Filament change using M600 / Filament extrusion before restart print
 

Filament change using M600 / Filament extrusion before restart print  

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Markarndt
(@markarndt)
Active Member

Dear,

I print some parts with different filament colors, so layer 1~10 are in blue, 11~45 in grey, and then from 46 onwards again in blue.

In Prusaslicer I added the color change, which will add an M600 in the Gcode.

What happens now is:

  • after printing Layer 10, the Extruder moves to a position for Filament change
  • I have to unload the Filament
  • confirm that unload was correctly
  • Load new filament
  • remove the extruded filament under the nozzle
  • Confirm that loaded correctly

Now it starts to get strange, cause before the Extruder moves back to object to resume the print, again filament will be extruded.

Why is it happen? I tried to remove the extruded filament before the Extruder moves, but it doesn´t make any sense to me.

I even generate the M600 manually, means but editing the gcode in text editor. But same behaviour.

Any idea how to avoid this?

Kind regards,

Arndt

Best Answer by Neophyl:

@markarndt

Its part of the printer firmware and is designed to work like that.  You cant alter the behaviour unless you want to modify the firmware yourself.

If I recall correctly the reasoning is as follows

it primes the extruder to resume printing with the new colour, you are supposed to gently grab the previously extruded filament without removing it so that when the extruder does move back to start printing and ejects that little bit extra it gets pulled away as its attached to the bit you are holding.

So the correct sequence should be

  • after printing Layer 10, the Extruder moves to a position for Filament change
  • I have to unload the Filament
  • confirm that unload was correctly
  • Load new filament
  • remove the extruded filament under the nozzle   <dont do this
  • Confirm that loaded correctly
  • Grab hold of the extruded filament, use tweezers.
  • Wait for extruder to move back to printing position and extrude the extra bit
  • this pulls off all the excess and it starts printing again
Posted : 17/11/2020 11:10 am
Markarndt
(@markarndt)
Active Member

Remark:

Printer is i3 MK3S

Firmware 3.9.1-3518

Posted : 17/11/2020 11:23 am
Neophyl
(@neophyl)
Famed Member

@markarndt

Its part of the printer firmware and is designed to work like that.  You cant alter the behaviour unless you want to modify the firmware yourself.

If I recall correctly the reasoning is as follows

it primes the extruder to resume printing with the new colour, you are supposed to gently grab the previously extruded filament without removing it so that when the extruder does move back to start printing and ejects that little bit extra it gets pulled away as its attached to the bit you are holding.

So the correct sequence should be

  • after printing Layer 10, the Extruder moves to a position for Filament change
  • I have to unload the Filament
  • confirm that unload was correctly
  • Load new filament
  • remove the extruded filament under the nozzle   <dont do this
  • Confirm that loaded correctly
  • Grab hold of the extruded filament, use tweezers.
  • Wait for extruder to move back to printing position and extrude the extra bit
  • this pulls off all the excess and it starts printing again
Posted : 17/11/2020 11:50 am
Markarndt
(@markarndt)
Active Member

@neophyl

Thank you for your fast answer.

Concerning the firmware modification: I don´t think that the printer will ever work again when I touch this 😉

I will reslice my print tonight and try again using your recommondations.

Thank you!

Posted : 17/11/2020 12:11 pm
Neophyl
(@neophyl)
Famed Member

I think this has been raised as an issue multiple times over on Github and each time the issue has been closed with it being stated its designed like that.  I just remember seeing the issue and the reasoning and how you are 'supposed' to do it.

Not that it actually makes any sense to me really as I would question why that extra bit is  need to extrude as surely confirming that the filament is correct will have already primed the nozzle.

Posted : 17/11/2020 12:26 pm
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