Describes how stretch film is stretched

1. Direct stretching is to complete stretching between the tray and the stretching film. This method has a low tensile magnification (about 15%~20%), if the tensile magnification exceeds 55%~60%, exceeding the original yield point of the film, the film width is reduced, the puncture performance is also lost, and the membrane is easy to break. And at 60% elongation, the tensile force is still very large, and for light goods, it is likely to deform the goods.
2. Pre-stretching is done by two rollers. The two rollers of the roll pre-stretching are connected together by the gear unit, the tensile magnification can be different according to the gear ratio, the tensile force is generated by the turntable, because the stretch is generated in a short distance, the friction between the roller and the stretch film is large, so the film width is not reduced, and the original puncture performance of the film is also maintained. No stretching occurs during actual winding, reducing fractures due to sharp edges or corners, and this pre-stretching increases the tensile magnification to 110%.
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 pallet. Therefore, the adaptability is stronger, light, heavy, irregular goods are applicable, due to the low tension during packaging, so this method pre-stretch rate up to 300%, greatly saving materials and reducing costs. Suitable film thickness 15~24μm.