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Cannot tighten the X-axis belt of i3MK3S+  

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prusanewuser
(@prusanewuser)
Honorable Member
Cannot tighten the X-axis belt of i3MK3S+

Hello, I upgraded from i3MK3S to 3S+ over a year ago when the kit came out. I got the Tension Meter for the GT2 belts of i3MK3S+. However, no matter what I did, it points to Min when I tested the tension on the X-axis belt. The Y-axis belt is in the middle so it is OK.

I followed the steps in:

Adjusting belt tension MK3/S | Prusa Knowledge Base (prusa3d.com)

already. The X belt value is: 164 while that for Y is 279. To tighten the X-axis belt further, I would need to rotate the X-axis motor counter-clockwise more. However, the top two screws would not be able to pass through the holes on the mounting surface of the motor. 

What is wrong? Does that mean it is time to replace the belt as it might not be able to sketch more?

Best Answer by Diem:

I cleaned and lubricated the smooth rods already before I created this thread.

Good

With the belt removed, it is super easy to move the extruder along the X-axis rods by hand. Turning the stepper motor by hand is also smooth except for the stepper nature of the motor.

That's how it should be.

About the idler bearing, in Step.6, are we supposed to tighten it or make it loose? It was very loose when I disassembled the parts. Actually I made a mistake using a shorter screw over a year ago. The screw did not go through the nut probably over time but here was no problem.

This is where I think your problem may lie.

If you get the screw tension wrong the idler can twist out of line and rub against the side of the housing, it's possible to crush the housing if the screw is too tight and it's possible to collapse the inner ball race if the belt is too tight...

But if you hit the sweet spot it runs smoothly with very little resistance.

Cheerio,

 

 

623h

Posted : 08/08/2022 8:48 pm
Artur5
(@artur5)
Estimable Member
RE:

For both X and Y belts, 275 is the 'ideal target' given by Prusa.  260 to 290 is OK. 250 to 300 acceptable. Over 300 it starts getting too loose. Lower than 250 too tight.  It sounds counter intuitive but high value = loose belt and low value = over tightened.

If your X belt value is really 164 and not a typo, then it's way off. I never heard of such low figure. On the other part, the 3D printed tension meter says that it's almost below minimum. Contradictory ?'. Yes and no. When the printer performs the belt calibration, it doesn't measures the actual tension but the resistance felt by the stepper motor when it moves the extruder along the X axis. Thus, you may have a loose belt but if the bearings are damaged or strongly squeezed by the X-carriage back, you'll get a very low value (or directly an error before the belt test is completed).

For what you say, my guess is that you need to trim a little bit the X belt in order to get more tension but, again, if 164 is the real value of the X belt test, there's something wrong elsewhere. Can you move by hand the extruder along the X axis without feeling roughness or uneven resistance to advance ?.

This post was modified 2 months ago by Artur5
Posted : 08/08/2022 9:52 pm
fuchsr
(@fuchsr)
Famed Member
RE: Cannot tighten the X-axis belt of i3MK3S+

In your situation I'd completely disassemble the X-axis and start all over again. I figure it's more likely something went wrong during the upgrade rather than a bad belt.

Posted : 08/08/2022 10:32 pm
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE: Cannot tighten the X-axis belt of i3MK3S+
 

For both X and Y belts, 275 is the 'ideal target' given by Prusa.  260 to 290 is OK. 250 to 300 acceptable. Over 300 it starts getting too loose. Lower than 250 too tight.  It sounds counter intuitive but high value = loose belt and low value = over tightened.

If your X belt value is really 164 and not a typo, then it's way off. I never heard of such low figure. On the other part, the 3D printed tension meter says that it's almost below minimum. Contradictory ?'. Yes and no. When the printer performs the belt calibration, it doesn't measures the actual tension but the resistance felt by the stepper motor when it moves the extruder along the X axis. Thus, you may have a loose belt but if the bearings are damaged or strongly squeezed by the X-carriage back, you'll get a very low value (or directly an error before the belt test is completed).

