Some infill not reaching walls ?

jens55

I only retract 1 mm and no retraction on layer change.
Can you elaborate how high PA can cause issues with infill ?

OBELIKS

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.

jens55

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 !

DocTrucker

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?

T3P3Tony

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.

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
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.

Phaedrux

@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.

jens55

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.

jens55

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

jens55

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.

jens55

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!