Cooling Idea: 4 Fans?

[nerdwarrior 19]

Hi everyone,

 

Proper part cooling is essential for nice prints, especially with PLA. I, like a lot of people, thought it would be nice to improve this, so I set out to do some research.

What I've essentially found are two main solutions: blowers, which have the benefit of higher static pressure and focused airflow, and axial fans, which have the benefit of high airflow. The former allows for rapid cooling of the plastic coming straight out of the nozzle, which is useful for small features, while the latter allows for even cooling over a large area for larger/faster prints. In other words, focused airflow is bad when the printhead moves quickly away, and wide airflow is bad when the printhead is moving over a small area. 

 

My idea for a (potentially new?) cooling solution is to incorporate both styles of fans in my UMO+. My idea is to have a pair of blowers, one on either side of the hotend, focusing air right below the nozzle. Next to each blower will be an axial fan cooling the large area behind the blower. That way, plastic can be cooled as it comes out of the nozzle, so it's quickly set in shape, and more cooling can be provided by the axial fans as the printhead moves away. I'm currently working on CAD and CFD visualizations for this, but life is pretty busy, so it may take a while. 

 

The best idea I have thus far for controlling these fans would be to have the blowers connected to the FAN output and the axial fans connected to the LED output. Then, in firmware, the M106 command (fan on) can be set to also send power to the LED output, perhaps at some constant or changing factor of the blower speed. 

 

For specific fans, I'm looking at two BFB03512HHA-AF00 blowers (12V version of the UM3 blowers) wired in series on the FAN output, and two EBM-PAPST 24V 40mm axial fans on the LED output. 

 

Please let me know what you think of this idea, and feel free to contribute! 

Worries, questions, or solutions are all welcome. 

 

Thanks!

-nerdwarrior

[nerdwarrior 19]

Update and slight issue:

 

I've conducted some CFD's with various shroud setups, and the results are both encouraging and disappointing.

 

Just the blower, mounted 20 degrees from vertical:

 

Blower and axial, blower 20 degrees from vertical and axial mounted straight behind (so that bottom of the fan colinear with bottom line):

 

Here's the problem: I initially forgot that by wiring the blowers in series, each would receive less power and thus have less airflow. So, when I compensated for that in the second CFD, you can see that the air from the blower doesn't get as close to the nozzle. From my initial testing, moving the blower closer to vertical brings the airflow closer to the nozzle. However, with the current setup, that would also turn the airflow of the axial closer to vertical, leaving a larger gap between the blower and axial air:

 

 

At this point, there are a couple of "solutions": a) my rough estimations of airflow (1.66 CFM for a single fan, thus ~0.83 CFM each when in series) are wrong, so mounting 20 degrees from vertical is okay, or b) design a wedge behind the blower fan to make the face opposite the axial fan less steep, making for smoother airflow. 

 

Would anyone be kind enough to offer their expertise and input? 

 

Thank you!

 

Edited September 1, 2018 by nerdwarrior

[JRDM 5]

Hi, I'm not seeing the images, is your image host down?

[nerdwarrior 19]

8 hours ago, JRDM said:

Hi, I'm not seeing the images, is your image host down?

 

Sorry about that. Is it better now?

[JRDM 5]

Yes.

 

I think the first one is the best. You want to cool the part as close to the nozzle as possible while trying to avoid cooling the nozzle itself. All the other cooling blowing elsewhere doesn't help you.

Edited September 2, 2018 by JRDM

[nerdwarrior 19]

10 hours ago, JRDM said:

Yes.

 

I think the first one is the best. You want to cool the part as close to the nozzle as possible while trying to avoid cooling the nozzle itself. All the other cooling blowing elsewhere doesn't help you.

 

I agree, the blower configuration for the first one is better. However, it was done with a CFM slightly higher than the fans would be able to supply if wired in series. 

The idea with the axial fan on the side is that when the print head is moving fast, the blower won't provide enough cooling time (it moves away), so the airflow of the axial fan moves directly over the freshly printed part. 

[JRDM 5]

Why are you wiring the fans in series? I don't think you're at risk of blowing out the fan control FET, assuming that's what you're worried about. I can look up the part but I believe it's a 1.5A FET and you're probably only using 0.4A to 0.5A of that at full blast with four 30mm fans.

 

Anyway, the slope of the cooling air is pretty shallow and that still makes the cooling area pretty broad. And you might be surprised how much it helps to cool the plastic just as it comes out the nozzle.

[nerdwarrior 19]

10 minutes ago, JRDM said:

Why are you wiring the fans in series? I don't think you're at risk of blowing out the fan control FET, assuming that's what you're worried about. I can look up the part but I believe it's a 1.5A FET and you're probably only using 0.4A to 0.5A of that at full blast with four 30mm fans.

