EuroWire March 2018

Technology News

Active tension control for winding and unwinding of sensitive products

THE acquisition and archiving of process data is becoming increasingly important in production processes. This development can also be observed in the wire and cable industry. The demand for continuous process monitoring has risen over the years, especially when winding or unwinding sensitive products, such as glass fibres or fine wires for medical applications. has equipped unwinders with tension force measurements on request. Initially, the main focus was to support the machine operator with a better visual control to the set tension force. The product was guided with a fixed angle over a payoff pulley, at which the current deflection of the pulley axis was detected for calculating actual product tension force. This value was then shown on a display in [N]. If necessary, the operator could adjust the settings of the tension force. Kurre has further developed this process in accordance with the constantly increasing requirements. Instead of a simplified visual tension force control, the focus is now on continuous monitoring of the entire winding process with active control of the product tension force. Especially with very sensitive products, tension force peaks can damage the wound material. These can occur, for example, as a result of a short time loose when changing layers or in points where the product undermines itself. During the unwinding process spontaneous friction occurs, and the rotating coil has a jerky movement – often invisible to the human eye. Sometimes an unwinder can even become a rewinder for a short time. Kurre Spezialmaschinenbau

▲ ▲ Active tension control

useless sections can be separated out in a later process. The setpoints and tolerances are either specified directly on the operating panel for each winding position (and can then also be transferred to the integrated coil recipe), or are specified by a higher-level control system via bus interface. Integrated in a rewinding line, unwinding and rewinding can be regulated simultaneously with the aid of the Kurre actual tension control. If the current winding diameter is known at all times, there is no need for a fixed enlacement at the measuring roller. The outlet angle can then be determined from the existing parameters at any time. This means that even more consideration can be given to special product-specific properties (eg avoiding alternating bends). In the production of various flat products (eg flat belts with wire core) the active Kurre tension force control is used to ensure that all wires entering the extrusion process are supplied with exactly the same tension force. In this way, a lateral twist of the finished product is effectively avoided from the beginning. The active Kurre tension force control is possible for both single and multiple winders. It is equally effective in all speed and tractive effort ranges and is now used in more than half of all Kurre projects. Kurre Spezialmaschinenbau GmbH – Germany Website : www.kurre.net

In order to ensure that the wound material still meets the high customer requirements, Kurre is able to continuously record the actual tension force on the product via an active tension force control system, compare it with the target values including specified tolerances, and immediately correct it using the pneumatic pressure control on the dancer. The tension force spikes are automatically absorbed by the dancer’s damping effect. All setpoints and actual values can be saved periodically in CSV format at a desired frequency. Thus, any evaluation of the winding can be carried out, eg tabularly or graphically in Excel. In combination with a length counter, even the exact positions of the individual values on the coil are known, so that, for example,

New digital controller for HVT-series AC Hipots Haefely Hipotronics, a developer and provider of high voltage test systems and measuring devices, has launched the new 100kV HVT-DI series AC Hipot testers. These are modern digital solution to AC field-testing of bucket trucks, aerial platforms, vacuum interrupters, breakers, switchgear and other electrical apparatus. Each model includes a portable digital control section and bonnet, and is complete with an input line cord, interconnecting cables and ground lead. The HVT-DI is a valuable tool for factory and acceptance test on: • Aerial platforms • Bucket trucks • Switchgear, vacuum bottles and vacuum interrupters • Hot sticks, gloves and ropes • Hydraulic hoses Haefely Hipotronics – Switzerland Website : www.haefely-hipotronics.com

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March 2018