Five-Layer Feedblock Designed For Flat-Die Extrusion And Web Converting

December, 2001

Extrusion:

Five-Layer Feedblock Designed For Flat-Die Extrusion And Web Converting

Extrusion Dies introduced a five-layer co-extrusion feedblock that uses the company's Accuflow technology (May '00 PA, p 39). In multi-layer, flat-die extrusion and web converting, a feedblock shapes each stream of polymer into a layer, then combines all layers into a single 'sandwich' structure to be distributed by the die manifold into film, sheet or coating.

With conventional feedblocks, operators must exchange one set of flow inserts for another to make adjustments for required changes in product dimensions; this prolongs startups or makes it necessary to stop production. By making use of a single set of readily adjustable combining spools, instead of multiple sets of flow inserts, Accuflow feedblocks are said to accelerate startups, speed up repeat runs and eliminate downtime.

The new combining spools are streamlined, split-body devices that reduce potential for polymer degradation and permit finer layer adjustment. EDI says it can also equip Accuflow feedblocks with mini-heaters that refine the dimensions of the combined structure by controlling viscosity at points along the width of the feedblock channel.

The new five-layer feedblock has upper and lower bodies which, when joined, form the flow channel for the multi-layer structure. Building a five-layer ABCBA structure occurs as follows: 1) two 'Y'-shaped adapters (shown as four halves in the photo) split the melt streams from the A and B extruders into two; 2) each of the resulting four streams enters one of four cylindrical combining spools and 3) the spools add the B sub-skin layers to the C core layer, then add the A skin layers.

To make changes in layer thickness, the operator adjusts a screw on any of four pivoting devices and makes corresponding modifications to the extruder output rate. The pivoting devices have numbered scales that simplify returning to previously run products.

Extrusion Dies, Inc.
Chippewa Falls, WI Circle 110