I have a simple sketch with a construction circle, an arc that lies on it, tangent to 2 lines (which happen to be emanating from another circle with similar constraints).
I don't see a way to constrain the sketch so that the arc stays on the "outside" of the figure, and the overall profile is convex. There are 2 solutions to the constraints, and I don't see how any of the available constraint types can ensure the geometry I want.
Hi @rmfuhrer,
Thanks for using the Fusion 360 Forums!
I understand you would like the convex profile from the example you included in your original forum post.
Below I have created a screencast outlining what I believe is the solution to your example:
If you have further questions or concerns, feel free to reply to this response and I would be more than happy to help.
Please select the Accept as Solution button if a post solves your issue or answers your question.
Cheers,
Adam
Adam James
Moldflow & Netfabb Technical Support Specialist
* Learn * Screencast * Downloads * Troubleshooting
Your solution still allows the ends to flip concave to the profile if you drag it around in the right way. I believe the OP is asking if there is any way to force the ends to always maintain the convex orientation.
Of course we don't have any way to directly constrain the direction of a tangency.
There is a work around to this deficiency, but it involves somehow forcing the total length to always be longer than the distance between the center points of the arcs, and so cannot be applied while the length is still unconstrained.
A better way, if you desire to leave the length unconstrained, is to just leave full circles at the ends. In this way the convex profile is maintained regardless of how the circles orient. The only functional difference is that you'll have to click three times instead of once to select the entire shape when you go to Extrude it or whatever.
@rmfuhrer I accepted @chrisplyler's reply as the solution ( As an Autodesk ExpertElite I can do that) because it provides the two best solutions and the #1 I would have suggested as well.
There is not need is such a simple sketch to trim anything. You can select the three profiles and extrude them together. If they are adjacent they will auto-conmen into one solid. Saves time and behaves more stably.
@rmfuhrer wrote:
In particular, I noticed that, as you moved one arc around, although the profile seems to remain closed, at times a bit of the arc extends past the points of contact between the arc and the lines. (A little "dangling" bit of arc is vislble.)
This could be three things:
1. Then end of your arc is not Coincident restrained with the end of the line. Although if this is true, it would become very obvious as you dragged it around.
2. If you drag things around in such a way that the radius dimension leader line is running off in a direction that doesn't cross the arc, Fusion will add a little dimension line arc of its own at the end of the leader. If your sketch elements are constrained and have turned black, this little arc might be mistaken for a continuation of the real arc. Like this:
3. Occasionally I have noticed that two Coincident items will APPEAR to be apart, even when they aren't. I guess this is some kind of display inaccuracy. I've only ever noticed it when zooming WAY WAY WAY down into stuff.
@rmfuhrer wrote:
Honestly, as a point of order, I think it would have been more appropriate for you to leave it to me (the original poster) to accept the solution, if I thought it adequately addressed my question.
(OTOH, if I had left the reply unaccepted for a long while, then IMO it'd make sense for you to accept on my behalf.)
In theory I agree.
In practice across over 10k posts and 1k provided solutions I have to say that it isn't unusual that people accept the first posts as a solution that that seemingly solves a problem. Many people never try an alternative solution even when presented, which in this case would be a mistake.
Something you also might not be aware of is that more than one post can be accepted as a solutions. If you feel another post also addressed you problem appropriately then you can still also mark that as a solution as well. I just did not want Chris's solution to be overlooked.
