CONFERENCE REPORT: AIMCAL
Guidelines for selecting the optimal system
Guidelines for selecting the best winding process and rolls used in web handling; and a comparison of centre-surface winding system were the subjects of papers presented by Davis-Standard at the AIMCAL Web Coating and Handling Conferences held in Prague, Czech Republic.
Selecting a winder
While the well-established TNT (tension, nip, torque) principles have been proved and modelled at the Web Handling Research Center at Oklahoma State University, determining which of these (or the proportional amount of each) to use for proper winding of different types of materials under a specific set of conditions is still considered an ‘art’.
This paper is a guide to selecting the best type of winder to consistently produce high quality, defect-free rolls of web material. It discusses how the winding principles are used on different types of inders and product parameters for each. Today’s web producing and converting lines often handle a variety of substrates resulting in wide tension ranges at ever increasing processing speeds. All web handling requires that a web is conveyed straight through a process without distortion or defects.
A converting process or film producing line both require the use of idler rolls, pull rolls, spreaders and edge guides in order to provide control of a web as it is conveyed.
Without the correct size and application of these devices the web might not track properly, could wrinkle, may be distorted or could result in a web break.
Understanding the selection process assists in successfully processing web materials to maximise the productivity and profitability of the web producing and converting line.
Winding sensitive substrates and laminates requires a precise winding system that takes into account material behavior and surface characteristics. In the winding process, web shifting and wrinkles can easily occur when the incorrect tension parameters and configurations are chosen. Driven or non-driven contact winding in combination with a centre-driven winder provides the best results for sensitive materials. Determining how to control the correct nip pressure during the winding process is one of the most critical questions in regard to material.
Reel hardness, tension across the finished reel and side accuracy of the reel are equally important. Starting the winding process directly on the core is one of the most critical points. This type of transfer for highspeed winding with and without core preparation is a further big engineering challenge. This paper compares systems including those with integrated multi-lane slitting and high speed winding with short cycle times for small batch sizes.
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