I’m working on this new cooling shroud for my Printrbot Simple Metal. The one in the photo is a test print to check fitting, so I printed it quick and dirty (0.6 noz, 0.3 res) and it ain’t pretty. There are a bunch of other shrouds and add-on fan setups already out there for this printer, but I thought I’d try keep it “simple” using the original fan and keeping the clean look of the printer carriage while improving cooling to the right-side of the print. Also, this keeps the nozzle easily visible and accessible for tip changes.
Let me know what y’all think. I’d also like to see what other PB users have done.
Axial fans like this don’t work well with small ducts. They just can’t generate enough pressure to push much air through the small opening. Switching to a radial blower fan will make a world of difference… I’d really recommend going that route before spending much more effort on duct optimization.
@Ryan_Carlyle I bought a blower fan for $5 on eBay and it pushes WAY more air than my axial fans. Like it’s not even a comparison. They aren’t bad for heatsink cooling but the blower fans are definitely better for filament cooling.
Blowing into open air, a 40x10mm axial fan pushes more CFMs than a 40x10mm radial fan, but it’s over a much bigger area so you get a lot less velocity. We want velocity targeted in a small area. Radial fans are just better for the application here.
@Ryan_Carlyle is right this is page tests a number of ducts and both types of fan…
http://www.desiquintans.com/coolingtests
nopheads post is good as well…
Well, you could use some extra printed blades in your shroud to increase the static pressure. This principles is used in high pressure axial fans. But you’ll loose CFM.
@Ryan_Carlyle i still don’t get it as to why ultimaker uses axial fans!. i myself use a 50mm radial fan with a shroud similar to the mendel 90
Here’s some more info on the effect of adding additional fixed blades @Sven_Eric_Nielsen is referring to, to increase the static pressure.
Seems to do the trick.
Work by @SgaboLab
http://www.sgabolab.com/2016/12/pc-fan-booster.html#links
@Wim_Vanhee that’s a real thing you can buy, not just a maker experiment. Tubeaxial fans etc. Digikey has a bunch if you want to buy one. They’re pretty intermediate in performance behavior between normal axial fans and radial blower fans.
I wonder is a printed cone w the blades would improve it too. And you can print things not possible to injection mold, so why not progressively change the angle too 
On the print cooling fan, this could really help.
Brook
+Ryan Carlyle, I know. Not trying to present this as just a maker experiment. Bit of a strange assumption there.
I just like the demo of the principle by sgabolab and I’m surprised that this is rarely (almost never?) used considering all the axial fan shroud designs that are around. It would seem that a shroud design for an axial fan is a bit of a wasted effort without one of these. Also wonder if many people consider the CFM and static pressure ratings of the fans they buy, nor what the effect is on the application they have in mind.
In the end the goal is to bring down the temperature of the print, preferably without cooling down the extruder nozzle. So the shroud should be moving as much air as possible over the freshly printed parts and keep that air away from the nozzle. Right? Seems to be a second common mistake in shroud designs. Often directed towards the extruder nozzle in stead of the print.
Anyway, considering fanjets, it seems incorrect to presume that axial fan systems are not good at producing high static pressure. Maybe it’s more a matter of form factor? What fits best for which application? Radial fans do seem like a better, more compact fit to hook up to an extruder.
@Wim_Vanhee almost no one looks at fan specs. People who do almost always pick a radial blower. Vane-axial fans are bigger and don’t perform any better through a nozzle/duct than a blower. We want highly targeted airflow at high speed, so it’s all about pressure and nozzle design.
Pointing the airflow directly at the nozzle is totally fine if the hot block is insulated – people worry way too much about it. You get really good print quality and the print is a little weaker from the more rapid cooling. But a ring of airflow around the nozzle is probably the best all-around solution.
Fan specs matter most. CFM. Blower fans are better but almost any radial fan is fine for Printrbot hotend cooling, they don’t require much. Part cooling fans are a must so a high CFM blower fan is a must.
A really thorough study was done on fan shrouds- and they absolutely DO make a difference. The guy who did the study concluded the best is a wide mouth cone fan. The all-around circle style is neat but no real advantage in the tests.
My take: if you like it or it’s working for you- dont fix it. If you have special needs (big tip, high speed) tweak away!
