Carbon fibre tubes are stiffer than steel

When Soma Engineering was researching alternative solutions to the steel rollers used in its printers, it discovered a company that could make rigid and strong carbon fibre composite tubes.

In 2004, when leading flexo printer manufacturer Soma Engineering was researching alternative solutions to the steel rollers used in its printers, it discovered CompoTech, a Czech-based company that has established a solid reputation for providing rigid and strong carbon fibre composite tubes to a range of industrial applications.

Although other companies claimed to provide high performance carbon tubes suitable for printer rollers, none could match the performance of CompoTech's tubes, custom designed and manufactured using its bespoke zero degree axial fibre laying process.

Vibration is a common problem in the printing industry - the greater the vibration, the lower the final print quality.

And the extent of vibration experienced is highly dependent on the elastic modulus (or stiffness) of the tube used in the rollers.

CompoTech was able to supply Soma with carbon tubes with a material modulus greater than 400GPa - considerably stiffer than its current steel rollers.

The stiffer the roller, the less vibration, and the faster the machine can operate.

Whereas other carbon composite parts can achieve a similar stiffness, it is only CompoTech's manufacturing process, which has been well researched, developed and optimised over the past ten years, that can achieve this in a tubular shaped component.

From the outset, CompoTech has worked in partnership with Soma to create a solution that fits the manufacturer's exact requirements - an approach CompoTech takes with all of its projects, and which is of great value to its customers, as Pavel Cernohous, R and D Manager at Soma, attests: "We have found it easy to work with CompoTech on the development of our new components, and we know that they will use only the latest materials and technologies in doing this".

"In addition, their versatility during the testing period has filled us with confidence that we are getting exactly what we require to make our printers stand out in the market place".

The first step in this collaborative process was a site visit by CompoTech to investigate Soma's current operation and to define the outcomes required by the client.

CompoTech's engineers then set to work to design the new carbon fibre tube.

CompoTech's proprietary software was used to optimise the design according to working conditions, such as working speed and temperature of the machines and anticipated tube loads.

This included analysis of: bending, shear and transverse stiffness, thermal and fatigue properties, end bonding suitability and surface definition - all of which interact to contribute to the overall performance of the tube.

Of particular importance was the bending stiffness of the tube.

This was analysed using a three point bending test, and, in conjunction with the Czech Technical University in Prague, finite element analysis software, which had recently been upgraded to include vibration analysis.

Following this optimisation, CompoTech manufactured a prototype, which was delivered to Soma in August 2004.

This first prototype was tested for suitability and performance, and, with Soma's feedback, a number of refinements were made, leading to the manufacture of a second prototype, which was delivered in November 2004.

The vibration test for the machines' rollers involves setting the machine to print a solid colour except for one thin band of no colour.

If a defect is present (such as a vibration), the thin colourless band will be curved.

If no defect is present, then the band remains perfectly straight.

The speed of the machine is increased until a defect appears, thereby determining the maximum speed at which the machine can run.

The higher the speed, the more productive the machine is.

When tests were carried out using CompoTech's carbon tube, the maximum speed achieved was far greater than achieved with standard steel tubes, and the eventual defect was less critical.

"CompoTech's carbon tubes have allowed us to offer our own customers a higher final print quality and at a greater speed", states Cernohous.

"And this has certainly given us an advantage in the marketplace".

Following the success of this test, Soma placed an order with CompoTech for the supply of carbon tubes for the Soma Flex MIDI 127-8-EG printing press.

Currently these new tubes are an option for customers, but as the benefits of using this new technology is seen by the market place, CompoTech is confident that its carbon tubes will become a standard feature.

In the meantime, CompoTech continues to develop and optimise its processes and designs to ensure that it can offer its clients the most cost effective option for high performance production tubes.

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