Cooling fan's on hotend?

Hey there,

As I await my Mix G1, I'm wondering what the purpose is of the fans that some people mount on their hotends. Isn't this the opposite of what you want out of a hotend? Im specifically referring to the one on the mendel tricolour that blows directly on the hotend itself.

Depends greatly on ur configuration and what hot end.ur.using. I don't know from personal experience but read is neededfor better pla print quality if using the mkivb hot end

Its easy for the temps of the hot end to climb higher than you want them. Keeping a fan on them helps keep it in check. Not to mention getting some airflow to your PLA prints can be a good thing for print quality too.

He is talking about fan on the hotend, not fan blowing on the print usually mounted on the hot end.

That's the unique design of the emaker/reprappro printers. The fan limits the heat travelling up the hotend to the stainless steel barrel and below. This makes the hotzone very small which is a good thing.

In general you want the cold end of the hotend to be cold so you can have a short transition zone where the plastic melts in order to have good control over the extrusion.

For the tricolor, you might want to cool the unused hotends down quickly when you switch.

If printing pla its prudent to insulate the "hot bit" and then blow a fan over the rest of the hotend. Stops the heat slowly creeping up the barrel causing the pla to swell and jam. I have killed a hotend by not using a fan, since I started to use one I have had no problems!

the fans are dual purpose. they carry away heat from the carriage so it does not melt or become fatigued by heat causing damage and also cools down prints so layers are below glass transition temp and do not deform when filament squeezes down from above.

without a fan the feed rate would need to be slow enough to allow filament to cool below glass transition ~60C for pla and ~105C for abs. since convention alone can reduce temp to less than 100C it is not always needed for abs to use a fan, however it is hard to reduce temp below 60C in a reasonable time for pla unless slow print rates are done.

this is why many rep-rap setups dual combine features of fan, and why some fans blow directly across the top of the hot end.

I use Huxley with the addition of a fan, which I experienced when making a certain angle, fanless results are more rounded at the angle that I'm printing, I was using ABS.