Policing the lines

For consumers, the safety of the products they purchase – particularly food – is of paramount importance. For producers, safety is also of vital importance, as are cost-efficiency and accuracy.

In the worst case scenario of contamination – a product recall – the costs could run into millions of pounds, especially if there are legal battles to fight, while the costs of overfilling, even by a fraction of a gramme, could also amount to a sizeable sum over a period. Hence the requirement to "police the lines". However, this activity must not impact on production line efficiencies, even though there is a constant need to strive for 100% security.

To this end there has been a myriad of computer systems and programs developed, some for general use and others which are industry specific. To achieve the required level of security in packaging operations, line manufacturers and checkweighing and metal detection equipment suppliers must work closely with their customers. From the customer perspective, apart from cost-effectiveness, knowledge and choice are two key issues and this is probably an area where a harmonious relationship is called for above many other areas of packaging.

For all this to work packaging technology personnel need to be able to explain critical elements – particularly for checkweighing – in a straightforward, easy to understand fashion. Ishida's Pete Johnson is fortunately one such person as he unravels the important elements that customers need to understand. "The checkweigher is often referred to as the 'policeman' and this underlines the importance of its role in ensuring that packs are the correct weight or contain the necessary components as stated on the pack, enabling companies to meet a variety of legal obligations. It is also important to remember that although checking for the correct weight is the main function, the machine can actually perform a wide variety of other tasks.

"In a nutshell", says Johnson, "a checkweigher checks, classifies and segregates by weight. The segregation means the rejection of packs that are too much over- or under- weight, but equally it can be used to check that various components in a package, instructions, coupons, lids etc, are all included.

"Beyond this there is the verification of the correct number of products in a pack, classification of products into weight grades or checking package mixes against weight limits to keep the solid to liquid ratio within the established standards. Indeed, a whole wealth of statistical data can be provided to both monitor and improve the overall efficiencies of packaging production lines. The key to this for the customer is that there is the confidence that 100% of all packs are sampled not just one in 10."

Overfilling problems

Loxtons – an award winning food-manufacturing company based in Stockport, Cheshire, which produces a range of ready meals for the hotel and pub industries – had a problem with overfilling of packs and required a checkweigher that could be integrated into the existing line. Mettler Toledo provided and installed a Garvens Combi Checkweigher, which is both a checkweigher and metal detector in the one unit. Weights are measured and metal-contaminated products are detected quickly and precisely on the production line. The rejection of "bad" products is ensured by two pushers so that metal contaminated and off-weight products can be separately rejected. Paul Durbin, managing director of Loxtons, explained his choice criteria. "We had to have a cost effective quality solution. Mettler Toledo have the benefit of being able to offer a wide range of products that are ideally suited for food processing which is what we needed. We use the equipment for checking and weighing individual portion dishes in the assembly area so it is vital that the instruments we use are highly accurate and reliable. The checkweigher is easy to use, easy to clean and it has been successfully integrated into the existing production lines without any problems, minimising downtime and inconvenience."

Another solution for Loxtons was also required in the assembly room where different elements of the final dish are brought together to create the complete meal. Here Mettler Toledo's Viper scales were installed as Paul Durbin again comments. "This equipment is again easy to use and clean. The unique PrintCard system for the checkweighers was easy to install and, as a result, our production line has become more automated and has improved efficiency by speeding up the end-of-line checking procedure."

Traceability legislation

While product safety is obviously a key element increasing legislation is also having an effect on food production lines. One such piece of legislation is the recent traceability laws enforced in January 2005 under the EUs General Food Law legislation (178/2002) which states that food manufacturers must be able to trace food through all stages of production, processing and distribution.

With this in mind Advanced Dynamics has introduced into the UK the Tesab TC3 checkweigher, which is a fully automatic stainless steel machine complete with the latest Windows XP-based management software. This machine has been developed especially for the food sector, including those dealing with meat and poultry, dairy and fresh produce, and is capable of handling pack weights between 10g and 40g at speeds of up to 75m/min. The software provides optimum communication possibilities to other computer systems and many operational parameters can be stored in the computer memory. This versatile machine also has the additional option of a metal detection facility.

According to Advanced Dynamics director Malcolm Little, "the real benefit of the Tesab TTC3 is its intelligent management software. It is easy to operate and feeds back accessible and logical information that would otherwise be difficult to track."

The wide variety of machines available in this sector means that almost any requirement can be bought "off-the-shelf" or with minimal customisation. One example is Ishida Europe's DACS-Zenith checkweighers which have been installed at Dubai-based confectionery. manufacturer Seville Products. The company has a high production throughput of its 17.5g chocolate bars and the DACS-Zenith was specifically developed for high-speed food applications with low target weights.

It operates at 600 bars/min and allows for identification of even the slightest deviation from pre-programmed parameters, to deliver accuracy within 0.02g. "Weighing accuracy is an important part of overall product quality, yet because our lines operate at high speeds it was vital to find a checkweigher that would not affect production efficiencies. The DACS-Zenith checkweighers from Ishida have proved ideal for our needs," comments Seville Products.

UK sales and service manager of Mettler-Toledo Safeline Mike Bradley says the last few years' heightened food sector focus on consumer safety, coupled with a growing need to scrutinise other goods like pharmaceuticals, has meant a flourishing market for metal detection equipment.

The company should know. Although in business for just 16 years, today it claims to be the world's biggest industrial metal detector manufacturer, selling three times the number (around 7,000 in 2004) of its nearest rival, Japan's Anritsu.

At September's PPMA exhibition it will unveil a new conveyor metal detector, the R Series Profile, which it believes represents the biggest step change in performance since the mid 90s launch of Safeline's Signature range – the Signatures were reportedly the world's first high frequency metal detectors to offer comparable performance to those operating at a conventional setting.

Designed primarily for today's highly automated food production plants, the Profile was developed to be "future-proof", largely around the features Safeline's FMCG customers told it they required. Bradley explains: "In particular, its design should address growing food and pharma producer demand for equipment that will run trouble-free 24 hours a day, seven days a week, with minimal operator intervention.

"Additionally, with suppliers to the big retailers having to pare every penny from production costs, line managers view excessive downtime as a disaster. The Profile is not only the fastest, best-performing conveyor metal detector available today but, with features like failsafe condition monitoring, through which an alarm system linked to the coil alerts operators of potential problems long before a breakdown can occur, should give years of uninterrupted service."

The Profile also features a new change free running mode, allowing numerous product types that exhibit a product effect to be inspected without changing detector settings. The company says that unlike other "single setting" detectors, it uses multiple phase filters to measure and memorise each individual product profile and combines these to deliver one "change-free" setting for multiple product inspection.

Performance monitoring

Special features to assist user validation and performance monitoring include real time histograms that display product characteristics, while the Profile's memory stores data on every product passing through the unit.

The Profile also offers fully ethernet connectivity, enabling internet downloading of software upgrades and allowing production managers to monitor several detectors' operation remotely.

Alongside its metal detectors, which account for 80% of revenues, Mettler-Toledo Safeline also makes X-ray machines, usually preferred for specific applications like checking aluminium foil trays and identifying non-metal contaminants like bone and glass.

Mettler-Toledo Safeline's new Series 10 X-ray machines feature a computer-controlled "low energy" X-ray generator and powerful computer data analysis system, enabling them to detect minute density changes that can mean product contamination or deviation from specifications.