Uneven, rough, curves after slicing

[Mortimer 0]

Hello,

I am slicing an stl file exported from Fusion 360, but when I do so, a smooth curve is sliced into an uneven, rough shape (see attached). Does anyone know why this is happening, or, more importantly, how to fix it? Thanks for the help!

[gr5 2,230]

1) I'd try printing it.  It might not be as rough as you think.  Or did you already?

2) Is it printing fast/slow/fast/slow in this area?  If so then *reduce* the polygons that Fusion outputs.  It's counter intuitive but if you have more than 5 or 10 triangles per mm it really slows down the printer.  I can explain if you want.

3) There's a new alpha version of cura out that supposedly handles thin walls better.  I haven't tried it yet.  But there is definitely the burtoogle version of cura which definitely handles thin walls much better here:

https://github.com/smartavionics/Cura/releases

[Mortimer 0]

Thanks for the reply!

1) I did print it, and unfortunately it was just as rough as what the preview showed. 

2) I didn't watch the printing, but I'll try another print and keep my eye on it. I increased the number of polygons and it still had the same rough surface... I didn't think about reducing them.

3) I'll try both versions and see what they can do. Thanks a lot!

 

Hopefully, I'll have a promising follow-up post soon!

[GregValiant 1,351]

If there was a prize here for the ugliest slicing you'd be the front runner.

 

Another thing that can have an effect is the Mesh Fixes | Maximum Resolution.  As @gr5 mentioned, turning down the resolution can help make the "average" more of a circle.  Setting the Maximum Resolution for my Ender from 0.05 (a lot of stuttering) to 0.5 made a huge difference.

[Mortimer 0]

Thanks @gr5 and @GregValiant!

 

Some updates: to eliminate issues the thin walls might be causing, I exported just the problem section and scaled it up 300% in Cura.

 

I tried both of the Cure versions gr5 recommended. The Alpha wouldn't slice it at all. The burtoogle version was every so slightly better, but still pretty bad. 

 

I also tried exporting it at different resolutions. In the pics, the top is medium resolution, and the bottom is low. I have the maximum deviation at 0.5, but that's actually what the default was on my profile (Anycubic Mega-S printer). Increasing it to 1mm or even 2 or 3mm sadly didn't help.

 

The curves that I'm having trouble with were made from ellipses that were then trimmed and offset in Fusion if that helps anyone figure anything out.

 

Thanks again for the tips so far!

Edited January 26, 2021 by Mortimer
one more pic added that's zoomed in closer

[GregValiant 1,351]

When trimming an ellipse the remaining shape is still an ellipse, but when I offset one in my older version of Mechanical Desktop it turns into a spline.  Splines are certainly different to deal with.  That is especially true if they become part of a loft.  The smoothness between the control points comes into play.

 

If it's legal, post that here as a 3mf file (File | Save Project).  Who knows.  Maybe somebody will see something.  All those facets are an issue though and they might still be in the model.

 

[Mortimer 0]

Thanks @GregValiant for the idea. Even if the offsetting does something unusual, like creating a spline, the outside of the model is formed from the original ellipse, and yet it is having the same problem when I slice it.

Here is the 3mf file. I hope someone can figure it out!

Just please note that I had to use an add-in to export it as a 3mf, and that add-in can only export with poor quality and at a 1:10 scale. I've also included an stl (medium refinement, and to scale) in case that helps.

 

Thanks for the quick replies!

CamperForHelp.3mf CamperForHelp.stl

Edited January 27, 2021 by Mortimer
added a missing word

[GregValiant 1,351]

It's definitely the model.  The walls show all the deformations for me that they did for you.  I uploaded it to NetFabb in case it just needed repair, but it came back the same.

 

As it happens, I'm a Tin Can Tourist myself.  We have a 1972 Shasta Compact that I re-did.  I made a bunch of these trailers (and the drink coasters that go inside) to sell at the spring TCT rally that has now been cancelled.  I think it has the kind of finish you are shooting for so I've attached it.

 

 

Happy Camper Trailer.3mf

Edited January 27, 2021 by GregValiant

[gr5 2,230]

Well you can decimate the model (reduce polygons) - that might help a lot.  Or it might wreck some of the dimensional accuracies.  Anyway I've used this tool many times.  I've reduced models by 10X 100X and even 1000X polygons and some models will still look just as good.  It depends on how big the print is and other factors.

 

Anyway meshlab is extremely easy to use and a very useful tool in your toolbox.  And free.

 

http://www.shapeways.com/tutorials/polygon_reduction_with_meshlab