Hi, I'm new to the forum and I'm posting here cause I haven't seen a channel on fixturing.

I am designing a vacuum fixture for 5 axis machining that is going to be about 8" tall because I need to machine top, side, and bottom of part. I usually have a really tall fixed material and I wanted to give it a go with vacuum. Material is going to be wood just for information, non porous, hardwood.

In order to know if the the tangent force of the tools I'm using are greater than the vacuum holding force I need to calculate the vacuum pressure. However I'm not entirely understanding something.

The amount of holding force depends on the surface area shared by the two objects and the vacuum level. In the picture I attached, I created a simple vacuum cup and I was wondering if anyone knows if the surface area shared refers to the blue or the red area. The understanding of this aspect I think is important in the design of the pod.

Thank you in advance.