 

Anyway, the slope of the cooling air is pretty shallow and that still makes the cooling area pretty broad. And you might be surprised how much it helps to cool the plastic just as it comes out the nozzle.

 

I'm not worried about the FET, and I totally agree that the air should be focused right below the nozzle. The problem is, I'm not quite sure how to go about fixing it, as the duct was originally designed with ~1.6 CFM in mind, before I realized that the fans would only be capable of running at ~0.8 CFM. Do you think narrowing the duct output would increase the pressure too much?

 

The fans have to be in series because the BFB03512HHA-AF00's are only offered in a 12V, not 24V, package. Ideally, the fans should be wired in parallel so as to not have to worry about equally dropping voltage, but I haven't found a decent 24V blower that's as compact and nice as the BFB03512HHA-AF00. Would you have any suggestions?

[ultiarjan 1,223]

the fans used in the ultimaker3 (partnumber on github) are available in 12V and 24V

 

[neotko 1,417]

3 hours ago, ultiarjan said:

the fans used in the ultimaker3 (partnumber on github) are available in 12V and 24V

 

 

Afaik, unless they released a new model on the last year, um3 model is the same he already posted, and it’s only available on 12V and 5V. UM use them in series not parallel and they work just fine. 

 

https://eu.mouser.com/datasheet/2/632/BFB30x30x10mm-515772.pdf

Edited September 3, 2018 by neotko

[ultiarjan 1,223]

ah yeah, Neo is right, it's 5Volt and 12, not 24V, sorry...

 

[nerdwarrior 19]

Thanks, @neotko, for clearing that up!

 

Since I evidently cannot get full airflow because the fan is not available in 24V, I tried extending the fan duct a bit to better direct the air. This seems to work, and I'll probably be ordering parts soon. Stay tuned!

 

Edited September 8, 2018 by nerdwarrior

[geert_2 557]

A problem with a strong and very local airflow is that it cools the glass too much in some areas, especially when printing small objects. Even with the standard fans on my UM2, I have measured temp differences up to 15°C when printing tiny models in PET: in these areas the bed was cooled to ca. 75°C instead of the set 90°C. This might affect bonding of the model.

 

Personally I feel rather like putting a 250mm desktop fan (like used in summer) in front of the printer, at a distance of 1 or 2m, set at slowest speed. This provides lots of airflow to evacuate excessive heat, but it is nicely distributed over the whole printer.

 

[nerdwarrior 19]

13 hours ago, geert_2 said:

A problem with a strong and very local airflow is that it cools the glass too much in some areas, especially when printing small objects. Even with the standard fans on my UM2, I have measured temp differences up to 15°C when printing tiny models in PET: in these areas the bed was cooled to ca. 75°C instead of the set 90°C. This might affect bonding of the model.

 

Personally I feel rather like putting a 250mm desktop fan (like used in summer) in front of the printer, at a distance of 1 or 2m, set at slowest speed. This provides lots of airflow to evacuate excessive heat, but it is nicely distributed over the whole printer.

 

A legitimate concern, @geert_2. I'm hoping that for PLA this won't be too much of an issue, and if necessary, I can turn down the blowers slightly while leaving the axial fans on high. Does that sound alright, or do you think the cooling would be too irregular?

[geert_2 557]

The above is just from experience via trial and error. I am not a specialist in air flows.

 

When I needed extra cooling, like in the hot summer we had (>30°C), the desktop fan at lowest speed, and from some distance, worked very well. This gently cools the whole model, but not too much the nozzle itself. It just removes excess heat in a gentle way.

 

I also tried blowing compressed air directly on the model, just below the nozzle, but this would cool the nozzle too suddenly, and cause temp fluctuations, and errors if done excessively. So the airflow has to cool the model, but not the nozzle. It should solidify the printed lines immediately so they are stable, but not too much, so the next layer still bonds well. And the glass should stay hot enough to preserve a good bonding (especially with my "salt method" for bonding, without any glue). All this is not an easy balance.

 

This is why I would not exagerate in adding fans. Just my personal view, but of course you are free to see things differently, and your models and circumstances may differ from mine.

 

I have never had any problems with PLA with the standard nozzle fans, although cooling runs at 100%. Bed temp then is set to 60°C, which might locally cool down a bit to 50 or 55°C. This is not too far away from room temp, 20...25°C, so cooling is not excessive.

 

But I did have issues when printing PET, where the glass temp is much higher and thus the local cooling effect seems a lot bigger. Glass is an insulator, so I guess it can't keep up with the local heat loss. I had to increase the set glass temp from 80°C to 90 or 95°C to get good bonding. So that after cooling locally, it would still be around the desired 80°C for this sort of PET.

