Disappearing constraints when updating a body created by rectangular pattern

[k.kosciuszkiewicz]

Hello!

I designed a parametric box in Fusion 360, where the body is created by performing rectangular patterns on extruded features. Next, I created a side cut by projecting the body and drawing a diagonal line. The side profile sketch is fully constrained.

Before parameter change

However, when I change the count of repetitions of the feature (increase box1_count and/or box2_count), the sketch is not updated correctly. Even though the projection is updated, the constraints between the projection and the line on the sketch are removed.

After parameter update

I tried this workflow on plain extruded bodies, and cannot reproduce this behaviour. This makes me believe it must be related to performing a pattern. I also experimented with changing the compute method on the pattern, but it did not affect the issue.

I was looking for a more robust way to design the part parametrically (previously I sketched the whole box, but found it difficult to update). Any help on how to do this parametrically is appreciated.

The design file is attached to the post.

Best regards,

Krzysztof Kościuszkiewicz

[TrippyLighting · Accepted solution]

The reason the constraints are automatically deleted, is because the projection after the quantity change is from a different/new edge. If you use a few simple formulae in the sketch it'll work fine.

See attached model.

[k.kosciuszkiewicz]

Thank you! You confirmed my suspicion that calculating the total size is the solution here.