Belt tension broke the plastic  

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Cowasaki
(@cowasaki)
Active Member

i fitted the 3s upgrade and was very happy with the results but after reading about popular issues I found my x axis belt tension was 287 so slightly outside the recommended amount. I couldn’t tension it enough to get any more so removed all tension and got the belt another tooth on. After that I tensioned it and got 276 but then then little bit of plastic exploded off the x motor bracket at the bottom (the hole with the bolt that has the tightening bolt too). The prints are perfect and it’s kept it’s tension but I’m not sure for how long. I’m going to print all the parts just in case as if one breaks I can’t print them! So PETG or PLA? 

 

Also so how does the printer measure the belt tension because I cannot see how I could get it any tighter so can’t image how anyone could get anywhere near 240 without something snapping. It pings like a guitar and prints perfectly so I’m thinking whatever measures the tension is out of calibration. 

Posted : 05/06/2019 11:02 am
Neophyl
(@neophyl)
Famed Member

You want to print replacements in PETG like the originals.

Also the belt tension values are not really tension but a measure of friction in the system.  You cant really go by them, the only real way I've heard of is to measure the deflection of the belt with specific weights.  Personally I just go by feel.  Not very scientific but its worked so far.

Posted : 05/06/2019 1:17 pm
Cowasaki
(@cowasaki)
Active Member
Posted by: Neophyl

You want to print replacements in PETG like the originals.

Also the belt tension values are not really tension but a measure of friction in the system.  You cant really go by them, the only real way I've heard of is to measure the deflection of the belt with specific weights.  Personally I just go by feel.  Not very scientific but its worked so far.

This is my issue with it.  The tension is perfect as far as I am concerned now.  The prints are spot on but the tension reported is absolutely at the top of the range on both axis.  I have enough PETG from the 3s update to probably print a set of plastics, 200g ?  certainly enough for these bits then maybe get some more PETG.  I might print one of the alternative X Axis mote ends with the camera mounters well......

Posted : 05/06/2019 4:37 pm
Tim
 Tim
(@tim-2)
Illustrious Member

The belt tension numbers on the LCD are useless for knowing belt tension.  They are nothing more than the TMC driver currents required to move the axis. And belt tension does not affect that.

The only way to know belt tension is to measure it.  Gates recommends the Deflection method. Apply 250g, or about 8 ounces force to the lower belt, and it should deflect 15/64" ...  this is about 8 pounds tension.  1/4" belt is spec'd at 2 pounds minimum.  Motor shaft is spec'd 11 pounds maximum. 

It is always wise to get more than one opinion...
Posted : 05/06/2019 4:46 pm
Nikolai
(@nikolai)
Noble Member

PR should remove this numbers from the regular user menu. It's causing more confusion and broken parts then it helps.

@darren-h6: Just forget about this numbers. They are not being used for the print process and as tim already mentioned they are only showing the TMC current is needed to move the axses. Maybe just watch some youtube guides how the tensions should look like to get a basic idea for the right tension. Or do it the scientific way described by tim.

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Posted : 05/06/2019 6:55 pm
Cowasaki
(@cowasaki)
Active Member
Posted by: nikolai.r

PR should remove this numbers from the regular user menu. It's causing more confusion and broken parts then it helps.

@darren-h6: Just forget about this numbers. They are not being used for the print process and as tim already mentioned they are only showing the TMC current is needed to move the axses. Maybe just watch some youtube guides how the tensions should look like to get a basic idea for the right tension. Or do it the scientific way described by tim.

I'm happy with the tension I have now and getting really good results.  I just thought that the figures were out as it right at the limit.  I'm leaving it as it is now.

Posted : 05/06/2019 8:14 pm
Tim
 Tim
(@tim-2)
Illustrious Member

If you tensioned sufficient to break plastic, you are probably damaging the motor bearings.

It is always wise to get more than one opinion...
Posted : 05/06/2019 9:23 pm
Cowasaki
(@cowasaki)
Active Member
Posted by: Tim

If you tensioned sufficient to break plastic, you are probably damaging the motor bearings.

When the plastic went the tension reduced back to only a little more than original and that is about right to me.

Posted : 05/06/2019 9:35 pm
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