001-12 Lohr, 2012-05-31

Industry Article: Excellent for Printing

More flexible printing and processing

More flexible printing and processing with faster changeovers: These are the key requirements for automation in printing and converting machines.

One of the factors impacting in the quality, flexibility and productivity of printing machines is automation

Although e-books, netbooks and smartphones are in effect in direct competition with the printing and publishing industry, digital technology is at the same time opening up new concepts in the industry. It allows for printed information to be produced quickly and in high quality, yet at a low cost. The printing industry is incredibly innovative, as it has demonstrated recently through the new technologies and machines presented at drupa 2012. In order for these innovative technologies and machines to also be appealing in terms of quality, flexibility and productivity, automation is a crucial factor. This is where Bosch Rexroth comes in, providing customized solutions tailored precisely to the industry's needs.

Shorter product cycles, new production concepts and materials, and ever smaller batch sizes are a challenge for OEMs as well machine operators around the globe. Modern automation concepts make it possible for printing machines to work reliably, quickly and with extremely short changeover times, all while maintaining the same level of quality.

As a supplier of drive and control systems, Bosch Rexroth has been actively involved in printing and converting since 1993 and has continuously driven the automation of printing machines forward. With expertise in all drive technologies, the company is able to advise clients across the various technologies and supply the entire automation concept from one single source. This is an important factor, as printing machines not only use electrical drives but also linear motion technology, pneumatics and hydraulics. For OEMs this cuts down on the number of interfaces. If components work together smoothly, this also reduces the cost involved in integrating the engineering. From the many applications Bosch Rexroth has realized for packaging, newspaper and label printing, its experts know the levers that enable OEMs to shorten their time to market, and allowing printers to respond flexibly to customer requests while delivering the desired quality. Numerous industry leaders are using Rexroth automation solutions.

Quality: Digital printing requires constant web tension

Digital printing processes have broadened the possibilities offered by traditional printing, adding personalized print products, very short runs, or print-on-demand. In addition, modern digital printing machines have such high web speeds already today that for medium-sized printing orders, they can provide an alternative to sheet-fed offset printing, for instance.

Compared to the traditional printing processes, the requirements as to web transport are higher in digital printing because it is contact free. Therefore, having non-distorted and stable web tension is fundamental for overall print quality and machine productivity. Direct drives minimize problems with torque ripple and increase the preciseness of the web transport through stiff mounting to the transport roller shaft. In order to ensure constant web tension, a dancer can be inserted in the material web path. A closed-loop web tension control maintains the center position of the dancer. The dancer position is sensed via a potentiometer. Rexroth's electropneumatic pressure regulators compensate changes in tension caused by a reel change or out-of-roundness in the material reels, and quickly and precisely adjust for any disturbances of the dancer roller.

The benefits of having a complex tension control can be seen especially in hybrid inline machines that combine printing, embossing, cutting, die cutting and laminating. Tension controls work for paper and cardboard as well as for a variety of foils with their variable elasticity. As a result, set-up times are shorter, which leads to less waste after a job change. Moreover, OEMs could integrate them quickly and easily into the control system as a pre-programmed technological function.

Flexibility: Modular machine concepts shorten delivery times and can be expanded easily

Nowadays, it is possible to print newspapers including inserts such as advertising flyers on and the same machine. As a result, companies working in publication printing use a smaller number of more powerful and flexible machines. Flexibility is also a key requirement in packaging printing, because it is characterized by extremely short life-cycles with machines having to be able to not only realize different print formats but also several printing and finishing processes. In addition they have to be able to work with a variety of substrates of varying quality because packaging printing is also about visual and tactile appeal. This makes individual process steps such as embossing or varnishing more and more important. Therefore, there is a growing trend to line up machine modules for these additional process steps for inline production. This requires processes of different durations to be combined with each other in such a way that the line speed does not suffer. Intelligent cam functions make it possible to couple continuous web transport with semi-rotary movements, thereby enabling active web buffers to increase the process' productivity. Rexroth's linear modules offer a reliable and uncomplicated complement to the overall solutions.

