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Extrusion Coating Die Innovations Increase Coating Uniformity, Reduce Downtime and Scrap, and Save Raw Material

Published on 2006-09-06. Author : SpecialChem

CHIPPEWA FALLS, WI, U.S.A. -- Advanced extrusion coating dies provide unprecedented control over coat weight and edge bead formation while simplifying changes in product width, it was announced by Extrusion Dies Industries, LLC (EDI), which will highlight these capabilities at CPP Expo 2006 (Booth 9520). These improvements provide processors with enhanced product quality and consistency, reductions in downtime and scrap, and savings in coating materials, according to Sam G. Iuliano, product manager.

Extrusion Coating Die Innovations Increase Coating Uniformity, Reduce Downtime and Scrap, and Save Raw Material
Dual deckle die, with two manifolds for coextrusion coating, is shown with lips pointing downward. Bronze-colored component at bottom center is actually two internal deckles (one for each manifold) in a "V" configuration. Bottom-most component is the wedge-shaped external deckle. At right is hand wheel for moving deckles into and out of the die to vary product width. Just visible behind the die is the wiring for the Autoflex ® gauge profiling system.

The superior performance of the new-generation dies results from the development of innovative die components that EDI now can incorporate in any of its extrusion coating systems, according to Iuliano. The components include:

  • Varying-geometry manifolds. Multiflow ® V manifolds distribute melt to target width more uniformly than conventional "T"-shaped manifolds, reducing the fine-tuning required at the exit lips. A special version of this design, the Multiflow V-G, has a varying-geometry central section and constant-geometry end sections that accommodate full internal deckling.
  • Dual-deckle systems that combine the effective sealing capability of external deckles with the superior flow of internal deckles, which eliminate stagnant areas in the melt stream. The two deckle types once were viewed as mutually exclusive, noted Iuliano, but EDI has combined them in a single quick-adjusting system operated in tandem with the same drive mechanism.

"Processors report that internal deckles used alone require considerable skill and experience to adjust without leakage problems, while external systems are not as streamlined and do not provide edge bead control," Iuliano said. "Although internal-only systems frequently need to be shut down to deal with leakage issues, the dual deckle can run leak-free for several weeks. Downtime typically is reduced by a factor of 4 to 6."

  • Edge profile controls incorporated in EDI's CL-EPC ™ full-bore internal deckles consist of adjustable blades that make it possible to minimize the size of the edge bead, reducing coating and substrate waste. "With LDPE, the width of the overcoat on each side of the product can be reduced from the 15 to 20 mm range to 5 to 7 mm," Iuliano said.
  • Controls to ensure uniformity of coat weight, enabling processors to achieve target properties with the least amount of coating material. EDI has developed two keys to this control:
  1. Longer lip lands than on standard extrusion coating dies. While lip lands range from 3 to 10 mm in length on many extrusion coating dies, EDI has determined that lengths in the range of 10 to 25 mm reduce die swell and increase control over lip tuning.
  2. Improvements to the Autoflex ® automatic gauge profiling system, which carries out lip tuning by means of closely spaced, thermally-actuated translator blocks that are arrayed along the flexible lip of the die and respond to feedback from a downstream gauge scanner. In the improved Autoflex system, these blocks are mounted outside of the die body, eliminating much of the thermal "cross-talk" caused by heat transfer from the body to the blocks. In addition, the blocks are produced from highly thermally conductive beryllium-copper alloy, which increases their speed of response to gauge-scanner signals; and they have a larger stroke, which increases the range of lip adjustment.

"Automatic gauge profile control typically reduces profile variation from the +/- 4 to 5% range with manual controls to a range of +/- 1 to 2%," Iuliano said. "And in some cases operators can now achieve tight-tolerance steady-state control within only ten minutes after making a significant width change, substantially reducing downtime and scrap."

For coextrusion coating, EDI offers processors a choice between multi-manifold dies, which provide the greatest degree of layer-thickness accuracy and uniformity; and die/feedblock systems, which make it easy to change the number, order, and ratios of layers. EDI's Accuflow ™ feedblock is adjustable without removing the feedblock from the production line.

EXTRUSION DIES INDUSTRIES, LLC is a leading international supplier of flat dies for sheet, film, extrusion coating, slot die coating, and pelletizing. The company designs and manufactures dies, feedblocks, deckling systems, vacuum boxes, and related equipment. Its European subsidiary is EDI GmbH in Reichshof-Wehnrath, Germany. In the U.S.A. and Germany, EDI operates facilities dedicated to reworking its own dies and those built by other suppliers, and it has licensed a third rework facility in Japan. Headquartered in Chippewa Falls, Wisconsin, U.S.A., EDI sells half of its dies outside the United States.

Source: Extrusion Dies Industries


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