Nozzle path is ok but some sections are not printed
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@Phaedrux said in Nozzle path is ok but some sections are not printed:
@jens55 I'm thinking it's related to PA and the long bowden tube combined with the fat nozzle and volcano. Perhaps in this combo pressure advance is backing off the pressure too much too soon.
While it could be related to the items you mention, I can't agree with the 'pressure advance is backing off too soon'. The issue happens after the nozzle has traversed a bunch of the model (to stay within the print) and it happens at the beginning of the new extrusion starting.
Further, PA seems to be right on the spot as the 'lines' pattern that starts and stops constantly shows nothing unusual.
Now it is quite possible that my fundamental understanding of PA is flawed in which case it would be nice to understand why a short stop of the filament flow followed by a start works ok but a stop flow followed by a bunch of non printing moves followed by an extrusion start would cause a delay.As mentioned earlier, I can only explain this in my mind if the filament in the nozzle had a chance to cool and expand a bit in the retracted position and the extruder had to work against the resistance of breaking that not-quite blockage.
I obviously am missing some magic incantation here someplace .....
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@Phaedrux said in Nozzle path is ok but some sections are not printed:
Do you happen to have coasting enabled in cura?
No.
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I just saw it first hand .... printing fine, a number of non printing moves and then, when it starts to print again, there isn't enough filament coming out of the nozzle.
This does not seem to happen if there are only a couple of short non-printing moves. It is definitively related to the inactivity of the nozzle.I will turn retraction off on my next print test ......
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Last test for now ... RETRACTION DISABLED, print speed 30 mm/s 15 mm/s for first layer.
I just saw it again .... after doing a number of long non printing moves because of combing, there is no filament being extruded when the printing moves 'should' be starting again. I just saw three lines (about 3/4" long each) that should be laying down material but behaving as if the nozzle was not primed. A tiny drip here and there before a line starts forming. Exactly the same thing that occurs at a bigger scale when the print first starts and it prints the skirt in order to prime the nozzle. This particular example was more of a missing print area then before. I am not sure why it went on for three lines before recovering and starting to extrude again.?????????????
Edit: The only thing that seems to fit is that there is enough material drooling out of the nozzle during the non-print moves that there is no material in the nozzle to print with.
There is no obvious excess material where the nozzle passed during it's non printing moves but it could very well be squishing/distributing so thin that I have not noticed it. -
Slow down the unretract speed?
I've never had good results with combing. I usually run with it off.
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@Phaedrux said in Nozzle path is ok but some sections are not printed:
Slow down the unretract speed?
I've never had good results with combing. I usually run with it off.
The last test was with retract disabled so I assume 'unretract' speed doesn't apply.
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With retraction disabled I'd imagine the problem would be worse.
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I think that this explains why the missing filament on the last print was worse (because of no retraction). Maybe I should try increasing the retraction ?
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No change with going to 2.0 mm retraction. I am now back to 1.4 mm.
I am now printing with no combing and 0.5 mm z hop to eliminate the stringing and so far things are actually looking pretty darn nice!
Although I don't have absolute proof, I am assuming that the liquid filament drools out of the hot zone during the combing moves and then, when it comes time to print again, there is no filament available because it leaked out.
I welcome suggestions how to fix this if there is a fix.Although I am currently printing in PLA and using Z hop is working ok, it generally creates a mess when printing in PETG and most of my prints are in PETG.
@Phaedrux, you indicate that you mostly print with combing off. Do you use Z hop for PLA to reduce stringing? What do you do when printing PETG - still without combing? Z hop ?
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I don't really have a stringing problem but I am using a 0.6mm nozzle and V6 titan aero. So less of a drool problem. 1mm retraction. Same for PLA and PETG. No z hop. No combing.
The reason I suggested lowered unretract speed is that I sometimes notice a bit of flow hesitation at line start with some filaments.
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Are you running a direct drive setup?
Well I can only hope that all my problems will go away when I switch to the BMG LGX extruder with a Mosquito clone hot end that should show up with the next boat from China (the BMG LGX will be here next week)
I have been waiting for a while to get rid of my bowden setup and finally decided to go for it when I saw the BMG LGX. -
Just pulled the latest print off the build plate. It is definitely the best print at 1.4 mm retraction, no combing and a 0.5 mm Z hop .... but it still had some stringing on it - fairly thin stringing and I could have probably removed that with a heat gun fairly quickly.
Anybody have any suggestions about reducing drooling or is this just something that comes with a bigger nozzle that one has to live with?
I am using a clone chimera setup with a clone Volcano hot end and a clone volcano 0.8 mm nozzle.
I would actually like to hear from somebody with a real Volcano hot end and a real Volcano nozzle and get their take on the drooling issue .... maybe it's just because it's clone stuff ..... -
@jens55
I read something about dynamic retraction, where the additional amount of filament fed back with G11 depends on the time spend between G10 and G11 (IIRC).
I think it was in the FW wishlist section.A big nozzle with anti-drool would make you rich. ( I would buy one
)
A long time ago I proposed to drill four 0.4mm holes close to each other instead of a single 0.8mm hole. (Only for the last mm or so)
That would result in the same cross section, but the sum of circumfences is twice as much. In my mind the circumfences are responsible for keeping the filament in.I'd use a big nozzle and long Bowden combo for Infill only, if I had a dual nozzle setup.
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@o_lampe, the nozzle you are trying to build is already available. I don't recall who makes it but I just tripped across it a few days ago when I was looking through a suppliers catalog.
It obviously doesn't come cheap. -
@jens55
Again my idea was stolen ... the world is a bad place[quote] It obviously doesn't come cheap.
Maybe it's not easy to build? Drilling is risky, waterjetting impossible. Maybe etching would work?
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@o_lampe said in Nozzle path is ok but some sections are not printed:
A big nozzle with anti-drool would make you rich. ( I would buy one
Someplace in the back of my mind there seems to be mention of nozzles with shutoff technology possibly spring loaded. That would prevent gravity from convincing liquid filament from drooling. I think that was a system in the early days of 3D printing and was likely abandoned because of reliability issues.
I am very fuzzy on the entire thing so don't take my word for it.I'd use a big nozzle and long Bowden combo for Infill only, if I had a dual nozzle setup.
There are a lot of parameters that are linked between nozzles (at least in Cura). I don't think you can run two different sized nozzles for the same print job without custom programming of some variety.
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@jens55 said in Nozzle path is ok but some sections are not printed:
I don't think you can run two different sized nozzles for the same print job without custom programming of some variety.
I've set it up in PrusaSlicer and sliced a big part. The result looked OK on the screen. The real advantage is, that you can use fine layerheights for the perimeters and print infill only every two or even three layers with big mama
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@o_lampe, I realize the incredible advantages. It would nicely combine resolution and speed and would be ideal for a lot of things. I just hadn't seen it before.
It would also be a great concept with smaller nozzles if for example you could use a 0.4 mm nozzle for the interior of a model and a 0.2 mm nozzle for the outside. All of a sudden you could combine high resolution with a reasonable print time. -
@jens55
Right! But I failed with my implementation of the chimera.
The second nozzle always scratches off the fresh tracks.
Now I follow the IDEX-route.
