rev 1.0: inital release
addition 1: two variants with precise dimensions (only for printers without deviation)
addition 2: housing 14.3 variant - for bearings with 14.3mm height instead of 14.0mm standard
Printing technical parts with my Elegoo Mars resin printer I noticed a very strong measurement deviation within the 0-2 mm range above the printing base. Thanks to Jan Mrázek findings about this issue it is clearly a design flaw of the z-axis gear.
Instead of making modification inside the housing with loosing the warranty I tried a design on top of the z-axis, so you do not need to open anything for installing this mod. The z-stabilizer is mounted on the upper side of the axis using the rock solid axis cover as the fixing point.
Additional to the 3D printed parts you will need a proper bearing that is capable of taking forces along the z-axis without tolerances. This build uses the standard angular ball bearing of type 3200 2RS TN or as an alternative 5200 2RS TN with 14.0 mm height. (Now with an alternative housing part for 14.3mm bearings) Choosing a good bearing brand and spending some money is a wise decision for getting a stiff axis.
All parts are designed to print OK on a non modified Elegoo Mars machine taking into account that the first mm are off. Nevertheless machine tolerances may require further workmanship. If you need more precise part data or your printer is OK as it is, collect the "precise" versions of two files.
Installation: De-install the upper axis cover by removing the two screws. Take the seat screw and turn it down some distance. Then put the bearing over the axis and screw in the endcap part until it is fixed in place.
Then up-screw the seat while holding the endcap plus axis in place and screw everything together as a tight fixed sandwich. This fixes the bearing in its correct position.
Reinstall the axis cover or put it into the housing part and fix it later on. Now insert the bearing with axis into the housing. It should fit tight without moving in axis direction.
For calibrating the right fit it it sufficient to move up the print arm close to the z-stabitizer. Everything gets in place automatically. Ready to print!
Print the housing part directly on the base but with internal support! Find attached the fitting CiTuBox file and as a fast start a direct printable file for all needed parts. The file is calibrated for printing with black Elegoo Resin. No hollowing needed.
Try some calibration objects and enjoy the new unleashed full precision of your Elegoo Mars. (see staircase print after installing this mod!!) Have fun!
update: I would advise NOT to print the both screws with black Elegoo resin. It turned out black is too brittle. Elegoo grey or similar resin does much better and breaks not that easy.