Stretch film packaging must be stretched, and the mechanical packaging of the tray is stretched and pre-stretched. Pre-stretching is divided into two types, one is roll pre-stretching and the other is electric stretching.

        Direct stretching is the stretching between the tray and the surrounding film. This method has a low draw ratio (about 15% to 20%). If the draw ratio exceeds 55% to 60%, it exceeds the original yield point of the film, the film width is reduced, and the puncture function is lost. The film is very Simple break. And at 60% elongation, the pulling force is still very large, and for light goods, it is likely to deform the goods.
        The pre-stretching is completed by two rolls. The two rolls pre-stretched by the roller are connected together by the gear unit, and the stretching ratio can be different depending on the gear ratio. The pulling force is caused by the turntable, because the stretching is in a short distance, and the friction between the roller and the film It is big, so the film width is not shrinking, and the original puncture function of the film is also adhered to. There is no stretch on the actual wrap, reducing cracking due to sharp edges or corners, which can increase the draw ratio to 110%.


The stretching mechanism of the electric pre-stretching is the same as that of the roll pre-stretching, except that the two rolls are electrically driven, and the stretching is completely independent of the rolling of the tray. Therefore, the adaptability is stronger, and the light, heavy, and irregular goods are applicable. Because the tension is low during packaging, the pre-stretching ratio of the method is as high as 300%, which greatly saves materials and reduces costs. A suitable film thickness is 15 to 24 μm.


In summary, the use of stretched film is very wide, and many domestic categories have not yet been touched. Many of the categories that have been touched have not been widely used. With the expansion of the use range, the amount of stretched film will be greatly increased. Its market potential is immeasurable. Therefore, it is necessary to vigorously promote the production and use of stretch film.