Posted by: @adaddison

Question, for those of you that upgraded to GT1.5 belts, what belt tension are you running on them?

Using the new belt tuning wizard, I tuned the belts to 87Hz and 83.5Hz for the top and bottom belts, respectively, and the printer moves very comfortably.  Initially I kept the frequencies the same as on the stock belts, but I got some strange creaking that made me think they were too tight.  Then I noticed that my 1.5gt belts were thicker than the stock, so, assuming they're made of the same stuff, getting the same tension on thicker belts would require lower frequencies.  I measured the mass per length of belt for both the stock and the new belts and calculated the following:

Stock belts: 7.349g/m
1.5gt belts: 8.952g/m
Frequency scale: sqrt(7.349 / 8.952) ≈ 90.6% of the original frequencies.

Top belt: 96Hz * 0.906 = 86.976Hz
Bottom belt: 92Hz * 0.906 = 83.352Hz

However, it is very important that anyone doing this mod knows how they'll have to adjust the software to compensate for the differently sized pulleys.  The conventional wisdom is to utter the "M92 98.44 98.44" magic incantation at the beginning of your gcode.  It seems that people have just accepted this as necessary, and indeed it does work (despite leaving your printer in a weird state afterwards), but unfortunately it makes no sense.  The new pulleys are slightly smaller than the stock, and so they need to rotate more (take more steps per mm) to cover the same ground.  The only explanation is a firmware bug.

To that end, I have a PR up that discusses the problem in more detail, and provides a fix for anyone who's comfortable building/flashing their own firmware: https://github.com/prusa3d/Prusa-Firmware-Buddy/pull/5062

I’m currently experimenting with high-temperature settings on my Core One using PPS, PPA, and maybe even PEI, so VFA isn’t too much of a problem with the parts I’m printing.

But:I’ve ordered some 1.5GT parts from Asia so I can finally get rid of the VFA when I print with glossy filament again.

I am about to upgrade from 3s+ to 3.5+ and changing to poly bearings at the same time.

My small tests say that they are much better.

Looking at the VFA in the video didn't bother me, have been getting those for about half a year on my first printer (ad5m pro). Had no idea those were bad, the ones I get aren't terrible but really noticeable on shiny filament.

As for the belt fix, would upgrading to 1.5mm belts need new drivers?

I've seen mixed reviews on the VFA, with a lot of people stating perfect quality on their core ones and lots saying they have terrible issues. I haven't seen any reviews on the software update they released earlier this month to fix VFAs, has anyone here seen better results with this?

Thanks.

Posted by: @adaddison

Question, for those of you that upgraded to GT1.5 belts, what belt tension are you running on them?

Between 80Hz and 85Hz on both belt with the old method.
Works like a Charm. Almost no VFA.

-J

Posted by: @teamd3dp

Interesting discovery for me today while running a PA calibration on our Qidi Q2 at work...I see prominent belt ripple along the pure X movements.  🤔.   Granted this isn't a VFA test, but so far I'd seen only very smooth walls from this printer.

-J

I think Qidi use speed exclusion zones in their slicer profiles to avoid belt ripple problem speeds - the PA test might have overridden that?