[Cerrado] Fine tune your MK3 X axis  

Re: Fine tune your MK3 X axis

Yes exactly. I will add this to your github ticket then

Re: Fine tune your MK3 X axis

I have observed something else on the x-end-idler on my MK2s but I tried to reproduce this on the MK3 parts.

(click for bigger view)

In this image, the space for the screw head is bigger than the space for the nut. This means, with tension, the screw will tilt at about 1°. This is not a big angle but apparently it is enough on my MK2s to have the belt always on one side of the idler (bearing) and I could never have a belt properly aligned on the x-end-idler. Maybe it is more pronounced on the MK2s than on MK3, I did not check the hole diameters.

What do you thing?

Yes, I already pointed this out in another thread. This is causing belt rubbing on X axis. In addition, the stock idler pulley is a single bearing which exacerbates the problem. I printed a dual bearing solution. see link in my sig.

Re: Fine tune your MK3 X axis

I am going to order some dual bearing idler and belt pulleys for the rebuild of a new printer (which is BS in my opinion to have to do so) Anyone know the size needed? I will check the manual and see if it calls it out.

Maybe these for the smooth idlers?
https://www.amazon.com/gp/product/B072RJ4J37/ref=ox_sc_act_title_2?smid=A2K1WYI5NZ8QSW&psc=1
These for the tooth ones? 16T
https://www.amazon.com/gp/product/B075M3NCW3/ref=ox_sc_act_title_1?smid=A2K1WYI5NZ8QSW&psc=1

Re: Fine tune your MK3 X axis

I am going to order some dual bearing idler and belt pulleys for the rebuild of a new printer (which is BS in my opinion to have to do so) Anyone know the size needed? I will check the manual and see if it calls it out.

Maybe these for the smooth idlers?
https://www.amazon.com/gp/product/B072RJ4J37/ref=ox_sc_act_title_2?smid=A2K1WYI5NZ8QSW&psc=1
These for the tooth ones? 16T
https://www.amazon.com/gp/product/B075M3NCW3/ref=ox_sc_act_title_1?smid=A2K1WYI5NZ8QSW&psc=1

20 tooth seems to be the correct one.

On a sidenote I got a couple off of Amazon and the bearings were a little crunchy. If you get some was good bearings please share your source

Re: Fine tune your MK3 X axis

Pretty sure the pulleys are 16T

From Manual page "Place a GT2-16 pulley on the Y-motor shaft as shown in the picture."

Re: Fine tune your MK3 X axis

Pretty sure the pulleys are 16T

From Manual page "Place a GT2-16 pulley on the Y-motor shaft as shown in the picture."

It’s absolutely 16T on the drive side, however the diameter of the smooth idler is much larger than on the drive side. Compare the belt separation on the left and right side of the extruder in this thread and you’ll see it’s wider on the idler side. I have pulleys at home and will try to remember to take to work tomorrow and and snap pics.

Re: Fine tune your MK3 X axis

Pictures of 16T idler, 20T idler and smooth idler that came with the MK3...

Re: Fine tune your MK3 X axis

Hi Edward,
Where did you find these toothed pulleys?

Re: Fine tune your MK3 X axis

You can get pulleys from Misumi (like this https://us.misumi-ec.com/vona2/detail/110302651360/?KWSearch=GT2&searchFlow=results2products ).

I think we'd be much further ahead using a shoulder bolt or dowel through the idler pulley rather than the stock bolt. Having the pulley ID on threads is really counter-intuitive, the bearing probably isn't actually even fully used.

Re: Fine tune your MK3 X axis

I bought both on Amazon, about 9$ for five of them. I agree that we need a shouldered bolt or down pin, not point having bearings when not fitted properly. Now question is where do the get the bolts lol.

On Amazon look for Kingprint they have some decent pulleys, dual bearing.

Re: Fine tune your MK3 X axis

Using a dowel would definitely be easier (and much easier to find). But it would be as easy to remove.

I can't search through Amazon right now but something like this https://www.mcmaster.com/#90323a325/ would work with some tweaks to the printed part design. Plus you'd need an M4 nut on top of that.

Looking at it now I think using a dowel is the obvious choice haha.

Re: Fine tune your MK3 X axis

I got my toothed pulley's at Amazon as well.

Re: Fine tune your MK3 X axis

I have observed something else on the x-end-idler on my MK2s but I tried to reproduce this on the MK3 parts.

