Breaking the mixer shaft forced me to disassemble version 7. It had leaked around the screws that lost AL in the last assembly. The mixer seal was still in perfect shape with no evidence of leaking even while I was feeding it without it spinning. That's really good news.

Decided it was time to make another one.

Designed and built an all metal version.

• Eliminated 14 parts.
• It's cheaper to make.
• The tolerances required are more lax.
• Reduced thermal losses.
• Mixer is half the size.
• Mixed volume is 1/4 what it was.
• You can take it apart without removing the resistors. :)
• You can align the mixer motor without taking it apart.

In the negative column, it required a press and building an assembly jig as much of it was press-fit together. The previous version you could put it together with a screwdriver and two allen wrenches.

It worked great the first day! Just ran some garbage white PLA I had through all 5 channels to clear out the machining remnants. Sealing was perfect. Feeding was fine. More torque required to push, but still manageable. I also decreased the size of the tubes feeding the mixer, and decreased my nozzle size, so it is hard to tell if increase in torque required was related to the 'no PTFE liner' bit or not. If I was building these with CNC, I would probably change one variable at a time. :) That day is coming..

I ran it for a couple hours with no issues.

Came back out today to do a color test. Three of the five feed tubes were jammed. Two were jammed badly enough to require removing the bowden tubes to clear them. One jammed again even after cleaning.

I think the issue is my tube size for my all-metal design. All I could find in small diameter stainless tubing locally was ~2.1mm ID. That leaves a good gap around my filament for the 'piston' to creep back up the tube into the cold area, as I also didn't provide an interior taper in the hot-end area. My feed tubes were also not polished. I was just hoping for the best, but expecting the worst. The worst happened.

The same thing basically happened with my PTFE liners which were ~2.0mm ID. There it didn't matter at all though. The PTFE gives a little and the cold start obstruction just pushes into the hot area and clears without you ever knowing it was there.

A friend of mine with Amazon Prime ordered some correctly sized tubing for me so shipping wasn't more than the part. (Thank you Ezra)

I get to try again in 2 days.