Backlash-free shaft couplings in machines for décor printing

Whether warm wood colours, natural stone elements or sophisticated graphic designs - printed d©cor papers give furniture, flooring or other room elements a very special appearance. The d©cor papers are manufactured in a gravure printing process and are used in the wood materials processing industry for decorative surface design.

Rotodecor, which is based in Bielefeld in North Rhine-Westphalia, is a manufacturer of gravure printing machines. Besides gravure printing machines for d©cor and packaging printing, the company also develops and produces varnishing and special machines, impregnation systems, winders and rewinders as well as rotary die-cutters and packaging systems.

Georg Kliewer, Head of Technical Development at Rotodecor explains: "We have discerning customers who each have their own high expectations. Therefore, we also build customer-specific systems and machines. All our machines and systems are equipped with an extremely sophisticated, high-precision power transmission. From the motor via the transmission and right up to the coupling, there are only a few manufacturers who can meet our demands." Therefore, Rotodecor relies on the backlash-free and high-performance ROBA-DS disk pack couplings by mayr power transmission.

To achieve high-quality printing results in the gravure printing process, the drive lines in the machines must operate with precision. Georg Kliewer says: "The accuracy of the gravure printing cylinder is decisive. During the printing process, first the raw paper is unrolled, then the first print is executed, and then the next one is printed on top, etc. This means that every print must align exactly with the patterns below it. We work using direct drives here, and each printing unit has its own drive which has to be individually adjustable." Therefore, the shaft couplings, which are installed between the gravure printing cylinder and the transmission, operate with high precision and transmit torques accurately.

Cord Schumacher from the Design and Development Team says: "The couplings are an important part of the drive line. Not only in the gravure printing machines, but also in the rotary die-cutters for packaging. We use die cutters with a high level of accuracy +/- 0.2mm. For this purpose, it is necessary to be permanently able to readjust the position of tools or rollers during running operations within a range of 1/1000mm. The more accurately the coupling transmits the torque during this process, the more accurate are the results. Here, we require backlash-free couplings with a high torsional rigidity."

Backlash-free torque transmission

Therefore, Rotodecor relies on the tried and tested ROBA-DS disk pack couplings by mayr power transmission in their machines and systems. Adapted to the respective drive units of the various gravure printing and packaging machines, ROBA-DS disk pack couplings are used in numerous sizes and with various torques. The couplings transmit the torque backlash-free and in an very torsionally rigid manner, and compensate for existing radial, axial and angular shaft misalignments. As a result, they not only ensure accurate torque transmission, but also protect the bearing installed in the shaft train against unwanted loads, and therefore against unnecessary downtimes and costs. The ROBA-DS couplings are robust, reliable and temperature resistant. Furthermore, they are wear-free and therefore reduce the necessary maintenance expense to a minimum.

Georg Kliewer says: "The fact that the couplings are available with clamping hubs is great. As a result, the backlash-free function is also guaranteed for the torque transmission to the elements to be attached. Furthermore, ROBA-DS couplings feature an extremely compact construction and high performance density. In competitor products, couplings with the same nominal torque and also the same speed are usually larger."

And Cord Schumacher adds: "The high performance density of the couplings at a simultaneous low mass moment of inertia is crucial for the high dynamics of our rotary die-cutters. Today, using the ROBA-DS couplings, we can achieve cutting speeds of 450 m/min instead of 350 m/min. There is no comparable coupling on the market which provides higher performance density and simultaneously provides the required torsional rigidity."

In the case of ROBA-DS disk pack couplings, the nominal torques stated in the catalogue can be used without any restrictions. A reduction of the nominal torque due to displacement, overall load configuration or balancing requirements is not necessary. The ROBA-DS disk pack couplings transmit torques up to the nominal torque absolutely backlash-free and with a constant high torsional rigidity. The stated shaft misalignments can be exploited 100 per cent without influencing the transmittable torque.

For more information about ROBA-DS disk pack couplings please visit www.mayr.com.