(click for bigger view)

In this image, the space for the screw head is bigger than the space for the nut. This means, with tension, the screw will tilt at about 1°. This is not a big angle but apparently it is enough on my MK2s to have the belt always on one side of the idler (bearing) and I could never have a belt properly aligned on the x-end-idler. Maybe it is more pronounced on the MK2s than on MK3, I did not check the hole diameters.

What do you thing?

https://github.com/prusa3d/Original-Prusa-i3/pull/54/commits/54cff4f5bf5bfdcd2a92c526257153a4dee18d3d

Here is Xaxis idler with fixed pulley screw hole size, that should avoid belt slipage.

Re: Fine tune your MK3 X axis

I got my MK3 delivered (pre-assembled) last week and I noticed the X-belt twisting right away.

I tweeted (no reply for 2 days) and then mailed Prusa about it.

Got a pretty standard reply that I had to check if the motor pulley wasn't mounted reversed or something.

It was not, but I did move it a bit more towards the motor as the belt was too far forwards (visible with the naked eye) so I figured that might cause it to run into the forward side of the pulley.
It was a little better, but not entirely resolved.
I inspected the passive end and noticed that the pulley didn't seem to sit fully upright, the top part had a bit more space on the side than the bottom part.

So I mailed back
The mail had another question as well regarding a heavy hum from the PSU that started after a couple of print-hours, and I got a reply that that would be "fixed via the firmware", but they did not respond to my remark of the pulley not being straight.

It is actually grinding the belt, you can even see that in the video (it's chafed, on a brand new printer).
So I thought I was imagining things. And now I see this thread... Bit of a scandal

Here's the tweet for your reference:
https://twitter.com/blizzke/status/956905617167454209

Re: Fine tune your MK3 X axis

I have observed something else on the x-end-idler on my MK2s but I tried to reproduce this on the MK3 parts.

(click for bigger view)

In this image, the space for the screw head is bigger than the space for the nut. This means, with tension, the screw will tilt at about 1°. This is not a big angle but apparently it is enough on my MK2s to have the belt always on one side of the idler (bearing) and I could never have a belt properly aligned on the x-end-idler. Maybe it is more pronounced on the MK2s than on MK3, I did not check the hole diameters.

What do you thing?

https://github.com/prusa3d/Original-Prusa-i3/pull/54/commits/54cff4f5bf5bfdcd2a92c526257153a4dee18d3d

Here is Xaxis idler with fixed pulley screw hole size, that should avoid belt slipage.

You also want a dual bearing pulley. Screw hole fix alone is not sufficient.

Re: Fine tune your MK3 X axis

Just to be sure before make a order, do i need to order GT2 20T with 3 mm bore or GT2 16T with 3 mm bore? ( to substitute the 16T smooth pulley)
Thanks

Re: Fine tune your MK3 X axis

Just to be sure before make a order, do i need to order GT2 20T with 3 mm bore or GT2 16T with 3 mm bore? ( to substitute the 16T smooth pulley)
Thanks

GT2 20T.
I have already installed those (16T are too small)

Re: Fine tune your MK3 X axis

Just to be sure before make a order, do i need to order GT2 20T with 3 mm bore or GT2 16T with 3 mm bore? ( to substitute the 16T smooth pulley)
Thanks

If you read the print quality thread the toothed idler doesn't make any difference. In my case the bearings in the toothed pulleys I purchased are notchy so I ended up tossing them in the drawer and kept the smooth idlers that came with the printer in place, bearings on my idlers from Prusa are butter smooth.

Re: Fine tune your MK3 X axis

If you read the print quality thread the toothed idler doesn't make any difference. In my case the bearings in the toothed pulleys I purchased are notchy so I ended up tossing them in the drawer and kept the smooth idlers that came with the printer in place, bearings on my idlers from Prusa are butter smooth.

Just want to point out that while I observed no difference in my vertical line issues when using the toothed idler, according to the GT2 standard the smooth idler being used is still too small. There may be an improvement there we aren't seeing due to other issues. 😀

With the gates curvilinear profile (GT, GT2, GT3, etc), it's acceptable to run the teeth side against a smooth idler if it has a diameter equal to or greater than the effective diameter of a 40 tooth pulley of the same tooth pitch.

Re: Fine tune your MK3 X axis

Brigandier, do you know what the average diameter (effective) is on a 40 tooth pulley?