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Half-twist the Y belt on idler pulley...  

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patrizio.b
(@patrizio-b)
Trusted Member
Half-twist the Y belt on idler pulley...

Did anyone try to half-twist the Y belt, so the smooth side of the belt is in contact with the idler pulley? The half-twist would float on the center/bottom of the Y belt loop, so it would not create problems. I think the trick is used in some other machine to increase the belt grip, and eventually decrease slipping.
I'm currently trying it.

Posted : 20/01/2017 11:11 pm
JeffJordan
(@jeffjordan)
Member Moderator
Re: Half-twist the Y belt on idler pulley...

this would only increase the surface between belt and idler pulleye.
but why should there be any grip needed at the idler pulleye ?

in my opinion the belt grip is defined by the teeth of the stepper pulleye.
as long as the belt is moderately tightened and there are no slips or dynamic elongations of the belt, i can't see any effect on movement and/or precision of the y-axis.

the only thing that might occur is that it reduces the stress for the belt a little bit when it's teeth run unsupported over the plain idler... but then there is the dynamic stress of the twist...

if someone uses this "trick" and is satisfied with it, no problem. placebos really do work.

dem inscheniör is' nix zu schwör...

Posted : 28/01/2017 8:08 am
patrizio.b
(@patrizio-b)
Trusted Member
Topic starter answered:
Re: Half-twist the Y belt on idler pulley...

from what i know timing belts are not supposed to run on smooth pulleys... i've seen some complex serpentine drives and they all have toothed pulleys for driving and smooth pulleys for tensioning. This printer (and all prusa derivatives) seems the only thing on earth pretending it's right to do otherwise

Posted : 28/01/2017 12:18 pm
Grooperdude
(@grooperdude)
Eminent Member
Re: Half-twist the Y belt on idler pulley...

i noticed a difference when i installed a toothed pulley on my Anet A6.
(vibration artifacts diminished by a noticeable amount). I am currently looking for a good brand of 16 or 20 toothed idler pulleys..
The last batch of 5 i bought only had 1 perfectly round one . any suggestions? i dont think it matters what size the idler is either.
Plus, it looks like the smooth pulley that came wih the MK2S would be about a 20 tooth.
(i think that was on purpose since the belt has to connect to the upper portion of the x-carriage which causes the actual loop to be just slightly larger on the smooth pulley side. so kudos to prusa for seeing that. )

If anyone can lead me to some good Idler pulleys, it would be very much appreciated.

Posted : 25/05/2017 4:26 pm
tom.b6
(@tom-b6)
Trusted Member
Re: Half-twist the Y belt on idler pulley...

I used these.
https://www.amazon.com/gp/product/B01H3DSGAC/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Posted : 26/05/2017 1:09 am
Grooperdude
(@grooperdude)
Eminent Member
Re: Half-twist the Y belt on idler pulley...

Thank You Tom :)! i Just now ordered them. i will post an update on the quality when they arrive saturday

Posted : 27/07/2017 4:33 pm
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