WIP: Needs testing, small chance of fitment issues.
I have modified the KevinAkaSam Belted Z mod to work with the extrusions on the Elegoo Neptune printers and potentially any other printer that uses extrusions that have flat fronts and backs instead of slots on all 4 sides. https://kevinakasam.com/belt-driven-ender-3/
Most of the parts are going to be the same as the KevinAkaSam parts with the main exception of the main transmission housings and the bottom idler bearing mounts.
I did my modifications on the Low Profile Dual stepper variant with F623 bearing idlers. If there is enough demand I could possibly modify other variants just leave a comment or send me a message. If you want the single stepper variant there is an older version of the mod on thingiverse also but imo you're better off with dual steppers even if they're on a shared Y driver but you can also run dual independent on the stock board with the exception of the Neptune 2D as it's already using the 5th driver for the 2nd extruder.
My modifications to the transmission housings will require you to remove the 2 socket head cap screws on each side holding the top 2020 extrusion to the 4020 vertical extrusions and then installing the transmissions over the top and replacing the SHCS with longer M5x35mm SHCS. You will use the default inner bearing supports for the 8mm rods but they will switch sides and rotate 90deg to attach with the M5x8mm + T-nuts to the top and bottom of the 2020 extrusion instead of the front and back (see pictures). You may want to use some kind of spacer such as a feeler gauge or some paper folded over a few times to space the 80T printed gear away from the 2020 endcap to avoid rubbing.
For the bottom idlers they will fit as normal but you you will need to slide your T-nuts in to the side profiles of the 4040 and 4020 to secure them in place, 1 each with M5x8mm on either side of the 4020 and 2 each on the outside of the 4040 for each side of the printer. (The photo is just for visual of fit, it will install on the back of the 4020 as normal, I am waiting on parts for other mods that I will be performing at the same time as installing this, will update photos when I complete the install.)
For the most part you are going to follow the BOM and instructions provided by KevinAkaSam with the exceptions of above.
As I work on this project I will update photos and information / models / CAD on here. Be sure to join the KevinAkaSam discord if you have general questions or need help and if you need something specific to my modifications you can find me on there or comment / message me on here. https://discord.gg/xqpKrxt9FC
The author marked this model as their own original creation.