Extrusion die producing multi-channel hollow profiles is provided with cooling jets on the end of each die core where the jets comprise a spray or mist of water droplets dispersed in compressed air coming from a (common) spray generation nozzle located outside the die. The spray for each jet is delivered to and through the die head by an individual distribution tube. The spray delivery tubes are heat resistant, may be of "Telfon" (RTM-PTFE). The ends of the tube may project a few cm from the passages through the die cores. Used for chilling the internal surfaces of a complex hollow thermoplastic extrudate at a similar rate to the external surfaces, to avoid asymmetric cooling and associated thermal stresses or distrotion. Esp. applicable to dies producing relatively small bore profiles, because the core does not have to be large enough to accommodate a conventional spray head with separate air and water supplies to such a head at the end of the die core itself.
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