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Roots blower

Posted by leadinglights 
Roots blower
November 26, 2014 12:28PM
My hot end has an air ring around the nozzle with the air fed through a silicone tube from a remote pump, I have been using an aquarium pump but this cannot easily be controlled by the G-code. After spending some time looking at what was available I decided to make one.

The normal axial fan is not an option as it can't push much air through a thin (6mm bore) tube. Centrifugal fans are a little better, but one to give the required pressure would have deep blades like a turbocharger compressor and balancing becomes a problem. Piston and diaphragm pumps deliver more pressure than needed but at too small a flow - they are also noisy. The Roots blower is a good all round solution.

The completed Roots blower pump

Rendering of the CAD files

Rotors and body from an earlier try - clearance between parts was too large

The Roots blower working. Delivery is 15 l/min (0.5CFM)and maximum pressure is about 0.8kPa (3.2" of water)

For this to work well the printer needs to be very well calibrated - It wasn't but now is.

Re: Roots blower
November 27, 2014 02:13AM
Very nicely done!
Can you show a photo of the print head arrangement?

My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!
Re: Roots blower
November 27, 2014 04:26AM
Hopefully these will give the general idea. Please do not try Tekapeek (graphite loaded PEEK) shown in one of the diagrams - it was an abject failure.

View on bottom of hot end on a Mendel Prusa

Section showing parts

Section showing area fan/heatsink cooler

Edit: I have been looking for any photos showing the ducting, but the closest I have is a Youtube video. The silicone tube is clearly visible but the cooling was an older and inferior type.


Edited 1 time(s). Last edit at 11/27/2014 04:30AM by leadinglights.
Re: Roots blower
November 28, 2014 04:50AM
I had never heard of cuttlefish bone, or as insulation. Fascinating.
I'll be following your progress.
Re: Roots blower
November 29, 2014 02:12PM
I reported on my experiments with cuttlefish bone in [forums.reprap.org]

Briefly though: Cuttlefish bone is an exceptional insulator and can take the maximum temperature of any credible plastic extruder. However, it is very fragile. I use thin brass shim to build a protective box around the cuttlefish bone.

Re: Roots blower
December 09, 2014 12:40PM
I have just dropped the STLs and instructions for this on [www.thingiverse.com]

Re: Roots blower
January 03, 2015 07:49PM
This looks like a very nice idea for sure!
thanks for documenting your work here -
will look into it and try to adapt to my prusa i3.

my normal fan-cooling results in too much cooling down of the hot-end, since the air flow is not guided enough.


Edited 1 time(s). Last edit at 01/03/2015 07:49PM by Alexander1984.
Re: Roots blower
January 12, 2015 09:44PM
Nice job! Maybe I'll make one soon smiling smiley
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