Revised MGN12H Carriage for BMG and BLTouch with RJ45 mounts, "Over the Top" Style

There is a new version of this carriage at
https://www.thingiverse.com/thing:3615464
AND
an even newer one at https://www.thingiverse.com/thing:3688067 **
** I'd recommend that newest version instead for better rigidity and simpler printing and assembly! This older version left for reference

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This is a revision of a previous design, https://www.thingiverse.com/thing:3504020, "Carriage for BMG and BLTouch with Duct and RJ45 mounts, "Over the Top" Style". A reader said he would prefer if it could be used with thed0ct0r's "E3D V6 improved fan adapter with modded Prusa MK3 Layer Cooling" (https://www.thingiverse.com/thing:2769783), so I modified the design to be able to use that cooling system.

I wanted the part cooling duct to be fully height adjustable to be able to suit V6 or Volcano hot ends with ability to trim heights easily. So I made a revision of thed0ct0r's basic design, "Adjustable E3D V6 impr. fan adapter and modded Prusa MK3 Layer Cooling", https://www.thingiverse.com/thing:3512817 . That assembly is shown in some of the photos above, though the files here are only of the carriage and BLTouch mount parts. For the cooling system, also download one of the cooling designs mentioned here, or use the basic E3D V6 fan holder for the heatsink if you don't need or want a part cooler.

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This is designed for a Folgertech FT-5, but might work on other printers that use an MG12H slider on a 2020 bar. It is designed with these priorities:

1. to keep the nozzle close to the MG12H slider to minimize any effects of bearing tip. For that reason, the BMG extruder (operating direct) and motor are place above the 2020 bar, rather than the conventional placement (below the bar).
2. to include a BLTouch mount adjustable in height with guides on the slider
3. to include a mount for ans RJ45 socket board to simplify wiring (using the MDFLY dual RJ45 board w/screw terminals): https://www.amazon.com/gp/product/B01KHMFH1M/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

This has been tested and works well with the adjustable fan adaptor mentioned above. I have modified the "A_Plate" part for an different nut location to make adjustment of the BLTouch height easier with a Volcano.

Note: I had a broken trace from the factory in my MDFLY RJ45 adaptor board, which took a while to troubleshoot and patch -- so you might want to check for continuity from the screw terminals on it to the RJ45 connectors on your board before you wire it up and mount.

The "Over the Top" (of the 2020 bar) mounting is done because I don't like having the nozzle hanging down multiple inches from the slider bearings, which would happen with the normal mounting of motor and extruder below the 2020. The Titan Aero feels and behaves so nicely with the nozzle up closer. So this is my attempt to get the best of both worlds -- the tight minimum-lever placement of the nozzle along with the BMG's dual gear extruder.

BUT, this causes another difficulty -- on the FT-5, with this new mounting, the bed won't reach up to the nozzle! The nozzle (with a standard V6 hot end) sits only 10mm below the 2020 bar. So the bed has to be raised some (about 48mm from the melamine bed platform with standard V6, about 40mm with a Volcano). That wasn't be hard to do with some pieces .... https://www.thingiverse.com/thing:3518065

You'll also have to lose the cable chains, but I don't consider that a loss at all, I hate those things! Better, IMO, to just spiral wrap the cables and feed them from the top/back side of the chassis. That worked very well and looks much cleaner and more open than all the moving parts of a generally useless cable chain.

The carriage is set up for a short NEMA 17 motor (part number 17HS10-0704S, but should work with the smaller pancake, too). There is a spacer included that can be put behind the motor so the motor's back can be clamped with scews to the assembly, making it even more rigid.