QUALITY MANAGEMENT

If a tension of 4cN is required to wind this product, a fluctuation of less than 1cN will lead to breakage. However, even products with considerably higher tensile strengths require optimal tension control if a consistent process quality is to be ensured. Glass and other optical fibres demand a highly constant process tension during manufacturing to maintain low optical attenuation product qualities. Further requirements of increased production speed combined with improved efficiency set even greater demands on tension regulation.
No suitable tension control system being available on the market, company Supertek of Emden, Germany, developed an innovative electro-magnetic dancer unit which has already been successfully used to optimise finest wire, glass/optical, synthetic and natural fibre production. The electro-magnetic dancer function is based, as the name suggests, on the well-proven dancer tension control method. The secret of the electro-magnetic dancer lies in the physics of the working force generation within the device, based on a patented Supertek electromagnetic technique. This electromagnetic principle allows high-resolution tension setting coupled with active disturbance compensation, while maintaining highly constant tension forces. The EDL50 Dancer unit allows this operation independent of dancer arm positions and at highest production speeds.
Dancer tension control is a tried and proven method of actively regulating winding production processes. This tension control system employs motor drives for the transport of product between stations, as example by active spool drives instead of brake units. The function diagram above shows a dancer controlled re-winder system with payoff and take-up. It is assumed that the take-up winds product at a given consistent speed during the process. The payoff has to accurately follow this speed requirement in such a manner as to maintain desired tension in the product. This is achieved by passing the product over a moving, force-loaded pulley (dancer) in such a manner as to have the pulley impose such force on the product. The ensuing product tension has a fixed relationship to this force. In the diagram above any relative acceleration of the payoff will lead to a sinking of the moving pulley in position. Inversely, any relative deceleration of the payoff will lead to a raising of the pulley. This sinking and raising of the pulley position is referred to as ‘Dancing’, which has led to the synonym ‘Dancer’ as name for the device. Due to the ‘block and tackle’ principle of mechanical advantage, product tension is proportional to dancer force. A measurement system provides positional data to the payoff motor drive, usually through a motor PID controller system. This signal input causes the motor to accelerate when the pulley is raised, decelerate when the pulley is lowered with respect to a set mid-position. To maintain constant product tension, dancer force must also be held constant irrespective of the pulley position.
Conventional dancer systems, which usually consist of weights, pneumatic cylinders and/or springs, can only provide coarser tension control with corresponding tension fluctuations. This lies in the physical characteristics of dancer forces. Weighted dancers show a change in force F = ma through dancer movement alone. Mass inertia of the dancer weight leads invariably to a change in tension. Spring-type dancers show a force characteristic proportional to length, which is in contradiction to the requirements of constant dancer force. Even special pneumatic cylinders show such problems of maintaining constant force, which are not easily overcome.
Conventional methods therefore reach technical limits, especially by tension control of sensitive products. Company Supertek has therefore developed the Electro-Magnetic Dancer, which is capable of producing a highly dynamic, dancer position-independent constant product tension. The electro-magnetic dancer EDL50 allows analogue settable tensions from 0.0cN to 500cN with a resolution of 0.cN. Where other systems fail, the electro-magnetic dancer can allow the fast, precise and problem-free processing of highly sensitive winding materials. This provides new, efficient and economic production possibilities.
Supertek offer the electromagnetic dancer plus electronic control units as retrofit components in existing plant or for inclusion in new designs. We also offer a product pallet reaching from single component to complete payoff / take-up and re-winding systems.
Supertek will be presenting and demonstrating not only their newest-generation winding machines and systems but also the innovative Electro-magnetic Dancer at the wire 2010 fair in Duesseldorf at the Stand D 28 in Hall 10.

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