Unload script with 0.25mm nozzle - Ramming too punchy  

Unload script with 0.25mm nozzle - Ramming too punchy

Hi,

I've made some test prints with the new E3D Revo Six hotend and the full kit of nozzles.

With the 0.25mm diameter nozzle, the unload (at the end of the print) seems to be too punchy and let the extruder grind filament and bondtech gears skipping. Probably due to a too big amount of filament to "purge" (ramming?) just before unloading.

I use default PrusSlicer settings (v2.4.0) profiles, for MK3S+ and 0.25, 0.4, 0.6 and 0.8 mm nozzle (in MMU single mode).
Last firmware 3.10.1

In the end gcode script:

{if max_layer_z < max_print_height}G1 Z{z_offset+min(max_layer_z+10, max_print_height)}{endif} F720 ; Move print head up
G1 X0 Y210 F7200

---
G1 E2 F5000
G1 E2 F5500
G1 E2 F6000
G1 E-15 F5800
G1 E-20 F5500
G1 E10 F3000
G1 E-10 F3100
G1 E10 F3150
G1 E-10 F3250
G1 E10 F3300
---

M140 S0 ; turn off heatbedM107 ; turn off fanM702 CG4 ; waitM221 S100 ; reset flowM900 K0 ; reset LA{if print_settings_id=~/.*(DETAIL @MK3|QUALITY @MK3|@0.25 nozzle MK3).*/}M907 E538 ; reset extruder motor current{endif}M104 S0 ; turn off temperatureM84 ; disable motors

Is the red (---/---) part the "ramming" and cooling movements ?

How tho decrease this "punch" by lowering the speed and/or volume of purged filament ?

I understand that E2 is extruding 2 mm, with 1.75mm diameter filament it is corresponding to approx. 4.81 mm^3
Fxxx commands is difficult to evaluate the speed or duration of this movement, any ideas ?
I think something comparable to the ramming parameters curve you can find in the "filament sttings" in the PrusaSlicer.

If good unload parameters could be found for 0.25mm nozzle, it could be interesting to open an issue or submittal on the prusa github for a next update of firmware and/or PrusaSlicer settings updates. Because I thing that unloading commands from the LCD menu doesn't take in count the installed nozzle diameter.

Thank you for your advices and read you soon 😉

Ludovic