D-bot MMU

thingiverse

This is a multi-material upgrade for the C/D-bot and related printers, using the Prusa MK2/S Multi-Material Upgrade (MMU) kit. Required components: * Prusa MK2/S MMU kit * (4x) 600mm PTFE tubes * Misc. M3 and M5 hardware * Dupont crimp, pins & headers Optional: * BL Touch * Drag chain * 40mm fan adapter for hotend Although the Prusa MMU kit parts are open source and in theory you could obtain all the parts elsewhere, the retail cost of the 4x Bondtech gears is almost as much as the whole kit, and the custom metal cooling tubes and some other kit parts would be difficult (but not impossible) to source. Firmware: Included is a modified Marlin 1.1.6. Although 1.1.6 supposedly supports the motor switch board ("MK2_MULTIPLEXER"), I could not get it to work without these changes. Note: You will likely need to edit the Configuration.h especially if you use a different size bed or don't use the BL Touch. Electronics: The motor switch board takes a 4 pin connection from the RAMPS board (5V, GND, D40, D42, 5th pin unused), plus a standard stepper connector, and outputs to 4 stepper connectors. When connecting steppers to the switch, keep in mind the 2nd and 4th stepper cables must be reversed due to the motor/idler being reversed compared to the 1st and 3rd. Prusa does this in firmware but I gave up trying to get this working in Marlin. If using Prusa motors with the keyed connectors, you will need to reverse the wires or build a small adapter cable. Loading & unloading filament: Unlike a Prusa printer, this Marlin firmware does not have built-in LCD options for loading & unloading filament. You can do this using software like Pronterface or Octoprint. To load, push the end of the filament into the extruder until it just enters the gears, then send a command to extrude Bowden length + 60mm of filament, plus or minus a bit (660mm in my case), so that the filament stops in the middle of the metal tube. Note: If you have "prevent cold extrusion" enabled in FW, you need to either heat the hotend to print temp, or send M302 P1 first to disable it, otherwise it will not extrude. To unload, first send Tn command (where n is 0-3, the number of the extruder to unload minus one), then "print" the unload gcode attached here. This does a special ramming & tip forming procedure to ensure the filament is loaded and shaped correctly for the next print. The first couple of times you do this, retract the filament an extra 60mm so you can examine the tip in the Bowden tube. If the filament has a nice tip, you're good. If there is a string or blob at the end of the tip, you may need to tweak the unload gcode temperature or retraction distance. If you ever mess up the unload step, best thing to do is fully unload all filaments and start fresh, otherwise your next print will almost certainly jam. Printing: Use Slic3r multi-material edition or KISS slicer with the Prusa MK2 MMU print settings. I increased retraction to 6.5mm due to the longer Bowden tubes compared to the Prusa MK2. You can probably increase speed quite a bit later, but it's best to start slow until you get the feel of things.