Non-contact hysteresis systems for higher tension

A combination of Brakes and clutches managed by ZF's ERM controllers has proved to have the accuracy and reliability to replace DC drive based tension control systems in presses at Day International.

"With increased reel/roll sizes, more web layers and higher speeds being required from printing and processing machinery, integrated contact-free tension control systems are becoming the industry standard..." says David Morgan of ZF Industrial.

A combination of EBU Brakes and EKU hysteresis clutches managed by ZF's ERM controllers has proved to have the accuracy and reliability to successfully replace DC drive based tension control systems in three high precision presses at Day International (UK) .

The company manufactures rubber sheeting used for producing newspapers and banknotes in high-speed printing presses; a process which primarily involves attaching a layer of rubber to a fabric backing.

After considering a manual clutch system to replace the increasingly high maintenance inverters, the company engineers rejected the idea due to risks of contamination from dust particles, a problem conveniently avoided by the magnetic non-contact operation of the hysteresis units.

After twelve months of faultless use, Day International fitted a similar system to accurately control a three-way web of materials as they were joined and fed through an adhesive curing oven.

After continued success, the third main operation was also upgraded which involved feeding the sheets extremely slowly through the equipment that grinds the surfaces of the cured rubber sheets flat to tolerances of 10 micron.

By using such a versatile system engineers could reduce wastage and downtime, but also standardise spares, easily expand the systems to control new webs and integrate the complete set up with their current PLC.

ZF's EBU series hysteresis brakes have also been used successfully to eliminate wastage and maintenance downtime on a large shrink-wrapping machine at Iggesund Paperboard.

The old friction based tension control system was overheating, and by replacing it with non-contact ZF brakes, Iggesund has been able to achieve the exact tension required for the plastic to adhere to 3 ton rolls of paperboard being prepared for storage and delivery.

Easily integrated and open loop controlled via a PLC and a ZF ERM controller, the new braking system was able to accurately control the tension at all stages of the wrapping process, despite widely varying levels of resistance required.

The EBU series brakes used a magnetic flux to control the film tension in the machine, providing a reliable control solution that resulted in over 35,000 tons of paperboard being wrapped that year without any rejects or maintenance downtime.

Skanem Labels at Cardiff also found that a friction based control system did not have the accuracy or flexibility needed when upgrading their Gallus printing machines.

After one of their customers asked for a custom peal-and-seal type label that required an extra web to be fed into a printing machine, their engineers retrofitted the complete ZF tension control system including EBU Brakes, EKU Clutches and the ZF ERM Controller.

The speed of the printing machine was monitored by Honnigman sensors in the roller end shafts, which fed back to the ERM controller to provide the highly accurate operation required for a machine capable of producing over 3000 colour labels per minute from a 2000 metre roll of film.

ZF EBU Brakes are also being used by specialists RTI who manufacture, maintain and upgrade 35mm movie film processing machines.

Their latest equipment is designed to process a 1,200M reel of film every 20 minutes (3,500m/hr) and use larger reels than normal to allow for an increase in processing capacity.

However, the previous friction based braking system could not ensure a smooth transition when changing over reels: overheating occurring at the end of the on-wind process due to the higher reel speeds and greater stopping loads.

This new solution proved ideal as the ZF systems are easy to fit and commission, and ensure that the continuous process of the delicate film can be maintained without costly extended changeover times or threats of breakage.

ZF EBU brakes are now the tension control system of choice for new RTI machines and when upgrading existing equipment.

The tension control parameters have been calculated by suppliers DJ Automation, and are now stored enabling them to provide an off-the-shelf solution for future RTI machines.

The non-contact operation of the brakes allows for an extremely long service life and avoids the creation of dust particulates, making them ideal for environments where medical or food products are produced.

The ZF range of brakes includes a high power series that offers (continuous) slip powers from 250 to 2,000 watts and Peak capabilities of twice these figures.

Hysteresis clutches are also supplied, which are especially useful for winding-on applications in cable manufacturing or food packaging industries and the four different versions available cover most requirements with torque capacities ranging from 0.08Nm to 520Nm.

The range is backed-up by ZF, one of the most respected manufacturers of driveline technology in the world with production centres, partners and representatives on every continent.

In the industrial sector, ZF is at the forefront of developments, from individual units to complete systems solutions for all types of machinery and production units, including those used in robotic systems and the factory automation sector.

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