Some infill not reaching walls ?

Phaedrux

Nozzle size? 1mm wide lines is pretty intense.

Slicer?

Filament type?

Speed?

Infill pattern?

jens55

@Phaedrux said in Some infill not reaching walls ?:

Nozzle size? 1mm wide lines is pretty intense.
0.8 mm
Slicer?
Cura 4.3
Filament type?
PLA
Speed?
60 mm/sec but it never actually gets to that speed
Infill pattern?
lines

Done a bunch more tests and the missing infill happens at the beginning of an infill line.
I even went so far as to double (from 0.4 to 0.8) the pressure advance but it didn't seem to matter. There is a very distinct lag between the nozzle starting the infill line and material being extruded.
I will try connecting the infill lines and see if that gets me anywhere.

Thanks for your help !

jens55

Connecting infill lines doesn't help ... well it sort of does in that a connected line is a good line but wherever the line starts there is that delay again.
Changed to zig zag infill - same issue in that wherever the line starts there is that delay. It is as if it is supposed to be there

jens55

Changed to Gyroid infill and the issue is much less pronounced the infill line follows the outside wall line at the beginning but if you wait long enough for an infill line to start at the edge without following the outside wall you can see it's still there.
Removed 'gradual infill' option - same issue.
Removed infill wipe and removed 'infill before wall' option - still acting weird.

I think I have adjusted all the possible options relating to infill and the issue is still there. I think I am left with the conclusion that somehow the slicer can't properly calculate all the moves. Maybe this is an issue that isn't visible until you print ginormous lines ?

I will post on the Cura forum to see if there is anything that somebody might suggest.

Phaedrux

0.8 nozzle with 1mm lines is already starting to get outside the realm of "normal" printing and print settings and expected behaviour goes out the window.

Since it's at the start of a print line I wonder if it's retraction related. If you load the gcode in a gcode viewer that shows retractions and travels etc you may get a glimpse at what is happening.

Do you have retract on layer change enabled? Are you using combing? What is your minimum travel distance before retraction is used? How fast are your travels? Is retraction tuned already? Temperature?

Have you tried using Curas fine grained speed controls to reduce the acceleration and jerk for infill?

jens55

@Phaedrux said in Some infill not reaching walls ?:

Since it's at the start of a print line I wonder if it's retraction related. If you load the gcode in a gcode viewer that shows retractions and travels etc you may get a glimpse at what is happening.

I have only checked with the Cura preview system - can you suggest a Linux compatible gcode viewer ?

Do you have retract on layer change enabled? Are you using combing? What is your minimum travel distance before retraction is used? How fast are your travels? Is retraction tuned already? Temperature?

Retraction at layer change is off, combing is off, minimum extrusion distance window is 6.5 mm, travel speed is 120 mm/sec, not sure what you mean re retraction being tuned ... it is very limited because otherwise I get clogs. Print temperature is 210C

Have you tried using Curas fine grained speed controls to reduce the acceleration and jerk for infill?

No, I have not tried that. Currently infill acceleration is the same as print acceleration and the same with jerk.

jens55

Since the issues do not happen to print walls, tops or bottoms, why would speed/acceleration and jerk affect infill but not walls ?

Phaedrux

@jens55 said in Some infill not reaching walls ?:

can you suggest a Linux compatible gcode viewer ?

I've only every used the slicers viewer or online web viewers. There's a few out there to choose from. I usually just google gcode viewer and try a few.

Retraction at layer change is off, combing is off, minimum extrusion distance window is 6.5 mm

Turn on retraction at layer change. With infill first, and no retraction between layers, it would make sense that there's not enough pressure in the nozzle at the start of the infill line. For non structural parts this isn't really an issue since it's all internal. I'd also reduce the window from 6.5 to 2mm as it would seem you're losing pressure on your travels.

jens55

Turned on retraction at layer change, minimum extrusion window 2 mm, infill speed reduced to 30 mm/s, infill jerk reduced from 20 to 10, infill acceleration reduced from 3000 to 1000 and here is the result

The infill lines are cleaner and more defined as would be expected with the changes but you can see the big gap of wall to infill line

Phaedrux

@jens55 said in Some infill not reaching walls ?:

big gap of wall to infill line

Can you post a saved .3mf from cura somewhere so I can see the entire cura settings and gcode preview?

