I’m about to design a dual 40mm fan mount for the printer I’m making, and I’m curious as to what some of you recommend. How important is the “angle” which the air hits the plastic coming from the nozzle? For people who have tried many fan mounts, how does an “open” design compare to a mount with shrouds that push the air flow into one concentrated area? I’m looking for my mount to able to handle the cooling off both pla and abs.
I’ve got just the Thing for you…
John, I love it.
Wow that was convenient
That looks like big air to me! Too much?
@Cameron_O_Neill why woud you need two 40mm fans? The weight added to the moving X caret may not be worth it.
I’ve been doing a bit of research in this area recently so I’ll tell you what I’ve come up with so far:
Why use a cooling duct?
Cooling ducts are principally used to expedite the cooling of the extrudiate to a point below (or close to) it’s glass transition state. This prevents the material from sagging while it cools naturally as thus improves the quality of overhangs, bridges etc. This type of cooling is most useful with PLA as ABS parts suffer from poor layer adhesion and de lamination (as a result of uneven thermal expansion) if aggressively cooled in this fashion.
So, assuming the above is correct, the duct should be directed so airflow passes directly over the layer currently being deposited and ideally should avoid the layers below as much as practical. Airflow over the nozzle itself should be minimised as it could potentially effect the temperature of the extrudiate prior to leaving the nozzle (not sure if anyone has measured this though)
Anecdotally, with PLA, the more aggressive the cooling the better, although I wonder how this might effect layer adhesion if the plastic is cooled too much.
It also makes sense to have airflow from multiple directions as the nozzle is extruding material at every vector during perimeter deposition - a circular duct that goes around the entire nozzle is a popular option here.
+Tim There are a number of circular duct designs on Thingiverse for various hot ends. Properly designed, you should only need one fan unless you have an E3D or similar hot end. I designed one on Thingiverse for the E3D using one fan. It’s not ideal but works well enough that I haven’t bothered with a new design yet (I use it on ABS with a slightly evelated temp).
With a 40 mm fan (or similar), I believe you probably only need one. The only reason I designed mine mount with two is because the confines of the Printbot GO only allow room for about a 30-35 mm fan and the ones I found in that size didn’t push as much air as I wanted. Delivering air from two sides is just a bonus.
That said, designing a simple cone shaped duct to direct and intensify cooling is very simple. Designing a duct to direct air from a single fan and distribute it with any kind of even distribution around 360 degrees is a serious engineering exercise. While we are lucky to have the rapid-prototypers on hand to try out some different ideas, comparing the results in a quantifiable fashion strikes me as non-trivial as well.