Your biggest fan...

[mr_intensity]

Okay, kind of a dumb question:

Many 3D printers come with a fan, and I am never quite sure sure what it is there to do.

Is it blowing on the print head?  This would seem counterintuitive, as you are heating up the print head to melt the filament for extrusion.

Or, is it blowing just *past* the print head, on to the freshly extruded plastic to firm it up?

I am asking as I have an idea for a new print head, and the fan would be in an oddball position.  So I would use duct work to direct the air where it should go.

I just need to know where the air should go, so I design the ducts right.

[MisterAcoustic]

Hi mr_intensity,

I think the idea is that the fan should be pointed at the tip of the extruder, such that you don't take a bunch of energy away from your hot end, but you do cool the extruded plastic more quickly.

One thing this helps with is 'bridging' - when you are trying to cover a gap, and the plastic has to go from point to point over an area where there is no support. If the filament is being cooled straight out of the hot end, it's more likely to make a straight, non-sagging bridge, with less stringy-ness.

Stan