Hello, this is Lee.
Thanks to you guys help, I figured out how to fine undercuts on the surfaces.
By the way, when I'm making a mold with 'tooling', There's nowhere I can find how to control the gap value.
Without that function, It just like a left side of the image above.
But I wanna add some gap(or offset maybe) like a right side of the image.
The more I learn, the more obstacles are waiting for me)