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Necessity is the mother of invention. When the Ancient Greek philosopher Plato coined this phrase, he wasn’t talking about packaging integrity equipment. But had he been living a few thousand years later, he could have been.

Guaranteeing packaging integrity and eliminating defects such as leaky seals, faulty closures and incorrect pack-product combinations has never been more important.

“In the enormously competitive retail market, as much consideration must be given to producing consistent, structurally sound and defect-free packaging as is given to pack presentation,” says David Mercer, technical marketing executive at Mecmesin, based in West Sussex.

The drivers for this are numerous. Peco Europe sales manager Glen Oxborough lists several: “Firstly, brand owners are looking to protect their most valuable asset – their brand. Litigation resulting from packaging defects makes press headlines and requires costly product recalls. Secondly, more focus is being placed on Hazard Analysis Critical Control Point (HACCP) and risk management. Finally, the contract-packing market is highly competitive and each producer is looking for an edge to differentiate itself.”

This ‘necessity’ of consistently delivering flawless packaging has spawned a battery of integrity testing and inspection equipment, from leak detectors and torque testers to vision systems and materials testing.

What can go wrong?
Mecmesin’s Mercer says joint or material failures are potential problem areas. “From ultrasonic welds to adhesive bonds, joined parts will always pose a risk of failure. Films and foils sealed over polystyrene containers, foil blister packs, crimped toothpaste ends, drink cartons and sauce sachets are all typical examples,” he says. “Also, if the packaging material is not sufficiently strong, then failure can occur as a collapse, rupture, split, tear or crack.”

Mecmesin offers force-testing equipment ranging from benchtop stand-mounted force gauges to computer-controlled automatic systems and twin-column test frames, which can be fitted with dedicated grips and fixtures to carry out tests on packaging and materials. These include the joint-strength test (a generic tensile test to destruction on two mating components), the top-load test (a compressive test performed on containers to assess resistance to topload), pierce-force testing of foils and films, trouser-tear tests (recording the force required to commence and propagate a tear) and simple tensile or compressive tests on packaging material.

Earlier this year, competitor Lloyd Instruments, based in Fareham, Hampshire, designed a ‘jig’ for Diageo’s brand technical centre in Scotland. The attachment, which works with Lloyd Instruments’ LRXPlus materials-testing machine, tests the strength of the base of cardboard presentation boxes for whisky and other alcoholic drinks to ensure that the box will not give way under the weight of the bottle.

Materials testing
Lloyd Instruments export sales manager Carl Bramley says he is seeing increasing demand for materials-testing equipment as a result of the drive to reduce packaging. “There’s a lot of pressure on the packaging industry to reduce packaging. Obviously that can be done through design, but it can also be achieved by minimising the thickness of the packaging material. However, you have to be sure it isn’t at the expense of quality and functionality, which is where materials testing comes in.”

Closures can be another trouble spot, as Mecmesin’s Mercer explains: “Screw closures must be applied with precisely the correct level of torque. Too much may damage a waterproof cap lining and compromise the seal, whereas too little may leave the cap insufficiently tight to create a hermetic seal.”

Mecmesin has just relaunched its Orbis digital torque tester for screw-lid containers and is about to launch a new system called the Tornado. Both systems are small, portable, battery-powered and feature water-resistant cases. The Tornado also offers the ability to measure the two characteristic torques associated with tamper-evident closures (slip and bridge torques).

For peelable lids on containers such as yoghurt pots and daily-dose drink bottles, companies such as Mecmesin, Lloyd Instruments and Stable Micro Systems offer equipment capable of testing peel strength.

“You don’t want it to be really difficult to break the seal because you end up tipping the contents all over yourself, but then again you don’t want the seal to be so weak that ingressive microbes can cause spoilage,” explains Jo Snewing, applications manager at Stable Micro Systems.

The Peel Rig, an attachment designed for use with Stable Micro Systems’ TA.XTplus texture analyser, records the force required to open peel-back lids. Manufacturers can use this data to establish an optimum force.

Badly applied caps
According to Heuft sales director Dominic Metcalf, one of the biggest sources of supermarket customer complaints is badly applied caps on milk bottles. For this application, Heuft supplies charge-coupled device (CCD) vision systems to check bottles after capping but before heat sealing.

