Nordson Extrusion Dies Industries has developed a tuning insert for the extruder feedblocks which can be adjusted during coextrusion. Tuning enables film and sheet processors to reduce downtime and material waste while permanent flow inserts are prepared. They also help processors achieve greater precision in the ultimate thickness profiles of each layer across the width of the die, claims Nordson.
The feedblock shapes molten polymer from two or more extruders into layers in a sandwich structure that is subsequently distributed to full end-product width inside a flat die. In feedblocks such as the Ultraflow I from Nordson Extrusion Dies Industries, a specially machined flow insert yields a target cross-direction thickness profile for each layer, and any job change involving significantly different layer ratios or polymer flow properties makes it necessary to design and machine different inserts. The tuning inserts for Ultraflow I feedblocks enable processors to maintain production while being adjusted until the target profile is achieved and a matching permanent insert can be built.
“The new tuning inserts help processors to maximise run time and minimise waste during the week or more that is required to design and machine permanent inserts,” said Sam G. Luliano, Chief Technologist at Nordson EDI. “Because the tuning inserts can be fine-tuned ‘on the fly,’ it is possible to do several iterations, making small additional changes in very little time and refining the geometry with great precision before machining a permanent insert. This process eliminates the need to do several ‘re-cuts’ of the permanent insert before arriving at the target layer profile.”
Typically about 10 cm wide and machined from hardened stainless steel, a flow insert is specially designed to generate a corrective layer profile for a polymer with specific flow properties. The flow-adjusting component of the new tuning insert from Nordson Extrusion Dies Industries consists of ten segments, each of which can be adjusted to reduce or increase layer thickness by turning a corresponding screw. Once the target profile has been established, a measurement tool replicates the screw positions so that it can be used for producing a precisely matching permanent insert.
Ultraflow I fixed-geometry feedblocks can be designed to accommodate a flow sequencing spool that makes it possible to change the sequence of material layers without having to block off channels or disassembling the feedblock. Nordson Extrusion Dies Industries also offers the Ultraflow V adjustable-geometry feedblock, which, instead of interchangeable inserts, has built-in adjustable “combining planes” located where the melt streams join the central flow channel.