 

[zerspaner_gerd 382]

On 8/28/2018 at 10:44 AM, nerdwarrior said:

What I've essentially found are two main solutions: blowers, which have the benefit of higher static pressure and focused airflow, and axial fans, which have the benefit of high airflow.

 

There is yet the possibility to cool with "Berd-Air".

I once ordered such a pump and mitwerweile received, let's see if I get a cooling around.

 

 

With which program did you create the simulation?

[nerdwarrior 19]

14 hours ago, zerspaner_gerd said:

 

There is yet the possibility to cool with "Berd-Air".

I once ordered such a pump and mitwerweile received, let's see if I get a cooling around.

 

 

With which program did you create the simulation?

 

Nice! It horrifies my inner laziness, though...

Let me know how it goes!

 

I used Autodesk CFD (student subscription). 

Edited September 18, 2018 by nerdwarrior

[zerspaner_gerd 382]

So far I do not get good results. It whistles a lot of air but probably in the wrong place.
Water test looks good to me, unfortunately, have no way to simulate air currents.

 

If you want to see for yourself:
https://a360.co/2PQgmJO

Or here the CAD model

https://www.dropbox.com/s/qpnwcwl0p71bv17/Header Assembly Berd-Air Luefterhalterung Stand v17.iges?dl=0

 

greeting

[nerdwarrior 19]

Been kind of busy, haven't gotten around to actually finishing this yet. All the parts are here, though, and I'll probably have some time later this month after exams are over. Sorry for how long this is taking 😕

 

I'm pretty much a noob when it comes to firmware, but based on what I can see, the Amedee fork of Marlin is UMO+-ready, correct? The only thing I see that needs changing is the motherboard from 7 ("Ultimaker") to 72 ("Ultimaker V2.X"). Everything else seems fine for an unmodded UMO+ (thermal, motion, etc). Can someone please back me up on this? 

 

Thank you in advance! 

Edited December 9, 2018 by nerdwarrior

[nilrog 103]

That firmware is a fork and major improvment to the UMO+ firmware...and is what, afaik, everyone that tinkers with their UMO(+) printers are using.

You can easily build it with the webtool he put online at https://bultimaker.bulles.eu/

 

If you are modding the firmware you could download that tool and run it locally to compile the firmware...and if you make a new (awesome) change to the firmware send him a pull request 🙂

[nerdwarrior 19]

8 minutes ago, nilrog said:

If you are modding the firmware you could download that tool and run it locally to compile the firmware...and if you make a new (awesome) change to the firmware send him a pull request 🙂

 

Thank you for the information, nilrog!

Unfortunately, what I want to try is beyond what is offered in the webtool and requires me going in to change some gcode definitions. This I've done, but I'm just afraid that I've missed something in the configuration.h file. 

 

When you say download the tool, do you mean there is a way to generate the code (not compiled) that I can then modify? If so, that would be perfect, because I would be certain I haven't missed any configuration for my UMO+! 

[nilrog 103]

Yes, the tool is also on github, so you can download it and run it on your own computer. You need Arduino and a webserver, and the Bultimaker tool.

 

https://github.com/AmedeeBulle/Bultimaker

 

Once you have that setup you can modify whatever you want in the firmware code and compile it using that tool. Just make sure that the firmware source is his fork of Marlin/Ultimaker.

[nerdwarrior 19]

Great! I'll look into that.

Thank you!

[nerdwarrior 19]

Hello everyone!

 

It's been another year, I've finally managed to get the designs finalized and printed, the fans ordered, and everything installed (among a slew of other printer upgrades). 

A problem I've run into is that, somehow, I blew the blowers within maybe 5 minutes of running them...

I've tested the power coming out of the board, and that is working fine. It will drive any other fan. So the problem must be with the blowers.

My theory right now is that the fans act as inductors when they're turned off, which causes a back current. What bothers me is that, to the best of my knowledge, the main board should also already be protected (after all, we don't put flyback diodes on any other fans).

The fans I ordered ended up being the F00 variation of the blowers, with the built-in tachometers, as that was the only one on Mouser that could be ordered in low quantities (the non-tachometer version used in the Ultimaker can only be ordered in bulk). Perhaps the way the tachometer is internally wired requires it to be separately protected? I'm not sure how that would work, but it's the best bet I have right now.

I think I've run into the bounds of my limited electronics knowledge, so if someone could help me out, I would greatly appreciate it! 

Thank you in advance!

 

Best,

nerdwarrior 

[JRDM 5]

Did you make any progress? FETs tend to have built in flyback diodes to protect themselves to some degree but I suppose maybe four different fans interacting on the same line might damage each other anyway. Ideally flyback diodes are best put on the load. The other possibility is the fan has the incorrect label and the electronics were meant for a lower voltage. That shouldn't happen but it's not impossible.

Edited December 27, 2019 by JRDM