[Closed] Fine tune your MK3 X axis  

Re: Fine tune your MK3 X axis

Interesting and thoughtful!

I wished Prusa was now fast to release the reworked X axis parts. For me the wiggly X belt is one of the most unfixable issues that I have experienced. I wasted hours and hours in this.

Re: Fine tune your MK3 X axis

This is very interesting. The Z axis changes were harder to follow for me because the drawings confused me (I did not study them that hard when I read them). After seeing this post with its illustrations, was much easier for me to grasp, I will have to go back and study the other post more closely. What you are proposing makes complete sense and appears to be a definate design improvement. I wonder what Prusa's take on all this is going to be. Once I get my replacement hardened rods and get my lack table built, I think I am going to try and implement these new part designs. I look forward to hearing reports to see if there is any improvements. Unless someone stays with current settings/firmware and does extensive before and after testing, it may be hard to quanify the improvements. Factor in any changes to the firmware and/or the Slic3r profile, it may be hard to track. I would love to test this all out. You got an extra 40 hours a week I can borrow... 😯

Re: Fine tune your MK3 X axis

George, I've added more information about the Z axis. An image that might show the problem a bit more clearly. So please, take a look at the Z-axis post again.

Re: Fine tune your MK3 X axis

I just saw this so please ignore my post on the Y-axis thread asking for this. Had you considered the two-piece bearing holder backplate? I thought that one may be more functional for getting at things but this will work. These will print after the Y-axis prints are done. Could have doubled up if I caught it sooner.

This is what I had in mind for a backplate:
https://www.thingiverse.com/thing:2731484

This is what I had in mind for adjustment(not sure if dimensionally correct due to MK2 design:
https://www.thingiverse.com/thing:2078121

Thanks for all your hard work. Perhaps I will just start with these on my not yet assembled MK3 and compare them. That would be a great chance to see the difference.

Re: Fine tune your MK3 X axis

I was wondering if I would split the X-carriage-back into two parts or keep it in part.
Area51 has made an excellent solution to the problem, but I chose the second method for not having to unscrew any detail.

But if I remeber right then the split X-carriage-back part could also be used because I have not moved any screw holes or changed other important dimensions.
Regarding belt tensioners, I have not had time to look at it, so your link was interesting, thank you.

Re: Fine tune your MK3 X axis

First off, thanks for all the effort you've put into this. I'm watching all three of these threads closely.

Question: How does your X end idler differ from Prusa's original? Does it have any adjustments like the ones discussed in the 'squeaky MK3' thread below? It seems that there was some agreement on the X idler pulley being off axis and needing to be corrected in order to keep the x belt from rubbing and twisting on it.

https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/squeaky-mk3--t12309-s60.html

Re: Fine tune your MK3 X axis

Interesting analysis. I think this is pretty far down the Pareto of problems, but good work. I plan to wait for the new X parts form Prusa and not mess with these "legacy" parts for now.

I I have also added two small rib's on the X carriage that helps lock the drive belt so that it can not slip. I read somewhere that this had happened.

How sure are you that you got the rib in the right place for the teeth? I predict frustration for some folks trying get their belt on and tight.

I hope you get your printer soon so you can test your ideas. From concept to reality doesn't always play out precisely, I have learned.

Re: Fine tune your MK3 X axis

How sure are you that you got the rib in the right place for the teeth? I predict frustration for some folks trying get their belt on and tight.
I hope you get your printer soon so you can test your ideas. From concept to reality doesn't always play out precisely, I have learned.

The position of the tooth is based on a 1.38 mm toth belt with 2 mm tooth space, neutral bearing of 1.004 mm.

To find the right position for the teeth (different on the right and left side) I used the features available in Inventor to distribute the teeth along a drive belt. The brake wheel dividing diameter was used to calculate the position of the tooth.

Re: Fine tune your MK3 X axis

Awesome works RHDreambox, thank you!

Re: Fine tune your MK3 X axis

Anyone tested this?

Re: Fine tune your MK3 X axis - wait!

I printed these last night and started using them on my just-arrived MK3 kit. I discovered that your X-motor mount has incorrect depth for the smooth rods - about 10mm too shallow compared to the part in the kit (vers B3 on the part.) Which makes the X-axis 10mm too wide to fit the Z-axis lead screws. The idler-wheel part seems fine. The kit I just received had 370mm rods for the X axis. Is that longer than older MK3 kits?

