Hi, I just noticed that my fan is blowing upwards, that is, away from the hotend. I was of the impression that it was supposed to blow air at the hotend. Or is it supposed to suck hot air away from the hotend?

It should blow air onto the hotend, maybe double check the manual to make sure you installed it the correct way.

Quote

Assemble as shown below with the fan label downwards and the wires exiting nearest the
leftmost screw in the picture.

The label on my fan is pointing downwards. I checked if I attached a wire the wrong way around but couldn´t find anything like that either.

Edited 1 time(s). Last edit at 01/26/2015 02:19PM by Lumpengnom.

fan lable should be facing down, as into the ducting.... if you feel the opening around the hot end you should feel air coming out when on.. if you do then your good.... not all the air goes to the hot end, so yes it will have some air coming out at the fan, making it feel as if its blowing the wrong way... this is because the fan is blowing into a small space and the outlet is even smaller, so when the air gets "compressed" in the smaller end its gets whats known as reversion at the fan itself... the air has no place to go but back out thru the fan... also, the fan is directed at a flat surface so the flow isnt efficient and again causes it to bounce back... DL the fan duct from thingverse with the angled fan mount... much better flow...

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Nophead Mendel90 Remixed in aluminum
Marlin v2.0
Matterhacker Control (latest)
Ramps 1.4
Sainsmart LCD
MK2B heatbed
E3dV6 hotend .4mm tip
1.75mm filaments
dedicated 12v33a psu
dedicated 12v5a laptop psu mod

It is strange. When testing my fan like discribed in the manual with "M106" it blows downwards. But when I print something it blows upwards.
I opened the gcode file which was created with Slic3r and it states for example "M106 s199" but I couldn´t find anything that looks like it would be reversing the fan direction.

is your fan a 3 wire or 2?

if your using the 3rd sensor wire on the fan, the Slicer is telling it to slow down with the M106 (fan on) s199 (speed voltage rate, PWM rate) which is not full power... full power will look like M106 s255...

if your using just the 2 wires (red/black) then it will be full power all the time...

when in use, the power is regulated by slicer, hense your s199, so your fan doesnt have enough speed to push the air, and your reversion happens easier... when your not using the fan during a print, it receives default full power so it appears to push the air as it should...

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Nophead Mendel90 Remixed in aluminum
Marlin v2.0
Matterhacker Control (latest)
Ramps 1.4
Sainsmart LCD
MK2B heatbed
E3dV6 hotend .4mm tip
1.75mm filaments
dedicated 12v33a psu
dedicated 12v5a laptop psu mod

It is a 3 wire fan.
You were correct, it was just the reversion. I tried it by disassembling the fan and printing something and the fan blew in the correct direction. Thank you for the detailed explanation.

It doesn't make any difference if the fan has two wires, or three, as only 2 are connected to the electronics. The speed is controlled with PWM. The third wire is for sensing the speed when connected to a PC motherboard.

If you place your hand near a small fan that is sucking it feels the same as one blowing because the airflow cools in either direction and that is what you feel, not the pressure. Holding a piece of paper near it to see which way it is pulled is more reliable. Or holding something smoking near it.

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[www.hydraraptor.blogspot.com]

Or that.... ^

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Nophead Mendel90 Remixed in aluminum
Marlin v2.0
Matterhacker Control (latest)
Ramps 1.4
Sainsmart LCD
MK2B heatbed
E3dV6 hotend .4mm tip
1.75mm filaments
dedicated 12v33a psu
dedicated 12v5a laptop psu mod