Top marks for no marks

Damage to the surface of sensitive paper and board in the form of marks, scratches and bruising is a severe problem faced by converters. Caused by physical interaction in the sheeting machine this damage means that tonnes of coated paper and board have to be taken back following customer claims.

In addition to high quality printed advertising growth requiring good quality papers, a growth driver for coated paper and board is the consumer goods industry. Global consumer board consumption is expected to grow by over four per cent by 2012, with China being the driving force. With the consumer evaluating food and cosmetics by the quality and look of the packaging board and print quality, requirements are highly specific in these markets.

This is a challenge for today's paper mills and converters since coated paper and board grades are very delicate to convert. In addition, they are facing increased cost pressure due to smaller order sizes and shorter delivery times. This has has also resulted in the need for an absolutely minimal amount of damage to material stocks.

Damage to the surface results in insufficient product quality and more waste. These marks are also the key to less efficient order processes because of sub standard surface print and resulting claims. Marks and scratches on sheets are main reasons for lower efficiency and productivity -- something that no converter can afford in the face of stiff global competition.

How can this be addressed? The folio sheeting process has basically been the same for over 50 years. It comprises unwinding, slitting, cross cutting, overlapping, stack forming and palletizing.

This conventional sheeting process has impact on the finished goods. Loss of quality occurs due to mechanical influence from the top and underneath to the sensitive surface of sheets. Engineers at ECH Will, a company of the Körber PaperLink Group, made an analysis of conventional sheeters and identified the following critical sections: the sheet transport behind the cross cutter, the catching station working with top tapes, the overlapping system with fingers, and top tapes at the overlapping station. Brake rollers used to reduce the speed of the sheets may also damage the surface. The only answer is the reduction of the sheeter's speed. Thus the surface of the material is only marginally marked or damaged.

This is, of course, a very pragmatic way of solving the problem. But why rely on such an old fashioned as well as inefficient procedure? Our engineers started to design a completely new technology without top tapes in the catching station and no brake rollers in the overlapping station. The result was the FS PRO folio size sheeter. We believe it is the world's first sheeter that makes mark-free sheeting a reality at an industrial level. The machine converts the finest paper qualities from 50 - 400g/m².

Instead of top tapes in the catching station and brake rollers in the overlapping station, the sheeter is equipped with a vacuum belt system that works from the bottom at the back end of the sheet to slow down and transport the material. It uses electrostatic charge for multi web production. So marks are avoided on the top as well as on the bottom of the sheets and the 'star sky effect' is also eliminated.

The FS PRO enables flexible handling of orders consisting of many different sizes. By minimizing operator interventions, the technology applied is key to profitable production. And the machine is not only 30 per cent smaller than conventional sheeters, it also runs at 300m/min (on 70g/m² coated paper) whereas conventional machines only reach a speed of 150m/min with similar material.

In order to demonstrate the benefits of the new mark-free sheeting technology, we have been running more than 100 customer tests. One of the tasks was to convert 250g/m² coated board. Result from a conventional sheeter running with one to two webs was a loss of 50 per cent or more of the sheets due to marking. The FS PRO also ran with one to two webs, and the sheets were not marked at all.

Four machines in the field are installed at customers around the globe and others are in production. With higher efficiency and productivity in their sheeting operations, these customers are said to be maintaining their competitive edge in the face of dwindling profit margins.