ThinKing March 2015: Non-stop production of composite materials –



ThinKing March presents continuous manufacturing of organic sheets on isobaric double belt press at Held Technologie GmbH

Held Technologie GmbH in Trossingen has developed the isobaric double belt press (DBP) on which organic sheets and other products can be continuously manufactured. The advantages of this method are that fiber composites made of carbon or fiberglass reinforced plastics (CFRP/GFRP) can be any length at all, the quality remains consistent and the output of the throughput process is high. This is important in working towards the mass production of organic sheets and consequently greater industrialisation of lightweight technology.

The Development Agency for Lightweighting Baden-Württemberg presents this innovation in the March 2015 edition of its ThinKing. Leichtbau BW GmbH uses this label to showcase excellent lightweight technology products or services from Baden-Württemberg every month.

Held Technologie GmbH knows all about innovation. Founded in 1949 as a polishing workshop for clock cases, the family firm from the Black Forest-Baar region (about one hour’s drive south of Stuttgart) is today a global market leader for high-performance isobaric double belt presses. The “Heather 5”, currently the biggest high-temperature and high-pressure double-belt press in the world, stands in the production halls in the Schura area of Trossingen.

Double belt presses are the ideal plant for the continuous production of foil and board material in a single pass. The double-belt press was first used to manufacture decorative laminates for the furniture industry, but it is also used, for example, to produce flexible base materials for the PCB industry, conveyor and transportation belts for various industries and flexible granules flooring material.

Two continuous steel belts are guided through the inlet and outlet around steel drums. Between them there are pressure plates in what is known as the reaction zone. Here temperature and pressure are applied to the materials being fed through.  Oil-based pressure cushions produce the isobar pressure. Separately controllable temperature zones enable individual temperature profiles to be created for materials such as foils or films, woven or non-woven fabrics, granules, powder or similar.

Temperatures of up to 400°C and pressure of up to 80 bar are applied to the materials fed in during the process. Heating and cooling to room temperature at constant pressure enable highly economical and top-quality production.

Held exploits all these advantages in the manufacture of organic sheets. The output material may consist of rolled and sheet products. These sheets are usually made of unidirectional warp. They can be positioned automatically and with great precision by a robot. Machine capacity is used to the full capactiy by working with adjoining sequences.

The fibers of the unidirectional warp can be laid at various angles, such as 0, 45 or 90 degrees, appropriate to the load and are only placed where needed. This procedure economises on weight and results in greater stiffness/rigidity.

After passing through the double-belt press the organic sheets can still be processed, for example in longitudinal or cross-cutting system, as required. Sheets can have a variety of lengths. “A continuous double belt press is the only option when it comes to long organic sheets,” says Timo Geiges, Senior Sales Engineer at Held Technologie. Another advantage is that, in contrast to static presses, isobaric pressure does not result in material warping.

The materials produced on Held machines are used in the widest variety of industries, such as aerospace, ballistics, furniture/flooring, electronics, construction or energy. Three complete isobaric double belt presses – including "Heather 5" – can be hired for test and production purposes in Held’s technology park. They can be used to develop and test materials or to produce samples or entire series. Held provides the operating personnel as well as development and production support.

Demand for Held Technologie's hire equipment is rising with the trend towards the use of thermoplastics. The continuous production of organic sheets on a isobaric double belt press is a tried and tested process. However, the market is still struggling to replace well-know materials such as steel on a larger scale with fiber composites. With around 50 employees the family enterprise believes composite materials offer great potential for isobaric double belt presses.

Further information about Held Technologie GmbH is available at

About Held Technologie GmbH

Held Technologie GmbH from Trossingen-Schura is a family-run, medium-sized mechanical engineering business. Founded in 1949, Held is today a global market leader for high-performance isobaric double belt presses.