March '15

For the Business of Apparel Decorating

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20 1 5 M A RC H PRINTWEAR | 87 JOB 1475 Date: Sept. 3, 2011 Client: Alexander Seitz Employee: Dominik Janssen Comments: (Table courtesy Sefar U.S.) Micrographs of screen meshes to compare the mesh size: - PET 1500 32-70W - PET 1500 48-55W - PET 1500 32-100W - PET 1500 48-70W - PET 1500 32-120W - PET 1500 48-80W the same platen, and all platens are parallel when the image is identical on each. If you only calibrate your press by the decade, stop and calibrate it. High-quality mesh that's tensioned properly on a calibrated press with an adaptive blade is likely to double the life of the screen mesh. Of course, the real cost is not the mesh or the retensioning but the downtime and cleanup on press. An adaptive blade has an edge that fits the mesh, a profile based upon the ink tack, and runs at maximum speed to allow for minimum pressure to make the mesh last longer. With screen mesh, it's difficult to feel or see the differences or changes in screen fabric. We take this gauze we cannot see and slap on some emulsion. Again, we've taken mesh and stencil and created a print screen, albeit not much of one. Figure 2 is a depiction of 330/23 screen mesh prior to the finishing process. It's 46µ thick with an irregular surface. Per cell of mesh, its cross section is an hourglass shape. After coating the garment side of the screen adequately, the hourglass turns into a funnel, and once both sides are adequately coated, the funnel transforms into a tunnel. Some recommend good mesh geometry, but the prescribed count is too high and fails because the stencil is too thick and the ink isn't that smart. The ideal stencil for the mesh above is approximately 46 microns with ap- proximately 3 microns below the bottom of the mesh and approximately 3 microns below the blade side of the mesh. This gives us an RzS1 and RzS2 for garment side and blade-side flatness of approximately 4.5µ. The coated mesh causes the stencil professional to admit defeat because there's no time to coat it properly with face and back coats. Let's round the numbers and say the screen coater gets $30 per hour. Your press is surely worth $300 per hour. Which do you think should take a few extra minutes? CHOOSE WISELY If we allow the mesh tenders of the world to select our mesh, they might put us out of business, particularly the ones flaunting their lower price. Making cheap mesh is easy, but maximizing quality and output seems im- possible. We want higher modulus yarns, the minimum count, maximum opening, and minimum thickness with a lower ratio of thickness over di- ameter and the same width and orientation every time. It should be angled on the screen if it's a finer mesh with a color that reduces halation and a tolerance on the counts, stress, and strain in both directions. Then, if the ink doesn't whistle through a high-volume mesh with an adaptive blade, you need to change ink. The right mesh goes a long way. 20 1 5 M A RC H PRINTWEAR | 87 pw It's shocking how many well-promoted anti-scientific stories exist about mesh. Below is a partial list of some of the more popular ones. • There is no lpi-to-tpi multiplier, but if there ever were, it would require tensioning on mesh. • Mesh doesn't precisely determine image reso- lution or edge acuity. • Mesh doesn't determine ink volume but is an indicator of maximum wet-film thickness. • Optimal elongation changes with the width and not all widths work the same way. • Not all colors of mesh are created equal when seeking resolution or edge acuity. • Thick yarns are not necessarily stronger than thin yarns. • Durability is a combination of yarn modulus, fabric mass, and thickness over diameter ver- sus usage. • There is no absolute "count." Warp is close, weft varies, and meter tensioned is inconsis- tently lower. • Ideal mesh is balanced for counts to stress strain. Typically, weft count should be higher. • Independent elongation of warp and weft is crucial. Tension is merely a compromised result. • The weft rarely needs stretching as far as the warp direction. • Tension meters don't differentiate between requisite or resultant elongation. • If you need more than 27N/cm 2 , you have the wrong blade, mesh, ink, or all of the above. • Mesh aligned squarely on the frame is possibly the worst angle. • Mesh pops are primarily because of squeegee blades on inconsistent presses. • Delta is key to printing tension. For example, a 110/80 should be lower than a 305/40 if the gap is the same. • Consistent tension corner to corner just doesn't make sense. • Cheap mesh may be the greatest fallacy of all. FALLACIES EXPOSED

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