Forging relationships

Sheffield Forgemasters Engineering has installed a giant press and integrated robot manipulator which exerts a load of 10,000 tonnes and is probably the only one of its kind in Europe. It is used to manufacture heavy forgings of up to 300 tonnes for use in applications such as turbine rotors, bridge supports and propeller shafts for ships.

The robot manipulator is used to pass ingots to the press for forging. At 15m high, 10m wide and 20m long, it is the size of a typical house. Using eight wheels, the manipulator travels up and down a 20m long set of rails carrying its ingots to the press.

The computer system has been installed by Dronfield-based Forgex to provide size control on forged items to ±1mm and to control the integrated manipulator. At the heart of the project is a control system equipped with Opto 22 controls supplied by System Devices. The controls handle the 700 points of I/O which are associated with the press, the manipulator and integration of the two. The control, comprising a remote analogue and digital I/O station from the main PC, is fed over a high speed 115 kbaud serial link. Each individual input and output interface has optical isolation.

Real-time control software running on a ruggedised PC system handles the 60 motors involved with the press and the manipulator, together with a hydraulic servo power pack and a set of proportional valves which control water pressure in the press to ensure that it can reach its peak pressure of 7000lb/in2. The PC uses a Bus card for digital I/O while the manipulator uses remote Mistic I/O to give a mix of digital, analogue and quadrature signals, to feed back the direction of motion of the manipulator. Six PLCs with isolated I/O modules are used to control motor starting and interlocking. All computer I/O is optically isolated, interfacing plant inputs at 24V DC and solenoid outputs at 110V DC.

“The biggest advantage on this project has been the use of the Mistic remote I/O system,” said Forgex managing director, Dr Mike Dickinson. “Although the manipulator is a mobile vehicle with a run of 20m, it only needed four wires because the remote I/O eliminates the need for bringing large bundles of wiring back to a central controller. This massively reduced the amount of plant wiring needed and the time to carry it out,” he added.