How to wire up dual extruder fans to ramps 1.4 board?

I bought a direct drive dual extruder off amazon and am wondering how to wire the fans up. Are the fans for the extruders meant to be on constantly? If so, then the wiring is easy (I should just connect them to 12V power supply I assume), but I wonder if I am losing any print quality or ability.

A related question is, what would happen if I just didn't use fans for the extruders at all?

I depends on what type of fan you are talking about. On my printer, I have two kinds of fans mounted on the X carriage: 1) always on fans pointing at the extruder body, and 2) G Code controlled fans pointing at the printed objects. The former are connected directly to the power supply (there is a switch in there so I can turn them off), and the latter are connected to the Controller so that hey can be turned off and on by G Code.

On my single extruder printer, the G Code fan is simply connected to pin D9 - it's what the firmware is expecting.

On my double extruder printer, I only have 1 circuit to control both fans simultaneously. Also, in this case, D9 is taken up by the second extruder. I put together a simple MOSFET circuit and I control it through pin D4. Marlin is already set this way. You can, through Marlin configuration, change to a different pin.

If you have the daughter board, you connect both the hot end cooler and print cooler (not used with ABS) into that. but I read something about needing to add mosfets to those connects to run more then 1 fan powered from the main 12V connections
Ramps 1.4 duel extruder wiring diagrams don't actually show and fans except for the ramps cooler connected to 12v in.

Are you kidding? A RAMPS FET will run up to 8 amps (the bed) or 5 (the nozzle) and most small fans draw more like .07 amps, so no need for anything other than tieing them both on . . .

- Tim

Quote
tadawson
Are you kidding? A RAMPS FET will run up to 8 amps (the bed) or 5 (the nozzle) and most small fans draw more like .07 amps, so no need for anything other than tieing them both on . . .

- Tim

I'm not talking about that connection I'm talking about the 2 pin fan connection that is often connected to a daughterboard/splitter.

It was as clear as mud . . . and it made no sense to talk about current limits of RAMPS is all that was being discussed was the ability or add another independently controlled fan And yes, another MOSFET will be needed for that, but not due to any possible current limitation . . .

- Tim

Ok I'll just connect the fans to 12V after tying them together. Thanks! I'm not sure I see the point of the fans though since the temperature stays pretty constant without the fans and also without the heat sink. But I'll leave them on because they're probably there for a good reason!

jessicabrenner , here is why you need two types of fans. PLA does not set up fast enough without the printed model being "frozen" with a fan. That fan is controlledwith software, If you do PLA, you will have better luck with it on.

The second fan is on the extruder heat sink and keeps the top of the unit cool so the plastic stays solid until it is almost at the nozzle. If you don't have that fan running at all times the entire head will get hot enough so that the material will melt and not be pushed thru the nozzle.

I think every nozzle printing PLA needs two fans, the one cooling the model may need to be set differently for the first layers, it should be controlled by the software.

Thanks kengineer, i will definitely add the PLA cooling fan.