I wanted to challenge myself a more delicate part, so I decided to machine the impeller from Pocket NC's tutorial section. I was thinking about going through the instructions and follow along but decided against it as I wanted to see what I could come up with on my own and only reference it when in a pickle.
I didn't have large enough stock at the time, so I just scaled the part down by 20% so it would fit in a 1.35" square block. I then created seven angled planes along the Z-axis, each facing a different arm of the impeller. I used adaptive clearing on each of those faces with a 1/8" bull nose bit to remove the bulk of the material, leaving 0.1" stock to leave.
Since I had some weird angles, the spindle was coming in at I ran into a slight issue I've never run into before. When loading the toolpaths, I noticed when coming in at a corner; it would cut as if it was a face perpendicular to the end of the bit, this meant it would cut a bunch of air before touching the stock. I was able to fix this by going into the rest machining area. There I changed the setting to "from stock setup," which meant it would only cut from the stock setup and pass through the air without spending time cutting it. Thankfully it wasn't an issue for the rest of the toolpaths as all I had to do was select the "from previous operations," and it wouldn't recut the same areas from different angles.
Then I took my 1/8" ball endmill for final finishing passes. I used a parallel toolpath and set the stepover to 0.01" and 30"/min, which ended up being a bad idea as the fins of the impeller where so thin that one of them shattered from the vibrations. I then cut the speed in half and reran it, the same outcome. Finally, I decided to just cut the stepover in half at 0.005," and that worked much better. I ran it at 30"/min and had an immaculate finish.
