How much air flow is needed for PLA?

Hey everyone. I have a Makerfarm Prusa i3 with a hexagon hot end, which requires a fan blowing on it at all times.

I had an interesting idea to make a fan shroud that would divert some air from the hot end, over to the extruder. A large portion of the fan is blocked by the extruder mounts anyway, so if I space the fan away and free that up, I should be able to take some flow over to the nozzle without effecting the hot end cooling too much.

I'm just worried that it would be enough cooling for the PLA. So how much air flow is actually required? Is having a dedicated fan really necessary?

Thanks!

Well, give it a try and tell us. Very early extruders worked without any fan, so I guess it's a matter of patience. With insufficient cooling you have to print slower to allow the heat going to ambient. Where "insufficient" starts ... who knows without trying it?

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Quote
Traumflug
Well, give it a try and tell us. Very early extruders worked without any fan, so I guess it's a matter of patience. With insufficient cooling you have to print slower to allow the heat going to ambient. Where "insufficient" starts ... who knows without trying it?

Yeah I've been printing without a fan for a while and I see the need for it. I'm working on a design but I'm just afraid it won't be adequate.

Usually you need to vary the speed of the fan so that its on slow for the start of the print and full for the rest.
This hel0s the bed adhesion. Or you may need more fan speed for smaller prints to cool them quicker.

But you need a constant fan for the hexagon to keep the cool end cool. On all the time the hot end is powered.

So i cant see how a single fan shared between keeping the hexagon cool and the variable fan for cooling the print could possibly work.

Ive got the hexagon hot end myself on my prusa i2 with a slim tiny 12v fan on constantly and a seperate variable fan, controlled by
marlin on ramps, for ninjaflex and pla. I mainly print abs but without a fan.
It works very well but does need the cooling fan on the cooling fins constantly.
It was quite a bit of work fitting that lot into a custom carriage for my prusa i2. Not a lot of room between the smooth rods.
I should imagine you have more room on the i3 so you wont save anything by combining the cooling of the hexagon and print with the same fan.

Gordon

I use a single blower with ducting blowing on both the cold end and hot end for printing with PLA. My cold end has enough surface area that it can go for 20 or 30 minutes without the blower without fear of jamming. Therefore, I can leave the blower off for the first layer. If I'm printing a really large first layer, I will turn on the fan at about 1/3 speed, just to be on the safe side, and I haven't found that this affects the first layer adhesion at all.