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Product category: Stepper and Servo Drives, Motors, Controls
News Release from: Lenze | Subject: Servo PLC
Edited by the Engineeringtalk Editorial Team on 30 August 2002

Drives enhance printing press
performance

Crabtree of Gateshead has initiated major improvements to its Morgan business forms printing press by installing Lenze drives.

Crabtree of Gateshead has initiated major improvements to its Morgan business forms printing press by installing Lenze drives The developments to the print towers have resulted in higher print quality, while the drives have simplified the press, reduced build time and enabled easy retrofitting

Lenze has supplied three drives and a touch screen control system for each of the towers on the press.

Today's printing market is such that printers of traditional business forms are experiencing falling demand as their customers opt for plain paper forms.

Crabtree of Gateshead has responded to this trend by offering a machine upgrade that enables these printers to diversify into more profitable areas such as process printing, mailers and labels.

To do this, the company had to ensure that its Morgan business forms printing press - which normally incorporates four modular print towers to produce the elementary four-colour printing process - could print blocks of solid colour without ghosting or losing fine detail.

One of the many advantages of the innovative redesign is that the press can now incorporate as many print towers as is required and can therefore reproduce as many colours as desired.

This is achievable without adding additional load to the lineshaft and having to upgrade the machine's main drive components.

Crabtree of Gateshead developed a software simulation of the inker roll configuration - selecting the optimum layout after evaluating over 350 different arrangements.

The selection was tested by building a fully functional prototype and eventually incorporating it into a modular print tower design that could be retrofitted to presses built over the last 20 years.

To alleviate the demands placed on the line shaft, a decision was made to incorporate independent Lenze drives for the inker, dampener and wash-up rolls.

This modification led to excellent speed holding and synchronisation of the inking rollers with no detrimental affect on print quality and introduced many other benefits.

The system, known as the Crabtree QPrint (Q for quality), reduces the load on the line shaft as the localised drives assume some of its functionality, resulting in a more efficient printing process.

The concept of independent drives is crucial to retrofitting older machines, where the lineshaft speed and direction of rotation is not always consistent.

For example, the inker drive motor - a Lenze 3kW, four-pole model fitted with a resolver - is driven by the Lenze Servo PLC, a servo drive with built-in PLC functionality.

The intelligence of the Servo PLC allows it to control other functions in the print tower including the dampener and ink-duct drives which have Lenze G-motion geared motors and vector inverter drives.

At the top of the print tower is a menu-driven touch screen featuring more than 80 software-simulated, push-button controls.

The touch screen communicates directly with the Servo PLC and has automated routines including, for example, wash-up.

Compared to the previous panel of buttons and knobs, the touch screen gives additional benefits of status and fault displays.

Apart from the easy retrofitting and upgrade of older machines, the independent Lenze drives offer many other benefits.

For instance, greater accuracy of speed synchronisation and control is achievable as an encoder from the line shaft controls the speed of the Servo PLC.

Moreover, two inverter drives track the speed of the press by a signal from the Servo PLC and ratios can be set to suit particular print requirements.

Indeed, without a mechanical connection to the line shaft, it is possible to run the inker motor in reverse for wash-up mode which has further simplified the print tower and means an independent wash-up motor is not required.

This has also resulted in improved wash-up performance.

As the Servo PLC requires no separate PLC in the control panel, this reduces build time and minimises control panel size.

CANbus connections simplify wiring and also shorten build time.

As CANbus is already integrated into the Servo PLC, it reduces the cost of the fieldbus connection.

Another advantage of the Crabtree QPrint is that the system can facilitate new business possibilities by reducing the load on the line shaft.

For example, a printing company with a four-colour printing press can add a fifth tower for a spot colour and perhaps a sixth tower for adding a follow-on varnish, without requiring a new main drive.

In the future, Crabtree plans to extend the modularity achieved by the Servo PLC to other parts of the machine, including the unwind, the sheeter and the rewind.

Further operator features, such as job parameter recording, uploading/downloading via disk and remote diagnosis through a modem line, will also be added.

The QPrint tower was conceived as a retrofit but is now the standard for new Morgan machines.

After nearly 18 months of field operation, improved performance of the prototype tower has been achieved from the new ink roller configuration.

Equipment supplied by Lenze builds on this improved performance by giving more features to the operator and reducing build costs. Request a free brochure from Lenze ...

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