The stripwinding Principle

The principle of stripwinding can in short be described as follows: A 0.1 mm thick high-strength steel strip material is wound around a core of high-alloyed and hardened tool steel. A core of tungsten carbide can also be applied. It takes 10 strip layers for each single millimeter in order to build the stripwound container product.

During the winding process, the winding tension is maintained and fully controlled. The optimal stress distribution is obtained by varying the winding tension from strip layer to strip layer. Thus, the winding core and the single strip layers are pre-stressed to a well-defined level providing a very high loadability and safety of the tool.

During the winding process, the inner diameter of the stripwound container product is reduced (or pre-stressed). As a rule of thumb, the contraction is approx. 1% of the original inner diameter of the winding core. In special tool designs we use a winding core of tungsten carbide, and in this case the bore contraction will be 0.5%.

The yield stress of the high-strength strip material is above 2000 MPa. This ensures that the stripwound container product behaves fully elastic - even under extreme high load conditions.

The Key Merit of Stripwinding

In a normal compression ring system (i.e. 1-2 rings), there is a maximum equivalent stress at the inside of the individual steel ring that leads to high stresses and local plastification. In daily operation, this will show as an expansion of the inner diameter of the pre-stressing tool, and result in reduced pre-stressing of the carbide die insert. This loss of pre-stressing may be as high as 30-50% of the prescribed inteference level. In the STRECON stripwound container product, the equivalent stress is equally distributed over hundreds of strip layers, thus avoiding local and damaging stress concentrations. In addition to the increased tool loadability, the stripwound container also remains fully elastic throughout its service life. In daily operation this means an interference of the carbide die as prescribed, e.g. 1.2 - 1.3%. No other tool systems offer such an enduring strength feature and system stability.