For inline production, modular and thus flexible machine concepts are the best solution. OEMs can focus their development work on individual modules which they can standardize and also put into operation individually. At the same time, this also helps shorten the overall start-to-finish time for customer projects and satisfy their demands for shorter delivery times.

Machine operators also benefit from the flexibility offered by machines built on modular concepts. They can add additional stations to their system without any significant effort and thus react flexibly to market requirements. This makes integrating an additional printing step, for instance perfuming printed pages, very easy.

Bosch Rexroth creates the necessary prerequisites for such a modular structure by using automation systems that can be fully decentralized. The controls for the individual machine modules are networked via sercos interface. This gives users the benefit of exact cross-communication in real-time.

Efficiency: Software support makes engineering faster

Demanding consumers, use of new materials, customized solutions with shorter delivery times and innovation cycles as well as constant cost and productivity pressure - these are requirements which the operators of printing machines pass on from the market to the manufacturers of their machines.

In order to be able to keep up with the increasingly fast innovation cycles, these manufacturers must shorten their time-to-market. Nowadays, the majority of the time involved in designing printing machines is dedicated to engineering activities - the entire process from project planning and construction to programming and activation.

This is where Bosch Rexroth comes in with its system solution "IndraMotion", which fulfills the industry's specific automation tasks. Ready-to-go machine functions are available as proven technology modules and function libraries. Complex processes such as electronic cams or register controls no longer require time-consuming programming by the responsible engineers, but only a simple setup. This supports the OEMs in their efforts to make their engineering processes more efficient.

Another benefit is the register control, which can be directly integrated into the Rexroth system solution. Without any additional hardware, the motion logic system takes over the register control by means of a pre-programmed PLCmodule from a licensed technology library. In addition, the register control takes advantage of the high degree of precision and functionality of the motion control system and makes corrections even before the register has a chance to shift. This enables OEMs to offer machines with comprehensive technology and a solution from one single supplies.

Productivity: Fast changeover while operations keep running

In this day and age, printers must be able to produce orders for shorter runs in a cost-efficient manner while maintaining the same high and reproducible print quality. And all this while under immense time pressure. This requires being able to switch formats extremely quickly. During those format changes, Bosch Rexroth's highly dynamic servo drives shorten setup times. After a sleeve or printing plate change, the operators set the register to the new print formats. With Rexroth technology, this requires just a press of a button. Continuously variable electronic transmissions immediately transmit the change and minimize paper waste already during startup. The automatically pre-set register then allows for production to resume quickly and synchronization to be done on the fly.

Moreover, the safety functions integrated into the drive also help save time because it is no longer necessary to turn the machine off while changing the plates.

Bosch Rexroth AG is one of the world’s leading specialists in the field of drive and control technologies. Under the brand name of Rexroth, the company supplies more than 500,000 customers with tailored solutions for driving, controlling, and moving. Bosch Rexroth is a partner for mobile and machinery applications, engineering, factory automation as well as renewable energies. The company covers the requirements and special needs of each of these markets. As The Drive & Control Company, Bosch Rexroth develops, produces and sells components and systems in more than 80 countries. In 2011, Bosch Rexroth, part of the Bosch Group, achieved sales of around 6.4 billion euros with 38,400 employees.

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The Bosch Group is a leading global supplier of technology and services. In the areas of automotive and industrial technology, consumer goods, and building technology, over 300,000 associates generated sales of 51.5 billion euros in fiscal 2011. The Bosch Group comprises Robert Bosch GmbH and its around 350 subsidiaries and regional companies in over 60 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. In 2011, Bosch spent approximately 4.2 billion euros on research and development and applied for over 4,100 patents. With all its products and services, Bosch enhances the quality of life by providing solutions which are both innovative and beneficial.

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Susanne Herzlieb
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