Re-Revised BMG Carriage for V6/Volcano, BLTouch +RJ45, "Over the Top" Style

There is a still newer version of this 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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In this version, the part that attaches to the MGN12 rail has been redesigned to be a single piece, to simplify assembly. With the previous version holding all the parts together while installing was a little difficult. This version should be more stable and strong. Also, in this version parts were added for attaching and clamping the belt to the carrriage so that the belt could be removed and reused if desired. If you prefer the "old way", you can still attach the belt using tie-wraps. The bars that hold the belt now also include a pattern for the 2mm belt teeth for tighter grip.

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 was designed for a Folgertech FT-5, but might work on other printers that use an MGN12H 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 from tipping of the bearing slider. For that reason, the BMG extruder (operating direct) and motor are placed above the 2020 bar, rather than the conventional placement below the bar.
2. to include a BLTouch mount adjustable in height over about 12mm with guides on the slider to keep it vertical.
3. to include a mount for an 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
   The two RJ45 jacks provide for up to 16 wires to be carried. But don't run the heater element wire, the current is too high -- use a separate 2 terminal higher current connector for that.

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 maximum stability 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:3719437

You'll also have to lose the cable chains (but I don't consider that a loss at all, I hate those things!). I used spiral wrap on the cables and feed them from the top/back side of the chassis. If you have any issues with the cable dropping too low (onto the print surface) or running into other things mounted in your printer, my "Cable Dangler" design is a nice effective fix for that issue (and makes the printer look much more open than when using cable chains):
https://www.thingiverse.com/thing:3613175

The carriage is compatible with about any NEMA 17 motor you happen to want to use with your BMG.

The "Plate" and the "Back" have insets for M3 Nylock nuts, which are highly recommended to simplify assembly with the BLTouch mount, and use of the belt grips. The best way to install them is to (before assembly) use an M3 screw to draw the flat part of the Nylock nut into the insets, which applies a high force.