Hotend fan

Hi,

I'm new to building a 3D printer and want to know, what is the cooling fan on the hotend is for ?

I have a J-head MK-VB with a gred geared without the option to install a Fan... do I need it ? (printing PLA and ABS)

If I install one, where should it point to ? the nozle or the piece being printed ?

Thank for shining some light on this neebie's mind :-)

J-F

you need a 40mm fan for PLA, point it at the insulator of the hotend to prevent jams , you can also point another fan at the part if you want.

ok, I see.. the insulator is small on the MK-VB but i'll give it a try.

Does blowing air on the part make the layers look more constant ? I printed a 20mm cube for calibration and some of the layers look a bit saged and uneven..

Thank.

If you build a thin pointy part sort of like the shape of a pencil standing on it's end, the plastic will not cool before the next layer is printed. The whole thing can start to look like an ice cream as the head just keeps pulling the whole sticky mess around and around. The fan will cool each layer as it is made so its a lot more accurate when it's complete. If you try to print the small 9 tooth wade extruder gear you might have a problem as it is very small and the layers complete before the part can cool. The large wade gear takes a while to print each layer so the plastic is cold before the next layer begins.
I fitted a fan and the gain was extremely huge. Even putting a regular table fan next to the printer blowing on the part made a huge difference for me.
Regards
Mike

okay, I see your point.

i'll try to install one ASAP :-)

Thanks

Nophead has made some interesting observations on the problem of PLA softening in the JHead Mk5B here: [hydraraptor.blogspot.co.uk]
He also proposes a solution which avoids the need for a special JHead insulator cooling fan.

You will still need a fan which directs its air flow toward the part being printed though as described by mikefiatx19. It has been said before but one way of reducing, if not eliminating the cooling problem, which tends to arise when printing small parts, is to print several of them at a time or add them to another print job so that the total time to complete a layer is substantially increased.

Alan

I have been printing for close to a week now, I get great prints with the fan off, with the fan on it seems to distort the print, I think I have the printing speeds set way low, it seems to give enough time for the pla to cool off before the next layer