NOTE 2: It is to assume that the MK2s' newer and "more precise" linear shafts will induce more play in combination with the RJZM-01-08! Please ask igus via their website to provide you a free sample of the bushings and try them out before buying the remaining quantities and modifying your printer! Alternatively, use the less expensive but also excellent (if not even better) RJ4JP-01-08 bushings. You can find the corresponding clips for them here: http://www.thingiverse.com/thing:1848700
NOTE: Project was updated on November 3rd, 2016 - Please read the project update notes below!
I upgraded my Prusa i3 MK2 with linear bushings (and shafts) from igus.
To be more specifically, the igus drylin RJZM-01-08 bushings with an aluminum shell.
Note: when you visit the igus website, you will find the product under the label RJUM-01. However, bushings for the 8 mm shaft diameter are called RJZM-01. They both belong to the same product category!
I also had a typo in the title and the description, missing the "Z" in the name. Sorry for the confusion!
Btw.: The shafts are called AWMP-08 and are made from aluminum. Way lighter than the stainless steel shafts coming with the MK2. The bushings also glide a bit better on them, but are also very good on stainless steel - my second MK2 uses the original shafts.
Back to the summary...
Being not a big fan of the zip tie mounting principle used for the original ball bearings by Prusa Research, I designed this clips that hold the bushings in place and are screwed directly to the metal frame of the heated bed. I used M3 screws with cylindric heads, and there is no interference with the MK42 heated bad.
One big problem of the zip tie system is that the bearings wiggle around and cant against the shafts, leading to unwanted friction, noise, and vibrations. Moreover, the original Prusa i3 MK2 assembly guide says, that the two bearings, which are mounted on the same side of the Y carriage, should be as close as possible to each other. But because the notch on the carriage has rounded ends, the bearings can get askew vertically when pushed against the round endings.
My design holds the bushings centrally inside the notch, which is fine both for the travel distance of the carriage and the end-stop functionality.
Please pay attention that you use the correct clips for the proper carriage side!!!
NOTE: This clips are only suitable for the igus RJZM-01-08 drylin bearings (with aluminum shell) and NOT for the ordinary ball bearings, as the igus bearings are slightly bigger in size.
If you like to use the igus drylin RJZM-01-08 bearings also for the X-carriage (aka. the extruder), please take a look at this Thing: http://www.thingiverse.com/thing:1853471
Please also take a look at my other designs, printer parts, and tools.
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any percentage above 0 should be okay
Printing is easily done without any support. You can use a brim to hold the parts more securely to the bed. But if you use a brim, make sure to clean every single bit off after printing. You don't want the bearings to rest against any unintended edges.
If you experience any friction while moving the mounted bushings on a shaft it is probably due to some imperfections of the printed parts. Look closely and carefully at your printed parts and clean (cut) off any bumps.
Don't cut away the seams. They are intended to secure the bushings at their notches!
I use M3x16 Allen screws with a cylindric head to mount the clips to the frame.
Videos and Project Updates
From the lessons learned of the lm8uu bearing clips project (http://www.thingiverse.com/thing:1848700) if updated also the igus bearing clips to Version 2 (V2).
- Bearings sit now tighter inside the clips, which prevents the bearings from wiggling and rotating.
- The clips are shorter by one layer (0.2 mm) now, which makes them snap better into the bearings' notches.
- The M3 holes are 2.6 mm in diameter now for better screw connection
- The clips are stronger in general
Please do not over-tighten the clips. One key for a smooth linear movement is to compensate for any imperfections by adjusting the pressure the screws put on the clips. Loosening one or both screws just a little bit can make a big difference. The clips will give you a much stiffer Y-axis than the zipties even if the screws are not tightened completely!
Just a small demo video at Instagram:
First the Y-carriage without the heated bed and the stepper detached. The carriage slides so easily on the shafts, that I accidentally flipped it against the axis' end. Notice that the camera is very near to the action (about 10 cm) and that even the tap of my fingernails against the metal frame seams to be very loud.
Second the assembled unit. This is the machine with the not dampened stepper motor.
I removed the V1 models as they seamed to have some issues.
V2 is the most current and best working version.