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Making Servo Driven Systems Easier
- Published: Thursday, 14 June 2012 16:34
Machine builders must strive constantly to improve their competitiveness. Servo driven systems are often a significant item in their build expenditure with high costs to purchase, install and commission.
The new Lenze 8400 TopLine drives take a slice out of those costs through lower purchase prices, small size leading to reduced panel costs and high performance that increases productivity. Programming software is simple and free - all contributing to reduced workload for the designer and machine builder
The 8400 TopLine is a servo drive for synchronous and asynchronous motors that sits at the top of the 8400 frequency inverter range. As such it is based on products in volume manufacture which leads to very competitive pricing in the servo drive market. Latest technology gives middle to high-end servo performance with compact dimensions. Synchronous and asynchronous motors can be run open-loop or, for more precise control, with feedback from incremental or absolute encoders. On board is software for positioning, electrical gearbox and management of holding brakes. Safe Torque Off to Category 4, Performance Level e, is a further option whose low cost is normally justified by a reduction in external safety components.
Performance levels of the 8400 TopLine drives are proven to be superior to larger and more expensive servos that were market leaders as little as 5 years ago. With the flexibility to handle different types of motors and feedback, TopLine suits the majority of applications in the power range 0.55 to 45kW, 3.0 to 89A rated current. Three typical applications that illustrate its use are palletising, food portioning and paper winding machinery.
Palletising machines require smooth positioning with medium to high dynamics. The 8400 TopLine scores highly here with 200% peak torque available for 3 seconds and smooth 'S' shaped ramps for acceleration and deceleration. Point to point positioning software is built into the drives so the higher level controller only needs to transmit the destination, reducing the amount of data transmission required and simplifying the programming. The palletiser control panel will contain 3 or 4 axes of drives and here the TopLine saves space. As well as compact dimensions, the drive has integrated EMC filtration and a braking chopper so reducing the component count and saving up to 50% of panel space compared to other servo solutions. Vertical axes will require a spring applied holding brake and here the drive has integrated software to switch a 24V DC brake coil. Feedback can be by incremental encoder or robust resolver in which case a homing cycle will be triggered after each shutdown. Alternatively, if homing is not possible, absolute encoders can be used. In applications such as these where some axes are generating power from braking whilst others are using power to accelerate, large energy savings can be made by sharing energy. This is done by linking the DC bus connections on the TopLine drives, giving a big reduction in the supply requirements.
Stop-start applications such as food portioning, paper cutting, etc., run at high cyclic frequencies of operation. Where the requirement for precision is moderate, it may be possible to combine the 8400 TopLine with a standard IEC framed asynchronous motor, albeit with feedback. High precision will demand the extra expense of a synchronous servo motor and control from a higher level IPC. This in turn puts a demand on the bus communications between the drive and the controller. Here standard plug-in modules are available for the drive with either of the fast realtime buses EtherCAT or PROFINET. Handling of the drives is easy during commissioning and any subsequent service. A single software program L-force Engineer covers all L-force drives and control products. Parameter setting can be done offline using a programmer with the plug-in memory module of the drives. Alternatively changes can be made online through a hot-pluggable port on the front of the drive.
Paper winding machinery and other web-based applications for plastic and foil require smooth delivery of torque and medium to high accuracy on a speed setpoint. The 8400 TopLine has as standard an electrical gearbox function, also known as electrical shaft. A separate axis bus links drives specifically for this purpose and precise control of speed, angle or torque can be achieved between the master and slave drives. Acting as an electrical gearbox, fine adjustment of gear ratio can be set between drives, and this allows tensioning of the web. Web tension is accurately maintained through acceleration and deceleration, even during emergency stops, reducing wastage and increasing productivity. The option of Safe Torque Off can be added allowing operators to work on the web without removing power from the drives. In this way the machine is ready for an instantaneous restart with an increase in productivity, but Safe Torque Off also leads to a reduction in component count and faster builds.
The 8400 TopLine servo drives have matching Lenze synchronous and asynchronous motors, also geared motors. To reduce procurement costs, even the power and feedback cables with plug connections are available. L-force Engineer software for parameterisation, commissioning and diagnostics is available free of charge and it also covers other drives and controllers. High performance together with positioning and electrical gearbox functionality suits this modular system to most servo drive applications with benefits of cost and time savings.
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