Vision systems keep watch on bottle quality

Supplying packaging to consumer drinks manufacturers is serious business, and so Rexam automatically inspects bottles in order to ensure that they are intact, clean and meet safety standards.

Rexam, a global enterprise that manufactures consumer packaging, is a world leader in plastic packaging for the cosmetic, pharmaceutical, food and beverage industries.

Rexam's plastic beverage container operations are located in Germany, Sweden and the Czech Republic.

Sweden is home to two plastic manufacturing factories for food and beverages as well as one tin factory and a glass-works.

Rexam's customers are large soft drink manufacturers in Nordic countries, such as Carlsberg, Spendrups and Coca-Cola.

They all have high expectations and demands regarding the quality, logistics and visual appearance of these plastic bottles as well as end-consumer satisfaction.

Rexam's bottle factory in Lidkoping, as well as other locations, manufactures 80% of all bottles sold in Nordic countries.

At Rexam in Lidkoping, beverage containers are manufactured in five shifts round the clock, all year long.

Rexam manufactures two main sorts of bottles, which are either refillable or recyclable.

Refillable bottles are washed and refilled up to 25 times, whereas recyclable bottles are filled once and then ground up to be reused as raw material for new bottles, fleece clothing or another product using polyester as a raw material.

By the end of the 1990s the company had begun to invest in vision systems in order to improve the quality and reduce the number of errors in the manufactured beverage containers.

Then the company got an order from an important customer to develop a beer-bottle made of polyethylene naphthalene (PEN).

These bottles have a more glass-like quality compared with PET bottles and can withstand higher temperatures during washing.

During the manufacturing of the PEN bottles, a problem arose with air bubbles appearing in a small number of them.

The customer was concerned that the bubbles would cause cracks thus risking contamination.

Rexam decided to implement vision systems from Cognex in order to develop a process of sorting out defective bottles thus eliminating the problem reducing the failure rate to almost nil.

"A strained customer relationship was transformed into a positive customer relationship once the problem was solved", recalls Urban Larsson, Production Manager at Rexam Petainer in Lidkoping.

"That was the gateway into an array of various quality-control projects at Rexam in other areas of our production and that is why the use of vision systems is one of our cornerstones".

Rexam has continued to invest in vision systems in order to ensure the quality demands of refillable bottles as well.

During the manufacturer's own filling operations the bottles are washed carefully.

A vision system quality-control check during manufacturing detects any bottles which contain objects or contaminants that cannot be washed out.

Cosmetic defects such as air bubbles can occur during the manufacture of individual bottles.

These are detected as the bottles are inflated.

Vision systems also check the seal with the bottle cap to eliminate the risk of leakage.

The appearance of the bottles has also become more and more important over the last few years.

Bottles with scratches, chips and imperfections such as air bubbles and other cosmetic defects which in themselves do not affect the function of the bottle are systematically processed through the use of vision.

Use of vision systems is a part of Rexam's efforts to become a resource-efficient company for improved quality and customer-satisfaction in the face of stiff competition.

With the use of vision systems, the quality of bottle manufacturing is assured.

The amount of unnecessary waste is eliminated through vision inspection.

"During the past five or six years, our investment in vision systems has really paid off", says Larsson.

"We have gone from doing manual random-sample testing and inspections of a production of several hundred million bottles per year, to a systematic inspection of everything that is manufactured".

"Through automated inspections, we have a wide cover which together with other quality-control measures minimises the incidence of error".

The manufacture of plastic bottles, which saw the launch of quality-control, is on-going, while new products are continuously being developed.

"Our choice of vision provider is based on Cognex knowledge and experience with vision technology and the needs of the packaging industry", says Urban Larsson.

"Cognex has developed and provided industrial vision technology for 25 years of cost-efficiency with a minimal or nonexistent rate of failure in production".

"Rexam uses the In-Sight type of vision sensors which are tailored for automated inspection and verification of quickly moving objects".

"PatMax software is used for property and object localisation, and works well when inspecting consumer-product packages".

"The visual and functional requirements are becoming more and more important in the packaging industry", says Larsson.

"Our customers attach more and more importance to the package's design".

"By means of a structured working method, preventative maintenance procedures and various improvement projects, we can quickly adjust our production to meet the various needs of our customers".

"Using a colourful collection of constant improvements, we have built up a reputation for good quality", concludes Urban Larsson.

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