All packaging methods having the use of stretch film must be stretched, and the stretching forms of pallet mechanical packaging include direct stretching and pre-stretching. There are two types of pre-stretching, one is roll pre-stretching and the other is electric stretching.
Direct stretching is to complete the stretching between the tray and the stretch film. This method has a low stretch magnification (about 15%-20%). If the stretch magnification exceeds 55%-60%, it exceeds the original yield point of the film, the film width is reduced, and the puncture performance is also lost. Easy to break. And at 60% stretch rate, the pulling force is still very large, and for light cargo, it is likely to deform the cargo.
The pre-stretching is done by two rollers. The two rollers of the roller pre-stretching are connected together 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 in a short distance, the friction between the roller and the film It is also large, so the film width does not shrink, and the original puncture performance of the film is also maintained. No stretching occurs during actual winding, which reduces the breakage caused by sharp edges or corners. This kind of pre-stretching can increase the stretching ratio to 110%.
The stretching mechanism of electric pre-stretching is the same as that of roll pre-stretching. The difference is that the two rolls are driven by electricity, and the stretching is completely independent of the rotation of the tray. Therefore, it is more adaptable, suitable for light, heavy, and irregular goods. Due to the low tension during packaging, the pre-stretching ratio of this method is as high as 300%, which greatly saves materials and reduces costs. Suitable for film thickness of 15-24μm.
In summary, the application field of stretch film is very wide, and many domestic fields have not been involved, and many fields that have been involved are not widely used. With the expansion of application fields, the amount of stretch film will increase greatly. , Its market potential is immeasurable. Therefore, it is necessary for us to vigorously promote the production and application of stretch films.