Pressing on to boost safety

Walsall-based Presscare has succeeded in breathing new life into two 600t power presses for Covpress using Pilz PNOZ multi configurable safety relays with diagnostic operator screens - improving press reliability, output, 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 nonautomotives such as Sky and Landis & Gyr.

Recently it needed to overhaul a pair of 35 year old automatically coil-fed 600t Wilkins & Mitchells sister presses to meet increased demand for pressed parts and turned to local press expert, David Walls of Presscare UK, to develop a solution which would improve reliability, in-feed speed and output capacity, and, of course, safety.

Safety-critical components Initially the Covpress job involved deciphering old diagrams and reviewing 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 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° 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 which would 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 Cstandard for mechanical presses, EN 692.

Previously Presscare had used an old DOS-based controller in such applications, but when this was discontinued it turned to Pilz and the PNOZmulti m2p expandable, software configurable safety relay. This is a Type Approved device for such press applications and the software contains precertified press-safety application function blocks. This makes the production of the Technical File for the machine 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 reduction in cabling; each safety function also has its own input which 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, thus improving uptime 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.

Productivity boost Carl Osborn of Covpress was impressed with the quality of the job: "The machine is now more reliable and faster. We're getting 3 to 4 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."