Prusa i3 MK2/3/S/+ Y Chassis Integrated Bushings (and Bearing Straps)

Having recently purchased an Original Prusa i3 MK2 (and now MK3/S/+), I was originally dissatisfied with the poor bearing mounting method that can easily introduce variability in the Y and Z axes.

Inspired by other overly-complicated solutions to the problem, I designed easily-printed straps that when used with 6x M3x10mm machine screws, replace the zip-ties on the MK2 without any other changes and fully capture the bearings from movement.

With the MK3 purchase, I found the U-bolts not ideal as even the thickness of the high quality powder coating on the Y-axis bed frame could cause variations in the bearing alignment, leading to the Y-axis rod scoring that we i3 owners are so familiar with.

That's when I decided to experiment, and here is the culmination of over 3 years of design iteration and over 14,000hrs (yes, thousand !) hours of print testing. If these integrated bushings printed in simple run-of-the-mill PLA don't improve your print quality, then you didn't install them correctly (yes, they do take a bit of work to “hone” to perfect zero-tolerance).

Easily installed on Prusa i3 MK2/3/+ by removing only the MK42 Y-carriage assembly (take a read through the notes section for details before embarking).

Enjoy your slightly improved (and now silent/non-y-axis-rod-scoring/wearing) printer ! <3

-=dave

Video of them in action: https://youtu.be/RJopBbkPseA

Below are my updates over the years in reverse-cronological order. Come with me on the journey…

2020apr26 Update - I've had a few requests for an idea that I should have thought of myself: with this latest release you can now simply re-use the existing "U" bolts that come with the MK3/S, eliminating the need for sourcing additional M3 bolts. I've also updated the OpenSCAD source to include this new bushing type as "mk3" which will work with the U-bolts for any MK3 version. I've also found that slicing with the latest PrusaSlicer (2.2.0 as of today) the ID of the integrated bushing version is no longer tight enough, so I've updated the source parameters to correct for this. Lastly, I've included a .3mf file for use with PrusaSlicer 2.2.0 (or presumably later) so that you can slice your customized version yourself and not have to spend several prints to get the right settings.

After over 3 years of continuous optimization, I can say with 100% certainty that this latest "mk3" integrated bushing version, when hand-worn in per the instructions by @nic print as good as the MK3/S is capable of with respect to bed play (since there essentially is none, but more importantly, no metal-on-metal contact so that bed resonances are minimized.

I suspect this will be the last revision of this part since, like many, I am hoping the Prusa XL (core-xy based) printer will be the next Prusa printer we all begin playing with. Meanwhile, the MK3/S keep plugging away as some of the most tireless workhorse 3D printers in the world.

Thank you to all who have reached out, commented, posted makes, and especially before-after prints showing the improvement. It feels nice to share something with others that makes an already excellent printer even better.

Don't forget, when it doubt, print it out !

Enjoy !

-=dave

2018aug19 Update - I can now confirm that using 3 "Rights" of the integrated bushing version works like a charm to replace the original bearings and u-bolts on the MK3 and takes what little noise was present with the original bearings down to nearly inaudible :)

Enjoy !

-=dave

2017nov18 Big Update - What is even better than ensuring your bearings are secured with rigid straps instead of zip-ties ? Making them one-piece printed and bolted in of course. I have been testing various printed bearings over the course of the last year and am finally ready to release what I am quite confident as the best Y axis bearing upgrade you can perform on your MK2, MK2S, or (most likely) MK3.

Video of them in action: https://youtu.be/RJopBbkPseA

The v1.0.2 straps are still there for use with original bearings of course, but for the quietest and most rigid bed attachment, these have been tried and true for over a year of active printing.

Big thanks to @nicw for all the empirical and objective testing, as well as for writing the installation/alignment instructions.***

Enjoy !

-=dave

2016dec12 Update - I'm glad so many of you have found these useful. I've made some small changes to make them even better (full history below).

Having recently purchased an Original Prusa i3 MK2, I was dissatisfied with the poor bearing mounting method that can easily introduce variability in the Y and Z axes.

Inspired by other overly-complicated solutions to the problem, I designed these easily-printed straps that when used with 6x M3x10mm machine screws, replace the zip-ties on the MK2 without any other changes and fully capture the bearings from movement.

Easily installed on Prusa i3 MK2 by removing only the MK42 heated bed element.

Enjoy !

-=dave

// history: // -1.2.2 - 2020apr26 - Added "mk3" bushing type for use with original MK3/MK3S "U" bolts instead of // M3 machine screws // - Adjusted bushing ID size down to match latest PrusaSlicer 2.2.0 profiles // - Added .3mf project file generated with PrusaSlicer 2.2.0 // - Added gcode for MK3 and MK3S // -1.2.1 - 2017nov19 - Integrated @andyhomes stringed LM8UU bushing library so will work with Customizer // - Fixed layerHeight calculation and other Customizer bugs introduced with 1.2.0 // -1.2.0 - 2017nov18 - Removed all bearing options other than @andyhomes version // - Added printed bearing install instructions from @nicw // -1.1.4 - 2017jul02 - Added @mightynozzle https://www.thingiverse.com/thing:2202854 option // -1.1.3 - 2017jun04 - Added @wbrucem https://www.thingiverse.com/thing:2144803 "heavy duty" option // -1.1.2 - 2017feb26 - Added @ksa https://www.thingiverse.com/thing:396232 option // -1.1.1 - 2017jan02 - Added @Argutus http://www.thingiverse.com/thing:1864526 option // -1.1.0 - 2016dec29 - Incorporated @andyhomes stringed LM8UU bushing https://www.thingiverse.com/make:282174 // -1.0.2 - 2016nov04 - Increased width of tabs and introduced adjustable screw length so holes don't go all the way through, to help some with poor layer adhesion causing PLA-printed straps to crack // -1.0.1 - 2016nov01 - Fixed incorrect tab thickness calculation (tab thickness would actually reduce when increasing shells or nozzle width, causing Customizer versions to potentially be unusable) // -1.0.0 - 2016oct11 - Released

Print instructions

Category: 3D Printer Parts Summary

I've included a .3mf file for use with PrusaSlicer 2.2.0 (or presumably later) so that you can slice your customized version yourself and not have to spend several prints to get the right settings. Note that because this mode requires disassembly of the printer, you may want to print several successive sizes of bearings in case your printer is slightly out of calibration, just to make sure that one set is “tight” enough for you to “hone” the bushings in to perfection.

Hardware :

MK3 (any version): Print 3x "Rights" and use the original u-bolts for attachment

MK2S: Print 2x “Lefts” and 1x “Right” and use the original u-bolts for attachment

MK2: Print 2x “Lefts” and 1x “Right” and use 6x M3x10 bolts and corresponding nuts for attachment

The v1.0.2 straps are still there for use with original bearings of course but deprecated. For the quietest and most rigid bed attachment, the integrated bushing versions are what you want.