I see no reason to have the main board stuffed under the machine, so I decided if I was going to do this main board upgrade, that I would also move the main board out and make an enclosure that will completely surround the board. This will make the board and wiring much easier to access and service as needed. I took Teaching Tech's Idea to higher level and this will accomplish my goal. This mount also has provisions to mount the Stock ENDER3 board, using standoffs, bolts and nuts as needed. You can use this to relocate the stock board, if you prefer. I have not tested this configuration, but see no reason this would not work. I was always frustrated by the lack of access to the main board, This gives me the opportunity to fix two problems at the same time. This is 3 pieces, a mount that slides into the 4040 rail, the main case and the cover. This is a work in progress, so the files can change. These files are the ones used to print the items in the picture. I have added these boards and boxes to both my ENDER 3's. Added new files to include a 3.0 version of the box with 4 - 4mm mounting holes on the back and also one with a 20mm fan and a new cover for this box as well. 02/19/2019 12:15 CST: I have modified the Case, Cover and Mounting Bracket files with various changes to improve durability, reduce material use and provide better wire access for the ribbon cables to various LCD displays on the 3.0 version. These are small changes, which are reflected in the latest files. 2.0 Version printed and mounted on my Red Machine and 3.0 Version on the Blue Machine. The 20mm 2.0 or 3.0 versions have not been tested to see if the fans will fit, since I do not have a 20mm fan. I found some small O-Rings from my stock of A/C O-rings that fit perfectly to hold the door closed tight against the main body.
Amazon Basics PLA/PETG
I did the main box in PLA, the Mounting Base and Box Cover in PETG. I was mainly using up some short runs of filament that were left over from other prints. These can be printed in your favorite filament. I used supports on these parts, the supports were very small. The box has wire pass holes in the back and bottom, I hope that I have allowed enough holes for all the wires. Wires will be transferred and arranged as needed when the new board arrives. The base slips into the side of the Left frame rail, it is a tight fit. The Main box secures to the base with M2 x 10 screws and washers. I opted for a fan cover to match my hot end cooler fan. Obviously the fan can mount as a push or pull fan. The fan cover file is included, it is PETG as well.