topic Re: Why is this Elliptical Arc not Constrained? in Fusion Support Forum

Why is this Elliptical Arc not Constrained?

todd.wild — Thu, 19 May 2022 16:47:14 GMT

I want to create a fully constrained elliptical arc. In the screen cast below I have applied all of the constraints I thought I would need but the sketch is still unconstrained. Could someone please advise?

https://knowledge.autodesk.com/search-result/caas/screencast/Main/Details/eb7ab109-3903-4cb5-b2ac-ea9a64231da8.html

Re: Why is this Elliptical Arc not Constrained?

jhackney1972 — Thu, 19 May 2022 17:51:19 GMT

Please attach your model containing the sketch in question. It will help me see your steps better and see what I can find. If I duplicate it I may not do the same steps. If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

Edit: In my experimentation I have found that when your break or trim the ellipse you loose the relationships to the major and minor axis created with the ellipse. These axis seem to be critical to the constraining of the ellipse and cannot be replaced with simple construction lines. In your sketch, the ellipse arc is constrained, it just does not change color or the sketch does not show fully constrained due to this. The ellipse arc is not going to move. I agree, it would be nice is the indicators did appear and this truly my be a flaw in the sketcher but you have what you need so you can move on.

Re: Why is this Elliptical Arc not Constrained?

todd.wild — Thu, 19 May 2022 18:11:46 GMT

I cannot share the whole model since the would violate company policy. I have attached a new file that contains the exact same sketch. If you open sketch1 you will see that the constraints are in place and it appears nothing can move but the line and sketch appear as unconstrained.

Re: Why is this Elliptical Arc not Constrained?

jeff_strater — Thu, 19 May 2022 18:26:14 GMT

ellipses, and especially trimmed ellipses, are not well handled in the Fusion sketch solver. I suspect the link between dimensioning the construction lines and the ellipse is the problem. Yes, your constraint/dimension system fully constrains the sketch, and the status today is incorrect. if you want to fix it, dimension the ellipse directly:

Re: Why is this Elliptical Arc not Constrained?

todd.wild — Thu, 19 May 2022 18:41:10 GMT

Jeff, Thank you. I did not realize that I could constrain the ellipse directly.