Hydraulic press uses PC-based controls

Staff -- Control Engineering, 5/1/1999

Castle Hayne, N.C.—A new hydraulic press can produce complex parts better and less expensively than mechanical presses, but it needs sophisticated control algorithms. Best Press Corp.'s new powder-compacting press forms powders into complex-shaped molded parts with uniform density using hydraulics control technologies from Delta Computer Systems Inc. (Vancouver, Wa.) and Tri-Tech Engineering (Saginaw, Mich.).

Besides a multi-axis motion controller that directs its cylinders and pistons, the new press' hydraulics are controlled by two of Delta's RMC-100 series motion controllers that communicate with a PC running Steeplechase Software's (Ann Arbor, Mich.) Visual Logic Controller software via a Profibus fieldbus network.

Best Press reports the most innovative aspect of the new press' control system is its control algorithm, which provides a smooth transition from controlling the hydraulics based on position sensing to control based on pressure sensing. Transitioning gradually from position to pressure-based control and actively modulating the hydraulics using proportional servo valves to add or decrease pressure in minute amounts through a process called 'dithering' allows Best Press to create a uniform molded product that achieves tighter tolerances than systems using discrete control.

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