Offsetting a complex shape

alex_4

I'm building a map with a cut out state that needs to move up/down through the map. To create enough clearance between the movable element's edges and the fixed element, I'm trying to offset the edges inward. That works on simple shapes, but when I get to more complex ones, I get a "Can only offset a single chain at once" message. This seems to have something to do with selection order - if I drag-select an entire object, this pops up right away. If I select segment by segment, it works correctly on simpler ones, but not on more complex ones. What am I doing wrong? 

Sketch for reference: https://cad.onshape.com/documents/30636060fb5c8b857ad961f5/w/cddcf6b4c973a8494dd80be4/e/f4336f0ae7c0b8d777a7c864

Cris_Bowers

You can use "move face" or "thicken" on the extruded parts. I found that setting the depth to 0.05mm kept most of the geometry intact. Just do a selection window around the states, then deselect the top and bottom faces of each. You will also need to flip the direction of the offset.

Cris_Bowers

You can use "move face" or "thicken" on the extruded parts. I found that setting the depth to 0.05mm kept most of the geometry intact. Just do a selection window around the states, then deselect the top and bottom faces of each. You will also need to flip the direction of the offset.

alex_4

Thanks. "move face" did it, but it still seems to handle self-intersection poorly. I had to manually smooth borders out to be able to do all states, and even then I'm stuck at 0.2mm at the moment.

jakeramsley

Does it help actually modifying the parts?  Can you just use them as tools to boolean subtract with an offset.

See the Boolean: Subtract section:
https://cad.onshape.com/help/Content/booleanparts.htm