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Z belt tension issue

Henk

Member
Printer Model
V2.4R2
Hi all,

I'm building a V2.4 R2 and having some problems with the Z belts.
I got all 4 Z belts installed and tried to tension them to 140Hz, the problem I'm having is that the belt part that goes from the gantry to the lower pulley stays lose.
On the picture I marked the belt part red.
I raised the tension to 200Hz but that doesn't help, the lower parts stay lose.
Since it happens on all 4 belts it must be me doing something wrong, any advise/tips?
 

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I cannot picture what you mean. How can you tension but the lower part not move? I would say go back and make sure the Z motor section is correct or just re examine the Z belt section.
 
I did take apart the z drive and rebuild them, but nothing was to be found wrong.
I can move the gantry up and down manually turning the pully on the motors without issue, so nothing feels like it's binding.
Holding the gantry in place and then pulling the long side of the belt I can get the red indicated part tensioned. But if I then tension to 140Hz and move the gantry up and down a bit pushing and pulling on the gantry the red indicated part of the belt will be loser again, and of course the other part of the belt is on a higher tension after it. It just doesn't feel correct to me.
 
Post some pics of your specific build.

The tension adjustment for the lift belt is at the top pulley.

Basically:
  • Have top tensioner fully loose (but bolts engaged with nut) (Z Idler, page 48 for the manual)
  • Pull belts tight through clamp plate at gantry (Z Belt, page 120)
  • Tighten clamp plate on gantry
  • Tighten top pulley to ~140 Hz.
 
I did follow that procedure every attempt, but I discovered something, I was using my phone and the spectroid app to tune and at first it seemed I was always close from the start between 123 and 130Hz. But now I realize it always shows a spike between 123Hz and 130Hz so I guess the 140Hz I saw was just a harmonic and I never had all Z belts equally tuned. I tried other apps but all have the same issue, somehow I have the same issue on my tablet. So now I guess I never had the belts tight enough and the lose red part of the belt is just due to the geared resistance of the steppermotor.
 
You will want to move the gantry up and down to settle the belts in. Then tune, move gantry again and re-tune. It will also need to be tuned after a couple spools are printed as the belts will stretch a bit.
 
I did follow that procedure every attempt, but I discovered something, I was using my phone and the spectroid app to tune and at first it seemed I was always close from the start between 123 and 130Hz. But now I realize it always shows a spike between 123Hz and 130Hz so I guess the 140Hz I saw was just a harmonic and I never had all Z belts equally tuned. I tried other apps but all have the same issue, somehow I have the same issue on my tablet. So now I guess I never had the belts tight enough and the lose red part of the belt is just due to the geared resistance of the steppermotor.
Ahh yes, it makes sense now. I go to great lengths to make sure my belts have nice even tension.
In fact I have a pretty complex print to help with tuning instead of relying on sound. I will see if I can find it.

Here we are. This tool is very accurate. https://github.com/Diyshift/3D-Printer/tree/main/GT2 Belt Tension Meter
 
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Thanx for that link, I'll be building one, waiting on the spring to be delivered, I fully gave up on tuning the belts by sound.
I did as well. I went through so many different methods too such as using my computer and mic setup to many phone apps.
The only downside to building the tool is all the different bits and making sure everything fits nice but the guide is excellent at helping with it.
 
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