If you run vertically you don't need the guide, that's correct.

I'm planning to donate/loan the operational machine to my local makerspace, and would likely end up mounting it vertically on a wall or post.

For now, it's just been running horizontally on the edge of my workbench - only about 30" from the floor. Perhaps operating at the height you suggest (and vertically so the extrusion doesn't kink as much while soft) will be good enough that a winder won't be needed. Probably best to just try it and see.

If the nozzle is ~48" off the floor and there's nothing in the way on the way down (table legs, etc) you shouldn't need a winder. I don't use on, and Iv'e extruded a few hundred kg. You also might try moving your filament guide a bit closer to the nozzle.

Yes, the power supply gets quite toasty. It isn't super efficient, but is within ratings. It is rated for 150% of the Filastruder's current draw, so it isn't being overloaded.

I'm running through a day of extrusion to clear out contaminants before I try making any filament for actual printer use, but so far so good!

It's pretty clear though that I need to use a winder. I can't let this sit for more than 10 minutes before the coil twists badly on the floor and causes either a kink, a thick/thin section, or an outright knot of filament at the nozzle exit.

Also, is it normal for the power supply to run very hot? Almost too hot to touch with bare hands - about like bare metal left out in the July sun.

If you contact me through the contact form on the Filastruder website, I can send you a square shaft/gear assembly. You pull the back off the gear motor and swap it out. The only other option is to try a thicker washer.

Even though it was clearly slipping, I had a heck of a time getting the socket off of the D shaft. But eventually it came off and as you can see, the key is very deformed:

What should my next step be? Do I need to try a different motor shaft?

The auger should slide backwards to compress the bearing. Once slid backwards, it will stay that way from the plastic in the barrel. You've assembled it fine, you just haven't slid the auger backwards to compress the thrust bearing.

I took the insulation off of the collar to reposition it properly. I'm guessing that the heating band is improperly installed, and should NOT be flush with the rear edge of the iron fitting like this? It should probably be towards the forward part of the iron fitting, perhaps flush with the front edge of it, yes?

Also, i rebuilt the flange assembly but this doesn't seem right. With ONLY the nylon spacers between the flanges, the compression bearing is extremely loose. You can see in these next two photos that there is probably a half centimeter of play. I'm not sure what's wrong here, but it definitely doesn't look right?

I'll need to remove the heater collar and iron fitting that attaches the nozzle to the barrel then.

It should be sticking out 1/4" with the thrust bearing compressed.

Don't worry about the spacers on the picture, you have an older revision than pictured.

I'll check for slippage of the socket as soon as I get a chance to.

And I'll change the nylon / lasercut spacers as you suggest before I run it again... and I guess I should also be able to measure the auger as it exits the barrel since I'll have those bolts pulled anyways. If I understand correctly - by "sticking out of the barrel" I believe you mean where that collar is attached (can't be seen in my photos because it is hidden by the double walls of MDF behind the forward flange).

It is definitely assembled incorrectly. The white spacers go between the flanges, not behind the back one. The lasercut spacers can go on the back of the back flange if needed.

The 1/4" sticking out refers to how much of the auger sticks out of the barrel (so the other end from where you measured).

I'm still 95% sure the hex socket is slipping based on the other things you described. Just because you can't get the hex socket off doesn't mean it isn't slipping. Leave the hopper mostly empty so you can watch the rotation of the auger. Mark it will a sharpie, you should see 3-4 RPM.