Is it just me or does the aero's heat sink cooling fan blow air down onto the print/bed? I've installed some deflectors to aim it away from the print.
This should not be the case, or at least not enough to make a difference. There is always some movement of air around an air cooled hotend, but usually not enough that it will affect the print. The Titan Aero should not blow any more air downwards than a V6 or a Cyclops would. Also, depending on the deflectors that you fit, you could restrict the air flow into the fins and reduce the cooling potential of the hotend, which can result in jams. In the extensive testing carried out here at E3D we have yet to notice any artefacts caused by the heat sink cooling fan, but if you do have pictures of the issue, we would be interested in improving this in further iterations.
I agree with you - the fan included with the Aero blows a lot of air, and the heat sink fins do not properly deflect it upwards (entirely). When close to the bed, and at higher temperatures (PETG) (85-90 degrees), my heated bed struggles a bit to reach temperature. Once I hit about 15mm from the bed the problem goes away. If its standard PLA, it reaches 55 degrees no problem.
Interesting you say this. I have just today installed 2 Aero's and I was thinking i had messed up with my part cooling fan mod... but now i have checked there is more air blowing down on the bed/part from the Aero than from the print cooling blower at the low speeds i am using! Basically I am getting corners curling on my parts now which is very new to me since using a PEI coated bed. As i changed so much I assumed it was me, but now i can feel its the Aero! need a deflector now, some how.
Interesting... I have 2 Titan Aero's. One Normal One Mirrored. On the Left one I get significant draft from the fan directly down. On the Left I get none, but 20cm or so to the left of that fan i can feel the draft on my hand... The Right Aero has a part cooling fan shroud on the right of the aero fan, the Left has the cooling fan shroud on the left of the Aero fan... It seems my left shroud is redirecting the air flow partially downwards as it cant blow left enough to miss my shroud. It seems air flows out of the left lower heat sink at about 30 degrees or approx 7 o'clock. If something is there, it causes turbulence. I will try some small parts with my right carriage which does not seem to observe the same issue as the left and see if the part curling from the bed is no longer there.
I posted a fan deflector on Thingiverse that i'm using with my Aero that seems to be helping. http://www.thingiverse.com/thing:2325332
I've got the fan flipped to suck air away from the heatsink to reduce this issue. So far the aluminum feels cooler than the regular v6 round heatsink so I'm not concerned that this reduces the airflow. There is still a bit of airflow on the fan output that seems to go downwards but a strip of tape should help that.