22 VALMET The rewinder as an enabler


Tissue products have increasingly wide ranges of specifications, and these can be enhanced using rewinders before conversion. Valmet offers this explanation into why rewinders are a key part of the process. PPL reports


C


onverting tissue paper to finished products is not always as straightforward


as it looks, especially if the final product has to be folded. Quite often a step between tissue machine and converting is needed. That’s where the rewinder comes into play. The mother reel coming from


the tissue machine is the first stage of a long converting journey before the tissue paper ends up in the consumer market as toilet rolls, kitchen towels, napkins, handkerchiefs, or the like. To convert tissue folded


products and in many cases rolled products, the mother reels need to be combined, or slit, or slit and combined, depending of the characteristic of the finished converted product. To enable this, mother reels are processed through a tissue combiner/slit rewinder machine.


The many roles of the rewinder Paper mills that have a converting plant integrated into their organisation produce mother reels from the tissue machine. The rewinder combines and slits those for wholesale dealers and/ or for their internal converting plant. Those that do not have any


converting plant will produce mother reels from the tissue machine and then combine and slit jumbos for wholesale dealers or converting companies. Companies that only convert


May/June 2020


A rewinder is the toolbox that enables the tissue machine output to satisfy every consumer’s need


tissue rolls, folded and interfolded products, can buy already combined and slit rolls from a wholesale dealer or mother reels directly from the mills. If the strategy is to purchase mother reels, they can use a rewinder for combining and/or slitting reels according to their production needs.


Key requirements for rewinding The challenge for the slitter rewinder is to produce a maximum number of combined and/or slit reels per day corresponding to a pre-defined specification such as the number of plies, number of slits and desired roll diameter. These combined and/or slit reels will be converted one more time by the converting plant (integrated or otherwise) to a finished tissue product to satisfy the market request. Any converting action has influence on the paper characteristic produced at the


tissue machine. The embossing process increases web thickness with a reduction in tensile, and an inaccurate tension control may have a negative effect on the percentage of crepe. The rewinder, even if frequently located in line with the tissue machine, could be considered the first step of the converting process and the rewinding challenge is to ensure that as much as possible of the original paper characteristics are preserved.


Another thing to take into


consideration is the fact that converting machines have different efficiencies and machine availability compared to tissue machines. The production capacity, according the converting or market demand characteristics need to be calculated in advance to avoid any potential delay on tissue machine production. When correctly configured,


the rewinder is the toolbox that enables the tissue machine output to satisfy every tissue


consumer’s need throughout the whole production chain.


Future enabler When selecting a rewinder, there are several key parameters that need to be considered to calculate correct production output by tonnage, number of plies, number of slits and desired roll diameter. Web width, basis weight, density and size of mother reel all have an impact on the production output. Crepe ratio influences how many


metres will be wound onto each roll while how many unwinding stands are required depends on how many plies are needed. More plies will consume more mother rolls from the tissue machine. The number of slitters depends on the desired finished roll widths. Finished reel diameter range and core diameters are also important parameters for the output from the rewinder. If there is a need for enhanced smoothness in the end product, a calendar can be added as well as other features. However, the most important thing is to select a rewinder that preserves the quality generated in the tissue machine with equipment that can adapt to any future needs that might arise in your business. Instead of a possible future bottleneck, the rewinder can be your future enabler. More information from Andrea Coluccini, product sales manager, tissue rewinders, at Valmet. Email: andrea.coluccini@valmet.com


Pulp Paper & Logistics


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