The first large press line ever to be equipped with the control architecture of PHOENIX CONTACT was the one standing in the Renault automobile production plant in Sandouville near Le Havre. INTERBUS stood the acid test when PC WORX, the automation software and the corresponding hardware were initially tested on an individual press refitted during modernization by the operator. In selecting these system components, the automobile manufacturer is treading new paths towards shorter cycles and a modular and distributed architecture.

In the following years, the French automobile manufacturer, Renault, invests in the control architecture of the press lines in all works; this applies both to new acquisitions and to modernization.

At the Sandouville site where the Laguna and Safrane models are produced, Renault modernized press 54 that had become too slow and was therefore no longer viable; in the same works, the new press line no. 11 was constructed. When in 1996 the Renault's planning department was looking for a new control concept, only a modular and decentralized one came into question for the company; it was to support faster processes and an increased output, it was to be as simple as possible to integrate and operate and flexible with respect to possible changes. The operator wanted to avoid the disadvantages of the former PLC concept that proved to be too complex.

The choice fell on INTERBUS with optic fibers instead of conventional copper lines and on G4, the PC control card and PC WORX, the PHOENIX CONTACT software. The decisive factors for this were the overall openness of the system components such as PC, Windows NT, IEC-1131 programming and INTERBUS, as well as the free choice of interface implementors on the market. Advantages that help optimize performance. Moreover, PHOENIX CONTACT offers an OPC interface, i.e. a uniform data interface by means of which any software can be used without needing a special driver. This openness familiar from INTERBUS and then consistently applied in control technology, made it possible for Renault to use the visualization of their own choice, here, Visual Basic.

An important part of the INTERBUS system is PC WORX, the universal automation software; an integral component of the Open Control automation concept developed by PHOENIX CONTACT. PC WORX with "SYSTEM WORX" and "PROGRAM WORX", perfectly supplementing each other, and with visualization software and open interfaces, comprises modular and expandable software products for planning, programming and visualization.

Renault is the first company to use PC WORX for large press applications. In this context, not only the software is important, but also the hardware, which in this case is a G4 PC card allowing uniform access to different brands of PLCs. "We are very satisfied with this control system. Compared to other brands, the G4 card works faster and is easy to install. With the new generation of cards, we manage to reduce the cycle time by roughly 50 % to approx. 15 ms", explains Marc Braun, the Renault project manager for automation and press technology. "Another important aspect was also the modular structure of the hardware. If, for example, the processor becomes too small for some reason, we simply replace it with a larger one, instead of developing a totally new card.

SYSTEM WORX allows convenient configuration and maintenance of INTERBUS, since errors and malfunctions can be easily located. In our opinion, PROGRAM WORX, on the other hand, is currently the most efficient tool for programming control systems in accordance with IEC 1131 ", continues Marc Braun. "Since service and research engineers have very different ideas about the requirements the software should fulfill, PHOENIX CONTACT had to satisfy both parties. Programming is now easier and more comfortable than before when we only used ASCII files."

PC technology qualified for press shops
This case study also shows that PCs can be used in press shops, despite the rough conditions and strong vibrations encountered. In the Renault works, the computer and its "normal" office monitor are located in a cabinet just next to press 54 with its capacity of 450 t and, depending on shape and size of the pressed pieces, up to 850 body components pressed per hour.

PC WORX in large presses for the first time
Each individual press along press line 11 has its own PC for control, visualization and communication purposes. The control system is a co-processor board integrated in the PC that also acts as busmaster. Except for the digital or analog input and output modules, the presses are equipped with encoders. The job of these sensors is to ascertain the press angle, thus determining the position of the press. Depending on the angle ascertained, the control system releases the press for charging and discharging.

Moreover, the press motors are coupled to INTERBUS via interfaces; the same applies to the cam controllers that communicate with the servo valves via the digital outputs. These values are used to control the ram, in order to achieve an ideal result. The connections from one press to the next, from press to corresponding robot and from bus to bus are realized by gateways supplied by PHOENIX CONTACT.

On the large press line 11, Renault has used robots for the first time for chaining; the automobile manufacturer used only to use feeders. The robots are equipped with a master/slave card. Via the master, each robot has its own INTERBUS network to control, for example, tool recognition and material acceptance. This decentralization markedly relieves the higher-level control system. The slave section networks all the robots, thus ensuring quick communication. Renault uses a regular bus with its own PC master so that the data can be made available directly in the higher-level networks of the works.

Outlook
Renault will also use INTERBUS, PC WORX and the G4 card for further new press lines or press lines needing modernization. In connection with this, the automobile manufacturer is equipping nine press lines and two try-out presses with the PC-based control technology. The entire control architecture of PHOENIX CONTACT has proven to be a perfect tool for press technology despite harsh environmental conditions. Short cycles and data exchange times as well as strict requirements for the software used are the key to this success.