Integrating control can be like herding cats
The idea of a ‘control system’ tends to conjure up images of a designed-in network, integral to a given line or plant at the time of installation. But what if your factory – like so many in the industry – has grown and evolved organically over time, incorporating legacy processes and software from different original equipment manufacturers (OEMs)? What does 'control' mean in this context? What are the challenges, and what might a solution look like?
Kinnerton Confectionery grappled with precisely this problem. From a mechanical perspective, its chocolate depositing and filling line was fit for purpose, Siemens business manager for food and beverage Keith Thornhill reports. “But the control and automation software had been through so many upgrades, there were conflicts in the system,” he says. “When it faulted, it took them too long to find the cause and to track down errors.”
The company brought in Siemens to establish a new control system for the entire line, spanning chocolate depositing, a cooling tunnel, fondant filling and pick-and-place.
The problem was finally cracked using the company’s Totally Integrated Automation platform, incorporating unified 12-axis motion control linked to a single programmable logic controller (PLC).
Kinnerton estimates that this has increased the line performance by around 15%. According to Thornhill at Siemens, the increased uptime meant that the payback period for this investment was in the region of six months. “With a single motion controller for the entire line, there are fewer trips to start with,” he explains. “And secondly, when there is a fault, the recovery time is much better.”
He continues: “We had to backwards engineer the whole control system. For each part of the line, the motion control software will tend to be written in a language that’s bespoke to that OEM. If that business is no longer around, and the software’s not available, how do you get to grips with that?”
Thornhill talks about another 20-year-old flow-wrapping installation at an unnamed biscuit manufacturer which involved not 12 but around 100 axes of motion. “We couldn’t get hold of the software, and again, we had to backwards engineer the code,” he recalls. “It took us six months or so.”
Little choice (Return to top)
But in those operations where overall equipment effectiveness (OEE) has fallen to, say, 30% because of line stoppages, manufacturers have little choice but to unravel those legacy control systems and superimpose a new one.
That process of unravelling, or – more positively – of integration, has become easier over recent years, according to automation, data collection and control systems supplier Omron. Over the past five years, for example, ethernet connectivity has largely replaced fieldbus systems as a standard for new installations.
“Before then, people would have laughed at the idea of ethernet operating in an industrial environment,” says marketing manager for automation Karl Walker. “Physically, it’s the same cabling and structures, but the protocols have changed to the extent that they are absolutely real-time: sub-millisecond. What we have now is a far more open automation architecture communicating between servo drives, PLCs, and so on”
The links between the different stages in production not only use the same physical networks as management-level systems such as enterprise resource planning (ERP), but integration and data exchange between the different levels is much easier, says Omron.
Walker, who also lectures at Cambridge University’s Institute for Manufacturing, emphasises Omron’s vision of ‘shop-floor to top floor’ dovetailing of control and visibility of data. Here, many larger enterprises will model operations on the international ISA 95 standard, he says. “Applied to business planning and logistics, this means that when an order comes in, the system will assess how many operators you have available, where you have spare capacity, and allocate production accordingly.”
Simplified layering within the operation is increasingly matched by simplification of controllers. Omron initially used ethernet networking to link into individual PLCs fitted with storage and processing units (SPUs). “We solved a lot of data management and integration applications this way, connecting shop-floor control with enterprise systems,” says Walker.
More recently, Omron developed its open Sysmac platform. “It’s more intelligent, more of a computer than a PLC, and we’ve integrated all aspects of control: logical sequencing but also robotic controls and safety systems,” he says.
Data exchange is much faster, he explains, but so far, there have been no database connections using Sysmac in the food industry.
Attitudes to automation (Return to top)
Some might say that this particular lack of food industry applications is symptomatic of attitudes to automation and control in the food industry as a whole – with a few higher-calibre exceptions, of course. A manufacturer may simply want to secure relevant production data without weaving this into an integrated control and planning network.
At ABB Measurement Products, global product line manager for recording and control Martin Binney deals with the type of business which has grown organically over time, rather than with larger operations boasting their own centralised control systems. “But, for a relatively modest investment, smaller manufacturers can have access to the same level of data recording, and so protect themselves from a traceability standpoint,” he says.
Traceability (Return to top)
Up to 24 inputs from connected measurement devices are available with ABB’s RVG 200 paperless recorder, says Binney. “This can record temperatures linked to specific batches, or temperature and pressure in a retort, for example. This is the next step up from the PLC. Increasingly, manufacturers are linking these devices with PLCs to do the data recording job.”
Paul Griffin, business development director at German-based software company CSB-System International, agrees with Binney that traceability and the ability to link product with a given batch and specific process parameters is more important to most UK food manufacturers than any centralised control function.
“For instance, one customer couldn’t distinguish between product supplied to two main retailers,” Griffin reports. “So, in the event of a recall from one retailer, it had to recall product from the other, too. Another customer was ‘losing’ tonnes of raw material. It might have been due to poor record keeping, or it might simply have reflected poor yield. We tend to come into companies on the back of problems like that.”
In terms of capability, CSB can integrate its technology with ERP or other enterprise-wide systems. “But in the UK, we’ve done a lot of telephone research in the food and drink sector,” says Griffin. “A huge number of companies still operate spreadsheet systems, paper-based on the factory floor, or a concoction of legacy systems. They may be measuring OEE in packing, if they’re lucky, but very rarely on the process side.”
Even where there is a manufacturing execution system (MES), its sophistication may be more apparent than real, says Griffin. “Some people say they can extract MES data from the line, when in fact, any correction has to be manually entered.”
As with Siemens’ example at Kinnerton, he says that any new layer of control has to interface successfully with existing systems, “even if the result is never going to be perfect”. For instance, CSB line control software has been installed in several large meat and poultry plants in Russia. “A single input-output system may have to interface with legacy equipment from half a dozen suppliers,” says Griffin. “We extend line control through processing and packaging, since this is the only way to provide full traceability.”
No uniform picture (Return to top)
Of course, it would be wrong to paint a uniform picture of an industry floundering in its effort to control the uncontrollable, and in the process throwing good money after bad.
Siemens quotes the example of Thatchers Cider. The family business has just opened a new £3M building on its Somerset site with two filling lines. “They’ve identified that they want to grow both in the UK and via export,” says Thornhill. “They want higher-tech equipment and control, but using effectively the same operator skill set.”
Because it is looking 10 years forward, and factoring in the possibility of continued growth, Thatchers is taking a modular approach to the new installation, Thornhill adds.
But even for today’s start-ups which are unable to predict patterns of growth, the option of integrated control is looking less elusive. As Omron suggests, open standards are gaining momentum. And Walker explains that end users are increasingly resisting any attempt by OEMs to lock them into closed, proprietary software.
Thornhill points to the Organisation for Machine Automation and Control (OMAC), which has been trying to establish international open standards. OMAC brings together technology providers, OEMs and end users such as Nestlé. But he admits, it remains “a small club”.
As a further example of convergence, Siemens has its own Optimised Packaging Line initiative, which aims to standardise communications across multiple OEMs in this area.
To what extent this type of initiative will include and favour the smaller end user remains to be seen.
