Extrusion International 2-2026

29 Extrusion International 2/2026 ing length while maintaining the same cooling length, leading to additional energy savings. Overall, such a system is more energy ef - cient because the cost and power of the blower is much lower than that of spray tanks, which can be elimi- nated due to IPC. Internal head cooling is needed for large tools, too. In- ternal head cooling is required for heads with a diameter of 400 mm or more. The higher the output rates, the greater the long-term tempera- ture increase inside the head. Air cooling inside the head can be easily installed, and the blower is connect- ed to the internal heater via a 3-point controller – it works like a heating/ cooling unit in a barrel. The head is closed and sealed inside, so the air blowing inside comes out via an exit air duct. The air ow is controlled and enters and leaves via small pipes. Air cooling keeps temperatures stable over the long term. Air cool- ing systems are ef cient and have low operating costs, and can replace old, complicated systems with cool- ing blocks tempered by an external unit using oil or water. This system works independent with the ipc sys- tem. This is important because only a independent system can lead to the optimum result. Wide dimension range We have a solution whereby the basic head, which has a certain melt outlet diameter, can be used to pro- duce pipes larger than the melt out- let diameter. This is made possible by changes to the mechanical de- sign as well as the excellent eccen- tricity. Furthermore, more pipe sizes can be produced using the draw- down method for most polymers. Three or sometimes four pipe sizes can be produced with one tool set, which signi cantly reduces changeover time. Easy handling This means that the die parts are lightweight and the die is mounted horizontally, making changes easier and quicker. Pusher screws allow the die to be removed if there is already a low- temperature melt between the die and the mandrel. A low number of screws and easy cleaning are also important design criteria. Low volume and small surfaces mean short residence times, leading to a short heat history for the mate- rial and short self-cleaning times. Colour-striped rings/unit Colour stripes are needed and can be co-extruded on top with a sharp border and as thin as possible. Common options include 3, 4, 6 or 8 stripes, sometimes double stripes or in different colours. There are many possible versions. There are two options for install- ing the CSR or CSU (stripe ring or stripe unit). The CSU is designed for all sizes and is mounted after the basic head. The CCSR ring version is mounted at the end of the die. Both have advantages. The decision is made on a case-by-case basis. Pipehead solutions / examples Monolayer heads Attached is an example of an up- dated single-layer head design in- corporating all these features. The head has a low volume, short pre- melt distribution and a helical spiral for a throughput of 1200 kg/h. It has a centring unit with a master die of 400 mm and a die set of 630 mm. It has internal head cooling by air and internal pipe cooling. The head is short in length and low in volume, and is suitable for 1200 kg/h with low heating power consumption. For larger dimensions, especially for larger wall thicknesses, the wall swelling process is used, whereby the wall thickness is de ned by compression, which reduces the Picture 13 Picture 14: 5 layer radial die Picture 15 Picture 12