“The caps are placed on the bottles, tightened and then heat sealed. If the cap is not applied absolutely square, the seal will not be effective,” explains Metcalf. “One of the problems with milk bottles is that they are very cheap containers – the tolerance of the bottles is all over the place. So you can get variations in bottle height.”

The Heuft system overcomes this by looking at the cap, taking a reference point – usually just underneath the cap – and calculating over-height (that is, a cap that’s slightly raised) to an accuracy of within 0.5mm.

At Brau this year, Heuft previewed a Tetra Pak leak-detection system. “A leaking Tetra Pak will sag a little so you get a slightly curved wall, so the system looks at the side dimension of the pack along with the fill level,” explains Metcalf. “It combines the two calculations, which allows it to determine whether the container has a leak.”

Once the preserve of pharmaceuticals, vision inspection is becoming an increasingly popular technique for checking fill level, cap position, tamper band presence, label presence and placement and data in a range of industries.

“In our labelling lines we are being asked to check for label presence, correct label information, both in text and barcodes, and even the accuracy of registration of the labels,” says Sessions of York machine division manager Peter Haw. “We can incor-porate camera vision systems, which will recognise shapes, sizes and colours of products, with operator warning systems, both visual and audible. Many of these innovations have been developed within the pharmaceutical sector, where the integrity and security of products is paramount, but their use has been readily absorbed into other areas where product protection is also of the essence.”

Vision inspection
One of the earliest adopters of vision inspection outside the pharmaceutical industry was Premier Foods, which now has 23 systems from Machine Vision Technology (MVT) installed on its canning lines.

As well as selling products under its own brands, Premier Foods manufactures private label products for the major retailers. One of the problems it faced was that of mislabelled cans. Cans couldn’t be labelled until they had been heat treated, which meant that in the interim there were unlabelled ‘bright cans’ at risk of being transferred onto the wrong line.

MVT designed a vision system that reads the barcode on each can label and matches it with the product code on the bottom of the can, at speeds of up to 1,200 cans per minute.

According to Peco’s Glen Oxborough, vision technology has moved on from a few years ago. Peco has just launched its Capscan for cap inspection and Labelscan for label inspection. It says that, unlike traditional vision inspection systems, where many individual inspection areas had to be identified for each product and size, the Capscan and Labelscan can be taught to look at the whole area with a single inspection window. The system can then be set to learn normal product variances, which Peco claims results in accurate and repeatable inspection, without the false rejects often generated by poor set-ups with traditional vision technology.

The end result is that brand owners can trust their packing machines to deliver products of which they can be proud – and customers retain their trust in the brand.

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A GASSY PROBLEM

One area of packaging integrity that has historically been overlooked by manufacturers is verifying the presence of MAP gases.

“Packaging companies have invested in the machinery to fill packages with the correct gas, but do not invest in the instrumentation to measure the effectiveness of the production, on-line or post-filling,” says Systech managing director Bryan Cummings. “Packaging machines often run out of gas, or the machine controls are not set correctly, thereby producing thousands of out-of-specification packages.”

Systech supplies residual gas (headspace) instruments to check gas consumption, semi in-line or post-filling, as well as controlling equipment to fit onto filling machines for MAP processing, controlling gas composition and providing early warning of faults.

Another potential issue for MAP users is leaky packs. “Because of the wet nature of the packing area and blood/fat from fresh food products, seal areas can become contaminated, resulting in poor seals, thus it is appropriate to test packs - even from new machines,” says Jenton managing director Richard Little.

Jenton, based in Whitchurch, Hampshire, manufactures the Ariana Seal Tester system for thermoformed food packs, such as those used for fresh meat. This is designed to take pack batches directly from a thermoformer and perform a seal integrity test on each pack before converging them to one line ready for single line operations such as metal detection or weight/price/labelling.

The system has multiple test heads - one for each individual pack in a matrix - so the bulk of the line cycle time can be spent testing. Jenton says this, combined with its latest control algorithms, allows very small test head movements to be detected, so even the smallest seal failures are picked up.