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FlashForge Creator Pro left single extruder fan duct
by DrLex, published
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Note: work-in-progress, although the current one is certainly usable, I may further tweak the design. I might try a different design if the deformation due to heat proves to be too problematic. Stay tuned for updates.
This is a variation on my dual duct. I only do a dual extrusion about 1 in 100 prints, and I figured it is a bit pointless to have the dual duct blow air at the inactive (and usually unscrewed) nozzle all the time. It makes more sense to also direct this air at the active nozzle. By blowing air from two directions, this design eliminates the ‘shadow’ problem of both the stock duct and my dual duct, and cools all sides more or less equally. If you're only going to print with one extruder, this duct will give you the best quality.
Of course this does not make the dual duct obsolete: you still need it to get proper cooling on dual extrusions.
The photos show a comparison of my 55° mushroom test on a PLA print between this duct, the v6 dual duct, and the stock duct. The result from the stock duct looks more decent than what I expected while I saw it being printed: it was curling up so badly at times that I feared I would need to abort the print. Somehow the upper layers managed to push down the curls again, but it still looks ugly. The result from my new duct shows almost no deformations and it has a near-flat top surface. (Note: you won't be able to get this kind of result on the 55° test with the stock nozzles, especially not if they have been worn out. This was printed with a more pointy Micro Swiss hardened steel nozzle, which allows to print steeper overhangs than a nozzle with a flat underside.)
There will not be a version of this duct for the right extruder. This is why:
- The left nozzle is closest to the fan, making it much easier to design a duct with two exhausts blowing at it. I don't see any practical way to make a similar configuration for the right nozzle, not even if the left heater block would be removed. The second exhaust would need to make a wide curve around the back, making it large, heavy, and very difficult to print.
- If you mostly print with one extruder and want to remove the heavy unused stepper motor to reduce ringing artifacts on single-nozzle extrusions, it is way easier to remove and reinstall the right stepper. (You do need to put something in place to trigger the X endstop.)
As with the dual duct, or any duct whatsoever, you must print this in a heat-resistant material because it is very close to the heater block, moreover this duct has even more material near the heated bed. I recommend ABS although it actually is not sufficiently heat-resistant if you want to use the duct during ABS or PETG prints. If you are able to print in polycarbonate, it is probably the best option if you often print with the bed at 110°C or the extruders at more than 230°C. However, the duct will probably hold up when printed in ABS if you add extra insulation (see post-printing section).
As with the dual duct, you should ensure the little hole next to the screw hole, is 2mm wide by reaming it with a drill or other tool.
This duct assumes your nozzles are at standard height, when in doubt you can re-level them with this tool, this is also correct if you have Micro Swiss all-metal upgrades.
To reduce the risk of deformation, you should apply some extra insulation. See the post-printing section on how you could protect the duct itself. You can also add extra insulation to the heater block (see photos for an example of extra insulation on the front side). This is also helpful to prevent the heater from losing its temperature due to air bouncing back on the platform or the printed structure while the lower layers are being printed.
Due to the special shape, installing this duct is slightly more difficult than the dual duct, but it is still quite straightforward. First slide it over the front X axis rod (tilt the duct if necessary to minimize stresses while doing this), then shift it in place and push it into the fan outlet.
A thin strip of rubber (like a piece of bicycle tire) under the little mounting tab can help to avoid that the duct vibrates and rattles.
If you have an older printer and yet have to install the blower fan, you may need to print the fan mounting bracket first.
Beware: this duct blasts a lot of air at your freshly extruded plastic. You may need to reduce printing speed or increase temperature for specific filaments. If you print too fast, the rapid cooling is likely to ruin layer adhesion, even with PLA. If you have a way to throttle down the fan, it is a good alternative to printing slower, but beware: even though your software may allow setting custom fan speeds, the FFCP does not have fan speed control, it is either on or off. You need to install custom firmware or add a PWM controller to vary the fan speed.
If you're going to do a long print with the fan disabled entirely, remove the duct to avoid that it will deform, especially if you're printing at very high temperatures, e.g. polycarbonate.
There may be updates on this design, use the ‘Watch’ button if you want to be notified.
If you appreciate the work that went into designing this duct, tips are always appreciated!
Same comments as for the dual duct: do not enable supports. Supports will block the inner passages, and the model is designed such that it will print well without supports. You may need some cooling to print some of the overhangs or the top layer of the main vent, for this purpose the stock duct should suffice. If you have problems with the corners of the print lifting, try a brim or a raft.
You'll notice that the left exhaust has a small triangular shape at its tip, which is only there to make it possible to print this without supports. Although it should have only a small effect on the airflow, you may get slightly better performance if you cut away this triangle with an Xacto knife as shown in this picture:
Protecting the duct against heat
If you're only going to print PLA with this duct, it will probably do fine if printed in ABS. Printing PLA does not require high temperatures, moreover the fan should be enabled all the time, which means the duct keeps cooling itself.
However, if you're going to print any filament that requires a very hot extruder temperature, a high heated bed temperature, or both, the duct will most likely deform from the heat, especially if the fan is not enabled all the time. Especially the left exhaust is vulnerable. If unprotected, it will stretch across the layer direction, and shrink in the other directions, and start warping upwards.
To mitigate this, I have tried applying some NASA-style thermal insulation to the critical parts as shown in the photo below. This is a layer of self-adhesive aluminium foil with a layer of kapton tape on top, and the tip of the left exhaust has an extra pair of such layers. I have yet to see how well this stands up against heat, but I expect it to be fairly effective. The aluminium should both reflect and distribute the heat, and the kapton should provide some extra insulation.
How I Designed This
I considered simulating the duct in OpenFOAM, but its learning curve is a bit too steep for something I will only be using once or twice. Therefore I used the same trial-and-error method as with the dual duct, testing exhaust shapes with the little windmill, as well as by blowing onto a water surface and a layer of fine dry sand. Eventually I ended up with an exhaust shape that, as far as I can measure it, blows air exactly at the place the other exhaust cannot reach. I would still like to do a proper simulation but I have no experience with this. Any help would be appreciated.
I noticed that the first version blew way too much air forward. I did most of my tests with the duct in free air, and neglected the fact that when mounted, the airflow would be inclined to get sucked against nearby structures. This did happen and it caused the heater and nozzle to struggle to maintain their temperature. This version improves upon this with a funky new exhaust design, and should also better aim its airflow in the horizontal plane.
Small update 2017/08/05: v2b
This is the same design but with a few minor changes that should make it slightly more robust, and also easier to mount with less risk of it cracking.
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FlashForge Creator Pro left single extruder fan duct by DrLex is licensed under the Creative Commons - Attribution license.
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- You must attribute (give credit) to the creator of this Thing.
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