Such a gap would seem to me that the infill overlap would need to be increased even further.

jens55

I may have a smoking gun here but not sure.
My bowden tube comes out of the extruder through a pneumatic connector, goes a while until it goes into a bowden connector /joiner (two pneumatic connectors back to back) and it then goes to the hot end.
Despite having little tube lock rings, there is noticeable movement of the bowden tube in the pneumatic connectors (three of the 4, no movement at the hot end). I'd say there is maybe close to 3 mm total movement between the three pneumatic connectors that move.
For some reason I think that pressure advance should take care of that situation but apparently it might not.
It is a good possibility that this issue also caused surface pockets that I previously posted about.
Question : Should pressure advance take care of issues with bowden tubes sliding in and out of pneumatic connectors to the tune of a mm for each connector ?
Bonus question: Are there specific pneumatic connectors that are known to hold the bowden tube rock steady ? (I am using cheap Chinese pneumatic connectors)

jens55

@Phaedrux said in Some infill not reaching walls ?:

@jens55 said in Some infill not reaching walls ?:

big gap of wall to infill line

Can you post a saved .3mf from cura somewhere so I can see the entire cura settings and gcode preview?

Such a gap would seem to me that the infill overlap would need to be increased even further.

We cross-posted ... I think I should deal with the sliding bowden tube issue before bothering you with the .3mf file. What do you think ?

jens55

I have found some couplers in my spare parts stash that ought to work ... more news tomorrow when I have the couplers replaced and have tried if this fixes anything.

Phaedrux

I'm not sure how PA would cope with the sliding. I suspect it would simply act as though the tube were longer than it actually is. But it could also mess with the timing of when pressure starts to build in the print head.

Getting that sorted out definitely couldn't hurt the situation.

Cheap chinesium stuff has its issues. Rarely get what you pay for imo.

If it doesn't help, post the .3mf. And your config.g for the complete picture.

jens55

Will do. Just printing another sample. The tubing slides a LOT less but still slides a bit. I might be forced to take the joiner out.
There seems to stil be a bit of a delay but I will try to tune it out with pressure advance.
As to how PA could (or should) help, it accounts for the filament compressing and relaxing as well as the tube movement as pressure is applied or removed.

If nothing else, it's been an excellent learning situation and if I can't sort it out then it will be a good reason to abandon Bowden in preference of direct extrusion (after all, it's only money )

Phaedrux

Yes I see what you're saying about PA accounting for it, but to me it feels like the slop for the slidinging coupler is different than just the fixed length of the tube and the compliance in that otherwise fixed system. I think it would be difficult to account for.

Have you tuned for PA at all? If so, it's obviously not having the intended effect.

I've heard people say good things about the capricorn tubing kits that come with their own couplers. So maybe that's a good quality option.

jens55

I use Capricorn but buy the tube in bulk without couplers because of the length I need.
I have tuned PA but it's obviously not doing it for me so will have to redo it ... especially now with the different couplers.

It just ocurred to me that I had adjusted PA with a width of 0.8 mm and it is quite sensetive to the extruded width so it likely was way off. A job for tomorrow ...

jens55

Doing some more digging I found this little tidbit on https://duet3d.dozuki.com/Wiki/Pressure_advance:

"You may notice that when using pressure advance there may be a gap between the perimeters and the solid infill lines. To combat this you may need to adjust the infill overlap value in the slicer."

I think I will need to revise my understanding of pressure advance because of this tidbit from the same page:

"actual_extrusion_speed = requested_extrusion_speed + (K * current_extruder_acceleration)"
where K is the pressure advance setting.

I suspect that you are correct and there is nothing in PA that would compensate for sliding bowden tube fittings.

deckingman

@jens55 For info, I had the same thing with Capricorn tubing. When I measured it, the OD was slightly smaller than cheap no name PTFE tubing. I printed some thicker clips which helped a bit but in the end, my solution was to ditch the Capricorn and revert back to the cheap no name tubing. No more slippage.

DocTrucker

Forgive me if I'm already repeating stuff that has already been covered but pressure advance is second to last, only to retract in the tuning sequence for me.

I've had this issue before. It appears as the bead not quite coming out in large enough quantities and there being tension in the bead as there is strength in the melt, it's not water like. You can reduce melt strength by getting the melt hotter, push out more material so that the tension isn't there, or go slower. The right answer is difficult to judge.

So my questions are:

Have you calibrated e-steps with no loading on the extruder drive? Ie just drive filament through the extruder drive but not into a hotend.
Have you picked a favorite temperature?
Have you tested/checked for any need for linear or non linear extrusion correction? This needs to checked over the whole print speed range and done as accurately as possible. With a rule you are really looking at +/-0.5mm over 100mm at best.
Have you done a square vase print to check wall thickness? Adjust filament diameter to get that correct. (I use firmware retract, so filamemt diameter is in the gcode)
Now I look at pressure advance.
finally check for retract and shoot for a value with a bit of comfort margin before stringing etc.

Then I play around a bit and discover my temps are too high or low and have to restart! The need for the linear and non linear extrusion correction are more complex with increasing bowden tubes and the closer you get to the throughput limits of the hotends. Likewise pressure advance for my E3D v6 with direct extruder is around 0.04 where as it was much larger with bowden. Around the 0.4 mark.