Since I first thought of designing my own impeller for a small test pump about a week ago, I have test printed several versions of it.
The original print looked like this:
You can see the ragged edges caused by Slic3r’s imperfect coverage for source material while it was printing:
I decided to remove the ring around the edge since the impeller seemed too small to need it and tweaked the support settings to get it to support properly:
You can see that the support is more complete:
(I think these supports look pretty cool, too.)
You can see that the nearest corner of the impeller blade is warped upwards slightly in the finished print due to the way PLA plastic cools when printed in thin layers, so I decided to try adding to my design a tiny “support rod” under the corner of each blade that can hold it downward as it cools to prevent warping, but is small enough to trim off easily after the print finished.
I also did a few more tweaks to the dimensions today to fit the shaft we’ve decided to use and changed to a different support pattern because it seems to print faster with straight line support patterns:
This version took about 2 hours to print, which isn’t too bad. The small attached support rods seem to have done a good job preventing the leading edges from warping. I might try it on the trailing edges, too, in a future revision.
This is the finished impeller after taking the support material off but before some final sanding:
Now the biggest question is whether PLA is strong enough for use as an impeller, at least for some quick tests. If not, I can try printing nylon, which I’ve used successfully before, but is more difficult because it has a lot more warping. And nylon is unfortunately hygroscopic, which means it absorbs moisture from the air. Thailand is really humid, so this is another reason that nylon is more difficult for me to print with.
If I can get away with PLA for testing, I might be able to try out a bunch of different designs and measure the pumping efficiency of each impeller design before settling on a single one. Number of blades, size of each blade, and pitch are all parameters I’d be curious to try varying.
Once I’m happy with a design, I can try printing it with nylon or even machining it from metal.