The heater band and other parts are not a limiting factor until you talk about quadrupling throughput.

Power scales with the cube of flowrate.

I wouldn't say you need to babysit it, just peek in on it every now and again.

I just wonder if it is worth the effort and cost of making it variable.  Does the set rpm of 2.5 extrude at the most efficient speed?  Would going with a higher rpm have anything to do with increasing the speed of the extrusion at all at this point?  Is it just the temperature of the heating band at this point?  I've read through most of the posts and I see the ramen effect happen because of high temps in conjunction with the type of material being extruded but no mention of the speed of the motor. 

You upgraded the motor on later revisions to go faster.  I wondered what the limit would be on the rpm in regard to the current heating band and setup.  With a variable motor, you could play with it to see exactly how fast you could extrude and still get quality filament.  You obviously did tests to come up with the original motor but then came out with a faster motor later on.  Now that the filastruder has been tested more by different people and different materials and with your idea of a new motor....I was just wondering how far it could go without changing the rest of the extruder.

But slow it down, no.  I'm about trying to speed it up.  I understand about not leaving the extruder running unattended but having it set up in the workshop and just staying in the workshop all day to get a spool of filament doesn't work with my work habits.  I can't babysit the machine and I can't leave it.  I'd rather start it, work on a project for 4 hours or so and then stop it and have a spool of filament.  Maybe its just too early in developement as a process to get that kind of speed from a DIY system.  I can live with small bits of filament until then but I may have to work on a fussion splicer.

Stated differently, why would you slow the motor down?

Absolutely. Next version will do away with the mechanical fuse by using a motor with a square shaft, and a PTC fuse. That's about a month away, though.

Count me in!

Again, in practice the motor should not be stalling.

http://en.wikipedia.org/wiki/Resettable_fuse

A regular fuse does not self reset, it blows once and is done.

Really there's no reason to fuse the motor as long as you don't start it without letting the polymer get up to temp, and you use an appropriate temperature for the polymer you're trying to extrude. Really either of the above can be disregarded if you just hang around the first minute or two of extrusion to turn off the motor if it stalls.

The new motor will trip the overload protection on the power supply before reaching stall current.

Lesson learned: a loud crack followed by no more extrusions, check your washer on the coupler:

The washer was originally intended as a mechanical fuse, to save the motor if it stalled while also allowing for misalignment. I've run one of them them over 400 hours now.

One user had luck with folding up a strip of paper and using that as the key. I have also had luck using a dowel pin, set in the corner of the square, with the flat side of the motor shaft slid against it.

In hindsight, the better option is probably a PTC fuse set for the stall current, and a dowel pin as described above.