Why doesn't this extrude work?

[Anonymous]

I'm still somewhat new to Fusion 360 and am having problems understanding why extruding a particular channel/slot is not working... I added a few slots to my sketch and went to extrude them to the same depth as other existing slots and got the error message listed in the attached picture. I was able to extrude within .01" of the rest of the channels but Fusion seems to be having problems with that last .01". I zoomed in super close and nothing looks odd or off to me. 

This is one of those things I can easily work around but it would be nice to understand why Fusion is having problems with it so I can avoid the situation going forward. The project is attached. 

[Anonymous]

Just to be clear, the error is "Error: There was a problem combining geometry together. If attempting a Join/Cut/Intersect, try to ensure that the bodies have a clear overlap (problems can occur where faces and edges are nearly coincident)."

[mroek]

@Anonymous

This is because your base sketch has (a lot of) issues. If you look closely, it is skewed, so at some point you're probably creating sliver geometry. If you always make sure you add proper constraints, and also fully constrain your sketch (turn on the preview functionality to color sketch geometry based on constraint status unless you haven't already), it is easier to avoid issues like this.

[eellenburg]

Try to simplify your sketches.  It's more difficult to apply constraints/dimensions when the sketch is so busy.

I've attached an example of your part using multiple sketches.  Note the dimensions may not match exactly.

[Anonymous]

Thanks folks, I really appreciate your thoughtful replies. 

I understand the importance of fully constrained sketches and most parts I create I imagine will be from fully constrained sketches, but a lot of what I'll be doing will be more free-form type inlay work, a lot of splines with offsets then extruded to make pockets and extruded the other direction to create the inlay pieces, with lots of little tweaks along the way. I still don't understand why Fusion can't extrude this particular geometry... am I asking for trouble using this software to perform these types of operations?

[mroek]

The problem is that you are creating invalid geometry due to how you've done the sketch. Redo the sketch, and retry. Your goal is perfectly OK, and Fusion can handle it, but only if the geometry is valid.