Machined a new impeller. Actually, machined three new impellers. The third one turned out.

Managed to lose the <1mmx2.5mm stainless steel collar I had so meticulously machined to fit my impeller shaft to help with sealing the latest version. It kept spinning on the shaft which defeated it's purpose. The only reliable way I found to keep it in place with the temperature shifts it will experience was to get a perfect friction fit while my collar was torch hot. I made a tool to remove it without damage and popped it off so I could use to it on the new impeller.. I heard it hit the floor. It's now keeping all my un-matched socks company somewhere. I've decided against making a new one and I'm going to try a larger PTFE seal to take up the space. PTFE is easy..

When I tried out my new impeller, it exhibited exactly the same issue as the old one. It contacted the walls of my mixing chamber intermittently when spun.

Turns out the old impeller was probably fine. I had just failed to clean all the melted plastic out of the mixing chamber. The last thing I printed was in clear and as I'm running out of the high-temp thermal compound, I didn't burn it out like I usually do.

Duh.

I've been pushing for smaller and smaller mixer impellers as the smaller the impeller, the smaller the volume of mixed filament, and the faster the color changes will be. I still get perfect mixing, and I'm now at ~2mm for my mixer..

I've gone past the limits of what I can reliably do in my garage, and I have been making up for it with iteration. Example... when I turned the last new impeller shaft, I had to let my thumb drag on the chuck to keep the play in my bearings from ruining the part.

So, I've decided to take a step back. When I eventually destroy this version, I'm not going to sweat building it bigger so I can machine the parts on the first pass with what I have to work with.

Once I can afford to replace my aging tools, then I'll see how small it can go.