Cleaning up an imported STL

[strmseekr]

Hi, I'm new to Fusion 360 and 3D printing and I am trying to modify a design on thingiverse:

https://www.thingiverse.com/thing:2377189

As you can see in the preview images on that page, if you slice the helmet vertically there is not 1 but 4 layers, and printing the inner 3 layers wastes a ton of material, and extends printing time by 10's of hours, so I'm trying very hard to remove them.

I actually have a couple of questions- first, what would be the recommended, simplest way to do this? Unfortunately the layers overlap in some places, do not overlap in others, and worst of all, intersect at some points, making them very difficult to isolate and remove. I guess I'm looking for an easy way to keep the outermost surface, delete everything else, and then thicken that outermost surface. To that end, I brought the mesh into Fusion 360, reduced the number of facets, and converted to BREP no problem. I then started deleting faces from the inside out, but this is an extremely time consuming task and since the layers intersect, the outermost surface sometimes consists of faces from one layer, and sometimes faces from another layer, and so you don't have a smooth, contiguous surface.

Also, *somehow* I did something that broke the file down into surface bodies, and they look like they're the ones that were created by the original designer (see attached) because they're very clean- one for each ear, one for the eyes and forehead, one for the cheeks, etc., and it's been a huge help, but I can't seem to repeat what I did when I try to import the STL file again from scratch... any ideas as to how that happened?

Thanks so much!

[TheCADWhisperer]

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@strmseekr wrote:

1. Hi, I'm new to Fusion 360 ... and I am trying to modify a (*.stl file).

2. ...what would be the recommended, simplest way to do this? 

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1. These are (or should be) mutually exclusive conditions.  I recommend going through all of the beginner and advanced tutorials and then in 6mths - to 6yrs of experience come back to the endeavor of modifying existing stl files (I'm serious - this is not beginner stuff).

2. https://forums.autodesk.com/t5/fusion-360-design-validate/how-to-work-with-irregular-and-organic-stl...

[strmseekr · Accepted solution]

Alright, well for anyone who happens to come across this and needs the answer, as I suspected, this is actually quite easy as long as you know how to do it. My second question was resolved by creating a cube that was as big as the helmet, then moving it on top of the helmet and doing modify -> combine and then getting the intersection. That broke the model up into its constituent bodies.

There are a couple of ways to solve my first question- you could just make bodies of different shapes and then subtract them from the original body, but I found it easier (if more time consuming) to go to the patch workspace, modify -> unstitch a face, go through and delete all the faces you don't want to keep, and then use create -> loft and create -> patch, and go around stitching all the faces together until you've got one solid body again.

This video was incredibly helpful: https://www.youtube.com/watch?v=s-LGmWBbZxY&list=PLEvfLYkThIByaOXr1b68dvaDsVNsRBXr

[TrippyLighting]

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@strmseekr wrote:

... this is actually quite easy as long as you know how to do it...

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... and are willing to accept pretty sub par results 😉

The .stl from Thingyverse was originally modeled as a quad-polygon mesh. It was not subdivided before conversion into a .stl which explains its very faceted nature. The original creator while making an admirable effort did not work very cleanly and also took a few liberties.

I reverse "engineered" this into a quad mesh and cleaned up the geometry a good bit. Then instead of converting a mesh into a BRep I converted the quad-mesh into a T-Spline and then NURBS surface. The results speak for themselves.

Achieving these results, however, is clearly not a beginners project 😉

[lichtzeichenanlage]

Impressive. 

[laughingcreek]

@TrippyLighting -which utility/program did you use for the quad conversion? 

[TrippyLighting]

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@laughingcreek wrote:

@TrippyLighting -which utility/program did you use for the quad conversion? 

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The zip file downloaded from Thingyerse contains several .stl files. The high Rez .stl ( BAK_v1.0.stl) was not going to be useful for what I was trying to do (way too many polygons) so I used the BAK_Cowl.stl file.

I opened this in Blender.

In edit mode in Blender I use the ALT-J key combo (Convert tris to quads).

Then I used a good bit of manual labor in removing triangles and restoring proper edge flow, something the original mesh clearly did not have:

[strmseekr]

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@TrippyLighting wrote:

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@strmseekr wrote:

... this is actually quite easy as long as you know how to do it...

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... and are willing to accept pretty sub par results 😉

Wow, thanks, man! You know, when I wrote that original post what I was really looking for was someone to provide exactly zero assistance and instead be a condescending ****. And BOY did you deliver. So well done, go pat yourself on the back and bask in the glow of how superior you are to everyone who is new to 3D modeling.

I have no doubt that you have discouraged other noobs who have less experience in dealing with dime-a-dozen assholes like yourself and that the community is smaller and less diverse than it would be without you in it.

Fortunately I was able to find actual solutions to my original questions by spending hours researching online and attempting brute force trial and error, all of which could have been easily avoided if you hadn't been so preoccupied with demonstrating just how profound and esoteric your deep knowledge is!

[TrippyLighting]

You  stated that this is actually quite easy in response to another user with vastly more experience than you who told you this is not a beginner project. I simply elaborated that better results take some skill and knowledge, but really aren't that difficult to achieve. It took me quite a while to get to that result and I had hoped to spark interest.

How you can take that as an insult is really quite beyond me.

I would be happy to show you how to do this and if you had paid any attention to this community then you'd know that I do that very frequently.

Given that you resorted to foul language and insults that is obviously out of the question now.

[emmerycheung]

@TrippyLighting This is a pretty late response but just wanted to say I saw your post and want to say Thanks.  Even though the OP didn't appreciate your response just wanted to let you know that someone out there did. 

[TrippyLighting]

Thanks @emmerycheung !

[lukaszlipnicki]

LOL

[whizbanger]

@strmseekr Wow, talk about having a distorted sense of reality, not to mention any sense of courtesy or manners.  How you could twist @TrippyLighting work to provide a helpful answer (complete with actual proof that it works) into something negative is beyond bizarre.  Do us all a favor & give your head a shake (or slam it in the drawer a couple times) before replying next time.