Printer's angel

Photo | Müller Martini
Marginal Column

Above: An Alprinta V hybrid machine with four offset print units and one flexographic unit.

Photo | Müller Martini

Printing cylinder change in just two minutes on the Alprinta V print unit with its continuously variable format.
Photo: Müller Martini

March 2012

 

Müller Martini is turning the market for packaging printing on its head: offset printing machines are expanding into new applications.

 
 

Colorful films, bags, labels in every conceivable shape – printing of flexible packaging must be inexpensive, fast and variable. That is why printers have been using flexographic and gravure print­ing processes to date, as they can handle extremely varied printing formats relatively easily. In conventional offset web presses, by contrast, material costs quickly mount up for format changes, as the complete printing cartridges must be changed out. This nullifies the great advantage of this process: the easy, rapid and low-cost production of printing plates by exposing them to light. The Alprinta V of Swiss company Müller Martini is now putting this advantage to work for the printing of flexible packaging – with continually format-variable offset web printing.

More variable with no shaft

This is made possible primarily through the use of an automation solution for shaftless printing systems from Rexroth. This modern technology, which is based on precisely synchronized drives – the “electronic shaft” – significantly reduces setup times. The lightweight carbon fiber cylinder of an Alprinta V printer can be changed out for a new format in just two minutes. Combined with the advantage of short lead times thanks to rapid exposure, this makes possible high flexibility in filling orders and increases productivity – which pays off particularly in frequent motif changes and orders with a low repeat business likelihood. This opens up new application areas for offset web machines and also enables their use for print runs for which sheet-fed machines have predominated to date.

One of the main elements of this solution is the motion-logic control. For instance, the axis interface of the PLC enables the relevant drive parameters to be accessed in the language of the machine program. The PLC engineering and the motion control of the drives thus become both simpler and more transparent. This enables the Alprinta V to succeed where conventional offset systems fail: processing of extremely thin and stretchable film materials for flexible packaging. For this application, Müller Martini developed the StretchCorrect TM process. The optimized interaction between the drive concept for the individual drives and the electronic gear unit makes it possible to adjust cylinder speeds at extreme precision. Process parameters can be switched at the press of a button.

User-friendly and safe

The control unit showcases its user-friendliness right from the commissioning phase. The seamless connection to the machine control elements means that machine modules can be flexibly combined. This cuts commissioning times and enables subsequent expansions of the machine to add print units or post-processing modules, for example laminators. The Rexroth automation solution also contains numerous pre-configured process-typical functions that replace elaborate programming with simple parameter setup. Functional safety is also an integral part or the system. The certified Safety on Board technology simplifies realization of machine safety and provides a further advantage. It increases availability, as manual format changes now require only setting targeted, individual drives in a safe state, without having to shut down the entire machine.

All tomorrow’s printing

Automated job handling that cuts down setup times so drastically and makes even small print runs economical is proving very attractive to printers. To date, 60 Alprintas have been installed in printing operations. For Müller Martini, this is an incentive to systematically advance variable-format offset printing even further. For the latest machine generation VSOP, this enterprise is one again using an automation solution from Rexroth: the Ethernet-based system solution IndraMotion for Printing – now also available as an upgrade for existing Alprinta machines.