9-layer extrusion die reduces thickness variations down to +/- 5%

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  • Yielding multi-layer film with two-thirds less layer thickness variation
  • Individual layer thickness variation reduced down to +/- 5%
  • Material savings, enhanced product quality

A Nordson EDI nine-manifold flat die, the first of its kind, has been successfully commissioned, producing nine-layer film from various resins. This advance in co-extrusion technology enables film processors, particularly those with high-throughput lines dedicated to a narrow range of products, to achieve tighter thickness tolerances for the individual layers in a multi-layer structure.

Individual layer thickness variation reduced down to +/- 5%

While the degree of improvement will vary with the application, in general Nordson EDI’s nine-manifold die technology promises to reduce variation in individual layer thickness from the +/- 15% tolerance often encountered with comparably advanced feedblock systems to +/- 5%, according to the company

“This greater accuracy achievable with multi-manifold dies enables processors to run thinner layers of the costly specialty materials often required for high-performance packaging films, while at the same time enhancing product quality and consistency,” said Sam G. Iuliano, chief technologist for Nordson EDI.

Nordson 9-layer sheet die - back view

Rear view of 9-manifold Nordson EDI die, with entry ports for the polymer streams shown in different colors. Visible at left is one of two outboard fastening structures designed to prevent leakage at either end of the die. At top center is a view of the upper portion of an Autoflex automatic lip adjusting unit (source: EDI Nordson)

Multi-manifold method provides greater layer uniformity and thickness accuracy

A manifold is a flow distribution channel inside the die whose complex internal geometry, engineered for a specific polymer, is designed to develop a uniform, streamlined flow and distribute the material to its full width. In a multi-manifold die, each polymer flow stream has its own manifold, and the layers are combined into a single structure only after each layer has been individually spread to its full width. By comparison, a feedblock combines multiple polymer streams into a narrow multi-layer “sandwich” that is subsequently distributed to full width in a single-manifold die. A main reason why the multi-manifold method provides greater layer uniformity and thickness accuracy is that it avoids much of the layer-interface deformation that occurs when multiple layers pre-assembled in a feedblock are then spread simultaneously through the die.

Nordson 9-layer sheet die

Cutaway view of 9-manifold Nordson EDI die, with polymer streams represented in different colors. The streams combine to form a single multi-layer structure which exits the die at left. Visible at upper left is an Autoflex automatic lip adjusting unit (source: EDI Nordson)

Distribution blocks in variety of optional configurations

For the delivery of molten polymer from extruders to a multi-manifold die, distribution blocks, situated just upstream of the die, are available in a variety of optional configurations. The simplest versions have a fixed design, delivering the polymer melts to the entrances of the multi-manifold die in only one, dedicated layer sequence arrangement. More sophisticated distribution blocks provide the ability to re-route melt streams to change the sequence of the layers via exchangeable selector plates. The most advanced distribution blocks, in addition to selector plates, include feedblock sub-assemblies which combine some of the melt streams prior to the die, allowing for product versatility and for a greater number of layers than the number of manifolds that are in the die.

Nordson EDI's Ultracart

Nordson EDI’s Ultracart rapid cleaning station can be designed to accommodate 9-manifold dies. Disassembled die shown here is a 3-manifold unit (source: EDI Nordson)

Options for simpler cleaning and preventative maintenance of the die

Many Nordson EDI four- and five-manifold dies are in operation worldwide without leakage issues, even at throughput rates approaching 5,000 kg/h. For the new nine-manifold die, the company designed additional fasteners outboard of the main die bodies (in the end plate assembly area) to ensure proper sealing. Nordson EDI’s Ultracart rapid cleaning station is also available to accommodate 9-manifold dies. In addition, the Autoflex automatic lip adjusting units on the die are modular and can be readily detached, allowing convenient access to the die body fasteners. These systems make disassembly and reassembly simpler for periodic cleaning and preventative maintenance of the die.

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