Extrusion International 2-2026

30 Extrusion International 2/2026 sagging effect. Large noz- zles can be segmented to allow for different tem- perature zones along the nozzle circumference to generate thermic centring of the polymer ow. For very large wall thick- nesses, the melt cooler is used – the melt is cooled in the die head, increasing the viscosity and reducing sag- ging. M ultilayer with radial spiral & helical spiral desig n The applications of mul- tilayer pipes are particu- larly diverse. Here are some examples: hot water and oor heating, non-pressure PP, sewer and waste (main layer com- pact, foamed or lled), water pres - sure, oil and gas, RTP, jacket for pre-insulated heat pipes and cable ducts with low friction, to name but a few. The solutions for pipeheads for these applications are therefore also diverse and adapted according- ly. In addition to the standard spi- ral geometries mentioned earlier, there are two more for low-viscosity melts and technical polymers. With these 4 basic geometries, a multi- layer pipe head can be designed for all possible pipe layer constructions. An additional option is the radial helical distributor. This is essentially a at helical spiral distributor. This geometry can be easily derived from the helical spiral. This construction is familiar from the Blown lm and was rst modi ed by CONEXTRU for pipes. This head is used for pipes up to 110 mm with 2 to 7 layers. It can be used as a single-layer addition up to a maximum of 10% of main layer up to 400 mm possible. Multi Helical Spiral Heads have all the same mechanical, rheo- logical and handling fea- tures as CONEXTRU's mono layer heads. The prod- uct line starts at 63 mm and goes up to 1600 mm, with 2 to 5 layers. In addition to barrier materials such as EVOH, there are also ver- sions for high-temperature and chemically resistant technical polymers such as PA, PVDF, PPS and PSU. Monolayer cross heads From the outset, CONEX - TRU relied on the spiral dis - tributor as the best solution for low pressure and precise melt distribution. The prod- uct programme of mono- layer cross heads begins at 20 mm and currently ends with the largest head for the moulding of plastic or steel pipes at 1,200 mm. In principle, there is no upper limit. While throughputs up to 1,200 kg/h are required for steel pipe insulation, throughputs of up to a maximum of 400 kg/h and layer thicknesses of up to 5 mm are required for plastic pipe insulation. Additionally, there are features such as wire insertion or coloured stripes. These are usually protective layers made of PP. CONEXTRU uses the same spi - ral distribution geometries for the PIPE EXTRUSION, EXTRUSION TOOLING Picture 16: PO 1200 CR Picture 17: PO 250 CR Picture 19: PO 44 400 CR IL EV