For what you say, my guess is that you need to trim a little bit the X belt in order to get more tension but, again, if 164 is the real value of the X belt test, there's something wrong elsewhere. Can you move by hand the extruder along the X axis without feeling roughness or uneven resistance to advance ?.

164 is the correct value. No typo.

I do feel resistance when moving the extruder along the x-axis by hand. What could be the reasons?

After loosening those screws behind the extruder a bit, X belt value is now 192 and the indicator on the Tension Meter is a bit below Min. Actually are we supposed to tighten the four screws at the back of the extruder very tightly or loosen a bit? 

 

Posted : 09/08/2022 1:13 am
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE:

 

Posted by: @fuchsr

In your situation I'd completely disassemble the X-axis and start all over again. I figure it's more likely something went wrong during the upgrade rather than a bad belt.

But I upgraded from i3MK3S to 3s+ long time ago when it was just released. Back in March, I also replaced all the bearings and rods to Misumi's. I could make the indicator of the Tension Meter in the middle of the range and it printed fine. Since two weeks ago, I noticed that vertical wall have Z banding so I performed a maintenance and recalibration. Then, I noticed that the X belt is at the boundary of Min in the Tension Meter.

Before creating this thread, I took the belt out and reinstalled. Problem is even with strong force, I could not sketch it anymore to make the indicator of the Tension Meter to move within the acceptable range. 

This post was modified 2 months ago 3 times by prusanewuser
Posted : 09/08/2022 1:18 am
Diem
 Diem
(@diem)
Famed Member

Check your X axis idler bearing is OK, if overtight the belt can cause it to collapse or to distort the carrier. 

Cheerio,

Posted : 09/08/2022 1:55 am
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE: Cannot tighten the X-axis belt of i3MK3S+

 

Posted by: @diem

Check your X axis idler bearing is OK, if overtight the belt can cause it to collapse or to distort the carrier. 

Cheerio,

What criteria should I use to determine if the idler bearing is OK?

For the past two days, I noticed that some strange sound came out during printing. Not so loud but noticeable. As I moved the extruder along the X-axis, it did not move smoothly. As mentioned, I changed all bearings and rods few months ago and it had been printing fine until recently.

Posted : 09/08/2022 1:07 pm
Artur5
(@artur5)
Estimable Member
RE: Cannot tighten the X-axis belt of i3MK3S+

 

Posted by: @prusanewuser

 

For the past two days, I noticed that some strange sound came out during printing. Not so loud but noticeable. As I moved the extruder along the X-axis, it did not move smoothly. As mentioned, I changed all bearings and rods few months ago and it had been printing fine until recently.

Did you pack with lube the inside of the new bearings before installing them?. The noise that you hear, is it like a harsh metal-on-metal creak? Have you noticed any scratches on the smooth rods, especially the upper one?

Posted : 09/08/2022 1:34 pm
Diem
 Diem
(@diem)
Famed Member

Clean and lubricate the smooth rods, check they are not damaged/scratched. Check the idler pulley is not clogged, out of line, or damaged (loosen the belt and try turning it with your fingertip, is it smooth?)

Peer in (with a torch if necessary), is it straight, is it rubbing against/wearing the housing?

While the belt is loose try turning the stepper motor by hand; is it smooth?

Cheerio,

Posted : 09/08/2022 4:24 pm
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE:

 

Posted by: @diem

Clean and lubricate the smooth rods, check they are not damaged/scratched. Check the idler pulley is not clogged, out of line, or damaged (loosen the belt and try turning it with your fingertip, is it smooth?)

Peer in (with a torch if necessary), is it straight, is it rubbing against/wearing the housing?

While the belt is loose try turning the stepper motor by hand; is it smooth?

Cheerio,

I cleaned and lubricated the smooth rods already before I created this thread. 

I disassembled the X-part and started all over again. With the belt removed, it is super easy to move the extruder along the X-axis rods by hand. Turning the stepper motor by hand is also smooth except for the stepper nature of the motor.

