Prusa i3 MK3S with MMU2S issue when selecting filament

General
1

With recent updates, I noticed that when printing to Prusa i3 MK3S with MMU2S, it asks me to pick filament from 1-5. I select it but then it goes ahead and try to load the filament all the way to heater block. Since I just hit print and heater nozzle is still cold, it keeps forcing to feed it through many times. After min or so it finally gives up and retracts. Little while after that, printer is heated up and ready to print so it'll feed again.

I think the selection of filament during initial print is a good feature but I think actual loading of the filament should be only done once the temperature reaches the optimal temperature.

2

こんにけは @Hiroaki_Morikawa!

This seems to be an issue with the Prusa firmware. Older firmwar versions pulled in the filament up to the extruder even the hotend was cold.
As a workaround I moved the "Tx" command to another position and heated bad and extruder beforehand in the Start Gcode section and also a sound as a signal to select the filament. This is my start gcode:

M115 U3.7.1 ; tell printer latest fw version
G90 ; use absolute coordinates
M83 ; extruder relative mode
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
M300 S440 P500
M300 S660 P500
Tx
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling

G21 ; set units to millimeters

;go outside print area
G1 Y-3.0 F1000.0
G1 Z0.4 F1000.0
; select extruder
Tc
; purge line
G1 X55.0 F2000.0
G1 Z0.3 F1000.0
G92 E0.0
G1 X240.0 E25.0 F2200.0
G1 Y-2.0 F1000.0
G1 X55.0 E25 F1400.0
G1 Z0.20 F1000.0
G1 X5.0 E4.0 F1000.0
G92 E0.0
3

どうも、早ζ€₯γͺθΏ”η­”γ‚γ‚ŠγŒγ¨γ†γ”γ–γ„γΎγ™γ€‚

I want to make sure I understand your reply correctly. Since this is a Prusa issue that I need to swap the start g-code on my slicer to have above statement, correct?

4

Yes, its is the start gcode for the slicer.
It works fine for me. A little more waiting until it's hot, but then it pulls in the filament as usual.

5

It is more convenient to place your Tx command between the M140 and M190 command. That way you do not have to wait with your filament selection until all temperatures are reached and the printer is heating up while you select your filament. The filament will load BEFORE your extruder and is fully loaded with the Tc lateron: this one is executed after the configured temperature is reached.

So:
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
Tx
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
M300 S440 P500
M300 S660 P500

6

I know, I had it before. But somehow the extruder denied to pull in the incoming filament.
Anyhow, I can try again.

I assume, that by a mod, the PTFE tube is 20mm too short now. and the filament chrashes into the gears.

I will do this:

EDIT:

At last, I put the Tx before M104/M140 else I get errors...