Bad Inconsistent Extrusion

JPH

Test using modified mini gcode: 8MMCYL_0.2mm_PLA_MINI_15m.gcode

Heaters are PID tuned. I'm not confident about the thermistor values. The bed uses a keenovo heater with built in 100k and the hotend is standard E3D parts.

Should the E3D thermistor be changed to these (T100000 B4725 C7.06e-8) and the bed stay with the default settings?

JPH

The file import tool didn't like the cura profile file type so I changed it to .txt

DOZER_PLA.txt

I varied coasting and pressure advance for different tests but the base profile is with no coasting.

JPH

As an additional odd note:
When I first installed the bondtech extruder the main gear turned with different amounts of backlash. Rotating it by hand it would tighten up slightly during part of its rotation then loosen and have a bit of backlash during other parts of its rotation. To see if it was a pinion gear spacing issue I tried moving the pinion further away from the stepper motor face but it didn't change. I also checked the bearings throughout but they were in good shape.

Phaedrux

@JPH said in Bad Inconsistent Extrusion:

Should the E3D thermistor be changed to these (T100000 B4725 C7.06e-8) and the bed stay with the default settings?

Yes. If you have the E3D thermistor you should update the settings, otherwise your temps will be off, which could explain some of the over extrusion/leaking.

Phaedrux

M350 E8 I0 ; test seperate extruder settings

I'd definitely stick to x16 with interpolation on the Extruder. Dropping or raising microstepping rarely solve anything.

Phaedrux

M82 ; use absolute distances for extrusion

Looks like you have your slicer set to absolute extrusion. Try setting it to relative extrusion. I don't think it will have an effect on your problem, but it's still the better way to go.

Also, have you calibrated the extruder?

https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+4:+Calibration/40#s165

JPH

@Phaedrux Thank you for saving the day

I went ahead and did everything you recommended, ran a new PID tune, and re-calibrated my extruder at the lower recommended feed rate.

The difference is night and day. I'm still getting some issues where Cura has dropped the feed for cooling but it is a massive improvement.

I bumped the minimum speed up from 10 to 20mm/s and that seemed to be the final tipping point. I'm not sure why that would make such a large difference though, unless its just preventing Cura from throttling the extrusion speed?

I might check later if changing firmware compatibility and gcode flavor to reprap would change Cura's behavior at those low speeds.

jens55

@Phaedrux said in Bad Inconsistent Extrusion:

M82 ; use absolute distances for extrusion

Looks like you have your slicer set to absolute extrusion. Try setting it to relative extrusion. I don't think it will have an effect on your problem, but it's still the better way to go.

Curious ... Cura allows to select relative extrusion but it also says that no matter of the setting, the gcode output is always absolute.
Apparently the slicer has an easier time working with the relative extrusion hence the ability to select the option.

Thoughts ?

Phaedrux

@jens55 Anytime Cura does something weird the answer is usually because Ultimaker.

jens55

Let me change my question a bit:
Assuming I use Cura as a slicer, should I select 'relative extrusion' in Cura?
Should I set M82 in config.g ?
Should I do anything else ?

Phaedrux

@jens55 I use cura and I set relative extrusion. I also have M83 in config.g. I assume you mean M83, because M82 is absolute. Also, even if you have M82 in config.g if you have cura set to relative, it will insert M83 into the gcode at the start anyway.

I don't think there is anything else to do.

jens55

Thanks !