Manufacturers turning to fieldbus network technology
gives manufacturers the opportunity to better control the food
process, claims developer Profibus. Fieldbus networks are already
used by many processors, and this trend looks set to increase,
writes Anthony Fletcher.
German-based technology group Profibus has launched Profinet, an Ethernet-based automation solution that it claims provides manufacturers with a scalable, high-performance migration path to the industrial Ethernet. Profinet is a significant development as it provides Ethernet migration not only for Profibus, but other fieldbus systems as well.
"It's a remarkable achievement that's due mainly to the technical excellence of Profibus, which can meet a very wide range of needs across the automation spectrum," said Profibus International chairman Edgar Kuester.
The group believes that Profinet satisfies the trend towards distributed automation systems. Kuester claims that it offers a flexible approach to automation for an increasingly global and Internet-dominated world.
Fieldbus networks are a special form of local area network dedicated to applications in the field of data acquisition and the control of sensors and actuators in machines or on the factory floor. Fieldbus networks typically operate on low cost twisted pair cables. They are optimised for the exchange of short point-to-point status and command messages.
This means that they can reduce the complexity of a control system in terms of the hardware outlay. There is also a reduction in the amount of PLC or DCS hardware requirements, and this reduces the need for large control cabinets to house such equipment and associated connecting hardware.
As cabling is reduced, the need for junction boxes, control panels and large cabling runs are eliminated. These advantages can relate to a direct cost saving.
Ethernet is the least expensive high-speed LAN alternative. Ethernet adapter cards can transmit and receive data at speeds of 10 million bits per second through up to 300 feet of telephone wire to a hub device normally stacked in a wiring closet.
The launch of the new technology marks a significant step forward for Profibus. The group recently announced that at the end of 2003, over 10 million Profibus devices had been installed in factory and process automation applications. This, claims the company, is a total substantially higher than any other fieldbus solution.
Profibus-DP technology was recently chosen by a drinks bottler in Germany to control its blow-moulding machines. The company needed to achieve greater flexibility so that the process could quickly adapt to different shapes and volumes of bottles.
To achieve this, two encoders, were installed to provide feedback during the transportation of the blank forms and of the final products. Another encoder coupled to a cable-spring converter controls the movement of the blast pipes when they are lowered into the mould cavities.
In addition, French fry carton maker Roberts PolyPro adopted Profibus technology after looking for a more efficient and up to date automation solution for a new high speed French fry scoop (carton) maker that would run at 1,800 ft/minute, or 260,000 scoops per hour.
The solution was to use Siemens S7-300 PLC and MM440 AC Drives networked using Profibus. A TP270 touch panel was incorporated for process setup and visualisation.
"By using standard motors and vector drives we had a lower cost, off the shelf solution, which gave significantly improved machine performance and maintenance," said PolyPro chief engineer John Young. "The Profibus network also eliminated costly and troublesome wiring."
Larry Matson, director of engineering, said: "We had higher line speeds and were able to optimise machine efficiency by maintaining ratios between the drives through to full line speeds - and we attribute that to the high speed communications of Profibus and the overall system architecture." Approximately 1.3 million Profibus devices are installed in process plants, of which 290,000 are Profibus PA devices with the MBP (Manchester-Encoded Bus Powered) interface conforming to IEC 61158-2 required for hazardous area use. This figure comes from research undertaken by the top-seven Profibus PA vendors representing about 90 per cent of the market, which also suggests 320,000 Profibus PA devices are now in process plants.
The remainder are Profibus DP devices in upstream (materials handling, etc.) and downstream (bottling, packaging, etc.) process applications. The group claims that Profibus DP, which shares a common communications protocol with Profibus PA, is the only fieldbus that can provide compatible networking technology for all parts of the process plant.
"By all accounts, the contribution made by Profibus to both process and discrete manufacturing is momentous, dwarfing those made by competitive technologies," said Kuester. "Furthermore, the market's enthusiasm for Profibus shows no sign of decreasing and we believe that we will double the number of installed devices to 20 million by 2008. This offers significant opportunities for member companies."
Profibus represents more than 1,200 member companies worldwide. It is the world's largest organisation for industrial communication, and is based in Karlsruhe, Germany. Along with Profibus, other networks products currently available include Filbus, Bitbus, WorldFIP, and Interbus-S.
