topic Constraint failure? in Fusion Design, Validate & Document Forum

Constraint failure?

deant.mobile — Wed, 17 Jun 2020 18:22:08 GMT

I've encountered a scenario where a drawing shows as fully constrained but there are multiple possible locations for the geometry. This manifests with items changing position when user parameters change.

I've attached a screencast of a simple example.

There is a large circle anchored at the origin that is dimensioned by a user parameter. There is also a radial line of fixed length with a vertical constraint. Two smaller circles of fixed size are present and each is constrained to be tangent with the line and the large circle. Where they end up in the geometry is dependent on their initial location, but both show as fully constrained. If the parameter defining the size of the large circle is changed they may change location in different ways.

Is there a solution that I am missing somewhere?

Re: Constraint failure?

jeff_strater — Wed, 17 Jun 2020 18:44:48 GMT

the screencast did not seem to make it to your post. Also, you could save us some time by attaching the problematic design here. Thanks.

Re: Constraint failure?

deant.mobile — Wed, 17 Jun 2020 19:35:36 GMT

I've attached the file and made another attempt with the screencast.

Re: Constraint failure?

TheCADWhisperer — Wed, 17 Jun 2020 20:46:12 GMT

There are two Tangent constraints to the Ø15 circle.

Edit: Oops, just read the original problem description again...

There are multiple possible solutions - so I think that logically, a scheme will have to be used where there is a unique solution (that matches the Design Intent) and is not dependent on the dimensions.

I have seen multiple examples of this issue that occur in Fusion, but not in the other CAD programs that I use.

Try just giving the url to the screencast rather than embedding it.

Re: Constraint failure?

deant.mobile — Wed, 17 Jun 2020 21:12:20 GMT

Screencast