Cut and extend...

[benfishr]

I have a question, I import a .STL file into fusion 360 and convert it to BRAP. Now usually I start deleting triangles to get a solid model. For some reason it comes up with errors. I want to construct a construction plane and cut to make two sections so that I can extrude that to a particular length. Can anyone help me with this?

[etfrench]

Try it without deleting the triangles which cause a failure.  The triangular faces only affect the appearance in Fusion 360.  Printing or milling won't show them (unless they're on different planes).

[SaeedHamza]

Don't delete the triangles, merge them instead in the Patch environment

[TrippyLighting]

Please share your design. The responses so far make a number of assumptions that may or may not apply to the .stl you are using.

[benfishr]

It's a piece from Thingiverse for a SD card holder but the holder is too small. I need to make the slot wider and the bottom slot higher. https://www.thingiverse.com/thing:2180452 Any help will be appreciated

[etfrench]

@jeff_strater: The BRep of this model doesn't seem to be able to be split.  Merge faces is also failing in the Patch workspace.

Note: Other converted BReps can be split.

@benfishr: At this point you would probably be further ahead to just recreate this in Fusion 360.

[HughesTooling]

The mesh is pretty bad, lots of overlapping triangles and internal meshes where the part was modeled badly. Shows what a toy 123D is compared to Fusion. I fixed the worst parts in Rhino, imported to Fusion and converted to a BRep. I made one surface transparent so you can see some of the internal meshes that shouldn't be there.

Here you can see some of the overlapping faces on the base I had to remove also the curved area on the inside had 2 meshes one on top of the other. Fusion File attached.