Cam has some machinery element having some
optional form. It gives an optional motion to the other side
by the direct contact.
It's enough for only one side. having an optional motion for
giving an optional working. So the other side is generally
used with a simple shape of roller or plane.
Cubic cam (three dimensional cam) generally
can make smaller capacity of occupying in space as compared
with plane cam.
And it is used to many automatic machine by making any glyph
cam or "rib cam" with working closed cam of reliability