Remote filament cooler OR fans handling back pressure

Good day everybody!

I am planning to add a filament cooling feature to my printer. But instead of loading a fan
on my hotend directly, I'd like to connect an air flow generating device to a flexible tube and
lead it to my hotend.

Of course, fans are the first idea to be used as the air flow generating devices. The biggest
issue is now that the air is not really travelling through the tube.

What did I test so far?

1. Use an axial fan and lead the air into the tube. Result: There's essentially not the slightest
   air flow travelling through the tube.
2. Replacing the axial by a DIY radial fan. Result: Again, the pressure drops significantly!

I think that the issue is the fans handling any back pressure by guiding the air into the smaller-diameter tube.

Do you have an idea how to generate a sufficient air flow? Would a regular, non-DIY, radial fan
maybe solve the issue?

Some analytics:
The volume current is dt_V=C*r**4*p where r is the radius, C a constant and p the pressure.
From there it follows that (r_new/r_old)**4 = p_old/p_new and therefore p_new ~ (r_new/r_old)**4.
This reveals that the idea of reducing the diameter later on is a bad idea!

Idea from analytics:
One should maybe design a DIY radial blower with the correct diameter right from the
beginning. Of course, the DIY blower would become a little smaller therefore.

Bests, Mardy :-)

"Idea from analytics:
One should maybe design a DIY radial blower with the correct diameter right from the
beginning. Of course, the DIY blower would become a little smaller therefore."

looks like you didn't finish you thought?

Anyway, the quality of the fan does make a pretty big difference. Noctua brand fans are known to be some of the best and sell their fans in many sizes. If you want extremely high static pressure fans, the thing that comes to mind is the high end pc water-cooling market, but those fans would be either 120mm or 140mm.

If you want maximum pressure, a blower from a CPAP machine is the way to go. Unfortunately, they seem to be a little hard to find. The American Science and Surplus store in Milwaukee has some for $8. You might be able to pick up someone's old CPAP machine at a garage sale and gut it, or check Craig's list.

Here's one doing its thing, cranked up to maximum, leaf-blower power- at more normal speeds they are very quiet:
CPAP blower

Here it is blowing some cold air- the blower is mounted on a cooler full of dry ice and the exit hose is from a CPAP machine:
cooler

These blowers have brushless DC motors but no built in driver. I used an ESC and servo tester ($8 + $5) from RC modeling to drive the blower.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Below is probably what you are looking for. It's a kit doing what you have described.

http://www.themakerhive.com/shop/viewitem.php?productid=28

Maybe try out an inflator?

The ones used to inflate air bed.

Intex Quick-Fill AC Electric Air Pump,
110-120 Volt, Max.
Air Flow 21.2CFM

Flexible tube to bottom of hot end

Those air bed inflators make hair dryers and vacuum cleaners sound positively musical. I think the motors usually have brushes and bushings instead of bearings that will wear out in short order. They are designed for low duty cycle operation and may overheat when run continuously.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

As a general rule fans are not good for moving air against any significant back pressure. Positive displacement pumps work much better - I have used both aquarium pumps and Roots blowers for this purpose.

Roots blower on Thingiverse: [www.thingiverse.com]
Air led through an 8mm id silicone tube to the printer head: [www.youtube.com]

Mike

This is technically a very interesting discussion but an easier way to get a part cooling fan with almost no additional mass on your effector (I am assuming its a delta as it really won't make any real difference to print head mass on any other type of printer), is to use something like this. [www.thingiverse.com] which I remixed. It cools PLA enough to produce the Marvin I have attached below at 0.1mm layer height.

As for what to do when printing ABS just put an elastic band around the duct outlet so no air comes out.