KraussMaffei Berstorff, the German plastics machinery provider, has recently offered its customers a new screw concept (High Performance Geometry/HPG) with number of benefits.
The new 36D twin-screw, single-venting extruders from KraussMaffei Berstorff are engineered to process PVC pipe formulations more efficiently. By eliminating atmospheric venting in this range of parallel twin-screw extruders, KraussMaffei Berstorff engineers have been able to use the whole 36 L/D length of the processing unit for optimal plasticizing and homogenizing of the PVC resin. This new extruder design, in conjunction with the optimized HPG screw concept, offers processors significant advantages.
The longer effective preheating zone means more flexibility for processing a wider range of formulations. Throughput is up to 10% higher than with double-venting extruders. A longer metering zone means a more stable process thanks to improved capability to build pressure and optimal control of the melt temperature over the whole output zone. Lastly, the longer mixing zone together with optimized mixing element geometry produces a more homogenous melt and outstanding optical pipe quality. It also improves dispersal of additives and blowing agent in the melt.
The new HPG screw concept makes it possible to drastically reduce process fluctuations in manufacturing highly-filled PVC pipe formulations. Plasticizing and homogenizing these formulations needs a much higher energy input, which is achieved in this case by substantially extending the effective preheating zone. The new 36D single-venting technology delivers outstanding performance in processing U-PVC, M-PVC, foamcore PVC pipe and pipe formulations that call for a very high proportion of chalk filler.