Colour changing  

New Member

Hi, the one pain I've found in colour changing is the residue. The extruder goes into the corner and does its business successfully. It asks to put in the new filament and asks if the new colour is showing. It extrudes some filament which is easy enough to remove. BUT it then gives out a bit more on the way back to the print which if low, is very difficult to remove and can ruin further printing. Could you include in the gcode so that the extruder returns to the front left and extrudes a bit of filament before printing in order that this doesn't happen? Not removing the excess so that it all gets removed together doesn't work because of the differences in temperature making it snap off still leaving the excess. Hope you understand!

Thanks loads, Philip


Posted : 03/06/2020 9:37 am
Prominent Member

This "feature" is part of the firmware and can not be controlled by g-code. Some sees this as a plus avoiding holes in perimeter (PLA). Other sees this as a problem as the extra extrude can be dragged around and make more damage than good (PETG).

The extra extrude has been discussed on the forum and reported as an issue several times:

[BUG] Extra extrusion after filament change #2502

Have a look at my designs on Thingiverse or on PrusaPrinters ;)...
Posted : 03/06/2020 10:40 am
New Member

Then why can't the firmware be changed to reflect this? It happens to me on PLA as well as PET so would seem more like a fault. If the extruder was made to go to the home point and do the initial line, surely this would prime itfit the new colour?

Posted : 03/06/2020 6:37 pm
Noble Member

Workaround: Don't remove after the first extrude. Hold on to the strand and don't pull it off until it is about to touch the print again. 


Since you left the first longer bit attached, pulling it removes the additional extrude easily.

Posted : 03/06/2020 6:54 pm
Famed Member

The firmware could be changed to work differently.  However the printer cant do the prime line as you suggest as depending on size of print if it went lower to the plater after the colour change the extruder could collide with the model. 
If you read the github posts about this you will see that the firmware is specifically written to do this.  While you and others may not agree with this process that is the way its been designed on purpose.   iirc you are supposed to grab it with tweezers before that final ok command and as it moves away it gets cleared.

You could start a campaign to get loads of people to request the change by piling on to the issue on github but beyond that the software is working as designed so the developers arent going to consider it a bug until popular opinion changes their outlook.

Posted : 03/06/2020 6:56 pm
New Member

Thank you for your help anyway. It's just very difficult when the extruder is very low. I appreciate your comments. I mentioned this on the Facebook group and received many replies to this topic that it was happening to them as well. 

Posted : 03/06/2020 8:08 pm
Eminent Member

You can add a Z movement to the M600 code to give you more vertical space to work with.

Posted : 05/06/2020 2:08 pm
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