Fillet does not work in sketch mode

[ndevenish]

I've been having trouble getting the last fillets done on a sketch I have been working on for practice.

I`m trying to Fillet the top-left corner by up to 10mm. However, as soon as I do the opposite side preview gets reduced by the amount I fillet. When actually telling fusion to do the fillet, the result is completely different from the preview again - the fillet is inverted, and the other side gets expanded by the fillet amount. I`ve attached a screencast of the issue.

I... think the sketch is this; I haven't extruded it so there it no solidity, and the previewer seems to display nothing:

http://a360.co/2a16tcB

[James.Youmatz]

Hi @ndevenish,

Welcome to the Fusion 360 Community!

I tried to open the link you posted, but I think it goes to your direct hub (which you need your login credentials to view )

Can you please share a public link (guide here on how to share a public link) to the file so that I can download it and take a peek? From the video, I'm not really sure what could be causing it and I'd like to play around with it a bit. 

Thanks,

[ndevenish]

Thanks! I couldn't find those instructions initially, though I did mostly follow them... I did have some issues submitting with the video included, so maybe that messed something up.

here's a new link: 

http://a360.co/2a0baRe

And I've made an archive file also, in case that still doesn't work (attached)

Thanks for the time!

[jeff_strater]

Thanks for sharing the design, @ndevenish.  This looks like at least one bug, maybe a whole bunch of them.  I'm not really sure why this design is so sensitive, perhaps there are some constraints that are not needed, but I haven't yet found them.

I will pass this to our sketch team, and see what they can find.

Jeff

[jeff_strater]

I had some success with this sketch if I deleted this equal constraint:

then, added the fillet, then created a dimension for the second curve, and set it equal to the first (same effect as the equal constraint).  Until we figure this out, this should be an OK workaround:

Jeff

[ndevenish]

Hi Jeff,

Thanks for looking into this. Unfortunately, the screencast you posted has, partly, the same problem - notice that when building the Fillet, the measurements between the points and the right edge jump down to (10-fillet radius) - with a fillet of 10mm you can see the driven value dropping to 1.109e-4 (and when you set the radius to 5mm, it contracts to 5mm). Look at the top right edges and driven constraint at 0:19 on your screencast.

Although It worked when I manually put in the fillets on the sketch I posted, I ended up with more misbehaviour - so i've actually solved this particular problem by reimplementing the sketch from scratch with a tri-fold symmetry rather than lots and lots of edge constraints. It's simpler, cleaner, (but doesn't find bugs!). Trust me to kill things on my first sketch!

I'd still be interested to know if any followups show that it is a bug/what went wrong. Should I leave this thread open, or mark as "Solved"?

[jeff_strater]

Yes, that behavior is somewhat surprising.  However, it is actually expected behavior, because of the midpoint constraint on the line.  Here is a simple case:

but when you add a fillet to one corner:

And this is what is causing the behavior you are seeing in your example (though your design is much more complex), as well.  Here is a screencast:

Hopefully this makes sense.

Jeff