Feedblock tuning inserts maximize co-extrusion line run time

Adjustable tuning inserts for the Ultraflow I feedblock from Nordson Extrusion Dies Industries (Chippewa Falls, WI) enable film and sheet manufacturers to reduce downtime and material waste while permanent flow inserts are prepared. They also allow manufacturers to precisely tailor the ultimate thickness profile of each layer across the width of the die. The inserts can be fine-tuned as the co-extrusion lines run and while the permanent inserts are designed and machined.

A feedblock shapes molten polymers from two or more extruders into layers in a sandwich structure that is distributed to full end-product width inside a flat die. Specially machined flow inserts yield a target cross-direction thickness profile for each layer. Job changes involving significantly different layer ratios or polymer flow properties require appropriately designed and machined inserts.    

"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," explains Sam G. Iuliano, Chief Technologist. "This process eliminates the need to do several recuts of the permanent insert before arriving at the target layer profile."

Typically about 4 in. wide and machined from hardened stainless steel, a flow insert is designed to generate a corrective layer profile for a polymer with specific flow properties. Each of the 10 segments that make up the flow-adjusting component of the tuning insert can be tweaked to reduce or increase layer thickness. Once the target profile has been established, a measurement tool supplied by Nordson Extrusion Dies Industries replicates the screw positions and can be used to produce a precisely matched 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 disassemble the feedblock.

Nordson Extrusion Dies Industries also offers the Ultraflow V adjustable-geometry feedblock, which has built-in adjustable combining planes instead of interchangeable inserts.