Many thanks for the detailed write up! I actually scheduled a tier-2 Skype session for Monday to (hopefully) walk me through all this live. I’m a bit uncomfortable taking all this stuff apart when I’ve only had the printer for a few days.
thormj
March 28, 2016, 2:45am
27
I kept killing the PTFE tube trying to print ABS (it does work, but it has to go from heating->printing->cooling without delay and my bed was taking its sweet time heating, so heat made it up from the nozzle to the PTFE tube and…), so now I replaced it. You can probably prevent failures by adding a cooling fan like for the all-metal hotends.
E3D - Good, but I got one of the ones from a bad batch. And it’s not fast to get them…
B3 Pico Innovations - Great… but the tube is thin and I snapped it off inadvertently. Also kinda long.
Hexagon - Great and pretty durable. I put the thermistor in and bend it upwards before sliding the silicone boot on so it won’t fall out.
The E3Dv6 has a Teflon tube to make it easier to use with flex (and since the PTFE is in the “actively cooled” part of the hotend, it won’t fail like the Robo3D version), but I’ve found a great pair of solutions for that:
1. Bore out the throat and put a PTFE tube from the hobbed bolt down to the top of the hotend.
2. When the hotend is clear (I made the Nylon Cold Pull thing on Thingiverse… works very well), spray some WS2 or HBN lube down it, insert a cold filament and spin it around. Do that 3 times, and the inside of the hotend will be noticeably slicker (before lube, it takes pliers to do the cold-pull. Afterwards, you can do it by hand – still a tug, but by hand).
The other thing that was problematic with my original Robo3D was the hobbed bolt… mine came in a way that kept filling itself with plastic and would stop extruding (consistently) after 4 hours (grr)… replaced with one from eBay.
Thanks much for all that info. A lot to digest but I will keep it all in mind (and this page bookmarked).
It sounds like you might have pulled molten plastic into the upper portion of your extruder when you tried to pull it out. This might have caused the plastic to cool down inside the plastic portion on your extruder. If this is the case you might have to take it apart and drill it out “carefully!” This happened to me once, so now I pull it out slowly at the plastics lower transition temperature so that it doesn’t solidify inside the upper extruder. All I did was pull the cover off and removed the idler arm and drilled it out. Then I took a round tapered file and smoothed it out. Adding an oiler to your filament feed will help prevent this from happening again, or what I do is just occasionally wide some virgin olive oil onto the filament once in a while when I am extruding a lot of plastic to clean out the hot end during a change over. Hope this helps and good luck!
Thanks for the info!
I did my Skype session with them yesterday and we manage to clear it by removing the hot end, heating it up, cutting the stuck filament flush with the top of the hot-end, then pushing it through the bottom using the small wrench.
Interestingly though, after my successful test print that followed, while the extruder was hot I tried to remove the filament so that I could change it and it won’t come out. Doesn’t move AT ALL when I tug on it.
So, while I’ve cleared my clog, I seem to be unable to remove filament, and that worries me…
Q: Do I need a different tube in order to print with PETG? The tech on the phone yesterday said something about that…
Are you releasing the idler arm by pulling it back while pulling up on the filament?
I’m not sure what the idler arm means, but I’m not doing anything but pulling up on the filament (per Robo3D’s instructions).
The idler arm is the spring loaded arm that applies pressure to the filament against the hobble bolt that drives it into the extruder.
Ah, okay. No, I’m not using that trying to remove, only when I load. Is that the correct method?
To remove I’m just heating the extruder to print temp, then tugging straight up on the filament. It doesn’t move at all.
Is it possible the screws are too tight on the idler arm?
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!
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Okay, well… I will try changing filament again when this next print finishes. Thanks for the tips!
It’s the weirdest thing. I push that tab back, and yeah the filament pulls out nice and easy UNTIL I’ve pulled about a 3" length or so out and then it just stops and refuses to go any farther.
Any thoughts appreciated!
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.
thormj
March 29, 2016, 10:21pm
42
It’s on the high end, like nylon and ABS… If you have a grooved insulator tube, your chances are better. If you go from bed heat to head heat to print (not the other way around), your chances also go up… Otherwise heat will travel up the filament and melt the ptfe tube.
What would the remedy be?
thormj
March 30, 2016, 2:34am
44
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:
Pull up the filament as far as it goes
Cool the hotend (just to make it easy for the next bits)
Remove the hotend.
Push the filament down and clip the ball off it so you can remove it.
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!
thormj
March 30, 2016, 2:37am
45
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.
