Equipment

Packers and producers are tapping into checkweighers as a source of intelligence.

On the face of it, the raison d’être of the checkweigher is to arm producers and packers with evidence that their products satisfy average weights legislation, should trading standards ever have cause to suspect them of short-changing consumers.

But as producers and packers are increasingly discovering, that’s not all they are good for. Checkweighers provide a wealth of data, from basic weight data to line efficiency information and throughput data. While this, in itself, is nothing new, advances in extracting and communicating that data are making it more meaningful and accessible to production and quality personnel.

“The value of the data that a checkweigher can collect has become increasingly relevant and valuable to our customer base. From that data, you can learn a lot about what your production line is doing,” says Martin Lymn, global product manager for checkweighing with Thermo Fisher Scientific (formerly Thermo Electron). “The regulatory element aside, the ability to leverage checkweigher data is probably the biggest thing our customers are wanting from a checkweighing product at present.”

The most common means of exploiting checkweigher data for process control purposes is to integrate the checkweigher and filler to provide servo-feedback. So if the filler is trending upwards or downwards, the checkweigher monitors the trend over time and has the facility, through feedback control, to send signals back to the filler to either increase or decrease the amount it is filling. For users this means greater cost efficiencies as product giveaway is reduced.

Manufacturers in the US have been using the checkweigher in this way for a number of years. European manufacturers have, however, been slower to harness the checkweigher’s process control potential, though Lymn says they are now developing a better understanding of the relationship between the checkweigher and upstream and downstream processes.

“The number of people buying the servo option has increased, particularly in the UK and Europe, where the checkweigher has historically been a regulation compliance function,” he notes.

It is nevertheless surprising how long this has taken, given the cost savings that can be accrued by eliminating giveaway.

“We have examples where, over a six-month period, the checkweigher has actually paid for itself and some, just by offering feedback control to the filler,” says Mike Bradley, manager of Mettler Toledo’s product inspection business.

These claims are backed up by Lymn, who says he has had customers in the US who have had payback from a checkweigher in a matter of weeks, and even days. By reducing their giveaway by what on the face of it seems a fairly small amount, when multiplied by the number of packs produced in a day, amounts to astronomical raw materials savings.

Another use of checkweigher data is calculating and investigating the causes of product waste and loss. Where a producer knows the weight of the raw ingredients that have gone into a batch, they can calculate raw materials wastage, as the checkweigher knows the total weight of the final batch. From checkweigher data the producer can deduce how much of that wastage is a result of underweight or overweight product. What’s more, if the checkweigher incorporates an open flap detector, it is possible to tell how much wastage is due to defective packaging, and if it is combined with a metal detector, losses as a result of contamination can also be calculated. In this way, says Lymn, the checkweigher can help producers build the bigger picture – where are the losses and what can be done to reduce them?

Bolton-based pizza and pizza crust manufacturer Stateside Foods is one company that has tightened control over raw materials usage by installing a combination checkweigher-metal detector and a data management system.

The machines, which were custom-designed by Cintex, part of Spectrum Inspection Systems, feature specialised laser cut guarding and a minimum damage reject system. Manufacturing information and control system (MIACS) line management software facilitates production of daily reports, which Stateside says have proved invaluable. “We now have good control over raw materials usage. Wastage has been significantly reduced and we have received rapid payback on the equipment,” says Steve Hardie, site general manager.

Checkweigher data can also be used to track deviations in multi-head filling. “Instead of just tracking average weight, which is what you need for regulatory compliance, you can actually track the standard deviation of each filler head. So the user can tell if an individual filler head is constantly over- or under-filling – or is simply erratic,” explains Lymn. “Say, for example, you have a 10-head filler with one defective head. Without a smart checkweigher you might know 10% of the product was being rejected, but you wouldn’t know why. A checkweigher that can monitor every filler head can trace it back to an individual head, making maintenance much easier.”

This type of data has always been generated by the checkweigher, but it is only with the advent of data communication and management information systems that production staff are able to store, extract and interrogate it electronically and remotely.

Finding a connection
In recent years, Ethernet has established itself as the industry standard network connection for linking a number of systems in a production environment. And, as Alan Johnson, group product manager with Spectrum Inspection Systems, parent company of Loma and Cintex, explains, this makes it much easier to link systems together. “If you’ve got a device which is Ethernet-ready – which our checkweigher is – it’s very easy to connect several systems onto the Ethernet network and give them an address, then you can start to transmit data quite freely across the network and view that data on any PC that is connected.”

Data management or management information systems that collect data from checkweighers and provide information that can reduce giveaway and exert greater control on the product process have also advanced considerably compared with just a few years ago. Off-the-shelf software packages have given way to systems which allow users to configure information screens and support themselves.

“The interest lies in having open systems, so manufacturers have the ability to configure screens the way they would want those screens configured in their factory,” says Johnson.

To this end, Loma’s checkweighers are compliant with object linking and embedding for process control (OPC). Loma says that, in most cases, manufacturers of data management systems can provide OPC-compliant interfaces.

Although data collection, communication and management might be a key focus for checkweigher manufacturers, there are still other areas of innovation.

Mettler Toledo reports increasing demand for customised combination systems which integrate checkweighers with laser marking and vision systems. “That means as well as doing the checkweighing, we’re marking the products and checking that the marking is correct. We can even put batch data on that links into the checkweigher and is read and confirmed. We call it a QA station rather than a weighing station,” says Bradley.

While most of the demand for these systems comes from the pharmaceutical industry, Bradley is getting more and more requests from the food industry. “It utilises the space for more than a simple weighing job, reducing the overall footprint. Space is at a premium in any production environment.”


Ishida gets fresh in France
An Ishida Fresh Food Weigher has transformed a French manufacturer’s packing operation from a slow manual process into an efficient automated line, capable of 35 packs per minute.

Manual packing of Le Magicien Vert’s ready meals, which include paella and fricassed lamb, was slow and labour intensive. However, the tendency of meal components to stick to machine contact parts precluded automation – trials with a multihead weigher found the weigher unable to cope with product changeovers and product clumping together.

Le Magicien Vert had all but given up on any hopes of automated weighing when Ishida came up with a solution in the form of its Fresh Food Weigher, which has its hoppers arranged in linear tiers. The weigher utilises the combination weighing principle, traditionally the domain of dry and frozen foods, and applies it to sticky products that are usually weighed and packed manually. 

Linear belt feeders and special non-stick hoppers with scraper gates avoid product sticking and ensure a smooth, reliable and consistent product flow through the weigher.

The machine is designed so that a single operator can comfortably supervise the eight belts, adding or removing product, or swapping product from belt to belt, to maintain an even flow.
Product changeovers on the weigher, which handles up to 25 different recipes each day, take around 15 minutes. 

The system has been operating at Le Magicien Vert for more than a year without causing machine-related downtime or requiring any maintenance.