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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

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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:

70deg.thumb.PNG.16c2540086b2740dbb6a2df7eba2db20.PNG

 

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

V4_Dual_Side.thumb.png.9f524b7fb4c5b5dd9074305ff7f93fe0.png

 

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:

V4_80_Dual_Side.thumb.png.09240d8404a4b8e36d481f7fe83552ef.png

 

 

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!

 

70deg.PNG

V4_Dual_Side.png

V4_80_Dual_Side.png

Edited by nerdwarrior

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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 by JRDM

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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. 

image.png

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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.

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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?

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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 by neotko

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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!

V4_70_Long_Side.thumb.png.b88ec18aadb54a18600b113f97dc4d76.png

 

Edited by nerdwarrior
  • Like 1

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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.

 

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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?

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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.

 

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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.

 

417638115_HeaderAssemblyBerd-AirLuefterhalterungv14.thumb.jpg.946b283bb9b61d66f65fa86a13f89f13.jpg

 

With which program did you create the simulation?

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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.

 

417638115_HeaderAssemblyBerd-AirLuefterhalterungv14.thumb.jpg.946b283bb9b61d66f65fa86a13f89f13.jpg

 

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 by nerdwarrior

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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.

1682532709_WasserTest.thumb.jpg.9f4c00ff24ba741ca8a25345d21064ba.jpg

 

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

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