Do we really need Fans?

Hi.

I am wondering: Do we really need fans?

The ramps need fan?

The hotend needs fan? Why not using kapton tape instead?

I am confused if i should install fans in my almost finished prusa i3 printer.

Thanks in advance.

I have an 80mm fan blowing on my Sanguinololu (and RAMPS when I was using that) just to increase the cooling on my mosfets and pololu steppers, better safe than sorry. Also fan on the extruder I think is mostly for PLA prints

If you use pla and want to build objects over 20mm high, a fan is a must! abs cools down below Glass transition temp quick enough that you can print it slowly without a fan. To print pla quickly and do proper bridging with abs and pla a fan is the best and easiest way to go.


ramps should have a fan if you are pushing more current thru motors. if the stepper driver overheats (like on a hot day) it will thermally shut down, meaning if you are mid print your steps will be not counted correctly and your object will skip in its position. If ramps are exposed outside of machine and have air flow, and are not restricted or walled in, then it is possible to use without a fan even at high power to motors.

Do hot ends need fans? yes/no. heat creeps up the barrel if it is not cooled. Many designs use the fan that cools the hot end to also cool the print.

If the hot end on the barrel has enough of it exposed to where when x carriage moves the air current goes across the hot end, and the hot end is designed for convection cooling then you may be able to get away without cooling it.

Hope this helps somewhat. Others may have more information.

A fan on PLA prints helps you go faster. In my experience, a fan on an ABS or Nylon print does harm.

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I'd be interested in what cases fans make things worse (apart from the noise, cost etc).

If we can address those, then perhaps using fans becomes the default option. I note that the Dimension teardown shows cooling at the extruder entry/exit and at nozzle exit, although they do use heated chamber.

If nozzles benefit from fans I would like to see designs with integrated fan ducts, rather than every users have to jury rig and experiment with fan setups. Heh, easy for me to say because I don't design nozzles But seems like it would improve performance and consistency to have a designed in solution.

Fans:

PLA
- Yes, directed on the print so it hardens quicker, and therefor helps a lot with bridging etc. It helps to package the hotend heater block in insulation so the heater block doesn't get cooled down by the fan.
- Yes, directed at the insulator of the hotend to keep is cool because PLA expands when it heats up and tends to melt and get stuck a bit before it reaches the 'melt zone'. You want a small-as-possible melt zone.

ABS
- No, don't point one at your print, the cool air will cool down the ABS too fast and it will shrink down and the print will get unstuck from the bed. It only makes warping and things like this worse.
- Yes, directed at the insulator of the hotend, ABS has to be printed at even higher temperatures than PLA, to keep your carriage cool and to make sure the ABS never gets stuck (it doesn't get stuck as easy as PLA), a fan that cools the insulator part of your hotend will definately help your extruder carriage's life expectancy.

Stepper drivers
- Yes! Put cooling elements on the drivers' chip and chill them with a fan. This will make sure you never get missed steps by overheating on the steppers. Minimalise the factors that can ruin your prints!

I have used 40mm fans for everything that I have installed. Since I print with ABS I only use a fan on the hotend insulator and a fan on the Sanguino, however I have insulated my heater block too because I wanted to minimize the radiation heat from the block that keeps the ABS plastic too squishy and soft during print. I want it to set quicker so bridging is easier and thin towers keep a better shape during print. I can actually touch the bottom part of my heater block with my bare fingers

Is this clear?

thanks for the replies.


what part of the ramps 1.4 should we connect the fans to the stepper drivers?

Hello,

Forgive me for highjacking this topic but this comment below has me wondering...

Quote
Ohmarinus
ABS
- No, don't point one at your print, the cool air will cool down the ABS too fast and it will shrink down and the print will get unstuck from the bed. It only makes warping and things like this worse.

I received 15 pounds (6.8kg) of 3mm ABS filament with my AO-100 so printing with PLA is not an option for me at the moment, maybe later when my ABS stash reduces some.

I'm having a lot of trouble printing small ABS parts. The plastic does not have time to cool no matter how slow I print. An example of small parts I printed: [www.thingiverse.com]

It helped that I had 4 pieces to print, but the pieces were not perfect because of warping under heat. When I tried a single one as a test beforehand what I got was a misshapen blob.

If I shouldn't use a fan to cool small ABS parts, please explain what I should do to print smaller parts successfully, apart from plating an excessive quantity of parts so the plastic has time to cool off when it comes back to the first part.

Thanks.

FYI I printed perimeters at 50mm/s and infill at 60mm/s. Should I go even slower?

A fan may be ok on a small part. But for large parts, it seems to contribute to differential cooling, which increase warp. Maybe the answer is to hit the part from all sides at once.

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rsilvers Wrote:
-------------------------------------------------------
> Maybe the answer is to hit the part
> from all sides at once.

You could use something like this

Crux Wrote:
-------------------------------------------------------
> thanks for the replies.
>
>
> what part of the ramps 1.4 should we connect the
> fans to the stepper drivers?

It doesn't need to attach to the RAMPS. It would run like a fan in a computer, on all the time the unit is powered. Use an available suitable rail on your PSU.

vegasloki Wrote:
-------------------------------------------------------
> Crux Wrote:
> --------------------------------------------------
> -----
> > thanks for the replies.
> >
> >
> > what part of the ramps 1.4 should we connect
> the
> > fans to the stepper drivers?
>
> It doesn't need to attach to the RAMPS. It would
> run like a fan in a computer, on all the time the
> unit is powered. Use an available suitable rail
> on your PSU.



thank you for the reply. i am using xbox 360 psu. i can connect the fan together with 5A on the ramps?

See this:

[forums.reprap.org]

Edited 1 time(s). Last edit at 06/19/2013 04:09PM by rsilvers.

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NormandC Wrote:
-------------------------------------------------------
> Hello,
>
> Forgive me for highjacking this topic but this
> comment below has me wondering...
>
> ABS
...
>
> I'm having a lot of trouble printing small
> ABS parts. The plastic does not have time to cool
> no matter how slow I print. An example of small
> parts I printed:
> [www.thingiverse.com]

I have seen the same thing on small ABS parts, or just parts that have quickly finished layers....especially if you have a fast printer (using the TAZ right now). I am in the process of adding a fan, and Slic3r can control it based on the layer finish speed....even for ABS.

1013 Wrote:
-------------------------------------------------------
> I am in the process of
> adding a fan, and Slic3r can control it based on
> the layer finish speed....even for ABS.

I am printing a giant bolt in ABS, and it is sticking well to my cloth bed, heated to as hot as it will go - about 65C.

I noticed that the printer was laying down a "solid layer every 50 layers" over the honeycomb infill (pretty much bridging due to the 10% fill), and it was not looking perfect, so I clicked on the fan to see if that improved this kind of layer. The fan came on, and a few seconds later I heard a "crack" sound. I looked at the part, and it split on the front.

I really think you want ABS and Nylon to not be cooled by air. In fact, you want to contain the heat in an enclosure:

[www.youtube.com]

That layer I was trying to improve did seem to get detectably better though - as fans help bridging. Even so, I am not sure I want to set up my profile to turn on the fan for bridging, as it can crack or warp the part.

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