In this instructable, I am testing axial versus blower fan performance for a 3d printer's print cooling system. After reading this instructable you will know the definitive answer with real data to what fan to use in this specific scenario.

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Fans:

5015 blower https://amzn.to/3Ppy4m8
4020 axial https://amzn.to/3uNJoAY

3D printers in the video:

Kingroon KP3S https://amzn.to/3yDvHWe
Longer LK5 Pro https://amzn.to/3chMvud

Step 1: The Problem

These are two completely different fan designs. The axial fans are designed to move a lot of air at low pressure, meanwhile, the radial or blower fans move low amounts of air at high pressure.

So what this means is that the radial fans can better force the air through the small ducts. But if that is the case why then there are plenty of enthusiast designs and even some companies that use a more traditional axial fan to cool the print?

Is this straight incompetence or there is something we don’t know? Well, this is why are going to perform multiple tests and find out.

Step 2: Unexpected

So, to test the theory I designed two identical ducts to fit each fan type. As we want to test a realistic scenario of filament cooling, it gets narrower in the middle and only then widens up to measure the outcoming airspeed.

And the first test results were… let’s just say even extremely surprising to me. The axial fan basically made no airflow with this type of duct compared to the radial fan. And I am not exaggerating… The airspeed we get is absolutely useless and won't cool anything. The fart will have more airspeed lol.

So yeah, this looks like a worst-case scenario… so we have to dig deeper.

Step 3: New Design

And to do that I designed another type of duct. This time offsetting the narrow part right below the blades, giving probably a best-case scenario to directly force the air through.

And do you think that improved the airflow? Well, yes, and it improved substantially! Now we are getting only around 30% less airspeed but also with 16% less power compared to the radial fan. So great, then it is a viable option, right? But I am afraid that it is not as simple as YES or NO.

Step 4: Airspeed on Real Designs

Please let me explain. You see we are not looking here for a fair comparison. If we did, we would compare same-size fans. The whole point of modifying the print cooling system in the first place is to get better performance no matter the fan type.

Step 5: Other Fans?

Because that gives better printing results on overhangs and we can print faster without turning small objects into blobs.

The only other reason is to lower the noise. But using an axial fan instead of a radial doesn’t really make it that much quieter, it is just a different pitch noise. And some designs can make it even worse (it depends a lot on the design).

And considering that axial’s fan pressure heavily drops with the speed I doubt that even Noctua fans (5000RPM) would be a good idea here. As they operate 1800RPM lower compared to my tested ones (6800RPM).

Step 6: Easy to Make Useless Design

But the biggest issue when using axial fans in this scenario is how it is easy to make a useless cooling design. These fans (axial) are not designed to force air through the small ducts and require a better understanding of fluid dynamics to make them even somewhat viable.

The airflow out of the duct can be unpredictable and hard to control. And I am not trying to sound like I am an expert in this complex field or anything. I am just trying to warn you that instead of an upgrade you can end up with a downgrade.

Meanwhile, when using radial fans, you already have pressurized air coming through a small area that is extremely easy to force through almost any type of duct. The fewer bends and the shorter the path the better results you will get. These are very basic principles and it is not hard to execute into a good working design.

Step 7:

That is why it was not as simple as saying YES or NO. But now you know that, yes, it is a viable option, but it is abad option when we have specifically designed fans for this purpose.

And if your ultimategoal is the silence then it is way better just to use two fans and run them on lower speed instead. Just be sure that your 3D printer doesn’t produce that annoying fan PWM noise when you lower it. But if it does then make sure to subscribe/follow as I will be making a simple part to heavily suppress it.

I hope this video helped you decide on your 3d printer’s cooling upgrade. If it did please give it a like. That’s all from me and I will see you next time!