These files are the result of me trying out the ideas on Alex Whittemore's and Jan Mrázek's blog posts on some design flaws in the Eleegoo Mars DLP printer. The Mars, while a super fun machine for the price, has too much play on the threaded rod inside the stepper motor housing. This leads to missing layers of up to 1.4-1.5mm height, most noticably when printing layers with larger horizontal crossections due to the drag on the Z axis. The solution is to add an extra spacer in the motor housing and replace the rubber damper with a solid plastic mounting block. Please read
for all the details.
Fun fact: The Mars, as many other budget DLP printers, has a slight halo effect, leading to about 0.1-0.2mm overexposure on the edges in XY direction. You can compensate for this by reducing the default exposure from 8 seconds to ~ 6 seconds for Elegoo resins.
If you are careful how you place the parts when disassembling the printer, the only cable you need to disconnect is the motor cable (see the picture).
The washer goes on the rod between the top motor housing and the spring washer, raised side toward the housing. The mounting block replaces the rubber silencer.
The top cap of the Z arm will not fit anymore afterwards, but as it does not support the rod, it is not necessary. Alternatively you could scale the block in Z direction and use longer screws to mount the motor.
After this tuning, I got less then 1% error in Z direction and less then 0.5% in XY direction.
You can check your success by printing and measuring the steptest file before and afterward on your Elegoo Mars and/or try one of the calibration cubes from thingiverse.
Kudos to Alex and Jan for the measurement work!
The steptest is to be printed in resin on your Elegoo Mars, NOT with PETG on your FDM printer!