Choosing the right technology for positioning applications

Positioning is common in a wide range of machinery - for example, lifting, rotary tables, conveyors, gates and doors. Such applications have traditionally been achieved by servo drives but today there are cost-saving alternatives. In particular, inverter technology can now be used to achieve the optimum balance between performance and economy - with Lenze referring to this process as Rightsizing.

The 8400 inverter drive models StateLine, HighLine and TopLine are said to open up new opportunities for positioning applications requiring all levels of complexity, from simple through to high-speed, high-precision positioning, giving cost savings for many machine builders. Only where true top-end performance is needed with the highest dynamics is it necessary to select a servo drive. The 8400 StateLine is more than capable of handling simple positioning in which movement takes place to a limit switch, with or without feedback. Frequencies up to 20 cycles per minute can be achieved. Without feedback, typical accuracies of +/-10degrees are possible.

Stepping up a level, the 8400 HighLine has high-speed encoder evaluation at 100kHz so it suits closed-loop positioning with high accuracy. Where an HTL encoder with 2048 pulses is fitted, an accuracy at the motor shaft of one pulse or 0.05degree can be achieved. Furthermore, this can be at rates of up to 180 cycles a minute, suiting demanding applications such as cross-cutters and rotary feeds.

While the StateLine and HighLine inverters operate with standard asynchronous motors, higher dynamics can be achieved by using the lower inertias of permanent-magnet synchronous motors. Here the 8400 TopLine is the answer, as it is well matched to the Lenze MCS servo motors and can utilise resolver and incremental encoder feedback.

Lenze scalable systems also encompass servo drive technology for the highest performance, where dynamic moves have to be completed in a few milliseconds. The 9400 servo range and the multi-axis ECS range are proven in applications such as robotics, high-speed packaging and materials handling. All these drives are programmed with the same L-force Engineer software, and have optional integrated safety that simplifies the control system.

Of course, every machine design is different and the statements above are generalised, based on field experience. If you want to know the Rightsized positioning drive for your machine, the answer lies in the Lenze DSD selection software. Lenze engineers can evaluate different options and predict performance and costs, including the costs for energy usage.

Follow the link for more information about Lenze frequency inverters and servo systems.