Missing Shell Line in Wall

[PartySausage 21]

I'm trying to understand what appears to be a missing shell line on the inner face of this model @Line #200.

It seems to be aligned & related to the top of a hole in the front face of the model & also occurs to a lesser extent @Line #100, which corresponds to the bottom of the same hole.

If I remove the hole from the model & re-slice I don't get the effect, so it's certainly something that relates to said hole. 

I also can't work out why the seam isn't continuous down this face when the hole is present compared to when it isn't there. I do have smart hiding enabled on the seam, although it is also configured to be at the back of the model so would still have expected the entire seam to be on this face.

I tried adjusting some of the settings relating to the seam positioning & wall count but non of the things I tried got rid of the effect so thought I'd put it out there to those more knowledgeable than me for comment

 

 

Overhead Cubby Drawer V3 (Hole) [Overture PETG, LW-0.4mm, LH-0.2mm, I-25%, T-E.235C, B.80C].zipOverhead Cubby Drawer V3 (No Hole) [Overture PETG, LW-0.4mm, LH-0.2mm, I-25%, T-E.235C, B.80C].zip

 

 

[Slashee_the_Cow 410]

Okay so here we go:

 

The "missing line" problem:

There isn't a missing line. What looks like one in the preview is a display artefact generated by the shell lines narrowing at that point to accommodate the thinning of the model. Layer 200 vs 201 vs both of them:

 

The "missing seam" problem:

Your missing seams coincide exactly with the layers consisting of the hole:

So why no seam during the hole? It's actually pretty simple:

It can be printed in one continuous line (just follow the red line with your eyes) because it just turns around at the gaps the for the hole. When it's a complete loop it's forced to start and stop each line because the lines are separated. The inner walls will also have seams, but Cura doesn't show them because they're not going to be visible in the final product.

[GregValiant 1,342]

You have "Hole Horizontal Expansion" set to 0.20 so you are getting that step.

Newer Cura versions have a secondary setting "...Max Diameter" that will allow you to turn that out.  You can set it to 150mm and that step will go away but Hole Horizontal Expansion will affect the entire large hole and not start and stop at the cross hole.

[PartySausage 21]

Thanks both for your investigations & explanations. Changing the "...Max Diameter" to 100 removed the artefact 🙂.

 

Changing that setting does explain how it's the void that constitutes the hollowed out model that is the 'hole' that was causing it.

With the same void being present in the model without the hole in the outer face I was originally thinking the same artefact should have been generated in that model too.

Having said that I've dug a bit further into these options and understand them a bit better now, with the realisation that the layers where the hole protrudes through the wall aren't 'closed' therefore the Hole Horizontal Expansion doesn't get applied to those layers so the walls would be 0.2mm thicker based on my setting

[GregValiant 1,342]

"...the layers where the hole protrudes through the wall aren't 'closed'..." 

That's exactly right.  When a hole is a hole - HHE is enforced, but when the toolpath can escape from the hole, then the hole ain't a hole anymore and HHE fails.  That new setting is meant to fix that.  You have three places on that model where it applies.  One is at the top of the "Big Rectangular Hole" where the flange continues up by itself, and the other two are the top and bottom of the cross-hole where the nozzle escapes from the inside and goes around the entire model.

 

I did an experiment and printed a Hole Chart.  My aim was to end up with "drilled" holes that are dimensionally correct.

For holes from about 3mm to 10mm an HHE of 0.20 made them real close to spot-on.  Above 10mm diameter, the required HHE falls off until at about 30mm diameter no HHE is required.

 

HHE is a correction for the "Snot Factor" which happens when the molten plastic wants to pull in toward the centerline of a hole.  The larger the diameter of the hole, the more likely it is that the plastic will stay where it was put.

[PartySausage 21]

I've only started exploring the Horizontal Hole Expansion settings fairly recently & was previously compensating for the discrepancies between desired & actual hole diameters in my CAD S/W.

Up to this point I'd only printed models with holes between 2-12 mm with my 0.2mm setting for HHE, which has been giving pretty accurate holes so I never saw a need to change any of the other settings. It didn't even occur to me that the gaping void in this model would in part be identified as a hole so the newly added setting to limit the HHE effect is a good catch all to avoid another gotcha in the future