A reconfigurable variable blank-holder force system (and method) for
producing sheet metal stampings comprises a portable hydraulic unit,
controlled by a digital control system and a knowledge-based expert
system to enable reconfigurability and an easy transition from the
try-out stage to production. The knowledge-base has a hierarchical
structure and includes stored information about part geometry, material
properties and press parameters. The expert system enables an operator to
determine optimal blank-holder forces, and to fine-tune through a
graphical interface unit. The optimal blank-holder forces are generated
by hydraulic force actuators, using a controller running a nonlinear
algorithm that accounts for valve nonlinearities, variable flow-rate and
numbers of operational cylinders. The portable hydraulic unit preferably
comprises hydraulic cylinders with quick disconnect hoses, a manifold,
servo-valves and a pump unit. A structured method to utilize this system
to produce sheet metal stampings is also described. An article embodying
the method is included.