Featherweight production

A medium-sized company found great acceptance and recognition in the automobile industry with the development of a reach spring made of fibreglass reinforced plastic – with Metzner, the company found a reliable partner in order to produce the reach springs in large quantities.

Glass-fibre reinforced plastic (GRP) has existed for a long time. The first, continuous glass fibres were manufactured industrially in the USA as early as 1935 and the first aeroplane made of GRP, the Phoenix from Akaflieg Stuttgart, was produced in 1957. The benefits of GRP are obvious: the material can be highly stressed, it does not corrode and thus does not break during coldness and never when pulled, a property which ensures a lot of safety. However, the essential characteristic is the weight: GRP is many times lighter than other stable materials such as steel for example. Nevertheless, many plans to use GRP components in the past got stuck at the start or never came to anything as machining GRP is anything but simple. 

The customer developed the first prototypes of a reach spring made of GRP in collaboration with the University of Darmstadt. The reach springs should be installed in commercial vehicles later and replace the five times as heavy steel springs. In order to achieve an optimum result, just under 60 thin GRP layers were cut out manually, placed on top of each other and compressed afterwards. The processing for a single reach spring took about one hour. When a world wide leading automobile manufacturer showed interest in this product, a solution was sought for manufacturing the reach springs in series production. The solution was: an automatic production line from Metzner.

Searching for solutions together

The system must be designed so that the 60 thin GRP layers are laid on top of each other automatically in the correct position in order to guarantee ideal quality later which was, however, a challenge due to the sticky material. The cutting length and the laying afterwards must be freely programmable in order to be able to produce different springs for various types of vehicle. In order to ensure cutting the fibreglass reinforced plastic without fraying, the shearing method was applied. As safety and quality are the most important for the automobile manufacturer, the material had to be checked for possible errors with a camera system after the machining. Metzner looked for the optimum solution for every; four months later, the first – of in the meantime three – production systems was successfully delivered.

Benefits

It was not possible until the automatic production line from Metzner for the customer to manufacture the GFRP leaf springs in quantities of around 1000 pieces per day and thus effectively function as a supplier for the automobile industry.