Selection on grid failing

clive_brett

I am trying to extrude a QR code for a display panel.
I have extruded a plain backing plate.
I then created a sketch containing a 25x25 grid by creating a 1.5mm square and then using the linear pattern tool replicated this 25 times in the horizontal direction with a spacing of 1.5mm.
I then selected the whole row and using the linear pattern tool, replicated this row in the vertical direction 25 times, using a spacing of 1.5mm.
I then fixed the top left corner with relation to the backing plate extrusion.

For the extrusion, I add to the backing plate.
Now when I click on a series of squares on the grid, they are highlighted as selected.
After several squares some of the edges of the boxes turn red and the extrusion fails.
By selecting different combination of grid cells, these error edges change position.

I cannot see the reason for this, so any help would be appreciated.
In other designs, by splitting the areas I have managed to track down the problem, but I am baffled in this case.

This is a test document I created

https://cad.onshape.com/documents/682350cdc55b18d1735bb587/w/b7dd329e4ba80bf760984e4e/e/6633e7c6f54364a588a3eace


Many Thanks
Clive

NeilCooke

You cannot have what is called non-manifold geometry (i.e. solid geometry without volume). This occurs when the edges of 2 cubes are touching. You will have to put a very small offset between each cube. 

NeilCooke

You cannot have what is called non-manifold geometry (i.e. solid geometry without volume). This occurs when the edges of 2 cubes are touching. You will have to put a very small offset between each cube. 

clive_brett

Many thanks for such a prompt reply.
As usual the answer is quite simple - when you have the knowledge and experience.
I shall rework the grid.
Thanks again
Clive