Stretch film packaging must be stretched. Direct stretching and pre-stretching are the stretching forms of pallet mechanical packaging. Roll pre-stretching and electric stretching are two types of pre-stretching.
1. Pre-stretching is done by two rollers. The two rollers pre-stretched by the roller are connected by a gear unit. The stretching ratio can be different according to the gear ratio. The pulling force is generated by the turntable. Since the stretching is generated within a short distance, the friction between the roller and the film
The friction force is large, so the width of the film does not shrink, and the original puncture performance of the film is also maintained. There is no stretching during actual winding, which reduces the breakage caused by sharp edges or corners. This pre-stretching can increase the stretching ratio to 110%.
2. Direct stretching is to complete stretching between the tray and the stretch film. This method has a low stretch ratio (about 15% to 20%). If the stretch ratio exceeds 55% to 60%, the original yield point of the film is exceeded, the film width is reduced, and the puncture performance is also lost
If it falls off, the membrane can easily break. And at 60% stretch rate, the tensile force is still very large, for light cargo, it is likely to deform the cargo.
3. The stretching mechanism of electric pre-stretching is the same as that of roller pre-stretching, the difference is that the two rollers are driven by electricity, and the stretching is completely independent of the rotation of the tray. Therefore, it is more adaptable, and light, heavy, and irregular goods are suitable. Due to the low tension during packaging,
Therefore, this method has a pre-stretch ratio of up to 300%, which greatly saves materials and reduces costs. Suitable for film thickness 15～24μm.
In summary, the application fields of stretched film are very wide, and many fields in China have not been involved, and many of the areas involved have not been widely used. With the expansion
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