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Posted · Blob after changing filament.

I keep getting blobs when I change filament to create lettering on some prints. I am using an Ender 3 Max and Cura  with the Post Processing script by Marcus Adams. After changing the filament and purging to get new color thru extruder, as soon as the nozzle gets back to the print, it creates a blob that gets smeared around. At first I thought I was leaving filament hanging on the nozzle but I watched it extrude as it was lowering to print. In the attached photo, you can see that the "T" is surrounded by the excess smeared PLA. Any help would be appreciated.

20250204_101821.jpg

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    Posted · Blob after changing filament.

    I'm not familiar with that post processor.  It sounds like it is purging over the model instead of at the park position.

    Have you tried using "PauseAtHeight" that is included with Cura?  ("By Height" doesn't play nice with adaptive layers or Z-hops but "By Layer" should be fine for any configuration).

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    Posted · Blob after changing filament.

    Is it possible that immediately after the purge, the pressure in the nozzle is higher than needed and when it starts the black part it overextrudes for a few seconds?

     

    I guess someone should look at the gcode.  Azbrewer can you post the gcode?

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    Posted · Blob after changing filament.

    Yes I can, the swap is at layer 5. It extrudes just as the nozzle starts back on the print.  Also, I tried using "PauseAtHeight", it wooks but I get an error that my firmware is not compatible. The print stops and I change filament and then I have to use the resume button in Octoprint to continue. I switched to the script I did because it supports the "M600" command which my printer likes. I am just trying to figure out the blob that smears.

    Untitled(1).gcode

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    Posted · Blob after changing filament.

    I have just tried it again and it is definitely extruding too much when it starts printing again after change. It is not part of a purge as it is right at the point where it restarts the job. I have changed from a bowden tube to direct drive, is that where my problem lies?

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    Posted · Blob after changing filament.

    M600 is all about how it is configured in the firmware.  If the firmware was originally designed for the bowden, then both the M600 retraction and primes are likely too much.

    From your gcode is this simple line:

    M600 ; Filament Change

    There are no additional parameters and so it is dumping everything on the "current firmware configuration".

     

    Go to MarlinFW.org and look up M600.  You will see that using other parameters you can configure it for your DD extruder.

     

    M600 [B<beeps>] [E<pos>] [L<pos>] [R<temp>] [T<index>] [U<pos>] [X<pos>] [Y<pos>] [Z<pos>]

     

    You may end up using the "Gcode Before" and "Gcode After" to get an acceptable outcome.  Depending on how that person wrote the script, you may have to hand code the extra parameters in.

     

     

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