If it's the same configuration of the wrapping machine, the cost of a pre-tensioned wrapping machine is higher than that of a resistance-tensioned wrapping machine.
(2) Based on the different stretching methods of the wrapping film on the wrapping machine, they can be categorized into two main types: "Pre-stretch" and "Resistant Stretch." The "Pre-stretch" type saves materials under the same conditions. The "Resistant Stretch" wrapping machine uses resistance for stretching, typically at a 1:1 ratio. In contrast, the "Pre-stretch" type has the film pre-stretched in the film head, resulting in a 1:2.5-3 ratio when unwinding. Therefore, the "Pre-stretch" type saves more materials than the "Resistant Stretch" type.

Pre-stretching is achieved by two rollers powered by a motor, with the pre-stretched rollers connected by a gear unit. The stretching ratio can vary depending on the gear ratio. The tension is generated by a disc. Since the stretching occurs over a short distance and there is significant friction between the roller and the film, the film width does not shrink, and the original piercing performance of the thin film is maintained. During actual wrapping, no stretching occurs, reducing breaks caused by sharp edges or corners, making it more adaptable for light, heavy, and irregularly shaped goods. Due to the low tension during packaging, this method can achieve a pre-stretching ratio of up to 300%, significantly saving materials and reducing costs. Suitable for film thicknesses of 15 to 35 μm.
The Standard of Pre-stretching Mechanism: During the rotation of the wrapping machine, the pre-stretching mechanism maintains the width of the wrapping film while stretching it to achieve the predetermined stretch ratio.
During the winding process on the winding machine, the piercing performance of the film remains the same as before stretching.
During the operation of the winding machine, if the film narrows, it is not pre-stretched regardless of how long the film can be pulled. This method has a low stretching ratio (about 15% to 20%). If the stretching ratio exceeds 55% to 60%, it surpasses the film's original yield point, causing the film to narrow and lose its piercing performance, making it prone to breakage. Moreover, at a 60% stretching rate, the tension remains high, which could potentially deform light goods.