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Fan shroud for I3 Bowden

Posted by dolon 
Fan shroud for I3 Bowden
August 15, 2017 02:02AM
I am seeing all types of fan shrouds, but not sure if any of them would suit an i3 type clone with a single fan and a Bowden Extruder.
The fan is mounted on the plate that holds the hot end.
I would like to make my own, but need some guidance on what it should achieve.
As I see it the aim is to cool the fins while keeping the air away from the nozzle.
However, I'm not sure about cooling the printed part. Should a separate duct be aimed directly at the nozzle or somewhere else?
Re: Fan shroud for I3 Bowden
August 15, 2017 08:36AM
The heatsink fan should cool only the heatsink. So using a tight shroud and a 30mm fan will be sufficient i.e. e3d v6 setup. A less ducted shroud may need a 40mm fan. Choose good quality fans here, you don't want it to fail. Sunon Maglev series are very good. The hotend fan should stay on all the time, so wire it to the PSU.

Part cooling fans need to be controllable, they are wired to your controller board's fan output (or on ramps to the D9 mosfet) the slicer controls the fan speed depending on how you set it up, it does this by sending M106 Sx commands where x is a value between 0 (off) and 255 (full speed).

Part cooling fans should duct air at the extruded filament, or at the print in the immediate vicinity of the nozzle (not as best you can the heater block or nozzle as this will cool it too much in some cases). Ideally from two sides (to minimise curling of overhangs), or from all sides using a ring diffuser, not that I've ever really had much success with these, you need fairly long nozzles to get them in close enough.

A debate exists about whether highly ducted, directional airflow or more diffuse airflow works best.

Axial fans (those we are most familiar with) work well if their airflow is not too restricted. Radial fans (blower fans) produce more airflow and tolerate slightly more ducting.

There are pumped air systems like Berdair which use an aquarium pump to push air along a tube to a metal ring diffuser around the nozzle, these are particularly suited to enclosed printers where the pump and air source can be outside the enclosure or to printers where a very small or light print head is desirable.

Personally I use a fan shroud with a 30mm heatsink fan, and then two 30mm sunon blower fans either side with small ducts bonded to them, many other ideas can be found here [forums.reprap.org]

Edited 1 time(s). Last edit at 08/15/2017 08:37AM by DjDemonD.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Re: Fan shroud for I3 Bowden
August 15, 2017 08:47AM
Thanks for your reply. I only have a 40mm fixed fan. I think my Ramp controller may have a socket for another fan, but I would have to create a mounting for it.
I have modelled a shroud that surrounds the heatsink, so will give that a try first.
open | download - shroud.stl (28 KB)
Re: Fan shroud for I3 Bowden
August 15, 2017 09:53AM
That should work but how is it secured? You don't want it falling off mid print. Some designs use a cable/zip tie on the other side from the fan, or you could design it to snap around the heatsink, but print it so the layers go from bottom to top as you have it orientated otherwise it'll split along the layers when pushed over the heatsink.

Ideally print these in ABS, PLA can and does soften near the lower end of the heatsink due to heat rising from the heater block.

Admirable that you've made your own but there are thousands of designs out there.

Edited 1 time(s). Last edit at 08/15/2017 09:57AM by DjDemonD.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
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