Musings and Experiments in 3D Printing Technology and Art
Friday, March 3, 2017
The "Tusk Fan Shroud"
I don't understand why many people feel they must blast their part, hotend and heated bed with lots of air. Consider this: blasting a large area with a lot of air can create more problems than it solves - problems like part warping, hot end temperature fluctuations, beds that can't reach and maintain higher temperatures and a host of others. A much better approach - particularly for common filaments like PLA, ABS, PETG, etc - is to direct the minimal amount of air as precisely as possible with laser focus.
I started experimenting and writing about this a few years ago. See Strategy #12 Be a Fanboy here: A Strategy for Successful (and Great) Prints for more details and examples of part warping due to too much air cooling. Here's a photo of an extreme warping example due to too much air:
Part on the left was cooled with a typical 25mm fan blasted at the part.
Part on the right cooled with my "soda straw" air duct (note the straws look far away, that is an illusion!)
This early soda straw air duct concept gave way to a slightly more sophisticated version using several soda straws - one on either side - and ultimately to a 3D printed or machined ring (Re: BerdAir coming soon...). I used this concept on all my deltas (8) until Berd-Air produced their bent aluminum tubing cooling ring. It precisely puts air where it's needed and it is also very low mass on the effector and very low profile so it solves multiple problems. But the air pump is noisy and large.
Recently I've refined my design to address the loudness issue by leveraging a normal 25mm fan or squirrel cage fan. I call this new version "the tusk" for obvious reasons (see photos below). The aluminum tusks allow positioning closer to the heater block for more precise air flow control.The photos below show it mounted on the effector of a SeeMeCNC Rostock MAX V3 with a soon-to-be released new Bondtech mini extruder I'm testing.
The "air shell" is low profile and can be located up and out of the way or even designed into an effector or platform if necessary. I'm showing a version with a squirrel cage fan but a standard fan tilted at a slight angle also works well. The tusks are 4mm OD aluminum tubes with 1mm holes. I have a printable jig that is used to align and space the holes for drilling. Then you crimp off the end of the tube. This has the additional benefit of allowing the crimp to be used as a sight to align the holes. With this arrangement, I have 100% clearance, something the three "hovercraft fans" of the stock V3 don't allow.
The middle hole on each tusk is centered with the nozzle tip. The air is directed 1mm below the nozzle and can be aimed as necessary with the sight crimps. With this precise air flow, you will not introduce thermal stress in your part (see link above), nor will you inadvertently cool your heated bed (especially important at higher bed temperatures), nor will it cool your hot end - especially if you use the E3D V6 sock (which I highly recommend for this and other reasons).
I have done smoke tests with this to study the air flow and can verify that it precisely streams air as claimed. The best part is, even with a 25mm fan I rarely ned to run more than 50% fan speed. The even better thing is, with this form of directed air flow, you can print longer bridges in PLA and ABS since the cooling air is in the right place to "freeze" the filament as its being drawn across the bridge. And part warpage is non-existent. And thin walls and posts/pillars like those in my fly fishing reel prints that are very difficult to print without distortion using the nuclear blast cooling method print perfectly every time.
If you'd like to try the idea, I've put STL and STP files for the Tusk Fan Shroud and STL for the Tusk Drill Jig on my Google drive: https://drive.google.com/drive/folders/0BxntGMCn8PVKOTFwU3F4NzNvNG8