Is there a way to extrude cut from a surface?

[ghertyish]

Hi, I'm trying to model the internal surface of the mouse http://h30434.www3.hp.com/t5/image/serverpage/image-id/53769i14FB8210D5BCAA52/image-size/original?v=mpbl-1&px=-1, I have this model which I've solidified because the rest feels solid:http://imgur.com/5nZxPh7 but I want to extrude the top surface down and cut out the material between to make the inner surface. I know you can offset the surface like this: http://i.imgur.com/O3Pw4OC.png but I cant figure out how to remove the material between.

[neomechanikos · Accepted solution]

There are several ways to approach it:

1. Do a thicken instead of solidify
2. Offset all of the inner surfaces, merge then do a solidify (remove)
3. Copy all inner surfaces as one, offset then solidify (remove)
4. Instead of thicken or solidify at first, offset the surfaces, merge, and then solidify the shell.

It really depends on how you want the inside geometry to appear. Merely offsetting the surface can lead to problems in areas of tight curvature and may not be conducive to the manufacturing process.

[ghertyish]

I don't know if I followed your method exactly but your combinations of offsets, thickens aand soldifies really helped. I offset the surface and solidified it, then trimmed the top part from the outer surface and thickened the remaining outer surface to meet the inner solidified surface. So thanks

[neomechanikos]

Few more. You can also:

1. Extrude cut up to the offset surface. Cut from the bottom up to the offset surface.
2. Surface replace using the offset operation. But that may be difficult to do here.