|
|
Size-reduction of thermoplastics reinforced by long and continuous filaments |
|
 |
|
|
|
Material utilisation of thermoplastics reinforced by long and continuous filaments to produce high-value, long-filament reinforced extrusion compo-
nents requires a gentle size-reduction of the materials to be utilised into lumps of grinding stock in order to achieve a large as possible filament length. The properties of the components to be produced out of this grinding stock are determined by the filament length to a large extent. |
|
 |
|
|
|
This is why the sizereduction unit used is of considerable importance. In a project supported by the “Deutsche Bundesstiftung Umwelt” [»German Federal Foundation Environment] M/s. WEIMA Maschinenbau GmbH, Ilsfeld, along with renowned partner companies developed the series WLK-F.
In the course of the research project all existing size-reducing units such as cutting mills, two- and four-shaft shredders as well as one-shaft size reduction machines were tested. The most promising results came from the conventional WEIMA one-shaft size-reduction machines of series WLK which have been consequently further developed in the course of the project with regard to the task set. Extensive size-reducing trials with most different components were performed and documented with different knives, knife arrangements, screen hole geometries, etc. Based on the results gained a new rotor with special knives and bed knives and special screen technique has been developed.
Most thermoplastics reinforced by glass fibres during cutting produce a high wear of the size-reducing tools and the rotor because of their high abrasion. For this reason, the rotor made of special steel which had been produced from the solid and possesses a particular profiling (V-tube) as well as a patented knife seat was plated with a renewable Hardox coat.
Through a flexible bed knife rail the exact adjustment of the cutting gap is possible. An exact and close cutting gap is a prerequisite for a high cutting quality. A too large cutting gap would result in a cracking load of the material and avoid to achieve long filaments.
Another important criterion when designing the machine was the fact that the machine is to be installed within the production environment, e.g. of an automobile purveyor. Merely for reasons of labour protective laws hardly any fine portion is permitted to be released into the air. For this reason a cyclone was integrated into the machine such that the fine portions are sucked off by vacuum within the machine body through suction slots. Besides meeting the labour protection regulations with regard to limiting values of fine portions in the air also the quality with regard to a low fine good portion in the produced grinding stock is safeguarded.
Thus the machines can be fully integrated into production processes with minimal employment of staff. In case of a certain filling level they automatically start to operate and they will switch off as soon as the funnel is empty.
Meanwhile the series has been used with numerous renowned automobile manufacturers and purveyors.
For more than 20 years WEIMA Maschinenbau GmbH have been building size reducing machines for quite different applications, among others for customers from plastics industry all over the world. The company employs about 100 persons and possesses branch establishments in France, Great Britain, America and more than 50 representations world-wide. Part of the production program, among others, are one-shaft size reducing machines, two- and four-shaft shredders, and cutting mills including accessories. |
| |
|
Top of page |
|
|
|
 |
|
| © WEIMA Maschinenbau GmbH · November 2008 |
|
|
|
|
|
