Unable to close sketch created from offsetting edge

shannon_mckenzie768

Hello, I am trying to close the sketch of the inner loop highlighted below. The loop was created by creating an offset from the outer edge (1), and then creating another offset edge (3) from the new edge (2). If I add a line AB and a line CD, the sketch closes for the top half of the loop, but not the bottom. I just want to extrude the inner loop. Thanks for your help.

jnewth_onshape

I got it to work. Those splines really don't want to be both offset and have coincident endpoints with one another (for some reason). I used a custom feature to find the open profiles in the sketch to show the lines that Onshape doesn't think are part of a closed profile (see screens). Then I started tinkering with constraints and modifications. The simplest to do was to delete the offset constraints on the profiles. This may not be what you want! But you can immediately see that the profiles go from open to closed and the extrude then works:

You can see it here:

https://cad.onshape.com/documents/67af1f013ccc2b7712067b8f/w/5594aaee2081eeee2076622d/e/07b939bf07b96cd0047f99ad

robert_scott_jr_

Shannon. Don't detect line AB or CD. Is it necessary to split the inner loop? Please post a link to tour document. - Scotty

shannon_mckenzie768

Points A, B, C, D were created when I did the offset. No, it is not necessary to split the inner loop. I just did that clicking around trying to make things work, and when I did I noticed that splitting it would complete the sketch for the top portion of the loop but not the bottom. I'm obviously very new to onshape, so feel free to tell me the better, easier way to create the above. I created the original sketch (outer edge) from two splines, so there is not a smooth transition from the top to the bottom. Thanks again for your help.

https://cad.onshape.com/documents/95a6a5b99d7722efbf8d7bd8/w/8301baad0231cab052054050/e/83de123621914f8a709d4922?renderMode=0&uiState=66f2e9f12833fb4cb2ac3cfe

robert_scott_jr_

Couldn't get this to work with two splines connected together. As demonstrated in sketch 1, adding a short 'bridging' line across the splines where they meet on the right took those meeting points out of the surface to extrude, indicating there is a problem with that small area. Couldn't figure it out. Hope another member with take a look; I'm curious. I'm suspicious it may have something to do with the way splines don't like to be treated.

Take a look at the other part studios for options.

• Scotty

jnewth_onshape

I got it to work. Those splines really don't want to be both offset and have coincident endpoints with one another (for some reason). I used a custom feature to find the open profiles in the sketch to show the lines that Onshape doesn't think are part of a closed profile (see screens). Then I started tinkering with constraints and modifications. The simplest to do was to delete the offset constraints on the profiles. This may not be what you want! But you can immediately see that the profiles go from open to closed and the extrude then works:

You can see it here:

https://cad.onshape.com/documents/67af1f013ccc2b7712067b8f/w/5594aaee2081eeee2076622d/e/07b939bf07b96cd0047f99ad

S1mon

Offsetting splines is one of the most brittle part of the Onshape sketcher (something it painfully shares with Solidworks).

Now that we finally get a clear indication of unconstrained sketches, I'm struck by how often I missed the end points of offset splines being unconstrained. The blue dots are practically invisible to me.

This is probably a situation where extruding as a surface or solid first and then offsetting or moving faces would work just fine.

shannon_mckenzie768

Thanks everyone! I created another sketch, and went through the same steps I thought I went through with the original sketch. However, the new sketch was fully constrained. I gave up on the original one. I appreciate everyone's help.