Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 09:52PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 09:57PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 09:59PM |
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JamesK
It's kind of difficult to tell from the photo - can you see where the gap starts and stops? If it's the extruder then the start/stop would probably be random compared to x/y, but as far as I can see the missing filament seems to always be for a complete layer. That almost suggests a Z axis problem rather than the extruder?
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 10:26PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 10:33PM |
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JamesK
OK, so here's a really tough thing to try and work out - can you count layers and see if the missing layers are preceded by one or more squashed together layers? That might indicate that your z axis is binding. How thin a layer are you using, and more interesting, how many steps does that work out to?
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 21, 2015 10:38PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 10:39AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 10:48AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 10:54AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 11:04AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 11:07AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 06:59PM |
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JamesK
Any chance of capturing the problem on video? That might give someone the insight they need to help. Might be tricky to get a good view though. We'd probably need a good view of the print head, the Z motors and the nuts where the Z threaded rods connect to the X axis, all at the same time!
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 09:53PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 10:09PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 22, 2015 11:06PM |
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JamesK
Wow, that's really strange. It sure starts off nice, and the speeds look very moderate. It's obviously a single perimeter wall, so what's actually in those gaps? There must be something or it would just fall apart. Is it that the filament has just changed colour, or become more transparent, or is there actually much less of it? As far as I can tell from the video the head movements don't look any different in the good areas and the bad. Does the extruder temperature vary much during the print?
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 08:29AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 08:47AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 08:48AM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 11:08AM |
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cristian
If you try to pull and release the wires of the thermistor repeatedly during the print (without damaging them of course), does the temperature read change abruptly?
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 12:36PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 12:43PM |
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cristian
If you clearly noticed that the filament stopped flowing from time to time, then it is not backlash.
Moreover, backlash is not "cumulative" in the sense that if at some point you have some apparently missing extrusion, at some other point you must have an excess of extrusion that compensates for that, and according to your description this is not the case.
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 12:55PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 01:06PM |
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cristian
Looks like jamming, so it may be any of the problems previously mentioned. You already excluded some of them, the next to try is for sure temperature.
To do that, I usually connect another thermistor to the board and I make it slide inside the hotend in the place of the filament. Then I make a dry print to see if the two thermistors give consistent reads during the whole print. It is not a 100% sure procedure but it can spot some faulty wiring/thermistors.
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 02:09PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 02:30PM |
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cristian
If the fan is blowing constantly and you correctly tuned PID parameters, the graph looks suspicious to me. There is something wrong with either temperature or its detection in my opinion. Or your thermistor is very, very imprecise but accurate (unlikely).
I had an issue with wrong temperature detection once, and in the end I had to re-wire the thermistor: temperature reads were drifting by 20-30 degrees, but the graph of course did not show it because of PID corrections. Besides jamming, the problem is that if the temperature is drifting a lot and you don't notice, you may melt something near or inside the hotend.
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 02:37PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 02:40PM |
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cristian
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geemoto
but the nozzle fan may be turning on and off.
May you produce the same graph with the nozzle fan also constantly on (or off)?
It is not optimal for printing quality, but it may remove some noise from the graph.
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 05:19PM |
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geemoto
Hmm, that's interesting. I could take the bed thermistor and kapton tape it to the hotend, it probably won't read the same temperature - but at least it should remain stable.
Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 05:24PM |
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Re: Inconsistent extruder feed, jams - tried new hotend with no luck June 23, 2015 05:27PM |
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geemoto
I realized that I actually have the extruder output data as well, so we'd be able to see if the extruder was simply outputting more power to compensate for the temperature swings, it doesn't seem to be the case - at least not to a huge degree