Continental Tyre SA is one of the country's leading tyre manufacturers and has a high-volume tyre production facility in Port Elizabeth. The competitive world of tyre manufacturing involves complex and quality-critical processes that need careful monitoring and control if high yield rates and profitability are to be maintained.
With this in mind, Continental has implemented a production monitoring system based on Wonderware's FactorySuite and other leading technologies.
Continental's range of radial passenger, truck and cross-ply tyres are all subject to manufacturing time constraints because of the ageing of rubber compounds. Dealing with this requires critical scheduling processes and the tight quality control of production compounds and rubber runs to ensure that they conform to strict specification criteria as set out in the QS9000, VDA6 and ISO9001 standards. This, in turn, leads to the necessity for quality procedures and testing of which Statistical Process Control (SPC), laboratory testing as well as tyre-uniformity testing are some of numerous tests done.
Prior to the commissioning of the new system, there was no realtime monitoring which meant that production information was paper-based and only available at the end of shifts. Continental therefore looked towards the implementation of a live, realtime plant floor information system that would address their critical planning, scheduling and decision-making needs. The system would also have to help improve production quantity while maintaining quality and reducing scrap. Other goals included establishing exact figures for machine utilisation, energy consumption and production costing and tracking information through WIP (Work In Progress) warehouses.
To realise these objectives, Continental would have to install PLCs for interfacing to all production processes and multiple scada (InTouch) systems to monitor and control the production processes as well as to monitor all the energy-consuming processes. Continental chose standard PLCs to connect to their radial tyre manufacturing processes but opted for a soft PLC approach using Wonderware's InControl for the cross-ply manufacturing facility. The system would also require MS SQL Server 7.0, a realtime database (InSQL) and an Internet Information Server (IIS) for the production information intranet website.
"Most of the development was done in-house," says Andre Retief, Systems Project Engineer for Continental Tyre, "but we also had the capable assistance of system integrators BC Automation and Alstom Automation, who were chosen for the level of technical expertise and local support they could provide."
Wonderware's FactorySuite, MS Windows NT 4.0, MS SQL Server 7.0, MS IIS, MS 2000 Terminal Server, Siemens L2 networks, Beckhoff I/O on Interbus-S, standard off-the-shelf PCs in industrial cabinets, Compaq servers and Polycomp displays, were all chosen as they are all tried and tested technologies conforming to Continental's standards.
The 23 InTouch scada workstation nodes in total contain approximately 25 000 tags, 2200 digital I/O points and 100 analog I/O points on production and energy monitoring processes throughout the plant.
"We adopted a bottoms-up approach," continues Retief, "because planning and decision support all have to be based on the realities of the shop floor. The manager's view-nodes are supported by FactoryFocus and MS NT Terminal Services on MS Internet Explorer. The system architecture conforms to fully scalable, open standards that contribute to easy repair, integration and expansion with minimal impact on production processes. The system is accessible via the company's intranet, remote NetDDE as well as PC Anywhere, and supports direct dial-up for fault monitoring if required. Insofar as redundancy is concerned, this is available via a master-slave PC configuration on the radial passenger tyre production unit because this is where monitoring is most critical."
Apart from the standard monitoring and process control functions, the scada nodes also provide information to the SQL databases for downtime monitoring, SPC, recipe management, item costing, machine utilisation, WIP and energy monitoring purposes.
"There is on-going development of new Intouch applications and scada nodes are being added to processes all the time," says Retief. "These are run in parallel wherever possible, until implemented live to replace or assist current process control measures. Apart from the Intouch applications, database and website development, the only custom software development was in the area of VB (Visual Basic) front-ends and drivers for barcode readers, scales and the Polycomp displays."
The new production monitoring system has realised Continental's business goals through the provision of more controlled processes, accurate realtime information for decision support, easier planning and scheduling as well as production and power costing and machine utilisation statistics.
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