Dust Protector for Prusa Mk4 and Mk3 Z-Motors

*****Note: Please read the complete instructions before printing this file. Most likely you will have to print this model at about 100% to 108% scale – so, if you don't measure your printer's dimensions before you print, chances are that the print will not fit properly.*****

A little bit, the Z-motor mounts of the I3 printers remind me of a meat grinder's funnel... dust, debris, tiny ooze strings and whatever else fits in there may occasionally fall in and pile up to dimensions that handicaps proper Z axis operation (especially in somewhat dusty environments or if you use LW filaments regularly). So I made this little accessory that minimizes that risk. I suspect it will fit the Mk2 as well, but since i can't try that, I depend on feedback concerning this.

I used medium-hard TPU filament to print mine - they fit in place like a cork, and as the two halves keep each other in position just by pressure, they can be applied or removed without tools and without having to disassemble any part of the printer first.
It is possible to use "hard" filament like PLA or PETG as well, but I don't recommend that - in that case you'd have to have a fussy eye on dimensions, as the parts need to fit the holes quite exactly with a little bit of friction (remember, you plug an FDM printed part into an FDM printed part). Scaling the objects by some zero dot something percent will not affect their function, but obviously, using a flexible filament makes things easier and safer.

Experience has shown that Prusa Mk3/Mk3S/Mk4 printers' parts dimensions have changed arbitrarily over production time. A dust protector that fits one printer perfectly may be too loose or too big for another one. The “plug” part of my dust protector fits a hole diameter of 22 mm, however, I have heard about cases where the printer's actual hole diameter was up to 23.8 mm. Of course, you can scale the STL in your slicer if this is needed to fit correctly.

Please, don't complain if the plug fits too loose for your printer. Instead, measure your printer's correct dimensions and scale the print if needed. There is simply NO CHANCE to design a print that fits all printers, so I had to choose the safe way.

Printing:
I've never had any problems printing this without a brim, no matter what material. However, some users reported that without a brim they had experienced bed adhesion problems. Well, I guess you know your printer and filament better than I do, yet I would say that in this case a brim would be the very last last measure I'd take to increase bed adhesion. First of all, if printing TPU as advised, adhesion should be “too good” rather than “too bad” anyway. If you use PLA or PETG and experience adhesion problems, prefer using some 3D printing adhesive like Magigoo, 3Dlac, or the glue stick supplied with vour printer, over using a brim.
Aside from the bed adhesion issue, there are no specific instructions for printing.

To equip one printer you'll have to print two sets in total. Mounting should be self-explaining (just look at the photo). Print one set first and use it as a test object: If it fits well, print the second one. If it does not fit well, do the scaling needed in your slicer and repeat printing.

Obviously, as I have no control nor idea what you do with these files, use them at your own risk and responsibility. However, I'd like to warn you not to use force to put the parts into place - if they don't fit in easily due to whatever reason, it will be a real pain to ever get them out again.

Update:
Due to popular request I added a “tight” variant with a smaller opening. This reduces the risk of even the smallest dust particles entering the hole, but if you want to print this file, be sure to have your printer well calibrated since over-extrusion may cause the edge to touch the spindle. I myself prefer the regular variant, but it's your choice now. 
I think I should stress that the outer dimensions do not differ between the two variants. So, if the “regular” variant sits loosely in your printer and you want it to fit snug, the solution is NOT to print the “tight” variant BUT to measure your printer's individual dimensions and scale the print accordingly.