Extrusion face selection - inner most with outer most

leon_smith793

Hi,

I am trying to understand how this extrusion was created.
https://cad.onshape.com/documents/6863de1af2465d1a223c6df2/w/ed0b2e5b8d0a50e5e601e3a9/e/bc9b0ed1e0c4f90891b79ebc

__________________
|a  ___________       |
|   |b                    |       |
|   |       _____     |       |
|   |      |   c     |    |       |
|   |      |_____|    |       |
|   |___________|       |
|_________________|

When I try to replicate it, always select A and B. I would like to extrude between A and C. Could it be that B was drawn from

NeilCooke

Hi @leon_smith793 all shaded regions in a sketch can be extruded. If you want just A & C to extrude, select them on the screen rather than the entire sketch.

leon_smith793

Thank @NeilCooke , every time I try to select A, I get A & B together. Maybe my sketch is wrong.

https://cad.onshape.com/documents/6863de1af2465d1a223c6df2/w/ed0b2e5b8d0a50e5e601e3a9/e/bc9b0ed1e0c4f90891b79ebc

NeilCooke

Sketch looks fine - worked OK for me?

leon_smith793

Thank @NeilCooke
What you have selected corresponds to A and B in my son ASCII art. Are you able to select select A and C, ie have a extend the solid to the next inner poly

NeilCooke

You can select any of them. However if there is a gap, it will create a new part by default. 

leon_smith793

Hi @NeilCooke

That is the essence of my question. I am trying to avoid a gap and a new part. I suppose I can draw to separate sketches, but logically the polygons belong in the same sketch.

I am trying to learn from a model I have found, and there they are able to achieve what I am trying to do. I had it behind the rollback bar and tried to recreate it. I have moved it above the rollback bar and taken this screenshot:




How did they achieve this?

Thanks Leon

NeilCooke

Sorry, I'm still not understanding what the issue is. Here, I just selected the regions to extrude, same as your image above.



Note that the Extrude is set to "New" - if you are trying to add this extrude to another part, use "Add".

leon_smith793

Hi @NeilCooke

Thanks for your patience. It has finally clicked for me. I believe the mistake I was making was clicking on the polygons and not the spaces between the polygons. I was therefore landing just on the other side of the region I was wanting to extrude.