Top is your part - mounted.
Bottom is kit part ver B3.
Notice the inspection holes indicating where the end of the hole is.
(please ignore the image distortion from shooting too close.)

It's a shame - I've always had X-belt alignment problems on my MK2 and MK2/S and this looked promising for the MK3. I do have the Y-axis tune-up parts installed and they seem to work just fine. I tried the Z-axis tune-up parts and actually had more adjustment with the kit parts - not much, but more.

Robert Wallace

Re: Fine tune your MK3 X axis

Thank you Robert!
I should be ashamed because I did not check this.
I assumed that the motor console was a mirrored copy of the idler console, but it was not!

The files are now updated, and I apologize for the extra work this caused 😳 😳 😳

Re: Fine tune your MK3 X axis

First off, thanks for all the effort you've put into this. I'm watching all three of these threads closely.

Question: How does your X end idler differ from Prusa's original? Does it have any adjustments like the ones discussed in the 'squeaky MK3' thread below? It seems that there was some agreement on the X idler pulley being off axis and needing to be corrected in order to keep the x belt from rubbing and twisting on it.

https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/squeaky-mk3--t12309-s60.html

RHDreambox, I never saw a reply to this. Does your redesign take into the account the issue I mentioned above? With all of the problems people have had with the belt rubbing on the X-idler pulley (rubbing, twisting, squeaking), clearly there is an issue there that needs to be remedied. I think an improved X-idler part definitely needs to address this, possibly before addressing any other potential issues.

Re: Fine tune your MK3 X axis

RHDreambox, I never saw a reply to this. Does your redesign take into the account the issue I mentioned above? With all of the problems people have had with the belt rubbing on the X-idler pulley (rubbing, twisting, squeaking), clearly there is an issue there that needs to be remedied. I think an improved X-idler part definitely needs to address this, possibly before addressing any other potential issues.

If the drive belt behaves strangely, it is because the end pulley or motor pulley is not mounted perpendicular (or in line) to the drive belt.
Either, the motor is obliquely mounted (can be fixed with a cable tie around the motor and rear end plate), or the front pulley is slanted.

Probably it is the front pulley that is oblique because the hole for the pulley's screw is too big. Screw and pulley can then stand at a small angle to the drive belt causing the drive belt to move to either side.
I can not see that the belt itself can cause these problems.

I have never claimed that the modified parts will solve all problems, but the risk of problems is significantly less because the mounting holes are smaller. The details refer to the title saying "Fine tune your MK3".

Edit:
My CAD model indicates that the drive belt location should be 10.5 mm from the motor body.

Re: Fine tune your MK3 X axis

First off, thanks for all the effort you've put into this. I'm watching all three of these threads closely.

Question: How does your X end idler differ from Prusa's original? Does it have any adjustments like the ones discussed in the 'squeaky MK3' thread below? It seems that there was some agreement on the X idler pulley being off axis and needing to be corrected in order to keep the x belt from rubbing and twisting on it.

https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/squeaky-mk3--t12309-s60.html

RHDreambox, I never saw a reply to this. Does your redesign take into the account the issue I mentioned above? With all of the problems people have had with the belt rubbing on the X-idler pulley (rubbing, twisting, squeaking), clearly there is an issue there that needs to be remedied. I think an improved X-idler part definitely needs to address this, possibly before addressing any other potential issues.

Prusa is about to release new X parts so I’m waiting to see if they addressed it fully.

Re: Fine tune your MK3 X axis

Has anyone adopted this yet, it's great work but I was wondering about the missing slot and narrow passage way for the cables. I be have not done it myself but a fellow MK3 sufferer had and was mentioning that.

Those might not be needed now but thought I would ask. I be have the gray PINDA so it's a little fatter. Thanks for all the work.

Re: Fine tune your MK3 X axis

Hello John,
I'm sorry for this. I have two CAD models I'm playing with and I accidentally posted details from the wrong model 😳 😳 😳

Here are the updated parts.

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?

Re: Fine tune your MK3 X axis

You are right, I think that's the problem at MK3 as well.
On my files, I have reduced the hole size, but I have not been able to test this because I have not yet received my printer.
It may also be as if someone mentioned that if the details were printed in ABS, the holes (material) would have shrunk to the correct size.