The big issue is the lack of insulation on the bottom, that and because it is running on only 12V. Running it on a separate 24V power supply (not sure if the azteeg can handle 24v, it may be able to) will definitely improve heating dramatically.
According to the Azteeg x5 Mini wiring diagram, it supports power supplies from 12-30v DC. However, I am not sure if it will provide 24v to the heated bed. It may just step down the voltage to 12v and provide that to the heated bed and hotend? Or, if it does put out 24v to the heated bed, isn't it also going to provide the same to the hotend? If so, you would need a 24v heater cartridge for the E3D as well. I am going to look into this a bit more later on. To start, I am going to add some cork to the bottom of the bed to insulate it. As it stands, the hottest I can get my bed to is 93C, and that was leaving it on to heat up for 45 minutes. Does anyone else have info on the Azteeg and 24v?
I opened up the schematic for the board and the power in ties directly to the extruder/bed power on the high side with fet control on the low side. With that said, if you want to run 24V you absolutely will need a 24V E3D module, but its good to know its an option since the currents will be much lower.
So I dug a little deeper and the fan for the extruder and for the blower would need to be updated to 24 volts as well.
Last Edit: Jan 28, 2016 16:58:23 GMT by macgyver03
Thanks for that info! I have also been looking into getting a 120v heated bed. Then I can control it through a relay or similar setup. That should give the best heat up times and would also cut down on the power draw from the power supply. The closest one I could find though was 200mmx240mm, so I'd have to get a piece of aluminum cut to fit it.
After thinking more about it last night, the low side control circuit opens up a unique option. I posted a snippet of the schematic below to talk through but basically you could easily add a second 24 volt 5A supply (able to power the MK3), tie the negative DC leads together, run the +24V output to the bed, and the low side control will still work exactly the same. The control circuit uses a N-Fet controller with an isolated driver which only requires the Vgs to exceed 1.8Vdc (typical) to drive the fet closed. As long as the negative DC terminals are tied together you can operate the board, extruder, fans, etc on 12V and just have a lower power 24V supply for the heated bed without any additional controls or relays.
Note that the +12V net you see at pins 3 and 5 originates from pins 3 and 4 of the fuse holder so running the second supply would either need a fuse added in line or you can operate with the risk of overloading the 24V PSU (I usually take option 2, just don't say I didn't warn you).
Last Edit: Jan 29, 2016 11:16:32 GMT by macgyver03