Usually, patches are used to reinforce components with CFRP. Inserting semi-finished fibre products into the diameter of a profile is more unusual approach. The idea for an internal reinforcement earned the June ThinKing award. Low weight, stability, stiffness and damping are the result of a lightweight construction solution for an embroidery machine that can also be transferred from mechanical engineering to other applications and industries.
Low weight, stability, stiffness and damping are the result of a lightweight construction solution for an embroidery machine that can also be transferred from mechanical engineering to other applications and industries.
The Baden-Württemberg State Agency for Lightweight Design will present the ThinKing for this innovation in June of 2021. Each month, Leichtbau BW GmbH uses this label to award innovative lightweight design products or services from Baden-Württemberg.
At a glance:
“Aluminium embroidery frames have created problems with vibration on multi-head machines over and over again. There was also potential to optimise the stability of the frame” explains Martin Hofmann, Head of the Speciality Machinery area at Tajima GmbH. The frames used on the embroidery machines can be up to 9 x 2.5 m in size, with embroidery generating tensile forces which the frames have to be able to withstand. Vibrations are a challenge for design and operation, primarily on high-speed machinery. They are also a cost factor, because they can result in increased maintenance requirements and reduced product quality. Components exposed to vibrations often need to be both lightweight and stiff – preferably with vibration-damping properties.
Stability, stiffness and damping
In industrial embroidery machines, the frame is used to move the material. The movements can reach frequencies of up to 1,200 per minutes. Therefore, low weight is important to improve dynamics and energy consumption, while stability and stiffness are key to the quality of the embroidery. CFRP applied to the outside of the frames to reinforce them is not very practical, so the only potential solution was internal fibre reinforcement. But how could resin-saturated fibres be inserted into the profiles after their construction? The successful solution to this question is receiving the ThinKing for June 2021.
Adding a fibre composite core to profiles
The method used to manufacture the hollow aluminium profiles internally reinforced with carbon fibres was developed in partnership with the Institute of Aircraft Design (IFB) at the University of Stuttgart. Fibre material saturated with resin is inserted into the standard aluminium profiles through a kind of reverse “wet pultrusion process”. The interior surface of the profiles is pre-treated to optimise bonding. Due to this unique structure – with aluminium on the outside (scratch-resistant, chemical resistant, isotropic) and CFRP on the inside (high-strength, very lightweight, good damping properties) – the solution combines the positive properties of both materials in a very effective way. All kinds of connection technologies, such as clips for standard profiles, can continue to be used, since the fibres inside the profiles are protected against mechanical damage by the exterior aluminium. The manufacturing process is able to optimise the mechanical properties of aluminium profiles – for example from Item or Bosch, which are very widespread in mechanical engineering – by inserting a fibre composite core even after they are manufactured. Ideally, this can result in up to 25 % material savings, as well as a 25 % improvement in stiffness when selecting profiles. It is possible to reduce weight by choosing a thinner aluminium profile, due to the improvement in strength. The improved properties of the aluminium profile also make it suitable for other lightweight construction applications. Better stability, paired with weight savings, result in less fuel consumption and longer ranges in terms of mobility.
Hybrid profiles open up new possibilities
There are also advantages for dynamism, material efficiency and energy consumption in mechanical engineering – as well as for new products. Tajima GmbH is already using initial profiles with internal CFRP reinforcement in pilot applications on its own machines. Thanks to their improved stiffness, for example, the company can now outfit vehicle carpets with heating elements, an in-demand application in electric mobility. One difficult aspect in terms of the durability of the hybrid profile is the bonded connection between the CFRP and aluminium. Tajima GmbH is looking for industrial and research partners to continue developing the technology and find a forward-thinking recycling solution.
About Tajima GmbH
Tajima GmbH has been selling and adapting specialised embroidery machines since the 1990s. Later, the company added tow-placement machines to its product range; the Institute for Polymer Research in Dresden was involved in developing these to get them ready for series production.