Boolean failed

Why the “difference boolean” (object red - blue object) fails?
The blue object is a group (5-cylinder). The boolean operation is not performed between a group and a simple volume?
To function must perform the boolean for each individual cylinder.

(5 Rhino SR7 64bit)
boolean failed.3dm (312.1 KB)

Probably because the blue cylinders don’t overlap nicely at the top. What I did in the file below was to draw a box around the top of the cylinders and the BooleanUnion command on the box and the cylinders. Then, I used the result of that to subtract from the red volume. That works as demonstrated in the file

boolean worked.3dm (390.1 KB)

Strange, because one by one the Boolean difference works, as a group not!
Anyway thanks

Exactly. Like I said, you can’t BooleanUnion the cylinders because they don’t overlap nicely. Therefore, a combined boolean difference is unlikely to work.

If you make the cylinders shorter, they will BD as a group.