Please see attached…
So…I’m trying to cut out the internal area of the (mostly) circular section of grid floor… none of the native tools are working for this and create weird geometries…
I just want to use the circular bit as a cookie cutter to leave the internal bit of floor for use in a model.
Any suggestions?
Cheers
NW
floor temp.skp (371.9 KB)
Circle Grid.skp (363.8 KB)
Here’s what I got when I selected all of it, right clicked, and chose intersect faces with selection. I then hid the grid, selected and cut all the geometry left, unhid the grid, chose edit group, and
paste in place. I did not bother erasing all the unwanted faces and lines. You can do that if you want.
This does indeed behave strangely with subtract. Solid tools sometimes struggles with multiple voids in plane. It gets confused about which to fill. In cases like this you can sometimes achieve success by reversing your cutter and target surfaces. Here I made a solid disc using inside faces of your hoop, and made it the same height of your original grid, then I made the grid oversize in Z axis, effectively making the grid the cutter and the disc the target. Then I use the Split solid tool to create three separate groups out of the intersections. Then I erase the unneeded bits. Does this get you the shape you were after?
floor temp circle.skp (340.1 KB)
If that circle is just a simple push/pulled surface, I would recommend intersecting a 2D face with the rectangles, then push pull that, rather than trying to use Solid Tools.
I agree with @TheOnlyAaron . It would make more sense to create the grid to fit the frame before making the grid 3D. Even running Intersect Faces on the geometry of the grid fills the openings.
I tried using 2D surfaces first as well, and intersecting the perimeter line. But the same limitation of filling in voids and creating a single surface happened, a version of the Bowtie problem I suspect. Perhaps I’m missing a simper 2D method, I didn’t play with it for long.
EDIT: I messed with it a bit more, and even though the initial merging of geometry creates a bunch of extra faces (not sure why), using intersect separates them back out and I was able to select the 2D face we were after, an easier method. 
