On The Road To Lean Automation
- Published: Monday, 28 May 2012 17:29
A key challenge facing industry today is the development of automation systems that offer data transparency and scalability while satisfying the constant demands for increased performance, additional functionality and cost reduction.
The fast developing concept of lean automation is, however, providing innovative and effective ways of meeting this challenge, says Stuart Greenwood of Eaton’s Electrical Sector.
The concept of lean manufacturing is widely known, as are the benefits it offers in terms of enhanced efficiency, continuous improvements in product quality and the elimination of waste. But what is lean automation? In essence, it is the development of automation systems that mirror many of the benefits of lean manufacturing.
For example, lean automation makes the design and implementation of automation systems more efficient, it facilitates continuous improvements in the performance and capabilities of those systems, and it provides scalability that eliminates wasted design effort by allowing the same basic design of automation system to be used for a whole range of machines.
In fact, lean automation slims down control panels, simplifies wiring, increases data transparency, reduces engineering and commissioning requirements, increases performance and reduces costs, and it does all of these things to a degree that is not even approached by any other automation concept.
So much for the theory, but what are the practicalities of lean automation? To answer this question, it’s necessary first to look at the two core technologies that underpin it. The first is bus-based control wiring systems (or lean panel wiring systems) for use in control panels, of which Eaton’s SmartWire-DT system is the leading example. The second core technology is the integrated HMI/PLC.
Lean panel wiring systems revolutionise the design and construction of control panels. All of the conventional control wiring is eliminated, replaced by a single bus cable that loops round the devices within the panel, including, for example, motor starters, inverters, pushbuttons and indicator lights. This single cable links all of the devices direct to the PLC or smart relay that forms the basis of the control system, thereby virtually eliminating the need for this unit to have conventional inputs and outputs.
The inherent simplicity of lean panel wiring systems means that modifications and updates can be incorporated easily and inexpensively. This same simplicity also facilitates the design of scalable and modular systems that are applicable to a whole range of machines.
In addition, these systems not only carry control signals to and from automation devices, but also data. This means, in principle that any control device, whether it’s something as simple as a sensor or as complex as a motion controller, can send data to the PLC for onward transmission to a high-level SCADA or ERP system, thereby providing complete data transparency.
Put simply, adopting lean panel wiring greatly improves the transparency of the automation system. Since fieldbus and network based field wiring already supports information exchange, the addition of lean panel wiring means, in essence, that any information about any aspect of the automation system’s operation and status can be made available wherever it is needed. This transparency is one of the key elements for lean automation, which is one of the reasons that the description lean panel wiring for the new bus-based systems is preferred.
Let’s turn now to the second core technology for lean automation – the integrated HMI/PLC. These devices have essentially been made practical by lean wiring systems, which mean that they have to make only minimal provision for conventional I/O. This has allowed the HMI and PLC functions, which are in any case closely related, to be brought together in a single compact unit. Compared with the use of a separate HMI and PLC, cost and space savings are the immediate benefits, but another key factor is that programming is simplified.
The best of the HMI/PLC products also have comprehensive communication options enabling them to readily exchange data with external systems. This means that the automation system is no longer an isolated island of intelligence, but a fully integrated part of the production plant capable of communicating directly with the IT systems that handle, for example, customer order scheduling and quality control.
Now let’s look briefly at how the move toward lean technology has already affected the design of automation systems, and how it is likely to affect them in future.
Many of the automation systems in use today are based on what might be described as “traditional” architecture, with a central PLC, a separate HMI and conventional wiring both in the control panel and the field. This type of architecture is, however, very labour intensive in view of the large amount of wiring needed. It is also inflexible and difficult to modify, and it provides a relatively poor level of data transparency, as the control wiring is, in most cases, unable to transport data to the PLC.
The first step forward was to replace the conventional field wiring with a fieldbus system and to start using remote I/O modules. This greatly reduces the amount of wiring needed in the field, and also makes the system more flexible. However, it brings only marginal benefits within the control panel and, in particular, does nothing to make the control panel easier to modify. It does, to some extent, enhance data transparency, as most fieldbus systems can transport data. Data from devices mounted within the panel, such as starters and drives, usually remains inaccessible, however.
Today, we can take another step forward and produce automation systems with an integrated HMI/PLC and lean wiring within the control panel, complemented by remote I/O modules and a fieldbus system for field wiring. (See figure 1). This architecture – which can be implemented with currently available products – gets close to delivering all of the central benefits of lean automation.
Less space is needed in the control panel than with the older architectures, and the amount of wiring is greatly reduced both inside and outside the panel, with a consequent reduction in costs. Flexibility is much enhanced and the PLC can readily access data from all of the key automation components. The greater flexibility and reduced costs of this approach also make other improvements – such as automating product changeovers on the machine that’s being controlled instead of relying on time-consuming manual resetting – practical and cost effective.
In the near future, it will be possible to go even further down the road to lean automation, by using a single bus-based wiring system inside and outside the control panel, thereby eliminating the need for a separate fieldbus. (See figure 2). This will provide further cost reductions, exceptional flexibility and complete data transparency. In short, it will meet all of the requirements that have been identified as being essential for future automation systems.
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