Tuning inserts for the feedblock that can be adjusted during coextrusion enable manufacturers of film and sheet to reduce downtime and material waste while permanent flow inserts are prepared, and to achieve greater precision in the ultimate thickness profiles of each layer across the width of the die, it was announced by Nordson Extrusion Dies Industries.
A feedblock shapes molten polymers 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. Typically about 10 cm (4 inches) 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.
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, according to the company.
www.nordsonedi.com
In schematic of new tuning insert for Ultraflow I feedblock, polymer flow for a five-layer structure is from right to left. Core layer polymer enters flow channel from far right. Next layer enters from ports at top and bottom, and its thickness profile is determined by bronze-colored flow-adjusting components. Entry of skin layer follows, again profiled by flow adjusters. Each adjuster is made up of ten segments, and position of each segment is determined by turns of a screw which is not shown in the illustration (source: Nordson Extrusion Dies Industries)
