Sketch on the plane from another sketch?

jmsaltzman

I often make a few sketches on the same plane, with features from the previous sketches used as reference. Each sketch needs a plane specified, but I'd prefer specifying the first sketch-- to use its plane-- for subsequent sketches I want there. The need to specify the plane on the second and third sketches independently seems redundant.

Is there a way to do this now? Or is there any existing item for this that I could upvote? Thanks!

jmsaltzman

The closest thing I've found is this question about sketching on the previous plane, but I think specifying another sketch is the most elegant way to relate sketches:

https://forum.onshape.com/discussion/comment/65303#Comment_65303

alnis

You can select a region from an existing sketch to sketch on the same plane as that sketch. Changing the first sketch's plane will also change the planes of the other sketches since those depend on the first sketch's region.
https://cad.onshape.com/documents/bc6f5b6ea0a4fdf0331f7d57/v/e405866e9a0eda21e40a3658/e/74ef4685e84a089c0914b314


However, in most cases, I believe a multi-region sketch would be more appropriate and easier to work with. Is it possible for you to share a screenshot of any specific modeling issues you're running into?

tim_hess427

@jmsaltzman - Mostly just out of curiosity - why do you want the sketch to reference a previous sketch, specifically? It's honestly something I hadn't ever thought of doing. 

jmsaltzman

That's exactly the issue @alnis_smidchens: specifying the plane from the content of the sketch, versus its plane, is different.

If that region (face) is edited enough, the subsequent sketch breaks. And I prefer not to have faces in earlier sketches: just measurements and guide geometry. It's not a problem, really, but it would be unambiguous and would suit the way I like to work

alnis

If you're fine with having an extra unused bit of geometry in the original sketch, you could add a construction circle, then make subsequent sketches on a mate connector defined by the circle's center. Then, as long as you don't delete the circle in the first sketch, it shouldn't break. However, the most robust option would be to construct a plane and use that plane for all of the sketches, changing the plane's definition if needed.

tim_hess427

I agree with Alnis - the best option is likely to pick your sketch plane (or create a new one if needed) and have all sketches reference the same plane. If you move the plane later, all the sketches should go with just fine. 

I'm not sure what benefit there would be to having sketches only reference other sketches. 

jmsaltzman

Thanks for these ideas! It's a matter of workflow: I'd like things to be more hierarchical than they are. I don't like having unused geometry, and I don't like parts breaking when I need to edit an early sketch. Having a sketch reference another sketch's plane means I could edit the original sketch, even changing its plane, and subsequent sketches would not break.

jmsaltzman

tim_hess427 said:
I'm not sure what benefit there would be to having sketches only reference other sketches. 

I want to be able to rip up and redo one sketch but still have other sketches go along for the ride without breaking. I don't like having related sketches needing to share anything but their plane sometimes. I can tell them all to use the same plane, but that is less elegant than just referencing the sketch and inferring the plane, if that's what a user wants. It's a weird thing I guess!

shawn_crocker

I would say just draw a small circle way out of of harm's in the first sketch. Use its face for the other sketches plane. Another thing that will come in useful to you is learning how to drop expectations that have no benefit to you. 😉

jmsaltzman

Thanks for entertaining the idea, I admit this is a frivolous! It stems from the idea of sketch hierarchy: I want to sketch on another sketch. Just like I can (sometimes) specify a line from a sketch line, an edge, or two arbitrary vertices, it would be logical to use a sketch as a sketch plane reference, since it would of course have a plane as well. The second sketch would be a child of the first sketch, and inherit its plane. I can dream a silly dream