Constrain concentric circle to projected circle

[atkinsnw]

I have two parts that fit together.  I normally start with the diameter sketch and then project it into a sketch for the bottom and top components.  In the base sketch the diameter of the circle is constrained to the origin and set with a parameter.  The base sketch is fully constrained and locked.  I project the base circle into the bottom sketch.   I then draw the circle in that sketch by snapping to the projected circle.   I'll be darned if I can get that circle in the bottom sketch to change diameter when I change the parameter that drives the diameter of the circle in the base sketch.

1. Am I just confused on how the bottom circle should be constrained by the diameter of the projected circle from the base sketch?  I have been working around it by just setting the diameter of the circle in the bottom sketch to the same parameter I used in the base sketch.   
2. Do I lock the diameter in the bottom sketch?  This seems to lock it to the current diameter and then when the parameter is changed in the base sketch the circle in the bottom sketch doesn't change.
3. I found another workaround where I draw a sketch line in the base sketch for the diameter of the circle.   The circle is then constrained by this line.  If I project this diameter line from the base sketch into the bottom sketch I can draw the circle using that and it changes with the parameter change in the base sketch.

It seems like I'm close, but feel that I should be able to just draw the circle in the base sketch and use it to constrain the circle in the bottom sketch.

Looking forward to your always insightful replies.

[g-andresen]

Hi,

please share the file 

File > export > save as f3d on local drive > attach to post

günther

[jhackney1972]

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@atkinsnw wrote:

 The base sketch is fully constrained and locked. 

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Probably depends on what you mean by "Locked" in your description.  A parameter and a full constrained sketch is all you need.  Attach your model as already asked for.

[jeff_strater]

The video below is how I interpreted your description of your workflow.  Am I doing something differently?

[atkinsnw]

Thanks for the quick responses.   Somewhere, somehow someone pointed me to another post that doesn't show in this thread.  They basically pointed to option 3 I had mentioned above.  The post indicated that the projected circle isn't really a circle but a spline and if I project something more useful like the radius and use that for my construction in the bottom sketch things should work better.

Let me know if that doesn't make sense, but it helps me improve my constrained drawing.

[atkinsnw]

This workflow does the trick.

1. Define parameter "diameter=10"
2. Create base sketch with circle of "diameter"
3. Create the plane to draw the bottom sketch
4. Project the circle from the base sketch
5. Draw a construction line for the radius of that projected circle
6. Draw circle on the bottom sketch linked to the radius
7 Change the "diameter" parameter and watch the magic work.

[jeff_strater]

"The post indicated that the projected circle isn't really a circle but a spline"

If you are projecting a sketch circle in one sketch into a plane that is parallel to the original sketch plane, the projection will always be a circle.  However, if the source is not a circle, or if the plane is not parallel, then, yes, the projection will not be a circle.

[atkinsnw]

Geometrically I agree.  The planes are parallel and the above process works, but I can't get the second circle to adjust with the projected circle.   Let me get this design done and off to the printer and I'll see if I can make a quick video for us to review.

[jhackney1972]

How about simply attaching your model?  Let the Forum see what you are doing. 

[atkinsnw]

In the attached model you can see what we have been discussing.  Here is the process and the problem.

1)
   a) Create base geometry component & sketch with "diameter" size circle on the XY plane.
2)
   a) Create "radius projected circle" component & sketch.
   b) Project the circle as a construction line from "base geometry"
   c) Create a construction line from the origin to the projected circle along the X axis.
   d) Draw the circle from the origin to the end of the radius line.
3)
   a) Create the circle projected circle component & sketch.
   b) Project the circle as a construction line from "base geometry"

   c) Draw circle from origin with radius that snaps to the projected circle.

Observations:
1) The radius sketch version is fully constrained and changes with the "diameter" parameter is changed.
2) The circle sketch version is not fully constrained and the circle doesn't change with the "diameter" parameter.  This is the problem that sent me down this path.  

[jeff_strater · Accepted solution]

I see the issue - I think it is a misunderstanding of what "concentric" means.  Everything is working as expected.  Concentric just means that the two circles share the same center ("coincident centers").  If you want both circles to be the same size, use the Equal constraint.  See the video.

But, if your goal is the circles be the same size, why do you need two of them?  If the projected circle is the size you want, just make sure it is not a construction curve, and use it directly, in whatever downstream usage you need it for.  If you want the second circle to be some measured distance larger or smaller, add a dimension between the two circles.

[atkinsnw]

Jeff,

Thanks for the info.  I hadn't thought about the equals constraint here.

Yes, you are correct on concentric.   
During this process I also figured out that I could use the projected geometry directly if I didn't make it a construction line.

All good.   Learn something in F360 everyday!

[davebYYPCU]

Did I miss something here?

The second circle and your drama can be avoided by extruding the first circle.

Might help…

[atkinsnw]

No you didn't miss anything.   My example was contrive to just show the problem that I was having.   I had some hold over bad habits from when I was a real noob.   There are many better ways to solve my problem, several of which I have found through this discussion.   

I was mostly confused because when you draw the second circle it snaps to the projection, but isn't tied to it.