Two lines at one of the UK’s biggest paper mills have recently been updated with new AC drives from Control Techniques.  SCA’s Trafford Park paper mill in Manchester produces a wide range of household paper products utilizing recycled paper. The two lines – one for toilet tissue and the other for kitchen towels – both needed upgrading to enhance reliability, product throughput and accuracy. 

The lines are now both equipped with Unidrive SP AC drives – the tissue line with 26 drives and the paper towel line with 16.  The drives range in size from 1.1 kW to 20 kW.

The functions of the drives on the tissue line are mainly position control, control of the belt height for the parent roll and tracking, and unwind and rewind control.  There is also a section that seals the cut end of the log and the high speed cutting of the log into individual toilet rolls.  Tension control is crucial to prevent web breaks and sheet lengths are controlled to an accuracy of better than 0.5 mm.  All the motors have resolver feedback to the drives and, within the drives, this is converted into a compatible scaled feedback to the master PLC for the line.

The drives on the paper towel line control all of the line functions including unwinding and rewinding, insertion of a new core into the log, the synchro bar to cut the log into sections, control of the diameter of the log and control of sheet length. Again, feedback from the Unimotors is by resolver signal that is scaled in the drive and retransmitted to the controlling PLC.

“In order to meet our production targets, both lines needed to be fitted with the latest drives,” explained UK2 Electrical RST, Paul Heywood, who is responsible for keeping the lines working day and night.  "We have been impressed with both their reliability and performance over the years so we naturally chose Control Techniques. The excellent support we receive from Control Techniques was a key factor in this decision.”

All of the drives were installed and commissioned by Paul Heywood’s own team, all of whom have attended Control Techniques’ Unidrive SP training course.  “We have been helped, when needed, through both upgrades,” says Paul Heywood, “and the support generally has been superb.”

The Unidrive SP range of AC drives is available for panel mounting, freestanding or in modular configurations from 0.37 kW up to 1.9 MW.  The drives are easy to install and commission and can be configured to operate in several modes including servo for synchronous permanent magnet motors / brushless servo motors.

Unidrive SP offers a wide range of system integration features.  Each drive can accept three option modules, allowing the user to select the level of integrated automation / motion control, connectivity and I/O needed.  In servo mode, as used at SCA, the drive operates as a high performance servo amplifier, matched to the Unimotor servo motors range and optimised for continuous duty applications due to its high continuous output rating.

SCA is one of the world’s largest companies in personal care products, the world’s third largest supplier of tissue and one of Europe’s most profitable producers of forest products.  Net sales in 2011 amounted to €11.7 billion.  Tissue products, including handkerchiefs, napkins, toilet paper and kitchen rolls, are produced at 43 facilities in 18 countries, including at the paper mill in Trafford Park, Manchester.

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