Offset failed with spline ?

andré_lemelin

Hello, I was wondering, is it possible that the Offset tool does not work combined with the Spline tool. No matter what I do, I always get the same error message: "Offset failed. One spline generated multiple offset curves." However, with the other tools (Line, Rectangle, Circle...), Offset works perfectly...

Here is a link to my sketch Thank you

https://cad.onshape.com/documents/08f5a4f57eaa7f2780921802/w/79fbe2859137679a4481706f/e/212af11deaf965272a6ae453

S1mon

You have some areas of very tight curvature. You can't offset a curve more than the minimum radius. In this case that's 0.031. Also offsetting surfaces can be more robust in extreme situations. Using surface offsets, I can offset to the inside by about 5mm and to the outside by 0.03mm before things fail.

If you broke your sketch into one spline per petal, you'd have a lot more ability to offset to the outside.

S1mon

The offsets I did here are surface offsets. I couldn't get 5mm using a sketch offset. This is a trick I learned with Solidworks which also applies in Onshape. Whatever the algorithms are for offsetting curves in a sketch are different than what's used to offset surfaces. Sometimes surface offsets are more robust or at least allow more of an offset than sketches.

S1mon

You have some areas of very tight curvature. You can't offset a curve more than the minimum radius. In this case that's 0.031. Also offsetting surfaces can be more robust in extreme situations. Using surface offsets, I can offset to the inside by about 5mm and to the outside by 0.03mm before things fail.

If you broke your sketch into one spline per petal, you'd have a lot more ability to offset to the outside.

andré_lemelin

For my part, if I try to indicate -1 mm as a value (to place the Offset inside), the tool gives me the same error message "Offset failed. One spline generated multiple offset curves". 

On the other hand, now, following your answer, I tried -.031 mm (for the interior), and the tool accepts my choice. Then I can change the -.031 mm Offset to -1mm.

There, it works. 

I find it a bit strange that I have to do 2 maneuvers for an action..

In any case, thank you very much for your response!!!

S1mon

The offsets I did here are surface offsets. I couldn't get 5mm using a sketch offset. This is a trick I learned with Solidworks which also applies in Onshape. Whatever the algorithms are for offsetting curves in a sketch are different than what's used to offset surfaces. Sometimes surface offsets are more robust or at least allow more of an offset than sketches.

david_veloz

I had the same issue and couldn't change the offset distance in the iOS app. The web-based app had the same error, but worked when I clicked into the offset measurement to adjust.