Sankt Augustin, Germany -- A new cutting unit from polyurethane machinery supplier Hennecke GmbH for CSM (composite spray moulding) plants has a chopped fibreglass metering system with ten times longer service life than other processes on the market. This new cutting technique significantly reduces downtime, maintenance and costs, says the Sankt Augustin-based company.
Use of chopped fibreglass in the form of rovings is often essential when producing composite parts using the PU spray process, with the fibreglass used as a continuous or selective reinforcement.
Fibreglass rovings allow for a less expensive base material than semi-finished products. Also, less glass is wasted during processing and they do not have to be pre-formed as semi-finished products do. In the CSM process, glass fibres are cut to the desired length with a cutting unit attached directly to the mixhead.
The 'Venturi' effect that occurs when the fibres are metered directly into the spray jet provides optimal wetting and saves time, since the mixhead does not have to be cleaned with solvents as is essential in an integrated fibreglass metering process.
Traditional cutting units cut the glass fibres to the correct length by using a knife roller which is next to a press roller. The knife roller and integrated blades suffer high wear and tear, shown initially by changes in the length of the chopped fibres.
Later this can lead to knife blades breaking, with bits ending up in the parts, Hennecke said.
Depending on the application, the roller has to be changed after cutting less than 100 kg of fibre. In large-volume production this can result in significant loss of valuable working time because of maintenance, the machinery maker said.
Hennecke's composites specialists have developed a new cutter which is attractive in terms of service life and ease of maintenance, and thus enables fibre-reinforced composite parts to be produced more reliably and in a cost-efficient way.
The new cutting process does not need a knife roller or blades. Its service life is increased by over 1000 percent, says Hennecke, and the process is only interrupted when the rovings are changed. The formation of atomised spray depositions is prevented thanks to the unit's special geometry, which has been specially tailored to suit Hennecke's spray mixheads.
The advantages can be enjoyed by both new and existing customers. Its modular design means the cutter can be rapidly and easily retrofitted to existing CSM spray mixheads.