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DRIVES & CONTROLSAC Drive TechnologyNew drives updateCopper rolling first requires the copper to undergo temperaturesranging from 600°C to 1,000°C during hot rolling, at the same timereducing the copper’s thickness to 10-15mm. It then undergoes thecold rolling and annealing process, which hardens the metal. Thesecomplex and delicate processes produce copper which is thenprimarily used in the electrical and electronics industries, such assubmarine cables and transformersaging cold rolling millUpgrading an old copper rolling mill with new inverters andservos has given the mill new life – and saved a lot of moneyA50 year old rolling mill was showing its age.Whilst the mechanics of this Robertsonmachine were still sound, the DC drivetechnology was causing problems withbreakdowns and costly downtime. The mill is used as aspecialist machine tool to form narrow strips of copperalloy and a replacement machine had been quoted at acost over £1million and a leadtime approaching twoyears. Therefore the chosen solution was to refurbish themachine and replacement of the drives at a fraction ofthat cost, with installation done by SEAR EngineeringServices and equipment and software provided by Lenze.SEAR Engineering Services is a small company basedin Derby providing an individual maintenance service fora number of large and small manufacturing companies inthe Midlands. It offers strong engineering support with anemphasis on minimising downtime and lost production.SEAR has a background inhydraulics and mechanicaldrive systems, so for thisproject it turned to Lenze,which was able toprovide the electricaldrive and automationskills necessary.The Robertson millconsisted of a pair of largeforming rollers driven by a250HP DC motor. Thehard but malleable copperalloy strips are manuallyfed into the rollers from theoven. Two further screwdown drives are positioned ateach end of the top roller. These adjust the roll separationin a range between 1 and 32mm. The customerrequirement was to replace the large and increasinglyunreliable DC drives. Improved safety was neededtogether with an accuracy and repeatability of the rolledsection down to 0.01mm. Important was a need tosimplify machine operation and get away from thesituation where the only person with the skills andknowledge to operate the mill was an employee pastretirement age.Modern drives solutionLenze was able to supply SEAR with both the inverterand servo technology needed. The main roller drive runsat a constant speed but needs adjustment according tothe type of strip to be formed. A Lenze inverter wasselected with a rating of 250kW, 475A, and with a150% overload available for 60 seconds. This drives asquare frame through-blown motor rated at 235kW. Thesquare frame option was chosen for its small size, butmainly because the through-blown ventilation can beducted out of the machine area – a customer requirementnot easily met with more conventional motors.The DC screwdown drives were replaced by servotechnology to achieve the 0.01mm accuracy required.As the existing gearboxes were in good condition, newsynchronous servo motors were fitted to them. TheseLenze MCS motors are compact and can be run down tovery low speeds without cogging torques. Control is setso that they always drive forward to the target position,so taking out the effect of gearbox backlash. Connectionbetween the gearbox and the motors was made usingLenze torsionally rigid metal disc couplings. These wereselected with locking bushes instead of keywayconnection to the shafts so that no further backlash wasintroduced. The synchronous servo motors are poweredby Lenze 9325 Servo PLC drives which act as a mastercontroller and slave for the whole machine. Theintegrated and powerful PLC means that no othermachine controller is needed.All three drives are fitted in a panel supplied byLenze and installed by an Engineering Partner. Systemcommunication is through the Lenze CAN system buswhich is integrated as standard, and features in not onlythe drives but also the extensive I/O used for machinemonitoring. Customised software written by Lenzeapplication engineers gives five pre-programmed menusfor roll spacing to suit different products. This isaccessible to the operator through a Lenze touchscreenHMI, with the alternative of control by a pendant remotestation with push buttons.Bringing a modern drive solution to solve problems ona 50 year old machine tool illustrates good teamworkbetween SEAR Engineering Services and Lenze. Theresulting solution is economical and close liaisonbetween SEAR, Lenze and the customer allowed theinstallation to be made in a short time window,minimising lost production. The new high power inverterexceeds the capacity of the old DC drive system and thecomplete solution with servo drives and panel hasresulted in easier operator control and increasedproductivity.MORE INFORMATION:Enter J325 on the enquiry card, or visit ‘latest issue stories’www.industrialtechnology.co.uk for further details from Lenze andmore stories on drives and control systems32INDUSTRIAL TECHNOLOGY • October 2008
More details: Write in 330 on the free information cardNEWMulti Axis SolutionsFrom light high speed componentplacing to heavy lifting and handling,HepcoMotion’s multi axis solutionswill allow increased productivity andimproved efficiency with reliableround-the-clock working.Our linear driving elements come from ourstandard range of proven products with orwithout the necessary motor/control packagefrom our systems partners; SmartDrives.• Custom engineered solutions fromyour specification• Standard driven elements used,good availability• Range of gearboxes, motors andother mechanical parts to suit• Frame building usingHepcoMotion MCS system• Rack, screw or belt drivenoptions. Supplied in assembledformat or as a kit of parts• Extensive before and aftersales serviceHepcoMotion ®Tel: +44 (0)1884 257000 E-mail: sales@hepcomotion.comTiverton Way, Tiverton, Devon EX16 6TG Fax: +44 (0)1884 243500More details: Write in 331 on the free information card 33
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