Further advantages of the single screw extruder
Further advantages the single screw extruder will be apparent from the following description and the drawings. It is understood that the features recited above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation without leaving the context of the present twin screw extruder.
This has the advantage that the process of matching the grooves is simplified compared with the groove helically arranged.
In a further preferred embodiment the width and/or the depth of the groove varies in a longitudinal direction, preferably the grooves depth decreases towards the downstream end of the melting zone section, preferably to zero.
In a further preferred embodiment of the invention at least one groove is provided also in the barrel inner surface (innerwall) in the area of the feed zone section, the groove extending parallel or helically relative to the longitudinal axis. Preferably, the groove in the area of the feed zone section leads into the groove in the area of the melting zone without transition. Preferably both grooves have the same lead angle.
This has the advantage that the groove extends continuously without any break along the feed zone and melting zone thereby further improving the output and the pressure build-up.
In a preferred embodiment the barrel is formed as a one-piece barrel and is preferably provided with a constant inner diameter. This measure has the advantage that the conventional and structurally complicated separation into a feed zone with a cooled grooved liner and a heated melting zone may be omitted. Thereby sheet production extruder manufacturing costs may be saved. Moreover, due to the good output of the overall system a cooling of the feed zone may be omitted which leads to operation cost savings.
In a further preferred embodiment the barrier twin screw extruder is formed with two or more channel pairs so that two or more solid matter channels and two or more melt channels are created single screw extruder.