Extrusion International 5-2026

27 Extrusion International 5/2026 Rotation in Extrusion Tools CONEXTRU GmbH / Austria is an engineering & manufacturing company well known for standard as well for very special solutions out of standard manufactures especially for pipe. The following discussion provides a brief overview of the state of the art regarding tools used in pipe extrusion with a rotating die and/or mandrel. D ie rotation of parts in extrusion tools is not a new invention, but not much used in practice. The short abstract is a review of products pro- duced with rotational parts in the extrusion tool. We can nd die rota - tion in blown lm lines, in extrusion lines to produce plastic nets also foamed and in pipe extrusion lines. In blown lm line the whole die is rotating, this to distribute thick wall spots along the bobbin. One solu- tion is to rotate mandrel rotation. To make nets also the mandrel is os- cillating needed in order to get the lines welded to each other. “Shaping” refers to creating a spe- ci c shape, such as twisted grooves, and “orientation” refers to creating a speci c structure in the melt, such as the orientation of llers. Applications PVC pipes with spiral ribs on in- side for in house sewer pipes - to increase ow down on vertical in - stalled pipes and to reduce noise – the water gets a rotation due to the spiral. PE / PP: Cable ducts – The pipe has grooves in oscillation arrangement to reduce the friction between cable and pipe inner surface. This leads to longer pushing through length of the cables for installation The pipe can be also a multilayer pipe with slippery inner layer. Geothermal pipes having spiral ribs on inside surface to generate turbulent ow – to increase thermal conductivity between the uid and the pipe. This leads to more energy transfer, as well as less pumping en- ergy. Colour stripe in spiral shape for indication of a special type of pipe Additionally, there are examples which were investigated, generat- ing bene ts: Pipes with hollow pro le in spiral shape – to increase ring stiffness of the pipe; pipes with glass bre layer in spiral shape – to increase pressure resistance; dredging pipes with spiral ribs inside, to bring the mud in rotation, to reduce or dis- tribute the wear on the pipes in- side surface. PE or PP pipes to generate a certain molecular structure to in- crease crystallinity and strength of the pipe. Pipes with ller – to bring the ller like glass bre or Talcum in a preferred direction to increase thermal conductivity or to in- crease strength There are some positive as well as some unrequested effects given due to the rotation. Rheolocical situation in der die gap Before we look at the rheological situation in the die gapwhen the die or mandrel rotates, we have to di- vide the materials into two groups. The rst group includes materials that stick to the walls, such as PE and PP. The second group includes materials that glide along walls, like PVC and ABS. The polymers that stick to the metal surface in the die are good for making ribs and also for creating a shear force that can arrange the ller or macromolecules. The most interesting situation is the effect that pipe properties have on mate- rials that stick to walls. The three pictures show the cor- rect analysis of what happens in the die gap. PIPE EXTRUSION, EXTRUSION TOOLING PO 63 R MD PE-RT Geothermic pipe with ribs inside – oscillation PVC hollow pro l pipe with spiral ribs inside Color strip in spiral shape