Noncontact brakes keep paperboard plant running

EBU series hysteresis brakes have eliminated both wastage and maintenance downtime at Iggesund Paperboard by replacing a friction based tension control system used on a large shrink-wrapping machine.

ZF's EBU series hysteresis brakes have eliminated both wastage and maintenance downtime at Iggesund Paperboard by replacing a friction based tension control system used on a large shrink-wrapping machine.

The machine wraps rolls of paperboard weighing up to 3t in plastic to protect them during storage and delivery operations.

By integrating the non-contact ZF brakes into a PLC based system, Iggesund Paperboard are able to control the levels of tension at all stages of the wrapping process more accurately and without wear, ensuring that finished products always reach customers in perfect condition.

Iggesund paperboard AB is one of the largest manufacturers of virgin fibre paperboard in Europe, producing a high quality range of products that are used for anything from packaging healthcare products to presentation graphics work.

Its UK production facility is situated in Workington and annually produces over 190,000t of paperboard from pulp, 40% of which (76,000t) is wrapped for distribution by just one machine.

The machine consists of a giant spool and a wrapping elevator that coats rolls of paperboard in up to five layers of shrink-wrap plastic.

During the summer, engineers at Iggesund Paperboard noticed that the friction brakes used on the system were overheating during operation, causing inconsistent levels of tension and an uneven coverage of plastic on the rolls.

Project Engineer at Iggesund Paperboard, Alec Pyne, explains that: "We were spending increasing amounts of time maintaining the system to no satisfactory effect.

The plastic wrapping was beginning to undo during storage and transportation operations, which may at first seem like a minor problem, but the machine is used to coat rolls of paperboard up to 1.8m in diameter, 2.3m wide and weighing over 3t.

The storage and handling of the rolls involves standing them on end using large clamp trucks, making the wrapping, especially the ends of the rolls, one of the most important ways we can avoid both wastage and customer complaints.

The potential losses in production time and increased labour involved in rewrapping the giant rolls led us to look for a more reliable tension control solution".

Following consultation with Warrington based drive system specialist, Newton Tesla, a new tension control system based on two ZF EBU series hysteresis brakes was designed and supplied to Iggesund Paperboard.

The EBU series non-contact brakes use a magnetic flux to control the film tension in the machine, providing a reliable control solution that has resulted in over 35,000t of paperboard being wrapped so far this year without any rejects or maintenance downtime.

Reflecting on the decision to recommend ZF brakes, George Newton, Managing Director of Newton Tesla, explains that: "The ZF units could easily be open loop controlled via a PLC and a ZF hysteresis controller to provide the exact levels of resistance required to make the plastic film adhere to the rolls.

This flexibility of control also allowed the wrapping machine to vary the tension at the crucial start and finishing stages of the process, ensuing that the ends of the rolls were wrapped perfectly every time".

The noncontact operation of the brakes allows for an extremely long service life and avoids the creation of dust particulates, making them ideal for test rigs and production environments where levels of air-born contamination have to be minimised.

The ZF range of brakes includes a high power series that offers (continuous) slip powers from 250 to 2000W 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 0.08 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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