No, your not doing it right! Take one hand and put your middle and index fingers on the spring screws, while with your thumb pulling back on the arm. Then you are releasing the pressure allowing you to use your other hand to pull the filament slowly up and out, so as to not pull molten plastic out with it!
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Gah, seriously!? I asked both techs I talked to what the proper procedure was, and specifically asked if I should be pushing the latch back like I do when loading, and they both said “no, just heat the extruder and gently pull up on the filament”.
Sigh.
Lol! There is the alt method of reversing your extruder stepper motor, but this would be more awkward and possibly pull molten plastic up with it!
Okay, well… I will try changing filament again when this next print finishes. Thanks for the tips!
3" sounds like the transition point between the hotend and the housing. Check alignment between the two. A good way to check is by removing the hotend. If its significantly galled by the threads then it wasn’t installed properly.
To reiterate - pull back on the extruder idler to release it from the motor. If you’re getting a hang after 3", it sounds like you need to unscrew the springs on the idler so you can get the filament out (it sounds like there’s a molten ball at the end of the filament that doesn’t want to go between the gap in the idler and the hobbed bolt).
If you unscrew the springs (and release the idler completely) and it still doesn’t want to come out, you have to cut it and remove it in 2 pieces:
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Pull up the filament as far as it goes
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Cool the hotend (just to make it easy for the next bits)
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Remove the hotend.
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Push the filament down and clip the ball off it so you can remove it.
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Reinstall the hotend.
Generally, when I’m pulling used PLA out, I only let it heat to 100C or so before pulling, that way liquid PLA never gets in the teeth or gums up the mechanism.
If this happens a lot, I’d make a PTFE support tube for the Robo3D; see PTFE support for Robo3D | Atlanta3D (I’m adding pictures as I write); bonus is that now Flex won’t kink in your Robo3D!
PS. I recommend replacing the 2 Phillips head bolts that hold the hotend in place with socket-head-capscrews (Allen bolts) – available at McMaster or Home Depot. Trying to worm out a stripped head is really annoying.