I put together this post with my experiences with various extruder builds and repairs http://steven.bitsetters.com/2014/12/31/adventures-in-extruderland/
I’m still in the middle of building and testing these things as mentioned in my post and have a few questions.
I built a “Fangtooth Guppy” 12v which needs a dedicated fan for the heat sink. Where should I plug this into the Rambo board? In the fan for the second extruder? I would like to keep that open if possible.
Also I bought some of these cartridges http://www.ebay.com/itm/5-x-Reprap-24v-40W-HotEnd-J-Head-Ceramic-Cartridge-Heater-1m-Wire-For-3D-Printer-/261524417407?ssPageName=ADME:X:AAQ:US:1123 I wired one up and tried to run the calibration routine, but it heats up so slowly that the routine times out. If I leave it connected long enough it will eventually reach up to 230c, but if I turn on the cooling fan the temperature drops off dramatically and won’t maintain temperatures above about 120c with the fan running. Any suggestions for using this type of heater?
Lastly where do I find the CAD files for the extruder parts? I would like to make modifications to the Fangtooth extruder body, idler, and mount.