Setting extruder steps per mm fails weirdly
I'm chasing down some pint quality issues and the first step on my to-do list is to verify that all of my extrusion parameters are correct. Firstly, that means calibrating the extruder steps per mm. I'm following this guide, not that there's anything special about it: https://mattshub.com/2017/04/19/extruder-calibration/ . I'm using octoprint as a g code terminal.
So my original setting as output by M503 was M92...E161.3, the default steps/mm value. I ran a 100mm extrusion and found that only 92.22mm went in, so I corrected steps per mm up to 174.91, saved the value, reset the printer, verified it was stored, and re-extruded 100mm. This time, 106mm comes out... what? So for giggles, I corrected the value again: 174.91*(100/106) = 165.01. Set and saved that value, and tried 100mm again. This time, 95mm went in.
What is going on here that I can't seem to linearly correct extruder steps/mm?
This is on the latest 3.1.0 firmware.
Re: Setting extruder steps per mm fails weirdly
Also, starting from a reset: the first time I run G1 E100 F100 (or any other feed rate), the extruder motor goes nuts. Like the feed rate is 100x - it just skips steps for half a second, makes a racket, then stops. Even if G1 E100 F100 is the very next command, that second try works fine. That seems like a firmware bug?
Re: Setting extruder steps per mm fails weirdly
Okay some more fiddling: I just noticed the following: s/mm=164.59, I ran G1 E100 F50, and the extrusion took 2:04.82 to finish, which is 104% of the 2 minutes it should have taken, and it extruded 104mm as well. Of course, I don't know how this is implemented in firmware, so maybe it doesn't indicate anything interesting that the feed rate is accurate. But it seems to me that it is interesting: if steps/mm were the only thing that's off, and I said "Extrude 100mm at 50mm/min" I'd expect that to take exactly 2 minutes regardless of how much filament extruded. So something is very wrong here.
Re: Setting extruder steps per mm fails weirdly
How do you extrude the 100mm ? Wtih octoprint ?
Why do you not use the Settings/Move Axisis/Extruder to extrude ?
Works fine for me.
Thomas
Re: Setting extruder steps per mm fails weirdly
I'm using the g code terminal in octoprint I guess mostly only because that way you can manually control feed rate too.
Re: Setting extruder steps per mm fails weirdly
So I tried using Pronterface instead. That eliminates the first-try grinding thing, so I suppose that has to do with octoprint's connect sequence or something. But the seemingly random extrusion times haven't gone away. It's as if real time control of the extrusion start/stop just doesn't happen. Like the processor wanders off and gets lost.