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Cracked X idler - reprint Mk2 or Mk3?  

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David H. Brown
(@david-h-brown)
Eminent Member
Cracked X idler - reprint Mk2 or Mk3?

After assembling the upgrade to 2.5, I think I must have the tension too high as the there's now a small crack (layer separation) on the back left (belt side, lock-nut side) of the x-axis idler right where the idler shaft goes.

It's still printing decently, so I will reprint that part, but does anyone have any thoughts about going with the Mk3 version instead of Mk2?

It seems ( https://manual.prusa3d.com/Guide/3.+X-axis+assembly/508?lang=en ) that they've abandoned the tension screws that push into the rods, which seems like it might be a disadvantage as they can help fine-tune the tension. On the plus side, after many people reported breaking a lip that supports the lock nut, they redesigned it with a bit of a bump for some extra strength right in the area I broke mine.

Anyone have any thoughts/experience on this part in a (former) Mk2S? Unless someone knows the Mk3 design won't work, I'll probably print one of each and see what happens.

https://www.thingiverse.com/davidhbrown/designs
Napsal : 09/10/2018 6:08 am
Jakub Dolezal
(@jakub-dolezal)
Member Admin
Re: Cracked X idler - reprint Mk2 or Mk3?

Hi David,
all the changes we have made are for a reason, I always recommend using the parts, which are designed for the specific type of the printer. Since yours is MK2S upgraded to MK2.5, you should use MK2S x-end-idler.

Latest parts can be found here: https://www.prusa3d.com/prusa-i3-printable-parts/

Assembly manuals

/ Knowledge Base
The guy behind Prusa assembly manuals...

Napsal : 10/10/2018 4:55 pm
serano.s
(@serano-s)
New Member
Re: Cracked X idler - reprint Mk2 or Mk3?

Apparently there is a known flaw with the design of the MK2 x-idler that causes misalignment of the x-belt. Mine has always shown symptoms of this (slightly twisted belt during motion), but it's never caused print problems. However I just noticed a hairline crack on the X-idler from over tightening during the MK2.5 upgrade. So, I was looking at the design of the X-axis printed Lucky Patcher 9Apps VidMate parts for the MK3 and they've made some small changes to address the alignment issue as well as a different tensioning screw. I don't see any reason why these parts wouldn't be compatible with the MK2 rods and hardware, unless the rods are a different length or some other esoteric problem. Thoughts?

Napsal : 03/12/2018 3:26 pm
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