Internal structures being seen on the skin

[rickyg32 2]

Hey all.

Sorry I don't have a photo at the moment. Was just thinking back to a part I printed this morning and sanded. I thought hey whats the cause of this defect.

So here is what I have seen.

I am printing items that are a bit thin. 12mm or less in thickness. The part has a horizontal channel for a piece of carbon fiber to be insert. For some reason on the surface of the part there is a bulge of sorts. This happens all the time for me and I am unsure what setting helps to correct that. I know sand paper does lol.

Anyway I thought I would ask.

 

Latest cura version on a direct drive ender 3.

Printing Polymaker Pre Foamed LW PLA

CE3PRO_Rhein-Flugzeugbau Fanjet 600 Elevator.3mf

[GregValiant 1,415]

I think you will need to revert to Cura 4.13.1 to fix that.

The Arachne engine of Cura 5.x adjusts the line width along the holes.

This 5.6.0 and looking along the wall you can just make out a variation at the hole.

 

Here in 4.13.1 that little bump isn't there.

 

I've never been able to tune that out of my prints.

Horizontal holes aren't to bad (as long as you know how to sand).

Vertical holes can have a ridge on either side of the hole as Cura adjusts the line width and has to move the nozzle over when that happens.  Here the line width adjustment has caused Cura to use three lines to get past the narrow wall where the hole is near the outer wall of the model.

 

 

 

 

[rickyg32 2]

Awesome thank you.

I thought I was doing something wrong.

I can install the older version.

 

Cheers

 

[rickyg32 2]

Hey Greg

I installed the 4.13.1 version and wow the print was bordering on perfect.

There is one weird issue that I hope to get a photo of and share. But this issue I suspect is tunable and minor in nature.

So thank you ever so much.

 

[rickyg32 2]

ok I finally got a picture of the issue with the 4.13.1 you suggested.

I think this is a tuning issue just not sure what to look at. IT's like it under extrudes after a hole.

 

CE3PRO_Rhein-Flugzeugbau Fanjet 600 Servos Landing Gear Insert.3mf

Edited January 21 by rickyg32

[GregValiant 1,415]

When I slice the file - those under-extruded areas on the left are occurring just before the outer wall finishes at that far left corner.  In the project file you have "coasting" turned off, but that under-extrusion looks like what happens with coasting enabled and the coasting volume is set too high.

I have never printed that material, but it looks as if the extruder is running out of gas at the end of those extrusions.

The red line indicates a single layer that under-extruded.  The blue arrows indicate areas that look good, and the yellow arrows are the under-extrusion.

Looking at the layers, there is no difference in the toolpaths between the blue arrow layers and the yellow arrow layers.  They all circumnavigate the model with the layer start and end at that left corner.  The under-extrusion is occurring at the end of the loop.  That c'bored hole interrupts that toolpath as the model becomes 3 islands and those extrude correctly.  Then when it turns back into a single toolpath all around the model the under-extrusion appears again.

These are general suggestions.

I would turn off "Retract before outer wall", "Avoid printed parts when traveling" and "Avoid supports when traveling".  All of those can contribute to "dry starts" of extrusions (admittedly, that doesn't seem to be the problem as the nozzle is traveling right to left in that image).  If you are having trouble with the nozzle knocking supports over then enable "Z-hop on retraction" as an alternative.

My Ender 3 pro is much better with PETG when I slow down the retraction and prime speeds to 25.  It's as if the material doesn't like being snapped back and forth at the nozzle.  If you pull air into the nozzle during a retraction it will take a bit to get going again.

 

Have you tried printing that material at a higher temperature?  195 is kind of low and the material may be stiff at that temperature and has trouble getting moving.  I see you have your "initial layer print temperature" at 240.  That's a really wide spread from 195 for the rest of the print.

 

Sorry I can't be more helpful.  Not having any experience with that material is a definite handicap.

 

 

 

[rickyg32 2]

Thank you for your insights.

I have been checking other forums for information on this particular material. Most people print at around 190 but I found I could never get the first layer down till I upped the temp. The other thing people have reported is having to up the flow as much as 20% to get a good print. Seems the extruder would starve in some way. So I printed a few parts at 110% flow and had no issues with them. I might try this part again with the higher flow and see if that makes a difference. 

I agree it's filament starvation of some sort.

Will let you know.

 

Thanks again.

 

[Slashee_the_Cow 494]

If you can't get the first layer down at 190°, then set Material > Printing Temperature Initial Layer a bit higher (not uncommon with any material) but leave the temperature  at 190° for the rest of it.

[rickyg32 2]

Hey Slashee_the_Cow

 

Yes that is exactly what I was doing. Run it hot for the initial layer and then drop it to 195 for the balance of the print and it works well.

GregValiant

I wanted to update you on my testing.

I ran the part  a few times doing so tests.

First I ran it at 100% Flow and 195c as the temp. I got the results you saw in the original post. Ick.

I then ran it at 100% Flow and 220c as temp. I got better results, but not by much. So temp had no affect on the results.

I then ran it at 110 flow and 195C as the temp. I much better results, but not perfect.

I then ran the print again at 120% flow and 195c and it was perfect. I then ran it again on a second machine to see if it was machine specific and the results where the same. Perfect. So the profile has now been backed up with those settings.

 

Thanks very much for your assistance. I can now get my project started except now I need a new battery in my UPS. Power went out for a second and the print went off. Always a challenge. lol

 

[GregValiant 1,415]

Thanks for getting back.  We're starting to get a decent base of "airplane" problems and solutions.  The electric powered models present a lot of challenges.