how to select the best cooling fan for my delta

I came across a home experiment that measured the effectiveness of different shrouds and fans on PLA overhangs here and the result definitely favored a 50mm blower vs a 40mm fan.
Now with a shroud to focus the airflow, the back-pressure will be high. Most of these little computer fans are made to blow freely. I made a shroud with a 30mm fan and had almost no airflow out the shroud nozzle. I found a fan that would fit, rated for high backpresure and it was NOISY, but it sure blew. In fact, it was too strong and would push the molten PLA around before it could even set. I discarded that attempt and am currently cooling with three fans near each tower blowing across the bed. Not very ideal.

Anyway, I am up against several criteria and hoping some people here have experiences to share.
1) Can your fan stop and start fast? This seems crucial if you want the high cooling for bridges and less blowing for elsewhere. What fan can keep up with those highs-peed changes? And a blower will have an even slower response.
2) Has anybody tried to mount and print with a blower ? ( a blower pulls in air from the large face like a normal fan but blows it out the edge, usually a corner). It seems like another attachment that will just weigh down the effector.

thanks

I think speed should not dictate fan effectiveness... Just turn the fan on intelligently. In S3D you can set bridging parameters to apply over a wider area then just the bridge itself, meaning your fan will have time to come on in full force. A fan that is already on will also get to max output quicker, so consider very low cooling for the rest of the print and only turn it up for the bridge.

I'm not sure I understand your second point.. Many people have used blower fans, with 50mm blowers being the most popular. The maximum cfm of fans seems to jump considerably when you hit the 50mm size. I have tried to use 40mm blower fans but I found the design inadequate and it couldn't deal with backflow very well. My next fan set up will be 2x 30mm blowers.

These days I've become quite a fan of nGen, it doesn't need any fans at all and still delivers stunning results on overhangs up to 45 degrees. I've found *most* colorfabb PLA to be the same as well, although you have to respect minimum layer times and try to print multiples if you can.

@Origamib
Thanks for your thoughts. I've been using Slicer since I know it fairly well and the two times I tried Cura it immediately drove the nozzle into the bed, sigh. Guess I should bite the bullet and start re-learning something else. There seem to be more and more options today. I've heard good things about S3D but of course 3D printing is an open-source world (or was) so paying a fairly high amount for the software was hard to consider. Guess I should commit as much time as possible with the two-week trial (I wish they would do 'print-hours' so I can take my time, I have a life!)

As for the fans, will 2x 30 mm blowers be >= 1x 50mm blower? I"m can't recall at the moment the relationship between radius and RPM and cfm and pressure for blower or fans but some of those have power of 2 relationships so two smaller things won't necessarily equal one bigger thing.

I will also explore nGen some more, I think I have some untouched colorfabb samples.

Thanks again, these are valuable considerations, especially S3D. I think I may have downloaded the trial way back but it expired before I could really do anything.

30mm blower fans are *way* more expensive (~$8 each on AliExpress, vs $1.25 for a 50mm one), and 12V ones aren't common, (Hopefully someone will point me to a cheaper source!) and do half the airflow (1.85CFM vs 3.6CFM for a 50mm). So I (being a cheapskate) would always go for 1 * 50mm fan over 2 * 30mm fans.

OTOH, 3.6CFM is way too much for print cooling, so probably 1 * 30mm fan would be good for that. Or a 50mm fan running at half-speed or so, controlled via PWM by Repetier/Marlin.

I have had a 50mm blower mounted on my hot-end; it seemed to improve things.

Out of interest, my Stratasys uPrint has *big* blower fans at the side of the bed for print cooling.

What (apart from the noise) is the downside of leaving the print-cooling fan running all the time?

Just for comparison I just bought a 30mm blower for $8 on Amazon. It is 3.2 CFM @ 12V. Since I'm only buying one or two and trying to make a really competent machine the price does not seem like that much to me.
Except for the bottom layers I tend to just keep my fans at 100% but they sit blowing across the bed from all sides, which won't do squat for print heights beyond 100mm or so (mine goes to about 450 in the center).

Quote
frankvdh
30mm blower fans are *way* more expensive (~$8 each on AliExpress, vs $1.25 for a 50mm one), and 12V ones aren't common, (Hopefully someone will point me to a cheaper source!) and do half the airflow (1.85CFM vs 3.6CFM for a 50mm). So I (being a cheapskate) would always go for 1 * 50mm fan over 2 * 30mm fans.

OTOH, 3.6CFM is way too much for print cooling, so probably 1 * 30mm fan would be good for that. Or a 50mm fan running at half-speed or so, controlled via PWM by Repetier/Marlin.

I have had a 50mm blower mounted on my hot-end; it seemed to improve things.

Out of interest, my Stratasys uPrint has *big* blower fans at the side of the bed for print cooling.

What (apart from the noise) is the downside of leaving the print-cooling fan running all the time?

The challenge to me is adequate cooling and making the carriage size as small as possible. It is possible to do this with a 50mm blower, but there are more challenges as you may have to place the fan above the carriage and duct it down to the hotend. It is also harder to give 360degree cooling, unless you have 2x 50mm or a ring shaped duct. Ring shaped ducts are hard to design and block the view of the nozzle, two things I'm personally not keen on.

If we are all agreed that a 50mm blower is too strong, 2x 30mm blowers may be the perfect answer!

To the OP, S3D is not necessary and I would agree it is overpriced. However, it has a few features that are unavailable elsewhere and it has a nicer work flow. 3D printing is not just a hobby for me so I was happy to lay down the cash, but I think a combination of slicers would achieve similar results just with added hassle. If you're interested in my views on S3D I did make a thread on it but feel free to PM me for more as I may not have updated the thread. Experimenting with filaments though I think is quite important...

Experimenting with filaments though is something I think everyone should do! If you don't get on with a filament, sometimes it's not worth the hassle... Similar brands/price points /materials can sometimes be drastically different to print.

I'm using 2x30mm blower fans like this:


And I'm quite happy with them. They are 5v but can be run at high voltages (with probably a reduced service life). They PWM quite well. I am also finding the diffuse airflow as they are setup now quite effective, rather than having them highly ducted.

Anyone suggest an extreme fan test to try?

I have these fans in my shop [www.precisionpiezo.co.uk] but that just as they were available in 10's so I bought a bunch.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

There are some over hang tests that really test a fan. But even easier is the bottom side of the ears on a Marvin.

A single blower fan running at 75% speed has been working fine. Initially, at 100%, I was also having issues air pushing the plastic around before it could cool. Why not just use the strong blowers and throttle down to the optimal cooling speed for your set up and call that the "max" ?