CFRP Bridge Adaptors Prevent Vibrations & Bounce, Avoid Loss of Speed & Quality

Using carbon fiber reinforced polymer (CFRP) requires a radical change in mindset, as there is probably no other material that can be so individually tailored to applications in modern construction and development, including package printing.

One process for producing CFRP tubes is filament winding, where carbon fibers are deposited in different layers as they wrap at different angles and are embedded in a suitable plastic. The rigidity and strength of the composite material, created in this manner, are directly related to the type and orientation of the carbon fibers.

For every industrial application, there are different static and dynamic load conditions. They have a significant influence on the potential quality of the material to be produced and inevitably lead to deformations in rollers, printing bridge adapters and air shafts.

All printers fear resonance effects or bouncing, which can lead to loss of speed and quality in their printing machines. When researching the causes, we often encounter natural frequency, which causes objects to vibrate when they are triggered through impact from a blow, for example.

Resonance excitation often occurs in the flexographic printing unit. For example, when print images interact with hard leading edges, this causes part of the printing unit to vibrate. As a minimum consequence, print quality is reduced, but often complete print failures occur. If this persists, it may even lead to damage to the printing system.

The standard measure to reduce these vibrations is generally a reduction in web speed, as this is the only way to reliably ensure that the printing machine is removed from the range of damaging vibration frequency. Printers therefore face the challenge of diminished productivity every time the printing speed is reduced, whilst every increase in printing speed means reduced quality.

Remedy RX

A possible remedy is comprehensive modal analyses of the components in the printing unit. With the help of this vibration analysis, natural frequency, natural form and the corresponding damping value can be determined for printing bridge adapters, air shafts, anilox rollers and chamber blades. The results of this type of modal analysis show that various components’ natural frequencies are stimulated depending on the web speed and print image.

Manufacturers of printing unit components should use these results right from the development and construction phase, to design their products to dampen the vibrations that occur throughout the entire system, as well as the associated energy on a linear basis.

Using this concept, one manufacturer developed a CFRP bridge adapter system that was put to the test by a renowned flexographic printing machine manufacturer. Together, they developed a very demanding test method that classified and evaluated the bouncing effect along the entire print width at various points at different speeds. The dot gain variation was also checked.

An additional quality criterion was the selected print motif, consisting of a bar pattern with a hard leading and trailing edge, which presented a great challenge for all components to be tested.

The result of the test series showed bridge adapters, especially in the critical center area (see Figure 1), generate minimal deflection at all speeds—100 mpm, 300 mpm, 375 mpm and 500 mpm—and display only a very low bouncing level.

Bridge to Quality

To benefit from the already excellent properties of CFRP material, the analysis method and manufacturing process described here was used to produce a bridge system that significantly reduces vibration and bounce in the flexographic printing method. In addition to the successful bridge adapter principle, a patented damping technology for air shafts in the flexographic printing unit is part of that system.

Numerous independent printing tests carried out by machine manufacturers and print shop operators confirm the functionality of this technology and play a major role in the optimization of the entire production process in flexographic printing.

About the Author

Bill Stahl is the director of sales and distribution for INOMETA GmbH, a German manufacturer of pneumatic and hydraulic adapters. Throughout his 25+ year career, he has held various positions in both print production and on the supplier side, supporting print manufacturers. Bill’s passion for the industry keeps him continually learning, as he is driven to share and help it grow.

This article describes the unique method INOMETA uses to optimize its INOflex (INObridge adapters and INOshaft air mandrels) to prevent vibration and bounce in the flexographic printing process. The pneumatic INObridge CP adapters are designed to be used with any press manufacturer and in accordance with the bridge principal, which INOMETA has been successfully using in manufacturing its hydraulic INObridge CH adapters for more than 20 years.