I have an Anet A6, where I uploaded Marlin 1.1.9, because the manual filament change on the stock firmware was really bad (90 % of the times it clogged the hotend). I've tweaked it a bit, and I'd say it works fine, but I have a problem with my filaments.

I'm printing in ABS. I want to make a 3 mm black plate, with an orange text/image on top of it. I've been playing with a test print and I can't seem to fix one thing. I swap the filaments and purge the nozzle, but no matter how much I purge, the orange filament keeps getting dark form some remnants of the black one.

Here's a sample of the original orange filament and different attempts with filament swap during print.

print sample

The orange has a recommended print temp. of 240-255 °C while for the black one its 230-250 °C. I've tried purging the hotend at different temperatures (240 °C, 250 °C) and I've been purging ridiculous amounts (like 1 meter). At the point where the filament looked clean I've resumed the print and it still came out dark. The continuous purging didn't clean everything and the extrusions and retractions during printing probably scooped out more of the black filament.

Have you ever encountered such a problem? Any tips of effective purging?

For the record: Other mods to the printer include frames to make the body more rigid, tensioners, and similar - nothing of importance. I did however change the hotend to an E3D V6 look-alike with a silicon shroud and nozzles to match, but this was waaaay back. I've never had problems with either of these filaments when printing single-colored things.

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    $\begingroup$ I experienced the same with black and yellow PLA. Probably too much filament gets stuck in the heat break/nozzle. You need to purge more maybe. What heat break are you using? I expect the all metal ones to be more affected than the Teflon tube lined ones. $\endgroup$ – 0scar Dec 6 '19 at 11:04
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    $\begingroup$ Out of curiosity, does the orange look how you would expect when printed by itself? It's possible that the hetaing/extruding process is changing the color of the filament somewhat. $\endgroup$ – Tal Dec 6 '19 at 14:35
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    $\begingroup$ If your hotend is clogging then you have problems with the filament in use; this has nothing to do with purge method. I agree with @Tal that you may be running way too hot and "cooking" the orange color. $\endgroup$ – Carl Witthoft Dec 6 '19 at 14:48
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    $\begingroup$ Instead of purging through the nozzle, it might be a good idea to use a cold pull to remove a considerable chunk of the materia.. $\endgroup$ – Trish Dec 6 '19 at 15:43
  • $\begingroup$ This is my second spool of this orange filament and never had problems. Its definitely not burning in the nozzle. I never managed to do a cold pull - it always moves the hot end carriage, so i'd loose alignment, not to mentioned that i once broke the original Anet heat break this way. They're terrible anyway. Now I have a cheap replacement heat break, but it still has a ptfe lining. The strange thing is that I do purge a lot until the extruded filament is clean. After i resume printing it gets dark again, as if the hot end has the old filament deeply clogged. $\endgroup$ – Wojciech Dec 6 '19 at 17:10

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