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European applications for the CC-Link industrial fieldbus

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CC-Link is very popular in Asia, and more widely used in Europe than might be thought. Nevertheless, machine builders exporting to Asia need to consider CC-Link more seriously if they are to be successful.

European applications for the CC-Link industrial fieldbusCC-Link is widely believed to be the strongest fieldbus protocol in Asia, and there are now over 850 compatible products made by partner companies, and approaching 4,000,000 installed nodes. So European machine builders, control companies and OEMs need to have CC-Link capabilities if they are serious about exporting to the world’s fastest growing manufacturing region.

Engineers in China, India, the Tiger Economies, Japan and across the Pacific Rim have long known that they cannot rely solely on low labour costs, and that automation is essential for the development of their economies. Predictable and consistent product quality is the greatest arbiter in today’s global markets. Low and lowering prices are increasingly a given, on-time delivery is expected, and regular product redesigns are taken for granted; quality is the one differentiator that manufacturers can offer.

It is not surprising, therefore, that Asia is building automated plants far faster than anywhere else in the world. And for device-level communications, the fieldbus protocol of choice is frequently CC-Link. Less well known in Europe, CC-Lick was developed by Mitsubishi Electric in Japan in the 1990s and released to the public domain as an open system in 2000. It was developed in recognition of the need for a rugged, flexible, high-speed and deterministic device-level network for manufacturing companies

CC-Link’s recognition in Europe is still low, with only 5 per cent of the CLPA’s (CC-Link Partners’ Association) members being European. But its recent installed base and growth is far higher than most competitor protocols, because so much control equipment used in Europe is of Asian origin. If the end-user or OEM leaves the decision of which protocol to use to the controls supplier, the chances are that CC-Link will be selected.

A great attraction of CC-Link is that it uses an RS 485 topology, so engineers feel comfortable with it, and it has the advantage that the wiring route does not have to be consecutive between field devices " which is very useful, considering that most installations are subject to constant minor reconfigurations through their working lives. Communications speed is 10Mbit, which is faster than most comparable protocols, and cable runs can extend to 12km, which is useful for large sites and for applications involving remote stations.

Most control systems are designed with a view to future expansion and development. CC-Link networks can be configured to include dummy stations that can later be converted into operational status using the hot-swap capabilities. Other features include auto-start-up, auto-recovery and self-healing capabilities.

Bottling plant application

CC-Link provided the flexibility that enabled Longslow Dairies in Colwyn Bay to buck the industry trend and supply milk in environmentally-friendly glass bottles rather than disposable plastic containers.

The improved control of the plant has increased efficiency from 60 per cent to 90 per cent, enabled a 30 per cent increase in throughput to be achieved, led to a reduction in energy consumption, and bottle breakages on the line have been all but eliminated.

Longslow Dairies' system was designed to be modular so that it could be installed in a series of steps while the plant continued to operate. A CC-Link communications backbone was installed around the dairy early onto which each newly-automated section was connected in turn. In all seven sections, each controlled by a local PLC, were added to the backbone. A master PLC providing strategic command was also installed and provides the portal for the proposed connection of remote diagnostic and maintenance tools and a high-level enterprise management system.

Much of the CC-Link’s data handling is real-time. For example, feedback systems constantly trim conveyor speeds to prevent bottle pressure build-up, a vision system checks for bottles that are dirty, misshapen or retaining rinse water from the cleaning processes, and production is just-in-time co-ordinated with the arrival of delivery lorries. Additionally the whole plant can be cleaned and switched over to orange juice packaging in less than 20 minutes.

Cable-laying application

Subsea cable laying engines have had to become very much more sensitive to cope with the switch from robust armoured copper cables to more delicate fibre optics. The tension with which cable is laid has to be constant, despite the movement of the ship in the ocean swell, necessitating constant monitoring and speed trimming of the multiple pairs of pinch wheels used to pay out the cable.

The latest generation of engines developed by Fraser Hydraulic Power of Newcastle uses a powerful PLC for controlling a PID loop for each pair of wheels. The PLCs communicate with one another and with an HMI via a CC-Link fieldbus network.

A major problem can occur when the engine is free-spooling cable onto the seabed, as this can turn the drive motor into a generator. Previously this has been addressed by incorporating a large braking resistor into the engine, but the precision control provided by the CC-Link allows the variable speed drive to switch instantly into a regenerating mode.

Operators have taken to the new Fraser engines, because they can be used from far smaller (and cheaper) vessels, and their precision control has reduced the amount of downtime due to cable breakages by an order of magnitude.

Effluent pumping application

Turnaround time on the cross-channel Eurostar train is limited, yet cleaning has to be to a high standard for this most prestigious of services. Emptying and cleaning of the effluent tanks has been upgraded to being fully automatic following an upgrade of the Lavatory Discharge Apron at the London terminus. It now sports over 40 PLC-controlled out-pumping stations, all connected via a CC-Link network.

The cleaning cycle at each pump is self-optimising and includes emptying, rinsing disinfecting. An operator merely connects the extraction pipe and waits for the cycling completion indicator to come on. Notably the system is programmed to recognise five different types of train and to select the appropriate cycle.

Foil rewind application

When Becatron Mechatronica in Belgium wanted to control energy usage on its 40 aluminium foil rewind machines, it decided to integrate their control using a CC-Link fieldbus. Each rewinder is quite energy-hungry, being heavy, high-speed and temperature-controlled.

Start-up of the rewinders is now sequenced over the CC-Link to prevent power surges, and machines that are not in use can be shut down between production runs to save energy. With the plant split into seven sections, each comprising two distinct system, a master controller is also required on the network. Originally a multi-drop RS 485 architecture was used in the control system, but the CC-Link has simplified the design and led to better control, faster reactions and improved reliability. Additionally noise immunity in this high-energy environment has been proven.

Payback for the CC-Link installation costs has been achieved in under one year thanks to the energy saved.

CC-Link is perhaps the unsung hero of the industrial fieldbus world. A powerhouse in Asia, its use in Europe is higher than most people realise, but there is a growing recognition that it must be brought to the fore if Europe is going to win exports to the fastest developing region in the world.

21 January 2008

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