The method of reinforcing elastic items with fibres made of different materials and thus influencing their properties has been around for a long time. Car tyres, for example, are given stability and robustness in this way, and garden hoses their flexible and resistant shape.
Festo has developed this principle further and has been working on membrane technology for several years. This has resulted in the Fluidic Muscle, a pneumatic drive which is modelled on the biological muscle. It combines flexibility and stability and can be used in different factory automation applications.
Membrane technology – precise arrangement of fibres
What is unusual about this technology is the precise arrangement of wafer-thin aramid fibres on just a few millimetres of a rubber hose. Depending on the size of the muscle, up to 240 fibres are incorporated with a wall thickness of just two millimetres. On the smallest model, around 60 fibres are distributed on two levels with a wall thickness of one millimetre. Despite the high number of fibres, none of them touch anywhere in the membrane. Depending on how the fibres are arranged, the properties of the muscle also vary.
Bernd Lorenz, head of Membrane Technologies at Festo, explains: “The arrangement of every single fibre is exactly determined and checked – that is absolutely critical with this technology. In this way we can have a direct influence on properties such as the rotary or contraction movement of the muscle.” The individual fibre is very fine and sensitive, with a diameter of between 0.1 and 0.3 millimetres depending on the size of the muscle. In conjunction and combined with the elastic material, they are extremely stable and elastic, however. At the same time, the physical and chemical properties of the materials used also play a major role.
The pneumatic muscle – interaction between different materials
“By means of this production technology, Festo was able to use the Fluidic Musle to develop a pneumatic drive that has very special properties,” says Bernd Lorenz. The muscle consists of a rubber hose with an integrated diamond-shaped fibre structure. Thanks to the combination of fibre matrix and rubber, the muscle is very elastic and can be stretched over a defined length without tearing. The muscle is hermetically sealed, works without any friction or jolting at all and is very precise. t does not leak and provides more power than comparable pneumatic drives of a conventional design.
Versatile application areas – the Fluidic Muscle in action
The Fluidic Muscle is already used in numerous applications. It has particularly excelled in three large application areas: as a clamping device, for example to fix wood panels in place, for very fast shaking and vibrating, for instance in the food industry for distributing bakery products on a conveyor belt, or as a pneumatic spring, for example in a Jacquard loom.