Fan on hot end

What is the reason for putting a fan on the extruder hot end?

Thanks

Nick

it's not really on the hot end, it's more just under the hot end.
it helps cooling the layer you just printed, and also helps on bridging and when printing small parts.

to stop the heat from propigating up the PEET tube causing the filament inside to soften and expand causing a Jam. Atleast thats why mine is pointed at my hot end.

Edited 1 time(s). Last edit at 03/22/2013 01:05PM by hendo420.

I thought it is supposed to keep the "cold end" cold ) ... in either case I think its a huge help for bridging in small parts and prevent sagging ..

In my research I've found 2 different fans around the hot end seem to be common.

The first is aimed at the PEEK tube above the heated nozzle. The purpose here is mainly for printing PLA which has a low melting point. You want to keep the tube cool so that the PLA doesn't expand or get mushy in the tube and does all its melting in the nozzle. I want to print PLA so I've been working on setting up a fan to do this. I also have a j-head with cooling slots in the peek tube so the air is ducted to blow right through these and not on the nozzle (so the nozzle can keep a steady temp).

The second fan that I see frequently is aiming at the work area right under the nozzle, This helps quickly cool the plastic so that it stays where it's put. I think it's quite useful for bridging so that the plastic solidifies quickly as it's being extruded to bridge any gap or overhang. This one I'm not quite as confident about and I haven't figured out exactly when you would want it and where. I don't have one of these setup yet but I probably will want one. I just don't know much about it.

Maybe one of the more experienced guys can help us understand more about it and recommend some good setups.

I would like to know more about this as well. I definitely see on some of my prints where I could use a fan and that's with abs. On taller fast prints the layers want to deform some because they can't cool fast enough and start deforming some

I would think if you have the right fan or an adjustable mount u can get one fan for both and have all ur bases covered

When I first got my printer I had set up a small box fan to blow on the build area for smaller prints so they would cool fast enough between layers to not distort. I didnt realize it at the time but it was stoping jamming(I didnt have a jam on any small prints).

So if you don't have a small computer fan to point at the hot end a small box fan works nicely and helps cool the print.

I think I need a fan for my printer (Prusa-Mendel printing 1.75 PLA with 0.35 nozzle).

I have encountered jams caused by heat traveling up extruder head collum which requiring much time and effort to dismantle and clear.

My problem is that I am not comfortable with electronics and electrical so really don't know where to start on installing the fan and having it controllable.

I have purchased a small 50mm computer fan. I am using standard computer type power supply. I use Ramps 1.4.

Can someone give me instructions or point me in the right direction?

Thanks,

Bob

Connect it to the D9 mosfet output if you want it controllable with M106 and M107, or across the 12V input if you want it to run the whole time.

Cobrageek hit it on the head. There are 2 reasons for fans.

The first is to prevent the hot end tube from getting too hot causing PLA to mushroom. This doesn't need to be a large fan - just enough air movement to break up the heat convection. I have a 25mm fan mounted to the side of my X carriage for this. I have an on-off switch for it, but it is NOT controlled by the RAMPS board (and therefore not controlled by the software/gcode).

The second is to cool the printed object. This can help with bridging, and also to combat curling on overhangs. I have two 20mm fans mounted fore and aft on my X carriage, and these are connected to D9 of my RAMPS board, putting them under software control.

I would hope to be able to control the fan's speed and on-off.

What is and where is D9 "mosfet" and its terminals (see like I said, not much electronics know-how)?
What are M106 and M107? Assume some software switch?

Bob

Look at your RAMPS, the terminals to the left side are marked D8,9 and 10. D8 is for the heated bed, D9 is for the fan, D10 is the extruder heater. (D8 must be used for the bed since its on a different power supply, but the other two can be reconfigured in firmware)

M106 and M107 are the gcode commands to turn the fan on and off. Send them from your host software or include them in your start gcode. M106 takes an S parameter which controls the PWM level of the fan, so you can send

M106 S127 to get half speed, M106 S255 to get full speed, or anything inbetween.

Thanks, doesn't seem too tough with your explanation. Thanks, much appreciated.javascript:editor_tools_handle_smiley()

Bob

I think d9 reference is to digital pin 9, in the pins.h file of firmware. if using marlin it will be hard to get to in the arduino tabs, so perhaps open the file in wordpad, do a search for == 34 which is the ramps configuration for 1.4. there it lists the pins that are associated with it. with ramps 1.4 the pin is set aside for another extruder. you can change it to be a fan pin.

Edited 1 time(s). Last edit at 04/07/2013 08:33PM by jamesdanielv.