Posted to Applications on Tuesday, July 10, 2012 Share:

Press control system upgrade improves productivity and safety

Walsall-based Presscare has upgraded two 600 tonne power presses for Covpress and a 100 tonne press for MiTek using Pilz PNOZmulti configurable safety relays with diagnostic operator screens - improving press reliability, throughput, operator usability and safety.

Covpress is a manufacturer of parts for UK-based automotive companies such as Renault, Vauxhall / General Motors, Jaguar Landrover, Honda, Nissan and Toyota. It also makes parts for non-automotives such as Sky and Landis & Gyr. The company needed to overhaul a pair of 35-year-old automatically coil-fed 600T Wilkins & Mitchells sister presses to meet increased demand for pressed parts. The challenge was considerable given that both machines were unreliable and their documentation was poor. Covpress turned to local press expert, David Walls of Presscare UK Ltd, to develop a solution that would improve reliability, in-feed speed and output capacity, and, of course, safety.

Initially the Covpress job involved deciphering old diagrams and reviewing the machines to see what could be re-used; this culminated in the need to redesign the complete control system and rewire both presses. Physically the upgrade involved the use of dual-channel solenoid valve control of the clutch and brake, which are critical to the safe control of the moving part of a mechanical press, cam box monitoring for stopping within 15 degrees of top dead centre (TDC), front and rear rising screens monitored by heavy-duty Fortress interlocks, and multiple emergency stop pushbuttons - all linked to a programmable controller to monitor these devices. Other operational parameters affecting the reliability and usability of the presses, such as air pressure and lubrication over/under pressure, needed to be monitored and displayed in an easy-to-read format for operators. All of this had to be done in compliance with the requirements of the C-standard for mechanical presses, EN 692.

Previously Presscare had used an old DOS-based controller in such applications, but when this was discontinued the company's engineers turned to Pilz and the PNOZmulti m2p expandable, software-configurable safety relay because it is Type Approved for press applications and the software contains pre-certified press-safety application function blocks. This makes the production of the Technical File for the machine considerably easier, as well as providing peace of mind to both designer and user. The Pilz PNOZmulti m2p is easily expandable so there is no daisy-chaining, which leads to a significant reduction in cabling (see 'before and after' photos, right); each safety function also has its own input that provides individual diagnostics for each function. The PNOZmulti configurator software permits integrated real-time monitoring via Pilz PMImicro diagnostic human-machine interface screens, permitting operators to quickly identify faults, such as lubrication under-pressure or a guard left open, thereby improving uptime and productivity. This was a major benefit for Covpress, as previously it was necessary to refer to a bank of flashing pilot lights to determine the cause of a fault.

Safety improves productivity

Carl Osborn of Covpress was impressed with the quality of the job; he says: "The machine is now more reliable and faster. We are getting three to four more strokes per minute, resulting in a previously unachievable 20 strokes per minute. This has definitely improved our productivity, but both presses are now also safer to operate, maintain and quicker to fault-find. The customised text signals on the Pilz screen fitted to the local control panel provide easily understood fault-finding information which our operators can act upon immediately. Far easier than deciphering banks of flashing lamps!"

In March 2012, Bob Hobbs, the Head Maintenance Engineer for Dudley-based MiTek Industries Ltd, contacted Presscare regarding an upgrade to a 100T press used for manufacturing products for the roofing truss industry.

He says: "There is often a lot of life left in a higher capital investment machine. We used Presscare's experience to provide a cost-effective electrical upgrade that would allow the machine to operate once again as reliably and effectively as a new one."

After closely examining the machine, Presscare again chose the Pilz PNOZ-multi m2p to form the heart of the press control system. Hobbs continues: "We have been impressed by the expert work carried out by Presscare, and their deployment of Pilz equipment has definitely improved the usability and stability of the press. We have also saved a considerable amount of money by avoiding the more costly replacement of the whole press in this current climate."

To find out more about Pilz PNOZmulti m2p configurable safety relays, visit www.pilz.co.uk and enter Webcode 5245 or email marketing@pilz.co.uk. To see the complete range of Pilz products for new design and retrofit of presses, visit www.pilz.co.uk and enter Webcode 1061. To reach Presscare visit www.presscare.co.uk or email enquiries@presscare.co.uk.