high speed rotation - possible?

[JohnInOttawa 103]

Good morning everyone.  I have been asked to support an application (impeller) that will have a high rotation speed and clearly also pressure increase per function.

 

This is an experiment so vane design will be a function of safe RPM.  I have input to that value.

 

My first inclination was to say that FDM would not be able to achieve either the strength or weight balance required for anything more than very slow rotation.  Then I thought, why guess, when I can ask here??

 

Has anyone successfully created high speed rotating parts with their Ultimaker (3)?  If so, could you share what worked, what didn't, and advice on materials, safe limits on part size, RPM, etc?

 

Thanks in advance!

John

[geert_2 556]

I once got wounded by a tiny 50mm computerfan running at overspeed, so the blades were ripped off and flew all across the room. And that was a standard injection moulded glassfiber reinforced nylon fan... (It was running *way* overspeed...)

 

So, 3D-printing any propeller- or turbine-like blades looks like a risky business to me. Airplane propellers and turbines are carefully X-rayed for cracks and voids. FDM 3D-prints are by concept full of such "cracks" due to the way the molten "sausages" are laid down. Also, the surface of the blades needs to be very smooth to get a good airflow, and the airfoil shape needs to be very accurate, both which you won't get with a 3D-print.

 

I think you would be better off making a mould from a real model (thus a duplicate), or if it is a new design, from a carefully post-processed and smoothed 3D-print, and then cast it in strong PU or whatever composite you want. If you cast in a transparent material, you can see any bubbles. If you select a slow-curing resin, you can evacuate the bubbles by vacuum and shaking or tapping. If the mould is big enough, you can also add high-strength fiberglass or other fiber reinforcements, around which you cast. Just like in real airplanes or good safety helmets. Plastic injection-moulded safety helmets are worthless crap, but the good helmets made from composite-resin impregnated fibers can be hit by a heavy hammer several times without fracturing. They don't come apart, which is what you might want.

 

[JohnInOttawa 103]

Thanks!  That sounds like a good approach to me.  I might print off the original in a wax in that case, maybe make a 'lost wax' mold and use the clear resin as you suggest. 

 

Much appreciated.

 

John