The stretch wrap packaging machine is divided into two types: post-stretch models and pre-stretch models. Post-stretch completes stretching between the loads and the stretch film. This method has a low stretch ratio (about 15%~20%). If the stretch ratio exceeds 55%~60%, it will exceed the original yield point of the stretch film, the stretch film width will be reduced, the puncture resistance is also to be lost, and the film is easy to break. And at a stretch ratio of 60%, the tensile force is still very large. For lighter goods, it is likely to cause the goods to tilt and collapse. If we want to increase the stretch ratio of the stretch film without reducing the performance of the film and ensuring the stability and safety of the goods, then we should consider using a pre-stretched wrapping machine. The pre-stretch wrap machine is divided into roller pre-stretch and electrical pre-stretch wrap machines. This article will introduce to you the characteristics of these two pre-stretch wrap machines.
First, roller pre-stretching is completed by two rollers. The two rollers for roller pre-stretching are connected together by a gear unit. The stretch ratio can vary depending on the gear ratio. The pulling force is generated by the turntable. Since the stretching is generated in a short distance, there is a gap between the roller and the stretch film. The friction force is large, so the film width will not shrink, and the original puncture resistance of the film is also maintained. During wrapping, no stretching occurs between the goods and the stretch film, reducing breakage caused by sharp edges or corners on the goods. This pre-stretching can increase the stretch ratio to 110%.
The stretching mechanism of electric pre-stretching is similar to that of roller pre-stretching. The difference is that the two rollers are driven by a motor.
The extension is completely independent of the rotation of the pallet. So it is more adaptable, applicable to all goods including light, heavy, irregular items. And because the tension during wrapping is very low, so the pre-stretch ratio of this method can be increased to 300%, which greatly saves the consumption of wrapping materials and reduces the packaging costs.
I believe everyone now understands the advantages of pre-stretch wrap machines!