29 March 1996


By James de Havilland

AFTER four years development, the powered film pre-tensioner from KO Pressure Frames will be seen in production form for the first time at this years Kemira Grassland event.

It is a system which employs driven rollers to pre-tension the film. Working in conjunction with a hydraulic link to the wrappers turntable speed, the film passing through the unit is kept at a constant stretch ratio regardless of changes in ambient temperature.

It will be recalled that on conventional stretcher units, it is the bale rotating on the turntable which pulls the film through a stretcher unit. On hot days, the film stretches further, leading to "necking" and a danger the bale will not be completely wrapped.

So that is the thinking behind powered stretchers. But it is the KO units ability to stretch film at rates of up to about 160% – twice that of conventional stretcher systems – which is of particular interest.

Which raises the question: Is this pre-stretcher being introduced to cope with a new generation of super stretch silage films?

"In industry, film used to wrap pallet loads can be pre-stretched to perhaps 300% or more," says KOs Ken Orpen. "This, understandably, enables far less film to be used to do the job. Individual pallet wrapping costs have dropped from over £1 a few years ago to around nearer 17p since the introduction of powered pre-stretchers and new films," he says.

These attractive savings are unlikely to be reflected in bale wrapping because the film has to protect as well as seal the bale, but there remains a potential for savings to be made.

"Films are now being developed which will be suitable for greater stretching. They may require an extra wrap to ensure the correct thickness of film is applied, but this will still use less film," maintains Mr Orpen.

He says a new supplier of silage films will soon be entering the UK, and these new products could add a new dimension to the bale wrapping scene.

"There are a number of interesting developments in plastics, including the use of a catalyst called Metalisine. This ingredient provides films with increased puncture resistance and a greater elasticity."

The new material is reported to have shown certain favourable properties but there remains a question mark over its air permeability – for a silage film an important quality.

Even so, Mr Orpen is confident for the future.

"The power pre-stretcher and new films will change the way silage bales are wrapped," he predicts. "The next couple of years will see the whole industry moving forward, and I think power pre-stretching will play an increasing role in reducing film used and improving the quality of baled silage."n

KOPressure Frames powered film pre-tensioner is designed to maintain a constant stretch regardless of ambient temperature.