Some infill not reaching walls ?
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@DocTrucker said in Some infill not reaching walls ?:
Have you done the checks for extrusion correction and single wall thickness?
Something is amiss. On the previous test prints I had excellent surface finish. This time, doing a vase print, I ran into terrible surface finish.
As it happens, I installed a new version of Cura so at this point I am not sure if the issues are related or not. I will have to do some more tests but am unable to do it this morning.Quite honestly, I had not considered under-extrusion because the prints, other than the one or two joints between infill and wall, were very nice. I did recently go to a new filament and never bothered to measure the filament diameter. I now realize that size is a bit of a problem at 1.68 mm which could very well have caused some issues. Even then, it's difficult to see why under-extrusion would cause gaps on only one specific section of a print.
I did notice that on previous prints, the two outside walls were not joined well. That part could easily be explained by under-extrusion but not the gap between infill and wall.Stay tuned for more tests but not right away ....
Oh, coasting is off.
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@burtoogle said in Some infill not reaching walls ?:
@jens55 said in Some infill not reaching walls ?:
Must be
... Got it downloaded, installed and it started up ok. It even flipped to the second printer without crashing ... wooohoooo
I will try running a print on it tomorrow.
Thanks!Unfortunately, it does crash when I loaded your .3mf file that you provided on the Cura forum. I have a workaround for that crash so I can make a new build that will load that project OK. I will do that now and put it on Dropbox.
It worked. No more crash.
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I backtracked to Cura 4.3 and backtracked some adjustments but no luck. The funny thing is that this issue only shows up on vase mode printing.
You can see proper wall building at the bottom and then it goes to excrement all of a sudden - very odd.
I also tried upping flow to 120% with no difference. I am currently out of ideas why this is happening because I printed in vase mode before with the 0.8 mm nozzle without any issues.Oh, I also reduced the trace width to 0.8 mm because I thought that maybe somehow that could have caused the odd vase print (I had only printed at 0.8 mm for vase mode before)
The sample you see was printed in vase mode, 0.8 mm width and 120% flow. -
OK, I think I am back on track. The issue was too much heat or too short a layer time. It would be interesting to understand why the first 15 or so layers printed fine and then it suddenly went to crap.
Now it's time to make sure extrusion rates are ok and once dialed in then I will reprint the model that was giving me issues.
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I get that with PLA if I forget the part cooling fan. The thin wall just gets too hot and goes wobbly.
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I did have the fan going but only at 60% and one layer only took 3 or 4 seconds.
The issue of the infill not meeting the wall unfortunately remains.
I tried up to 150% flow rate without the issue going away -
One last stab at this thing ... analyzing the gcode I get 14 mm3/sec extrusion rate with 0.8 mm trace width and 0.4 layer height and the selected speeds. I have PA set to 0.8.
To be on the safe side, I am assuming that the Volcano hot end is good to 20 mm3/sec.
How do I figure out the actual extrusion rate once the PA speed increases are kicking in? Am I likely to exceed the 20 mm3/sec magic number ?
I am getting slower and slower with the printing speed and I would hate to slow down even further just because PA increases the speed at the beginning. I would think that a short term speed increase such as PA needs should not require any de-rating of the printing speed ... but I have no clue ..... -
@jens55 said in Some infill not reaching walls ?:
I am assuming that the Volcano hot end is good to 20 mm3/sec.
Why assume when you can test?
https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+4:+Calibration/40#s177
I don't think that PA is likely to force you into exceeding the volumetric limit unless you're already really borderline. The volumetric limit isn't a hard wall, so even a little temporary excursion isn't very noticeable. The limit can also reduce itself due to cooling from pushing a lot of filament for a long duration. You can see the temp drop. But I don't think the short little ramp ups from PA are going to cause big issues.
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Thanks for that link. I will go through the calibration procedure as time allows in the next few days. Also thanks for your comments re PA and flow capacity.
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20mm/s on Volcano is OK if you have a decent extruder and extruder motor.
PA of 0.8 is on the high side and it can give you problems on infill. What are your retraction settings?But I would try a different slicer, just to eliminate the possibility of wrong settings.
