Is a combined checkweighing and metal detection system double trouble or half the hassle? Lynda Searby checks out the latest equipment to find out

Combining a metal detector and checkweigher in one system isn't a new idea - equipment designers have been making so-called ‘combi' units for years. Could it be, though, that the economic climate is prompting  food manufacturers and packers to opt for combi units instead of separates in a bid to reduce costs?

When Loma Systems launched its CW3 combined checkweigher and metal detector at last year's PPMA show, it reported that many of its customers had expressed interest in the combi unit due to the significant savings that can be made when purchasing a combined machine as opposed to separate units.

PCL Machinery, which refurbishes inspection equipment and has its own budget range, agrees that combi units are becoming more popular, but puts this down to the space - rather than the cost - savings they afford.

"If you have a checkweigher on its own, you need an infeed section, a weighing section and a reject section," says PCL sales director Kevin Hill. "With a combi system, the metal detector conveyor incorporates precision rollers at the end of the infeed to transfer the product on to the weighing platform. This eliminates the need for an infeed conveyor on the checkweigher," he says. "To save 300-400mm by installing a combi is a major factor."

Selo UK sales manager Chris Keenan agrees: "On most production lines space is at a premium."

But surely half a metre doesn't make that much of a difference in the overall scheme of things? "Half a metre might not seem like much of a saving," admits Sarah Ketchin, managing director of Fortress Technology, "but if you're replacing old equipment or upgrading an existing line, asking for an extra 50cm can be like asking for an extra five metres because they've got other pieces of equipment bolted down so you have to fill the gap that's there. Space isn't such a problem on new lines."

So it seems space rather than cost tends to be the primary reason for choosing a combi system. Even so, there is still a cost advantage to buying a combined unit. Weighing equipment supplier Sartorius says its combi units are on average 30% cheaper than installing a separate metal detector and checkweigher. This is roughly in line with the costs quoted by PCL's Kevin Hill.

"For a new combi system built to major retailer spec, you're looking at around £17,000-19,000. The normal price for a checkweigher is between £11,000 and 13,000, and the average price of a stand-alone metal detector is about £7,000. So a combined system will probably save you around £1,500," says Hill.

The other major advantage of buying a combi unit is that both metal detector and checkweigher are operated via one control panel. "If you change from one product to the next, the alterations can be carried out at one screen," explains Selo's Chris Keenan. "If you buy stand-alone units, you are relying on the operator to change both systems individually. I know of instances where product has had to be recalled because the operator has changed the programme on the checkweigher but not the metal detector. A combination unit removes this potential quality-control issue."

According to PCL's Hill, ease of operation is a major selling point for most food manufacturers. "A lot of firms like combined systems because they are easy to work. Their operators are not engineers or computer programmers; they are there to pack products and get nervous if the screens get too complicated."

Solid choice
In addition, Ishida Europe says combis offer better performance, as the metal detector is fixed to the checkweigher and cannot be moved out of position. Slightly higher speeds are also possible as a single frame unit is more stable and compact.

At this point, you might be wondering why anyone would choose not to buy a combi. Fortress's Ketchin admits she's not a big fan of the combi unit. "If one of the units fails, the whole line goes down because you can't metal detect, even if the problem is with the weighing rather than the metal detection system, whereas if they are separate units you can move a metal detector from another line or weigh product off-line."

Nor does she think the slightly lower cost of combi units is a deciding factor. "We recently secured an order where we are going to be supplying separate systems, and we won that against a company who was offering a combi, so I don't think cost is a major factor," she says.

John Stokes, after-sales and application manager with Thermo Fisher Scientific, believes the problems that arise when something goes wrong with a combi unit are one of the main reasons many companies prefer separate machines. "People have stepped away from the true combi because it stops their line if anything goes wrong with either machine," he says. "We get much more call for separate units, and I think that's due to their flexibility more than anything else."

It's not just in the event of a breakdown that individual units are more flexible. They are also more flexible in the event of a company's requirements changing.

"If a company later wants to upgrade to an X-ray system, they cannot easily dispose of the metal detector because it is tied to the checkweigher," says Torsten Giese, marketing manager of Ishida Europe. "And if a new product or pack that is longer is introduced, the metal-free zone (the distance to any metal items that will interfere with the measurements when the product passes through the metal detector) may need to be increased, which is easier with a movable, free-standing unit."

By contrast, free-standing units can be incorporated into combi systems at a later date. Sartorius, for example, says its Synus checkweigher can be turned into a CoSynus combi. "This means anyone who has a Synus checkweigher and later wants a combi unit can have this Synus made into a combi unit at a fraction of the cost of a new combi," explains the company's product manager QA systems Colin Maher.

Another reason Ketchin isn't so keen on combi systems is that while many companies have expertise in either metal detection or checkweighing, not many have equal experience of both. "The company that makes the best weighing system doesn't necessarily make the best metal detector. By buying them separately you can get the best of both worlds," she says.

However, while combis may not be experiencing a massive resurgence in popularity, the fact that some players in inspection equipment are looking at combined X-ray and checkweighing systems suggests that demand is strong.

X-ray specs
Mettler Toledo Garvens is leading the way in this field, having launched its XS3 AdvanChek at last year's PPMA. The system was billed as the first combined X-ray inspection system that fulfils all weights and measures regulations and the
firm says it is already proving popular with ready-meal
manufacturers.

From a technical point of view, combining an X-ray system with a checkweigher is more challenging than combining a metal detector and a checkweigher, which is probably why Mettler Toledo's rivals haven't been so quick to follow suit.

"The environment an X-ray needs is very different to the environment a load cell needs. There are all sorts of vibration and air-flow issues as you need to enclose an X-ray to make sure you don't get any radiation leakage. We looked at this some years ago and decided against it," says Thermo Fisher's John Stokes.

Mettler Toledo says it has overcome any issues and created a unit which saves approximately a metre in line length by locating the weighing conveyor underneath the same cover that prevents operators from coming into contact with radiation.

Whether more companies will rise to the challenge and develop combi X-ray or checkweighing units remains to be seen. No doubt, if the demand is there, there will be companies who will be willing to satisfy it. The machines' space and cost-saving benefits are obviously central to their success, but it seems in the perfectionist environment of inspection and detection these are not the only important requirements.

INSPECTION SYSTEMS ROUND-UP
• In September, Fortress Technology unveiled a throat metal detector believed to be the smallest of its kind. Designed for installation between a multihead weigher and bag maker, the Mini-tex is available with either a 52mm or a 109mm aperture.

• Thermo Fisher Scientific has introduced a new signal filter feature claimed to improve detector sensitivity by 20% on wet and conductive products. Branded IntellitrackXR (IXR), the feature has been added as standard to all APEX metal detectors. Earlier this year, the company also launched a new checkweigher for high-speed weighing applications. The Versa GP can handle line speeds of up to 350 packages per minute.

• Ishida Europe has extended its IX GA range of X-ray systems with the IX GA 2462 for smaller products of up
to 120mm in height and 240mm in width. The X-ray tube is said to require less power, which reduces running costs.

• PCL Machinery's new C2010 checkweigher is an economy system for food companies who want to supply major retailers but don't require any extra features from their equipment.

• Last year, Anritsu, represented in the UK by Selo UK, launched a dual wave detector that can operate two frequencies simultaneously. This means one set can be used to detect stainless steel and the other to detect ferrous contaminants.