MPCNC Heat Bed Requirements

Mostly Printed CNC - MPCNC Your Builds
#1

Hi

I have question regarding the requirements for a heat bed on my MPCNC that I’m currently building. I’ve order all materials from here (ie bundle kit, extruder, …etc.) The only thing I didn’t order was the heat bed because they were out of stock. I will be order one from AMAZON.CA (I live in Canada). Here are my questions:

  1. Is the Ramps board already setup for a heat bed? (I think I read somewhere that it was, but I can’t find that post anymore).
  2. Do I need to upgrade the power supply and if so is there any documentation on how to go about doing that?
  3. The heat bed sold here does not mention any thing about a thermistor. Is this required for the heat bead?

Thanks
R.

#2

The RAMPS is already setup for a heat bed, you feed the extra power in to the second two terminals from the 12V supply. The heat bed itself has power supply lines that plug into the second terminal block. You need the bigger power supply, normally the steppers handle things quite well with 5A, with the heat bed you need an extra 11A. There is a thermistor included with the heat bed, you plug it into the RAMPS where the resistor is for non printing applications.

#3

My suggestion is to get a MOSFET controller, this way it doesn’t burn out your RAMPS board

http://www.banggood.com/3D-Printer-Parts-General-Add-on-Heated-Bed-Power-Expansion-Module-High-Power-For-Chitu-Motherboard-p-1086965.html

This way you wire the power THRU this, and it only uses a small fraction of the power to trigger the MOSFET and the high current bypasses the controller all together

I have one of these on my Anet A8 3D printer (mainly because of the smoked traces on the board complaints)

Hope that helps

#4

Thanks…so the power for the head bed feed off the MOSFET controller, but how does the ramps control the temperature? Where does I connect the Themister from the headed bed?

#5

It pwm’s the mosfet, like flicking the power switch on and off as needed to maintain the correct temp, which it checks with the thermistor.

#6

So I connect the MOSFET controller to D8 on the ramps using the small connect on the mosfet and the Thermister connection does not change? Do I still need power going to the 11Amp terminal on the ramps?

Thanks r.

#7

You will leave the thermistor where it is, still power both sides of the ramps plug, and the new board.

#8

Thanks. Just to confirm (sorry for being a pain)…so I do plug the third connection on the MOSFET to the D8 port on the Ramps. Picture attached with of a connection to a ChiTu board with a blue circle identifying the connection on the MOSFET that I’m referring to.

Thanks R.

mosfet-connection.jpg
mosfet-connection.jpg700×875 90.3 KB

#9

I do believe so.