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I only retract 1 mm and no retraction on layer change.
Can you elaborate how high PA can cause issues with infill ? -
See here: https://forum.duet3d.com/topic/6698/pressure-advance-calibration/136
The bottom test piece in first picture PA goes from 0 to 1 and you can see that you get gaps on the change from slow to fast movement when you come close to 1. You could have the same issue.
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I did have that originally when I hadn't changed the fast speed from 120 to 60 for the calibration run but at 60 mm/sec it was printing nice an solid at 0.8.
The speeds I am currently experimenting with are well below that so no, that isn't a factor.
Thanks for mentioning ! -
0.8mm track width maybe cutting it fine. I'd give 0.84 and 0.88 a go with a suitable reduction in speed to maintain volumetric rate.
Maybe worth double checking the dot code on the nozzle to ensure it is a 0.8 too. Worth bearing in mind it may have worn larger too, not done any glow in the dark or filled materials?
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Just to throw my 2c into the mi. you appear to have identified a very specific failure mode: ~5mm gap when starting a new infil layer. The variations to PA, infil overlap etc (to me) are skirting around the problem. Given that all other features print ok, that means that your retraction, PA and the slicer's handling of these things in general is good. My money is its on a specific action that is happening before the start of infil on a layer only. can you try the following.
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A simple print (not in vase mode) where you have set Cura to print the outer perimeter first in a layer (before infil). The idea here is to test if its the retract on layer change that is causing the issue, or some cura setting with the start of infil
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A different slicer.
I would turn off all the extra features such as different acceleration/jerk for infil as they just add noise to the testing.
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@jens55 said in Some infill not reaching walls ?:
no retraction on layer change.
Why no retract?
With such a large nozzle there's going to be some drool and pressure loss when extrusion stops and travel happens leading to weak flow at the start of the next line.
I prefer to retract at all opportunities and use the retraction minimum travel to set whether or not to do a retraction for very short moves.
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It was simply a setting that was turned off in an effort to remove all possible sources of the lag. Also, with PA st at 0.8, I don't really need retraction anyway.
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I did some more testing/playing, increased the number of E steps a little and then failed miserably in trying to determine maximum extrusion rate. My extruder doesn't clic and it becomes a guessing game. Since I have already guessed on 20 mm3/sec, I will stick with that.
As part of the extrusion testing I lowered layer height to 0.2 and testing showed the issue of infill not reaching the sidewall is virtually not present at 0.2 mm layer height but quite obvious at 0.4.
All this was done with the 'main branch' that Phaedrux suggested.I am tired of printing test prints and nothing real ..... I am done with the issue as it can be worked around in several different ways such as random infill start, connecting infill ends and of course different kinds of infill.
I ordered a big pile of PLA at boxing week prices and dang it, I am going to print stuff, lots of stuff, more stuff than is humanly possible ......
Thanks for all the suggestions and discussions - lots of good points raised.
My final thought - it's a hardware issue, super long bowden tube, very high extrusion rate -
Update:
Last we heard was: My final thought - it's a hardware issue, super long bowden tube, very high extrusion rate.
Today I can confirm that once the extruder was replaced with a BMG clone, all the issues went away!
I had seen filaments silently (no clicking) slipping but I had no idea of the extent of the problem. It wasn't just an occasional slip here or there but systematic and consistent slipping, mostly at the point when a new line is started and the filament is sharply accelerated.
Happy Happy !!!!! ......
Oh, I should mention that the slipping happened at well below the theoretical extrusion capacity of the hot end .... don't know at what point things start slipping but i'd take a guess at 30 or so percent of the the theoretical extrusion capacity.
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I replaced my second extruder today.
My pressure advance figures went all over the place in the past - even with the same material and same conditions. PA settings are now identical on both extruders even though one is running PLA and another is PETG.
The cause for all the problems, as mentioned before, silent slipping of the filament.
I am absolutely amazed at how much time I spent trying to figure out various issues I had with this printer when all it needed was a properly working extruder!
