Tuning retraction and unretraction speed?



  • How are others doing this? As fast as possible without stepper stalling? Any detrimental effects from too fast? How to know when different retract and unretract speeds are needed?

    I suspect that an over extrusion after retract maybe indicating my settings are not ideal. This is not general over extrusion as I can see between some of the extrusion lines on the upper solid infill.

    12V Ormerod 2 hotend, Ormerod 2 extruder with herringbone gears. 2.0mm retract, 3600 speed on both. No additional negative unretract as that gives me gaps in certain circumstances.



  • I don't know how relevant other peoples settings or findings will be to your machine. I think it's one of those things that are very dependent on hot end and extruder design and non-Bowden set ups are likely to be very different to Bowden set ups - especially those with long tubes.

    However if it helps, on my machine I run high micro-stepping to give the extrusion resolution needed when mixing small percentages. So speed is limited by the step pulse frequency (about 200kHz) which in practice means about 1800 mm/min @256x micro stepping or 3600 mm/min @128x micro stepping. Having said that, either speed seems to work fine and I see no gain from using lower micro-stepping and higher speed. I've never noticed any difference with asymmetric retract/un-retract speeds (but that's my machine with a Diamond mixing hot end, multiple extruders and firmware retraction).



  • Yeah, got a feeling it's a case of pile on. Just trying different test pieces. Interestingly the seam was neater (not necessarly smaller) with higher speeds on my latest test which is counter-intuitive to my initial theories.

    I think pressure advance may be causing me issues too as the infill/perimeter overlap needed to be high to avoid gaps. Dropped that from my next test where I'm looking again at additional unretract.



  • If you have a PanelDue I've made a set of macros that makes it a lot easier to adjust parameters on the fly during a print to fine tune.

    https://forum.duet3d.com/topic/5993/firmware-retraction-tuning-with-macros

    There's a full set of macros for tuning most print parameters as well as just retraction.

    On my Titan Aero with 0.6 nozzle and 0.9 degree motor, I use x64 microsteps and 0.85mm retraction at 3600mm/min and 2600mm/min unretract. Depending on the material I might use a bit of extra prime on unretract, usually PETG.

    I used retraction towers to find the base settings, and they seem to work fine for most materials and models. If need be I'll change the settings during the print, and then transcribe those retraction settings into the filament specific start gcode in Slic3r.

    Also, don't underestimate the benefits of pressure advance and a fast travel speed on retraction tuning.


 

Looks like your connection to Duet3D was lost, please wait while we try to reconnect.