Constrain circle to a line?

[SGoldthwaite]

Is there a way to constrain the center of a cirle to a line such that the circle can move along the line?

[Anonymous]

Hey Scott, I just tried using a Coincident constraint between the center of a Center Point Circle and a line and moves as you describe.  Is that what you were thinking of?

Jesse

[SGoldthwaite]

When I created just a line and a circle, using the coincident constraint works and I can slide the circle along the line.  But I can't apply this constraint to a circle and line I have in another sketch.  I attached my Fusion 360 design: in sketch "Base" I'd like to constrain the 0.578" circle to the construction line that's going through it.  I guess there's another constraint in the way, but I can move this circle around and I can get it to cross over the construction line, so I don't understand why I can't apply the coincident constraint.

[Anonymous]

Well, I think I know the circle you were referring to, and successfully applied a coincident constraint with that construction line without problem.  Not sure why you couldn't do it.  Perhaps if you run into trouble again, try random stuff like moving everything around a little, or turning construction line to solid line, etc. But for now it looks ok. 

Regarding the sketch grid, that is strange.  I got it to expand my making some large construction lines around the area, but something seems odd there.

I've attached the updated file.  Hope it helps.

Jesse

[SGoldthwaite]

I tried to make a screencast showing exactly what I was doing, I did a couple versions, then on the 3rd take the constraint worked.  Which is weird because I kept trying the same thing a few times: I clicked on the coincident constraint icon, then clicked on the construction line, then on the circle, but the circle didn't change when I hovered over it, except for the last time when it finally worked.  I don't know what's going on, it seems to be hit or miss.

[Anonymous]

Yeah trying it again I had that happen to me.  It looks like to help the constraint solver get un-confused, move one geometry or the other away a little bit, then apply the constraint between them, and that should take care of it.  I do this sometimes when say endpoints are close together and difficult to differentiate, I pull them apart from each other a little and then apply the constraints.  

Hope that helps a little.

Jesse 

[SGoldthwaite]

Thanks for the tip.  I'll try that next time I have a problem.  

[Maowen_Zhang]

@SGoldthwaite, I also checked your file as @Anonymous, would it be due to the construction circles that close to the normal circle, as they're close and easy to select the construction circle ?  Currently coincident constraint couldn't be applied on construction circle and the construction line.  

[SGoldthwaite]

I don't think the constructions circles were the problem.  I was zoomed in petty close and all the geometry was easy to distinguish.

[Maowen_Zhang]

@SGoldthwaite, thanks for the info!  When the circle doesn't move after using coincident constraint, has the coincident constriant object (the small constraint icon) be created? It would be great if you could help get us a screencast when you reproduce this next time, it helps us resolve it. Thanks a lot! 

[SGoldthwaite]

Here's the screencast: http://autode.sk/1IqIqej

[Maowen_Zhang]

@SGoldthwaite, very good screencast! The first time you apply the conincident constriant doesn't work, because Fusion 360 currently doesn't support selecting circle and line to add coincident constraint. So your first operation similar as below. And need to select the circle's center point directly.  

1. click coincident constraint on sketch palette

2. select the line

3. couldn't select the circle, and couldn't add the coincident constraint

If you think this is quit inconvenient, please share your ideas, we could discuss with our UX to see whether need to enable selecting circle (not circle's center) and line to add conincident constriant. This might impact similar workflow little bit: select circle and a point to coincident point on the circle, etc.  

FYI.  Another thing about sketch constriant you might already notice:  there are two modes as below. 

1. click constriant button on sketch palette first, then select geometries to add constriant, command continue (not ended) in order to easily add multi same type constraints

2. select geometries first, then click constriant button, add constriant directly if have correct&enough geometries (continue select geometry if no), and command ends once constraint created. 

[SGoldthwaite]

I see a problem with selecting the circle center - you have more then one circle at the same center point, how do you choose which circle to select.  

I find the constaints pretty hard to use.  Sometimes it's hard to tell how things are constrained, even with all the tiny icons.  One feature that would be nice is some feedback when a constraint is applied, like a confirmation sound and maybe a little pop-up in the corner.  It would also be nice if when I selected some geometry, all the constraints associated with that geometry were highlighted.