climbed to 242 or so when I did the loosening.  Life was good for another 20-30 hours of printing.

Today, I had another major failure, so ran the belt test.  My number is back to 224.  But, the loosening the stop screw isn't going to help.  

Questions:

1) What to do?

2) I can't believe that running prints through the machine can somehow tighten the belt.  That doesn't make sense.  What would cause my belt test numbers to decrease over time?

3) Any pointers to other stuff to read that might help me diagnose the problem?

Many, many thanks!  Life just isn't the same without my MK3S operational.

 

Posted : 30/10/2020 3:18 am
JoanTabb
(@joantabb)
Moderator
RE: X-axis belt tension problems: very confused

I believe the test. Checks the aparrent friction on the axis to estimate belt tension

Maybe something is affecting the friction

Is anything binding?

Is everything free running?

  • Could the idler mounting bolt be a little tight

Do the bearings need lubricating?

 

Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 30/10/2020 11:49 am
Bill
 Bill
(@bill-2)
Active Member
Topic starter answered:
RE: X-axis belt tension problems: very confused

Joan,

Many thanks for your suggestions.  I am planning to take the x-axis apart this weekend and lubricate it all.

Bill

Posted : 30/10/2020 3:38 pm
JoanTabb
(@joantabb)
Moderator
RE: X-axis belt tension problems: very confused

Hi Bill, 
I wish you good luck for the week end. 
if you didn't lubricate your bearings during building,  a little, light application of lubrication, may ease your issues now, with little effort on your behalf.  

https://help.prusa3d.com/en/article/i3-printers-regular-maintenance_2072#rods-and-bearings

if this helps, you might be best occasionally applying a little lubrication, rather than ripping the printer to pieces, and leave that excitement until you have a bigger job to do... in other words Don't mess with a working printer!  🙂

I waited ages to change to a cool running Zaribo Extruder motor and eventually changed it, when the thermistor also needed changing! because at that stage the printer was no longer running! (I put a new Dragon Hotend in, at the same time)

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 30/10/2020 4:45 pm
Bill
 Bill
(@bill-2)
Active Member
Topic starter answered:
RE: X-axis belt tension problems: very confused

Joan,

Good advice!

My printer only has about 200 hours on it -- I bought it early in the pandemic and it arrived in late July.  Been having a blast with it ever since.  

I look forward to a day when I have pushed it so much that I'll need a new motor/thermister/hotend also!

Cheers,
Bill

Posted : 30/10/2020 5:10 pm
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