Ford upgrades to make press lines safer

To comply with the latest safety regulations, Ford's plant in Saarlouis, Germany has upgraded the safety systems on a transfer press by moving to a safety fieldbus network. Dean Palmer reports Ford's press plant in Saarlouis, Germany produces body parts for the Focus C-Max, including left and right side panels and dual parts such as the left and right doors. The machine that is responsible for producing these parts is a new, compact transfer press supplied by Schuler. The press forces reach 62,500kN and the dimensions are 40m long by 8m wide by 10.5m, with a 6m press bed depth. And, with an electrical driving power of 1,000kW, safety of the machine is critical. Ford recently developed a new workpiece transport system within the press line to replace the transfer system between the press levels, which was driven via mechanically controlled disc cams. Due to electrically controlled servo axes that optimise transportation in respect of the different tools used, the company can now increase the output of pressed parts from the line. The system is also very flexible, enabling simple adaptation to the respective tool. More than 200 different tool sets can be managed simultaneously. A press of this scale required an appropriate number of safety functions in order to guarantee the protection of operating personnel and plant at all times. The main risks on the machine come from the press slide, automation devices such as the modular tool transfer, tool conveyors and waste chutes. The safety of the press is guaranteed via a range of appropriate measures, including access control by enclosing the plant, guards, lift gates for tool changeover periods, light guards and optical sensors. These are supplemented by mechanical locks and emergency stop functions. Other safety systems include a safety valve which locks the die cushion on the press slide. All the safety systems are approved through standard software blocks within the programmable safety system at the plant in compliance with the latest regulations. To monitor the press, Ford uses a total of 18 emergency stops; 16 lift gates; 13 safety gates; five light guards; one press safety valve; five scrap flaps; 10 tool conveyors and 21 transfer locks. The high number of safety functions, the large mechanical dimensions and limited space in the control cabinet were the key factors in Ford's decision to select a decentralised control concept, based on the safe fieldbus system, SafetyBUS p. Safe operation of the plant is guaranteed by a total of eight PSS SB 3006 DP-S programmable safety systems, approximately 100 decentralised safe input/output modules and seven bridges, which enable safe data exchange between the two separate SafetyBUS p networks, all supplied by Pilz Automation Technology. Another potential hazard comes from the tool conveyors on the press which travel in and out of the press automatically during a tool change. The end limits of the tool conveyor need to be monitored. This is achieved via safe magnetic switches from Pilz's PSEN range. Like all the other sensors on the press, the magnetic switches are connected directly to the decentralised I/O modules on the safe bus system. This safety concept and the modular structure of the presses meant not only that the technical installation criteria could be met, but also that the engineering costs could be reduced through faster design times and faster on-site installation times. Operators at the plant also now have access to a comprehensive diagnostic package, which minimises downtime thanks to targeted fault diagnostics. Ford's press shop in Genk, Belgium has also upgraded its safety systems using technology from Pilz. The company has installed PSS 3000 programmable safety systems on all 300 of its press lines. The presses were upgraded gradually while production was running, using standardised software and hardware early in the commissioning process, including approval. In terms of programming the safety systems, all the different press types in the plant are now accommodated within a single safety programme. Sub-routines for the different press types are quick and easy to activate via coding at the inputs on the programmable safety systems. This means that all presses can now be operated via one safety programme with a fixed CRC check sum, which protects the programme from unwanted modifications. Optimisation in this area not only made approval by external auditors so much easier, but also saved costs as the process took less time.