Printed Model of Motor Cooling Fan Breaks Apart When Operating

[JimmyJack121063]

I had a model maker design an electric air compressor motor cooling fan due to the fact that I broke the original one and they are now obsolete and no longer available. The fan mounts on the end of the crankshaft that turns the air pump, which is on the end of output shaft of the electric motor. The motor is 3450 RPM. The guy who designed the model has made several modifications to make it stronger, but each one has broken into several parts after a few minutes of operation. I have noticed that if you hold the fan in front of a light, you can see several pinholes in the blades. I have tried increasing the infill to 100% and changed some of the strength settings to no avail. The fans still break apart after a few minutes of operation. Does anyone have any ideas of how to correct this problem or is a 3D printed fan just not going to hold up to the axial forces? I am printing this with PETG and have used both a 0.4 and a 0.6 nozzle.

[fred_dot_u]

It's possible that a nylon version of this fan would hold up better, but nylon can be challenging to print if you are the printing resource. As you are using PETG, another option would be to salt-anneal your prints which involves printing to 100 percent infill and burying the print in a ground salt bed. I've purchased and tested a coffee grinder by placing salt in it and found it generates very fine powder, suitable for this operation. You'd have that additional expense but they aren't particularly expensive. If you decide to go that route, seek a true grinder, not a chopper type mechanism. It's also important to clean out all the salt after done with the session as it will corrode the internal components when exposed to the slightest ambient humidity. The link includes a YouTube video examining the strength improvement. If you're satisfied with the appearance using a 0.6 mm nozzle, that's going to be slightly stronger than the 0.4 mm version.

If you pursue this option, please post your progress and results.

[JimmyJack121063]

Thanks for the info. I am having a printing service print this model in nylon for me and if that one does not hold up I will try the salt annealing process.

[airscapes]

you did not say where the part is failing. Are the blades coming off the hub? I would have added a fillet where the blade meets the hub to make that area much thicker. 3d printing and parts that taper are not the greatest do the the printing by layer.. so you unfortunately need to use very thin layers to get the tapered area as smooth as possible. The issue with that is you add more places to delaminate. Would it not have been possible to fabricate a mount directly behind the crank shaft to mount an electric fan to provide cooling? How big is that fan? Looks like only a few inches across.. something like a 120mm AC Rack cooling fan.. something like this https://www.amazon.com/SXDOOL-Coolin...f&gad_source=1

[JimmyJack121063]

you did not say where the part is failing. Are the blades coming off the hub? I would have added a fillet where the blade meets the hub to make that area much thicker. 3d printing and parts that taper are not the greatest do the the printing by layer.. so you unfortunately need to use very thin layers to get the tapered area as smooth as possible. The issue with that is you add more places to delaminate. Would it not have been possible to fabricate a mount directly behind the crank shaft to mount an electric fan to provide cooling? How big is that fan? Looks like only a few inches across.. something like a 120mm AC Rack cooling fan.. something like this https://www.amazon.com/SXDOOL-Coolin...f&gad_source=1

I will take a look at using an auxiliary fan like you suggested as I don't believe any 3D printed fan is going to be able to withstand the 3450 RPM of the pump. The fan is 138 mm. Blades are breaking in the middle of the blade. Thanks.

[RC_CadMan]

Excuse my ignorance here. I use resin printers. Can the layers you print be programmed to go in opposite directions like a sheet of fabric/fiberglass/composite? You definitely have a week point/joint in the material that is leading to catastrophic failure.

[JimmyJack121063]

Excuse my ignorance here. I use resin printers. Can the layers you print be programmed to go in opposite directions like a sheet of fabric/fiberglass/composite? You definitely have a week point/joint in the material that is leading to catastrophic failure.

It may be possible, but it would take someone smarter than me to figure out how to do it.