Extruder Linearity

[deckingman]

@wilriker One more thing you could add is the maximum attainable extruder speed for the chosen micro-stepping setting. You'll likely come up against this limit for retraction moves, and possible filament loading and unloading, as these tend to be much faster than normal print moves. IIRC DC42 said that for these extruder only moves, somewhere in the region of 20KHz would be the maximum. To check, one can do M122 and for earlier firmware look at maxreps, with later firmware, look at Hiccups. I can tell you that with 256x micro-stepping on my machine, I can retract at 1,800mm/sec with max reps of 40 but not 3,600 which has max reps of 744. But if I set micro-stepping to 128x, then I can retract at 3,600 mm/sec without any problems (max reps down to 40).

[dc42]

@deckingman said in Extruder Linearity:

IIRC DC42 said that for these extruder only moves, somewhere in the region of 20KHz would be the maximum.

It's more likely that I said 200kHz.

[deckingman]

@dc42 oops - typo

[deckingman]

One other thing to bear in mind is that with high micro-stepping, you do lose torque. At least I seem to be when exploring the upper melt rate of what the hot end is capable of. It might be a problem if your extruder motor(s) is/are a bit borderline to start with.

Edit. Scratch that. Losing torque at high micro-stepping probably is the case but in this instance I had been testing Capricorn tubing and it had slipped back out of the heat sink a few mm. This left a gap for molten filament to get into and cause a partial blockage., which was why the extruder was struggling.

[wilriker]

@deckingman I will add max and desired extruder speed to it, that's a good idea! Not sure if I try to do this before Monday, though.

I think there is another typo in your post as I doubt you actually retract with 1,800mm/second than rather per minute, don't you? But then retracting in less than one millisecond could considerably reduce print time when doing lots of retractions.

What I also want to do is to transform the spreadsheet into a small web page that @dc42 is hopefully interested in integrating into reprapfirmware.org.

[deckingman]

@wilriker Yes you are right. Should have been 1,800 mm/minute (30mm/sec). Same with 3,600 mm/sec which should have been 3,600 mm/min. I blame it on a lack of caffeine

[wilriker]

@deckingman Oooh, no more cold coffee?! That's bad! That would be like out of tea for me.

[deckingman]

@wilriker Just a temporary hiccup. The Tassimo machine has been working overtime to rectify the situation.

[wilriker]

See https://forum.duet3d.com/topic/6156/guide-how-to-select-extruder-microstep-setting.

[Phaedrux]

@wilriker good stuff. I look forward to playing around with that.