These turning bars are not free to rotate like steering rollers. Instead, they are designed so the web slides over them in a near frictionless manner that inhibits tension memory creation. To eliminate the friction between the web and the turning bars, the turning bars may be air lubricated for applications with films possessing high coefficients of friction, such as sticky films, or they may be specially coated for slippery films, such as HDPE or some PPs. Macro’s edge guide system consists of two turning bars (possibly more in custom applications) and one web edge sensor. The edge sensor measures one edge of the web and provides a signal that is used to quantify adjustments to the web position. The turning bars pivot simultaneously and in parallel to guide the web to the correct position without creating additional stresses in the web that could lead to finished rolls with tension memory. To ease startup, the turning bars are free to rotate during threading and can then be locked into place during operation.
Another advantage of Macro’s new compact edge guide is there is essentially no limit to the extent of edge guiding that can be achieved. If necessary, an adjustment equal to the complete width of the web, or even more, can be achieved. This sort of adjustment may be useful in cases where the web is to be permanently wound at a different position on a winder, without inducing tension problems or creating wrinkles. The system can be used for web edge guiding or randomization and is small enough in physical and operational size that it provides many options to processors in terms of positioning within the production line, including incorporating it into the winder. |
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The physical size of the edge guide is a mere 2 ft high by 2 ft deep (approximately). The width of the edge guide depends on the width of the web being used and the amount of guiding to be applied. For setups with a general lack of space, the size of the edge guide combined with its very small operational space requirement provides immediate benefits. The length of web required for the operation of Macro’s new edge guiding system is only about 2 ft, regardless of film width, which is drastically less when compared to other edge guiding systems. For the sake of comparison, a 4 ft wide web guided by conventional edge guides typically requires, 6 ft of web length before the edge guide, 4 ft in the guide, and an additional 6 ft after the guide to function with minimal tension problems. In addition, the distance between the turning bars is significantly less than that of the steering rollers of previous edge guiding systems, and this distance varies only if large movements of the web is required, such as with specialty applications.