Extrusion International 3-2018

36 Extrusion International 3/2018 PIPE EXTRUSION, TOOLING CONEXTRU has developed a pipe head system which can be used for a quite big range of layer structures as well as with different materials. As an example here the range of structures: A/A/A, A/B/A, A/A/B; A/D/C; C/A/B The materials are: A - PE or PP; B - PE or PP Regrind; C – PA or PVDF or PET, D- Adhesive. Pipes for Monolayer PE for water and gas, 3 layer PP-H for sewer pipe, 3-layer PE with regrind, 2-layer PE with PP protection layer, 3 layer for fuel transpor- tation and some more. One of the important requirements for flexibility is that the position of each extruder must be same for all pipe structures. Only a short longitudinal movement of few centimetres are allowed – only for mounting to the head. Of course the extrudersmust have this flexibility in terms of processing different polymers without changing screw. The extruders are optimised for that and instead of highest output – wide processing range is required. This can be achieved if extruder has corrosion resis- tance screw and barrel for processing corrosive poly- mers, have barrier screw design for and temperate grooved intake which can be operated at high tem- perature if needed. Gravimetric system for output control is also a must in case of co-extrusion at differ- ent output levels. The multilayer head have adapter connection which allows that the extruder can keep the position as it is by extruding different layer structure. But how this is possible? This is possible if in between the multi spiral chan- nel head and the extruders is an adapter block which brings the melt of each extruder to the right distribu- tor of the head. For each layer structure – as shown before – is a spe- cial adapterblock designed. Multipurpose Multilayer Pipe Head – a new System for more Flexibility in Pipe Production Multilayer pipe heads are established in the market since many years. The number of layers are depending on product and application from 2 up to 7. Usually a multilayer head is designed for a certain pipe structure and is used just for this structure only. Quite often pipe head manufacturers are asked about flexibility in using the head for other layer structures and unfortunate the answer is in most of the cases that the particular head is not designed for this kind of flexibility