Merging faces in imported STL turned into BRep...some work some do not

[nkloski]

Hi all....I imported an STL file into Fusion 360, and comverted it to a BRep object...that went OK, and I desired to merge the many faces into a much smaller number of faces.

If you see the attached screen capture, the top of the object is one smooth face.  Originally it was a whole bunch of triangles, but I was able to use the Select Chain command in the Merge command, and the tool automatically selected all faces and made it smooth...e.xactly the desired behavior.

But if you look at the selected faces in blue:

Fusion 360 does NOT automatically select those faces, no matter if I sleect "Chain" or not...I would have to manually select all faces to Merge.  How can I select the faces all the way around to merge them into one cylindrical shape?

I have attached the file as well as the screenshot to this post.  Thanks!

[joel.palioca]

Hello,

Could you please attach the original .stl file or the .f3d file?  Right now the file that shows up is a .stp file and I want to make sure I replicate your workflow correctly so that I can help you out.

Cheers,

[Phil.E]

Use the Selection Filter, the View Cube, and window selection.

Step 2: window select the faces you want to merge. Because your part is round, and there are faces inside it, this will not completely do the trick, but it should help!

By turning off Select Through, the window selection will only grab the visible faces, not those on the backside, but also not those on the inside.

[nkloski]

Hi Joel..here is the foot file, thanks!

[nkloski]

Thanks, Phil! Is the reason fusion did not select all of those outside faces because there are also inside faces? The top faces selected perfectly, I am wondering why those side ones did not. It would be awesome to just somehow select the two loops for the top and bottom, and tell Fusion to merge all faces between those loops, but the auto-select would be even better!

[schneik-adsk]

This is actually a pretty difficult problem.

You got lucky because when you used the merge command the edges the faces you have selected made a small patch that looked smooth. It was not actually a cylinder. If you try to select all the faces and create a smooth patch it will create a patch but if you look closely at it it will be very wrinkled. It will be wrinkled because it's taking the top edge which is faceted and basically creating a minimum energy surface to the other, bottom edge which is also faceted that faceting of edges will introduce a waviness or pinching of the surface you create.

The team is working on converting mesh models to analytic B rep models. This would allow you to detect the approximate or precise diameter of the selected faces and replace them all with a perfect cylinder, or plane. This technology is a ways off so in the meantime the best thing to do is to use work geometry on the faceted faces, create sketches and then model a new body using the mesh as reference or underlay.

[nkloski]

Thanks Kevein...upon thinkign about what you said, yes it does sound like a difficult problem. I am always a fan of suggesting augmentation of computer thinking with human intuition...have the program ASK me if something is intended to be cylindrical, and base the resulting model on the answers that I give.

Now to your post: I understand 2/3 of what you said...I know how to create sketches, and model a new body, but are you referring to something specific when you say "use work geometry" ?

Also, I would assume that what you are saying would apply only to those rounded features....I have downloaded a few STL files that had flat areas, merged them, and 3D printed them with no problems in the mesh at all, so is it just for the rounded surfaces?

Thanks!

Nick

[schneik-adsk]

Just the rounded surfaces.

As to my work geometry point. I will use the three point plane under the construct panein the modeling workspace to place a plane using three planar points on a mesh face that should be flat.  This way I can ensure I am working with a perfectly flat plane in the right place on the model.

[nkloski]

Gotcha, thanks!

[ddbacker]

Sometimes it works sometimes not (when the faces are concave): fusion freezes completely.. after 5 minutes waiting I quit... again and again..

Strange that this program does not function well doing quite "simple" things such as merging surfaces..

Maybe something to do with the origin of the body ?: a to a body converted, "multifaces" .stl file..

A fantastic program but with some very essential flaws.. sometimes very very slowly... I mean very.

[TrippyLighting]

Modifications of triangulated mesh files generally are not the domain of CAD software. Autodesk Meshmixer is often a much better alternative.