The result of an optimal winding process is a bale which is as uniform as possible, with no wrin-kling and with sufficient homogeneous strength for the next processing steps.
The material and time outlay should never be higher than the actual requirement. Process interruptions during the winding process due to broken winding cores, misshapen core ends or compressed core diameters interrupt the process, increase the production costs due to extended production times, a rise in reject rates and an increase in the use of materials and may also entail additional subsequent costs.
Insufficiently well coordinated parameters in the winding process, such as web tension, the tension status or the composition of the winding cores are often the cause of problems in the winding process or with the quality of the film bale.
Winding cores manufactured using aluminium instead of laminated paper often allow for an improvement to production efficiency in the winding process for in-house onward processing, often leading to considerable cost reductions.
In day-to-day production, winding cores are subjected to various loads. These include humidity and temperature, abrasion, braking and acceleration momentum, pressure due to the bale weight and bale tension, among other things, and may also be caused by clamping chucks and core shafts. They must also have as uniform and smooth a surface as possible, in order to avoid damage to the film material, wrinkling and uneven winding results.
Laminated paper cores are made of hygroscopic material, which means that they take on and emit moisture from the environment. A higher moisture content makes the tube core swell. When it is wound up, this will cause the inner diameter to shrink and the tube core is then often difficult to stretch out again. This then means that a time-consuming solution must be found to unwind the tube core. In extreme cases, this can mean that material which is actually flawless has to be thrown away.
On the other hand, an excessively low tube core moisture content can also lead to a smaller external diameter, making the lower bale layers loosen and causing the bale to telescope. This risk is especially high with very stiff films and can also lead to more waste.
The moisture content not only influences the dimensions of the tube core, but also the stiffness. The consequence can be greater deflection, which can entail quality issues for the bale, and the laminated paper core can even break as a consequence. Constant humidity during use and storage is therefore required for laminated paper cores, which often cannot be guaranteed during in-house processing. These moisture-related problems can be completely avoided by using INOMETA aluminium WinCore® winding cores.
Another frequent cause of broken laminated paper cores is high winding pressure. The winding process is made up of the bale weight and the transferred web tension, as well as the contact pressure from lay-on rollers during the winding process. Whereas the bale weight has a direct impact on the process efficiency, the contact pressure of the lay-on rollers and the optimal web tension is reflected in the quality of the bale. Aluminium tube cores demonstrate significantly higher pressure resistance than laminated paper tube cores.
Compressed tube cores and the associated problems, such as telescoping bales, tube cores that cannot be tensioned and blockages to automatic winding machines can be quickly and simply avoided by using aluminium tube cores, even when ambient moisture levels fluctuate.
Stable and constant processes are the rule when using aluminium tube cores. They also lead to additional, direct savings: thanks to the significantly higher tensile strength, it is much higher bale weights are realizable on aluminium winding cores.
Aluminium tube cores offer another important advantage in addition to this: the bale deflection is usually lower than with laminated paper cores and completely unrelated to fluctuations in moisture. The deflection of the tensioned, still stationary bale depends on the one hand on the tension status, i.e. whether clamping chucks or core shafts are to be used, for example, but also the ratio of the bale width to the tube core width, the rigidity of the film material and the tube core, as well as the weight of the bale, the wall thickness and other parameters. Compared with most ordinary commercially available laminated paper tube cores, aluminium possesses a rigidity which is ten to twenty times higher, meaning that the deflection of a bale with an aluminium tube core is often lower in comparison, with the same tension status.
The deflection of a laminated paper tube core is often already quite low at first glance if the design is good; further reduction to deflection can however make a noticeable difference to wrinkling with thin films. With thin materials, unevenness in the contact surface cannot be smoothed out as effectively as with thicker material; as they will warp more easily. A pressure load will also be created on the lower layers of film, meaning that films which are sensitive to pressure may also be damaged due to low deflection. Aluminium winding cores can reduce these problems, and thereby improve the overall quality of the bale.
In addition to deflection, the run out of the winding core can also have an influence on wrinkling on the bale. On the one hand, an uneven external diameter can prevent the winding material being uniformly deposited, which can lead to air pockets and wrinkles. On the other hand, the winding core does not rotate uniformly, preventing constant material tension across the entire bale width. INOMETA WinCore® aluminium winding cores are precision-straightened with a run out of max. 0.2 mm/m, which can only be achieved with great difficulty with ordinary laminated paper tube cores due to the production method. INOMETA WinCore® winding cores therefore allow for less wrinkling, improvement to the winding quality and less waste.
In addition to the other process improvements, such as reduced roll changes, fewer residual layers, reduced requirement for winding cores and stronger process stability, aluminium winding cores can be used for many years, as unlike cardboard cores they can be reused many times – up to 1,000 times or more.
The higher purchase prices resulting from the materials are usually amortized in just a few uses due to the process savings and savings on laminated paper cores. INOMETA WinCore® aluminium winding cores therefore contribute to cost and process efficiency for in-house production and film processing. In addition, INOMETA WinCore® winding core customers also benefit from greater economic sustainability thanks to the considerably longer service life and versatility of the product.
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