Trying to resolve print defect in outer wall - PS 2.6 / Elegoo Neptune 3 Plus

[Ray Price]

I've just about got my Elegoo Neptune 3 Plus dialed in, but have one specific problem with the outer wall of a gear that I print fairly regularly.  This gear prints perfectly on my CR6-SE with an identical profile, with the exception of the printer portion of the profile.

The attached photo shows the defect that occurs.  This apparently occurs at the layer change / seam.  

I've done an esteps calibration which did update the esteps, but didn't appear to fix the issue.

I've painted the seam into one of the groves of the gear, and the defect appears on the outer part of the gear right before/after that seam.  It seems that if I print just a single gear, the print turns out fine, but if I print 2 gears, the defect appears on both gears.

I've also tried slowing down the outer wall, but that didn't appear to help.

I print at 225 for the first layer and 220 all layers after that.  My next thought was to increase from 220 to 225 to see if that helps, since it seems like there is under extrusion at the layer change / seam.

Any thoughts or suggestions greatly appreciated.

The .3mf file is attached as well.

[Scott Bussinger]

Are the sides with the defects facing each other on the build plate? Is one face where the printhead leaves the first gear and moves to the second gear and the other face where the printhead leaves the second gear to move back to the first gear? If that's true, I'd guess it's related to stringing where the plastic is essentially pulling out of the nozzle as it's moving away to the other gear.

An easy work around in that case would be to change your slicer settings to print each object independently before printing the next one (so it would print one gear completely, then print the second gear completely). That would avoid the moves between the gears on each layer. Shouldn't affect your print time by much.

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From: 3d-printing-...@googlegroups.com <3d-printing-...@googlegroups.com> on behalf of Ray Price <r...@theraypriceshow.com>
Sent: Friday, November 17, 2023 3:03 PM
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Subject: Trying to resolve print defect in outer wall - PS 2.6 / Elegoo Neptune 3 Plus

 

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[Ray Price]

So, since I painted the seam to fall between two teeth of the gear, the layer change occurs at that same location on each model.  Hence, the defects don't face each other, they are actually both at about 12:00 on each respective gear.

The red arrows in attached point the approximate location of the defects.

It appears that once the layer starts, maybe the quick motion of the hot end as it moves to get out of the valley between the teeth is causing the issue once it gets out to the top of a tooth.  I'm hesitant to move the seam to the surface of a tooth since that will probably show.  My use case does have a single blank tooth (the rest of the teeth have stickers on them) so that might be what I have to do if I can't find any other solution.  Weird that the CR6-SE and my previous CR10sPRO had no issue with this.

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[Scott Bussinger]

If printing one at a time avoids the issue, it feels like stringing is causing at least some of the problems. You're printing PLA fairly hot at 225° (I typically print PLA at 200° though that varies from machine to machine) and that would probably make the stringing worse. Also, you seem to have a stringing problem that I've pointed out in the zoom in from your photo that I've attached. That slot doesn't appear in the .3mf file you provided so I'm not 100% sure what settings the gear in the photo is using.

I also attached a zoom in from your photo showing the perimeters of the gears. You've got underextrusion or some other issue here. With 3 perimeters and 60% Infill/perimeters overlap set, you definitely shouldn't be seeing those gaps on all the teeth.

[Ray Price]

ha, that "slot" is a tick mark I wrote on the core with a marker in order for me to be able to understand the "front" of the print as it sat on the print bed so I could orient the defect to the hot end travel :)

Greatly appreciate you taking the time to look at this.

I'll mess around with some print temps as a start and maybe look into flow rate tuning?  

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[Ray Price]

I think I got it.  Dropped the First Layer / Other Layer temps down to 215/210 and ran through TeachingTech's Flow calibration routine which identified that my extrusion multiplier was about 10% under target.

With both of those, a 2x print of the gear looks great.  May drop the temps a little more

Thanks again for the feedback!

[3D Printing Tips and Tricks]

You never state what material you’re using… so I’ll also assume it’s pla. Pla behaves like ice. It has a very tiny if any range of temp where it’s not liquid yet not solid. IOWs it goes completely liquid very quickly and vice versa.

Something I’ve been dealing with on the XL may apply here as well…

Keep in mind that when you increase the extruder temp it does more in terms of the overall extruder system then simply increase the temp in the melt zone. It also expands your melt zone above and below as well as increase the temperature of the melted, liquid material which in turn means it will need either more time to cool or a really good cooling fan. Expand the melt zone and the stuff stays liquid across more of the material path and beyond and the longer it will stay liquid… at times when you may not want it to be longer, hence the downward cooling. Move away from the just extruded stuff and it may not cool enough to fully fuse and it can easily get pulled away from the object.
Why so hot? Rule of thumb we learned 11 years ago; the temp at which you get fusion is the optimal temp. No more than that or you’ll need to make it cool very quickly, both after extrusion as well as above the melt zone.

[Kurt Wendt]

Andy - Great Answer! Especially, since - when I was at Essentium, for Obvious reasons - VERY Intense science about  extruders, hot ends, melt zone and more. So, yeah - its Critical stuff indeed!!!

Will admit - for the  Massivit stuff - its INSANELY Interesting about their Tech  and how it works! Kinda a Hybrid between FDM and Resin printing - and, that was indeed confirmed in the interview.

As such, the Science of 3D Printing is such  COOL  Stuff and it IS the FUTURE!

-K

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