So I am having fun with my new Printer, overall very impressive machine. I noticed that the larger fan cooling the plastic after extruded is sucking in the small end and blowing out of the fan part. I double checked my harness connection and it is red wire to red wire and black to black. So, IF it is supposed to be blowing air out of the small nozzle near the hot end, it must have been miswired inside the electronics enclosure. Guidance appreciated.
The fan might be bolted on backwards. The side with the X shaped bracket that holds the central fan piece itself is the back. Air flows front to back. You want the back pointed at the nozzle in this application.
Thanks for following up, I guess it is wired backwards then because the fan is bolted on correctly according to your description.
A follow up question - in terms of the two fans on the extruder, the small one cooling the fins vs the larger cooling the plastic, which is hooked to the Extruder 0 fan mosfet and which one is connected to (I am assuming) the pwm pins?
Poking around I worked out that it is the Extruder 0 fan (the mini fan on the fins is using the pwm pins) AND the fan cannot be reversed!!?! I wired it the other way and it refuses to move and just gets warm. I guess it is a one way fan and is going the wrong direction? going to bolt it with the x shaped bracket on the outside to account for the airflow, but would love to hear from the team if they have other thoughts.
I’ve never checked which fans plugs into where on the Rambo. Check the installation docs at:
https://ohai-kit.alephobjects.com
From your description, I would say the extrusion fan should be plugged to the PWM so that it can be varied during the print. The small heatsink fan should ALWAYS be on and receiving 5V.
The connectors have marks to show the connection pairings. If you switch up the small and big fan, the small will blow out due to the 24V.
To be clear, I did not swap the small and large fan, I understood the voltage differences. I was referring to switching the red and black wires for the large fan on the extruder. Typically most fans I have encountered will just run in reverse if you swap the ground and +5. This is what I thoroughly tried and did not work.
Ok. Just wanted to mention it…
The air flow you’re feeling could simply be the back pressure. Try removing the fan from the duct and check the airflow.
It is back flow you feel. Put a small paper on the end and you will see it is blowing correctly. You are not the only person that thought this.