About the idler bearing, in Step.6, are we supposed to tighten it or make it loose? It was very loose when I disassembled the parts. Actually I made a mistake using a shorter screw over a year ago. The screw did not go through the nut probably over time but here was no problem. 

https://help.prusa3d.com/guide/3-x-axis-assembly_167854

I tightened it and reassembled the machine. Now I could make the indicator of the Tension Meter in between Min and Max. So, the problem should have been fixed but it is very difficult to slide the extruder along the X-axis rods by hand. What is wrong? 

This post was modified 2 months ago 5 times by prusanewuser
Posted : 09/08/2022 9:00 pm
Diem
 Diem
(@diem)
Famed Member

I cleaned and lubricated the smooth rods already before I created this thread.

Good

With the belt removed, it is super easy to move the extruder along the X-axis rods by hand. Turning the stepper motor by hand is also smooth except for the stepper nature of the motor.

That's how it should be.

About the idler bearing, in Step.6, are we supposed to tighten it or make it loose? It was very loose when I disassembled the parts. Actually I made a mistake using a shorter screw over a year ago. The screw did not go through the nut probably over time but here was no problem.

This is where I think your problem may lie.

If you get the screw tension wrong the idler can twist out of line and rub against the side of the housing, it's possible to crush the housing if the screw is too tight and it's possible to collapse the inner ball race if the belt is too tight...

But if you hit the sweet spot it runs smoothly with very little resistance.

Cheerio,

 

 

623h

Posted : 09/08/2022 10:30 pm
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE: Cannot tighten the X-axis belt of i3MK3S+

 

Posted by: @diem

I cleaned and lubricated the smooth rods already before I created this thread.

Good

With the belt removed, it is super easy to move the extruder along the X-axis rods by hand. Turning the stepper motor by hand is also smooth except for the stepper nature of the motor.

That's how it should be.

About the idler bearing, in Step.6, are we supposed to tighten it or make it loose? It was very loose when I disassembled the parts. Actually I made a mistake using a shorter screw over a year ago. The screw did not go through the nut probably over time but here was no problem.

This is where I think your problem may lie.

If you get the screw tension wrong the idler can twist out of line and rub against the side of the housing, it's possible to crush the housing if the screw is too tight and it's possible to collapse the inner ball race if the belt is too tight...

But if you hit the sweet spot it runs smoothly with very little resistance.

Cheerio,

 

 

623h

So I should take apart again and play around with the tightness of that screw until I can move the extruder easily by hand while still having the indicator of the Tensioner Meter in between Min and Max? Any good way to get the tightness of that screw correct in less trials? I am concerned that removing and reinstall the parts made the connections lose.

Posted : 09/08/2022 11:14 pm
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE: Cannot tighten the X-axis belt of i3MK3S+

 

Posted by: @artur5

 

Posted by: @prusanewuser

 

For the past two days, I noticed that some strange sound came out during printing. Not so loud but noticeable. As I moved the extruder along the X-axis, it did not move smoothly. As mentioned, I changed all bearings and rods few months ago and it had been printing fine until recently.

Did you pack with lube the inside of the new bearings before installing them?. The noise that you hear, is it like a harsh metal-on-metal creak? Have you noticed any scratches on the smooth rods, especially the upper one?

Yes, I did.

Posted : 10/08/2022 12:56 am
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE:

I packed with lube before installation. No scratches on rods.

That strange sound occurs when the extruder moves by itself (e.g. during belt test). When I used my finger to lightly push the extruder down (finger on top of the extruder), that sound disappeared. When I disabled stepper motors and moved the extruder by hand, that strange sound did not occur but only normal bearing moving sound. Loosening those four screws behind the extruder lowered the strange sound to a minimal. What is wrong?

This post was modified 2 months ago by prusanewuser
Posted : 10/08/2022 1:08 am
Diem
 Diem
(@diem)
Famed Member

So I should take apart again and play around with the tightness of that screw

No  You should inspect very carefully for damage, cracks may only be visible under tension for eg.

Cheerio,

Posted : 10/08/2022 2:04 am
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