Drives bring improvements to corrugated board printers

Lenze PositionServo drives, servomotors and SMD series AC inverter drives are all being utilised on the latest-generation specialist printing machine for corrugated board. Used to change the height, position and pressure of the print feed rollers, the movement is relatively simple with a single axis of operation - but it requires both fast dynamic response and high precision from the servo equipment. The AC inverters are being used to control air fans that dry the ink during the four-colour printing process.

Cardboard material is auto-fed into the printing machine at high speed and passed through five sets of rollers positioned above and below the board. The first two rollers feed the board into the printing process, and subsequent rollers at the top deposit the printing ink, one colour at a time. The lower set of rollers controls the pressure exerted on the material as it is passed through the printing process. The thickness of the material ranges from 1-3mm for solid board and 1.3-8mm for corrugated board; for both types of card the position of the roller is critical to the print finish and smooth throughput.

Each of the lower rollers in the printing process employs two pairs of Lenze PositionServo 4.0A drives and accompanying Lenze servo motors; one pair is used to drop the lower roller's vertical position and allow a new sheet to be fed in, and the second pair is used for fine control while the machine is actually printing. Feeding in a new sheet previously required manual adjustment of the rollers and was significantly slower before it was automated. The machine can now switch materials automatically, thereby increasing the output significantly.

Rapid reactions

The PositionServo units have 64-bit processing and reaction times of 2us to adjust the position of the lower roller relative to the upper roller in tiny, fast increments during printing; this also creates a displacement effect, compressing the card as it passes through, creating smooth surface finishes, ironing out any material inconsistencies in the raw board and ensuring a consistent print finish.

A PLC controls the entire process and high-resolution linear encoders supply positional feedback; the servos therefore have a simple, but high-accuracy task to perform. Lenze PositionServo units are well suited to the task, since the set-up and operation is extremely simple using free Lenze MotionView software and matched Lenze servomotors.

Lenze SMD 15kW AC inverter drives are also used to precisely control the air volume produced by four drying fans that make sure the ink is fixed after each print colour is applied. Variable speed operation allows for a smooth start-up, and efficient speed regulation maintains a perfect print finish at higher speeds. The task is relatively simple using standard fan control parameters; the reliability of the drives and the ease of connection to the machine controller also make them an excellent choice.

Since there are eighteen servo drives and four AC inverters on each machine, cost was also a consideration. But the automation team at Lenze responsible for selecting the components assisted with the technical development and provided further technical support during commissioning. This, alongside genuine worldwide service and support, ensured that the project was a success.

The complete range of PositionServo drives from Lenze is designed to make life simple for machine builders and automation engineers that require a straightforward, cost-effective servo drive without any unnecessarily complex programming or set-up requirements. The compact PositionServo model is designed and manufactured to satisfy global standards for performance and interconnectivity, and is suitable for single- and three-phase supplies from 110-480V with a rated output of 4-10A and a 30A current peak.

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