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The Rumba Controller

As described on the previous page, my BFB controller is now mostly dead. A first analysis by someone who should know ("Just exchange the hot end. With BFB Touch it is always the thermistor that is burnt out.") was plain wrong. So what I needed was a new controller (BFB never reacted to my request for a replacement).

The new controller had to be fast, support three extruders, had to be OpenSource, and easy to maintain. As of early 2014 that left me with the Duet 3D plus Expansion Board, the Elefu RA 3D, the Megatronics 3.0, or the Rumba.

The Duet is simply too expensive. Sure, having the ARM CPU and the Ethernet connection is nice, but it was not clear which software would compile and run with it. The RA 3D seemed ok. The Megatronics had no documentation about the LCD controller - I still don't know if I can conect one.

So the choice came down to the Rumba as it was easily available (two days from order to delivery) with 7 Polulos (the Y axis has two steppers; I will piggyback two controllers for this axis), an ATMega that runs the Marlin software, and a nice power supply.


Delivery

All the parts were delivered today. The Rumba comes pre-programmed, so I was able to hook it to my Mac and connect via Pronterface. Yay! The Arduino IDE also found the controller, so there is a good chance that I can reflash a new firmware as soon as I have that compiled.

Looking good so far. I hope I can get something to move this week.


Firmware

I am using Marlin as the firmware for the Rumba. Against all my expectations and experiences, downloading and compiling the firmaware went almost flawlessliy. I managed to change settings for my full graphics display, recompiled, and uploaded the firmware using the Arduino IDE on my Mac and a USB cable.

There is one flaw though: I can set one or two extruders in the configuration, but activating the tird extruder makes the compile fail. I will find the details later. For now, I want to get the machine going.


Wiring Harness

Today I followed, measured, traced, and spied on all the lines that go from the 3D Touch circuit board into the machine. Pretty much everything maps onto the Rumba controller, using a somewhat complex wiring harness. Soldering should keep me busy for two hours or so, hopefully tomorrow.

  • the thermistor is 200k, but which one? I would like to get the curve right. (4338K beta value? 204GT-1? ATC Semitec?)
  • x, y, z, steps: 87.6195,87.4891,200*8/3,1000 ?
  • calibration
  • nozzle diameter is 0.5mm
  • build size (3 nozzles) 185x275x210mm