EXTRUSION: Fluid-Coating Die Boosts Accuracy, Adjustability

Multi-layer slot dies made more accessible by eliminating calculation in use of shims to achieve lip-face alignment.

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A new, patent-pending design for dual- or multi-layer versions of Premier and Ultracoat fluid coating dies from Nordson Corp, Chippewa Falls, Wis., reportedly makes it easier to achieve parallel alignment of the lip faces, which is critical for maintaining uniform, defect-free coating and preventing impingement of the lips against the roll.

In the standard design for Premier fixed-lip and Ultracoat adjustable-lip slot dies, operators make changes to the die gap—and thus the wet film thickness of the coating—by inserting thin metal strips, or shims, between the die bodies, then using more shims at the rear of the die to eliminate the resulting offset of the lip faces and ensure that they are once again in the same plane. Until now, use of these “offset shims” has been more complicated in multi-layer dies, requiring calculations to determine which shim thickness most closely achieves lip face parallelism. The new design makes such calculation unnecessary, ensures a more precise lip face alignment, and prevents human error.

Nordson has achieved this improvement by reconfiguring the die bodies of multi-layer Premier and Ultracoat systems so that the offset blocks, where the offset shims are inserted, are now in the same plane as the lip face. As in the past, body shims and offset shims are available in thicknesses ranging up to 0.060 in. With the new design, the accuracy of the offset adjustment is independent of body shim thickness.

Replacing multiple coating passes with a single product run means an increase in output and a reduction in machine use, energy consumption, and scrap. Additional cost savings result from control over the thickness of each layer, preventing over-use of expensive high-functionality fluids. At the same time, the converter has the flexibility of returning to single-layer production simply by closing the feed valve to the flow channel that is not in use.