What is the purpose of an extruder fan?

Hey everyone,
So I am new to 3D printing. I bought a solidoodle and have been working with it for a few months. I am now in the process of building a MendelMax 1.5 and have a question about the extruder fans. My solidoodle only has one heat synced to the extruder motor, but I have seen tons and tons of variants where the fans are blowing right at the nozzle in various forms. To me this seems counter intuitive, blowing a fan onto something your trying to keep hot.

So can someone explain what the purpose of this is? Is it to keep the extruder motor cool? To cool the recently extruded ABS? To keep any ABS parts near the extruder from melting? All of the above?

I'm just looking to understand the function of having a fan blowing right at my nozzle and where I am working. Thanks!

- Ryan

if your printing with PLA you need a fan on the insulator and some put it on the part to cool the layers faster too. Some also think a fan is good for ABS too .

I addition to the use with PLA, for All Metal Hot Ends, the fan is essential, to keep the thermal isolator cool, so that the filament only melts in the end of the extruder.
I mistakenly turned off my extruder fan on my All Metal Hot End, and the result is that the motlen plastic ends up filling inside the thermal isolator until it comes out the top, at which point it solidifies and causes a jam.


BTW. AFIK You can have an additional fan that blows down onto the print bed, that is controlled by the RAMPS board, separately from the extruder fan. This gets programmed into the GCODE and is turned on e.g. when each layer has finished printing. (to solidify it)

Thanks guys.

Seems more imperative for PLA rather than ABS then?

Its not imperative for PLA, but it can help.

Personally, my extruder fan (designed to cool the extruder), was making the PLA cool unevenly and wrap. So I've had to prevent the breeze from the fan getting down onto the print bed.

After preventing the air from the fan getting to the PLA my warping problems were cured and printing PLA now seems to fine.

For ABS AFIK, you definitely don't want a cooling fan. My personal experience is that any form of cooling on the ABS causes problems, in fact its preferable with ABS if you keep all drafts away from the printer.

I ended up making a enclosure / cabinet, to put my MendelMax in, to keep the ABS warm and allow it to cool more slowly.
If you look on YouTube [www.youtube.com] there is a video about putting sides on a Solidoodle for ABS printing. They mention using Plexiglass.
My local hardware warehouse sells sheets of clear acrylic, so that's what I used for the font of my cabinet. The rest I made out of wood.
But as your Solidoodle has a frame all the way around. closing it off would just be a matter of attaching things to the side.

Note. As in the video (link above), I'm now fitting an extractor to remove the ABS fumes, as they are not good for the health. However I suspect that rather than some sort of fan + filter, its going to be best just to vent the extractor fan to the outside e.g. via a tube to the window.

actually on my original printer, adding the fan helped the abs stop warping upwards, the already printed plastic was retaining too much heat, and it would just start warping, when I added the fan it cooled the already printed layers down. I think the issue with machine was the moving bed caused only the outside surfaces to cool off. When I added the fan it allowed the entire layer to cool evenly, although i did set the fan at a lower speed so it wouldnt cool the heated bed. now with my new machine i havent added a fan yet, the head moves in the x and y direction so the print stays stationary and its blocked from any wind drafts. so on a moving bed platform it can actually help stop upwards curling, but it should be set at a low speed.

Thank aduy. sounds like everyone's experience is different.

Thanks Roger and Audy, and I concur with the last statement.

For my solidoodle I do have it enclosded with plexi, before that when my ABS cooled it warped on the corners. It would pull the Kapton up form the print bed stretching it with sufficient force to cause bubbles underneath the tape, this drove me nuts until I enclosed my machine. Seems to me keeping my ABS warm and away from un-even cooling sufficiently helped. It helped the old wallet too, as Kapton isnt cheap

- Ryan

Edited 1 time(s). Last edit at 10/23/2013 07:39AM by rcullan.

the extruder fan can also cool planetary geared and direct driven stepper motors. The motor heat creeps into the drive wheel and can soften PLA at the pinch bearing.
I've had stepper motors reach 90-100C, with the amps turned up trying to get the torque up. I tend to use NEMA14 5:1 ratio motors now, which do take some amps (185 setting in RAMBO)
The gearbox section will heat up after about 1 hour.

the fan can also help cool any printed part there may be near the motor, keeping it from deforming/sagging or from screws loosening under their heads.