Feature Machine Safety
Presscare has utilised the Pilz PNOZmulti configurable safety relays to improve press reliability, output, operator usability and safety in two separate applications - for Covpress and MiTek
ovpress needed to overhaul a pair of 35 year old automatically coil fed 600T Wilkins & Mitchells sister presses to meet increased demand for pressed parts from UK-based automotive companies such as Renault, Vauxhall/General Motors, Jaguar Land Rover, Honda, Nissan and Toyota.
Both machines were unreliable and had poor documentation making the challenge quite a considerable one. David Walls of Presscare UK was called upon by Covpress to develop a solution which would improve relia- bility, in-feed speed, output capacity and safety.
A safety retro-fit
Initially the Covpress job involved deciphering old diagrams and review- ing the machine 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 chan- nel solenoid valve control of the clutch and brake (which is critical to the safe control of the moving part of a mechan- ical press), cam box monitoring for stopping within 15° of top dead centre (TDC), front and rear rising screens monitored by heavy duty Fortress inter- locks, and multiple emergency stop pushbuttons - all linked to a program- mable controller which would monitor these devices.
Other operational parameters affect- ing the reliability and usability of the presses, such as air pressure and lubri- cation 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. When the old DOS-based controller that Presscare previously used in such applications was discontinued, the company turned to the Pilz PNOZmulti m2p expandable, software configurable safety relay because it is a Type Approved device for such press applications and the software contains pre-certified press safety application function blocks. This makes it easier to produce the technical file for the machine, as well as providing peace of mind to both designer and user. The Pilz PNOZmulti m2p can be expanded so there is no daisy chain- ing, which leads to a significant reduc- tion in cabling. Each safety function also has its own input which provides individual diagnostics for each func- tion. The PNOZmulti configurator software permits integrated real time monitoring via Pilz PMImicro diagnos- tic human machine interface screens, permitting operators to quickly iden- tify faults, such as lubrication under pressure or a guard left open, thus improving up-time and productivity. This was a major benefit for Covpress, who previously had to refer to a bank of flashing pilot lights to determine the cause of a fault.
Power presses receive safety overhaul C
Right: the Covpress 600 tonne power press
faster. We’re getting three to four more strokes per minute, resulting in a previ- ously 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 decipher- ing banks of flashing lamps.”
Avoiding expense Improving productivity
Impressed with the quality of the job, Carl Osborn of Covpress commented, “The machine is now more reliable and
Left: Covpress - inside the panel - before and after
In March 2012, Bob Hobbs, the head maintenance engineer for Dudley- based MiTek Industries, contacted Presscare regarding an upgrade to a 100T press used for manufacturing products for the roofing truss industry. He said, “There is often a lot of life left in a higher capital investment machine. We used Presscare’s experi- ence to provide a cost effective electri- cal upgrade that would allow the machine to operate once again as reli- ably and effectively as a new one.” After closely examining the machine, Presscare again chose the Pilz PNOZmulti m2p to form the heart of the press control system. Hobbs concluded, “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 consid- erable amount of money by avoiding the more costly replacement of the whole press in this current climate.”
Pilz Automation Technology
www.pilz.co.uk T: 01536 460 766
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Enter 210 DECEMBER/JANUARY 2013 Electrical Engineering
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