Calibration Cube Issue - S3D

[Rara]

I just switched back to PLA from over a year of doing nothing but PET-G and I am having absolutely miserable results with the stock S3D PLA profile. I fired up Fusion, made a 25mm square, offset it inward by .60mm, extruded it, exported the .obj and loaded it up S3D. This is where things start going awry: it won't slice it unless I drop the extrusion width below .60mm (I'm running a .50mm nozzle, that's where the auto width puts it which I figured would be a good starting point?). Well, to be precise, it will slice one side of it but not the other 3. Drop the extrusion width to .59mm and I get a square. I made a new model with the same dimensions with no change. It's been a loooo-o-o-ng time since I've had to do this, but, a .60mm wall should slice with a .60mm extrusion width...right...?

[jimc]

Remember your wall width needs to be 2x your extrusion width. Only way you can do a single extrusion is by making that a solid cube and set top layers and infill to zero.

[Rara]

Interesting - that sounds familiar now that you mention it. But, why is that? Seems funny you can only do it, but only through indirect methods...

[jimc]

If you make a hollow cube then you have an actual wall to build. There are 2 surfaces to that wall. An inner and outer. Your perimeter setting is the # of extrusions on a surface that are placed to make up that wall. A solid cube has inly one outer surface so perimeters set to 1 with zero infill will give you a single extrusion on that outer surface

[Rara]

That's really interesting! That is good to know actually, explains a bit of "funny" slicing behavior I've had in the past as well. Thanks for the help, I appreciate it!!

[jsc]

Actually, jim, that's not quite true. You can build an explicit single perimeter wall, but it's tricky.

The issue here is that the STL coordinates are all in floating point, and due to roundoff issues, the slicer decides that something that is "exactly" .60mm is or is not bigger than .60mm. You can demonstrate this is happening, Rara, by taking your model and moving it around on the bed and reslicing it. You should see different numbers of walls appearing and disappearing for each attempt.

What confuses me is, why doesn't this happen for thicker walls as well? I often model things in exact multiples of extrusion width, and have never noticed getting a missing perimeter. In fact, I can slice a .60mm wall with a .40mm width and get a double perimeter wall....

[jimc]

S3d cant do single perimeter walls when the wall is modeled to a certain width. It can of course overlap the hell out of the extrusions to give you a wall smaller than 2x your ext width. Of course the more it does that the more overextruded that wall will be but thats another topic. You can get that to overlap so much that in the preview it appears to be single but its not. It will make 2 passes. Unless your seeing something else jin, s3d has always been that way and is prob one if the biggest feature requests out there.

[Rara]

Well, this is weird (I thought PLA was supposed to be easy!).

I'm getting .61-.63mm walls, so I could stand to turn it down just a hair, but it's not in bad shape. My overall width is coming out just a hair undersize; 24.97ish for a 25mm cube, but that isn't too bad either. But the problem is now when I set it to print 3 solid layers to see what the top/bottom layer quality, I'm getting lots of void area - hard to measure, but on the very top of the 3rd layer I'm getting a consistent ~.20mm gap between the extrusions and can even see daylight through the 3 layers in some areas. Any ideas on this one?

[jimc]

what is the infill like? is it fairly dense? is it printing cleanly? which pattern are you using and what is your temp?

[Rara]

Haven't gotten to infill yet. I'm printing at 220C with a V4, .50mm nozzle, and this is eSun's PLA+ which allegedly likes a bit hotter temps. Here's a picture for an additional ~1000 more words or so. Now that I'm zoomed in it seems I'm getting a little blobby in the corners too..