Then at the other end of the machine, the material rewind. Multiple converting functions can take place within an integrated system. For example, integrate a coater with a drying station at the beginning of the point of the process, and then additional converting stations for die cutting, laser cutting, lamination and/or pouching at the end. In this video, Scott Zwierlein of Frontier (a Delta ModTech company) provides us with an overview.īefore we get to the comparison chart, let’s establish some coating definitions. Delivery methodsĪs Scott mentioned in the video, there are essentially two methods of delivering web coating, and within those delivery methods are the coating methods themselves. Mechanical metering requires a flooded surface and a mechanical device to wipe away excess and set the thickness of coating. The following coating methods are used with mechanical metering: Reverse Roll Reverse roll coating is considered a roll to roll coating methodology for wet coatings. Its unique feature is the two reverse running nips: An application roller runs in one direction, the support roller in the other.Ĭoating is applied in excess to the surface of the application roller, and the coating is then regulated at the metering nip. With comma roll coating, the coating solution is either dispensed directly to the substrate and metered via the comma roll or the coating solution is metered by the comma roll onto an applicator roll then applied to the substrate.Ĭoating fluid is dispensed to the substrate, which then passes through a knife and roller. The knife meters the coating to the required specs.Ī roller applies the coating fluid to the substrate, and then a Meyer bar meters out the correct amount. Volumetric metering allows for the delivery of an exact volume of material to the substrate, which gives you the ability to control the thickness. With slot die coating, the coating fluid is precisely delivered to the slot die head, then applied directly to the substrate. With gravure, the coating fluid is delivered onto a roller with patterns engraved into the face of the roll. Excess material is removed with a doctor blade. Comparison chart: Choosing what’s right for you The volume of fluid in the engraved patterns is transferred to the substrate ensuring the precise amount of coating is applied.Ĭheck out our post for more on slot die coating. Now let’s compare the different methodologies. In the chart below, there are several key terms you’ll need to understand. We’ve already touched on the delivery method above. This is a measure of the thickness of the material. Fluid viscosity is measured in centipoises (cps). The more viscous the material, the less runny it will be. ![]() For example, the viscosity of water is 1 cps, while motor oil is 200 to 500 cps. ![]() The amount of shearing force that’s put onto the fluid when its being coated. If you take a plate with wet glue on it sandwich it with another plate then slide one plate but keep the other steady - that’s shearing. Shear level is based on speed and on distance between the plates. If they’re moving slow but are closing together, it’s considered high shear. If they’re moving fast but are far apart, it’s also a high shear. Shear can be damaging to materials if you’re moving plates too fast for the thickness coating.
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