Filet Limits and Where Do They Originate?

larry_hawes

I have an extrusion that fails to filet at a very small number and I believe it's because of a single very tight radius curve. Does that radius of the curve have a direct bearing on the filet size? Let's say the radius is .02 in. Is that the approximate limit of the filet size as well? Or is the correlation more complex?

john_mcclary

Edit: Original answer has incorrect Information
Better answer: The problem is the small corner fillets need to come after the overflowed fillet.

I this case, your upper limit is equal to your part thickness,

anything larger fails because Onshape does not have "fillet overflow" meaning it will continue to fillet until the shortest face reaches "zero-length". I know SW now allows overflow so it will just end up making a fillet that is tangent to the larger face, and tangent to the lowest edge of the shorter face.

The line marked A is the shorter face I'm referring to.
You can see when your fillet is equal to your height, then there is no line remaining (zero length)
the last image is probably what you were expecting, which is what SW refers to as Overflow.



I smell an improvement request...

larry_hawes

Now I'm thinking I might have missed a tangent constraint....

john_mcclary

do you have an image or a link? I'm confused about the question

larry_hawes

john_mcclary said:

do you have an image or a link? I'm confused about the question

Sorry about the confusion. The challenge (seems to be solved with an applied tangent constraint?) was applying a filet to a complex shape and having it fail with anything larger than .02". Was wondering if there's way to determine that failure point based on other parts of the sketch (filet radius etc.) or if it's a bit of crap shoot and the filet will fail when the sketch can no longer tolerate the filet size. 

https://cad.onshape.com/documents/c7ac382255c4440e75bf4ef3/w/1f3e5ec88beba41434f1492d/e/4acce76f9471456354ecfedd

http://www.youtube.com/watch?v=dmwkW3p9znI

john_mcclary

Edit: Original answer has incorrect Information
Better answer: The problem is the small corner fillets need to come after the overflowed fillet.

I this case, your upper limit is equal to your part thickness,

anything larger fails because Onshape does not have "fillet overflow" meaning it will continue to fillet until the shortest face reaches "zero-length". I know SW now allows overflow so it will just end up making a fillet that is tangent to the larger face, and tangent to the lowest edge of the shorter face.

The line marked A is the shorter face I'm referring to.
You can see when your fillet is equal to your height, then there is no line remaining (zero length)
the last image is probably what you were expecting, which is what SW refers to as Overflow.



I smell an improvement request...

NeilCooke

@john_mcclary - Onshape will do that "overflow" example you show there, but maybe it is not as tolerant on more complex geometry. If you have some examples that work in other CAD and not in Onshape then please send them to support (although we are using the same underlying Parasolid fillet API so it should be identical).

larry_hawes

I would be more inclined to attribute the 'problem' I had to user error and not a problem inherent in the software. Totally missed the simple limitation of the part thickness in the example above, and most likely missed other aspects of the sketch/extrusion that created the limits I think I experienced.

After changing the sketch and ensuring that the tangent constraints were applied correctly it seemed to correct the limits I experienced. For now I think the question has been answered and want to thank you as well for the replies.

john_mcclary

Ah, you're right @NeilCooke, my bad.

the small fillets are making it zero length, do the fillets second @larry_hawes

larry_hawes

Overflow. Interesting and I can see it applies overflow to the simple outline of the part ref'd above but not the interior sketch edges. Interesting and another piece of Onshape knowledge for me. Yippee...

john_mcclary

This was working the same in SW as it was in Onshape, the left image is SW the right is Onshape.

The problem is the small corner fillets need to come after the overflowed fillet.