Extrusion International 5-2025-USA

66 Extrusion International 5/2025 PIPE EXTRUSION The goal is to work with a minimum number of ex- truders and as little effort as possible to switch from product A to product B. Both pipes have a thin inner layer and a further, stronger layer above it. To accomplish this task, a distribution block was de- signed that comprises two ow channels: one channel for the inner layer and another channel above it for a thicker layer. The two extruders supply these channels with the respective layers. Due to its smaller dimensions, the ex- truder for the inner layer was speci cally optimized for higher output. Two layer die heads were then mounted on the aforementioned distribution block with two melt lines. Both melt streams are distributed by a spiral distribu- tor. A replaceable color stripe unit was mounted in the head, which allows the melt to be fed from above via a melt bridge from an extruder. The rst task was thus successfully solved using three extruders. To implement the second solution, it is necessary to dismantle the color stripe unit and install two co-ex- trusion units instead. In principle, it is possible to work with radial distribution here. However, this design has the disadvantage that it must be built with a larger di- ameter than spiral distributors. Due to the small center distance of the Y-distributor, small helical distributors optimized for throughput were used. The thinner layer further inside is fed via the same melt bridge and extruder as the heads. The same melt bridge and extruder were also used for the color stripe. A melt bridge with another extruder was also used for the thin outer layer. The throughput between the left and right strands is nely adjusted using screws in the melt bridge. Turn - ing these screws reduces the throughput. Practical experience has shown that this is not necessary. It is understandable that both heads have the same ow channel and the same temperature. As a result, the Products to make 2-Layer version 4-Layer version Y-Block with Layer Head Coex block for 2 outer layers