Real time networks, on-time operations

4 mins read

‘Real time networks’ mean different things to different folks: but ultimately it’s all about getting good information flowing fast around the plant/shop floor and up to the business. Geoff Lock explains.

As the CIM 2000 Show (NEC, Birmingham, 7—9 November) approaches, vendors are preparing the latest in real time factory networking for the industrial market. There will be products on display at the device (sensor/machine item) level, through fieldbus systems (intelligent digital plant networks) and on to higher bandwidth, ruggedised fast control networks – in fact everything that’s needed to keep automated plant, machines and factories running and communicating. There are different developments going on in different industry sectors and vendors reckon that digital networking can make new machines and plant much cheaper to install and run. So what are the important things to consider when looking at factory networking? What exactly is a real time network and do you need one to improve your business? ‘Real time network’ needs to be defined. Are we talking about a specialised, high-speed control network controlling some safety or production equipment or just a permanent link between production processes and the company’s ERP (enterprise) system? It seems that the term is used loosely to mean any permanently connected control network, as opposed to a system with periodic connection. But there are certain real time systems which have characteristics that guarantee response time, reliability and speed of response so they can be used in a safety context. So although commonly referred to in many parts of industry as ‘real time’, these functions can be divided into high-speed networks (the ones that don’t require a strictly guaranteed response time) and safety networks (the ones that do). “The majority of applications in industry don’t need a safety network,” says Kevin Prouty, manufacturing strategy research director for analyst AMR Research. “Many of these come from a time when you had to guarantee reasonable response, but now at least 80% of factory applications can use normal high speed networking. Safety networking need only be used where it’s really necessary. Design for the worst case and you’ll still find today’s high speed networks are adequate for many functions.” If you look at the hierarchy of communications in a factory, it splits neatly into three main parts. At the top is information processing (manufacturing execution systems (MES) and management information systems (MIS)), then control processing (programmable controllers (PLCs), human-machine interfaces (HMI) and automation) and finally the device level (sensors and valves). ‘Sensor to board-room’ integration of information systems involved connecting all these layers together, so that information can move between all three. As you go down the hierarchy, the amount of information involved decreases, but the criticality of response times increases. Safety networking is specialised networking which is much more likely to be used at the device level, although the trend is towards making the Ethernet standard the common denominator at all levels. “Ethernet-TCP/IP is a popular choice for many end users and for a wide variety of network applications,” says Richard McLaughlin from the International Manufacturing Centre at Warwick University. “It offers an abundance of compatible products, high data throughput, and commercially available components at relatively low costs. Plant-floor Ethernet devices will be required to interoperate with corporate information applications, as well as support control, often on the same network and customers will require that devices from different vendors interoperate on the same network.” If you have an application that needs a network, then the open standard of the immediate future for high-speed networking is Ethernet, which has been around in some form or another for more than 25 years. It is well understood, and the latest version is suitable for all but a few safety-based or critical applications. Ethernet is just a networking standard, but you need to have devices and applications which use it to advantage. Today’s fieldbus standards (like Foundation Fieldbus, Profibus and DeviceNet) will continue, but in future many of them will be available over Ethernet cabling. At the moment, though, there are improvements to be made to manufacturing flexibility by the use of this level of digital industrial networking as the basis of production set-up and control. New levels of flexibility are being achieved (see Ford panel) as well as improved control and integration of information management throughout the business. The drive is going to be towards more interworking between systems as e-business demands improved information flow within and from the production processes. And with new technologies, information flow is two-way, as has recently been illustrated by a US customer of Invensys-owned Wonderware. As a major food producer, the company has had to address the tricky problem of material traceability, yet in doing so by integrating information systems within the enterprise it has now been able to dramatically increase its ability to tune on-going production. “We’ve got a more realistic view of the production process – how products really run through the plant,” says William Friend, group vice president, supply chain management at JR Simplot’s Food Group. “One thing we’ve clearly done is gain control over inventory of production materials. Once the system was up and running and providing control, inventories were reduced by 15—20%. And inventories are turned faster with significantly better accounting of material costs.” At CIM 2000 there will be a virtual factory tour through which visitors can explore the potential for some of the kinds of improvements to be made by networking manufacturing systems together. There will be a practical example which encompasses an organisation from the boardroom to the factory floor, assisted by the likes of automation company Rockwell, ERP software giant SAP and enterprise asset management (EAM) and maintenance software firm PSDI. The exhibit will give an idea of what can be achieved, whether that is giving improved return on assets, optimising manpower or stock levels, better delivery, increased utilisation or reduced wastage. Go along and see whether some of the ideas can help your company become a winner in the global marketplace.