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| Posted on 3/17/08 at 08:38 AM | |
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The 230 mesh is quite close to a 4.5 x line count number. 4.5 times film line count gives the ballpark mesh count, also 4 can be used as the multiplier. Unless you are printing tight sim process on black I would increase mesh count and lower thread diameter. bump up to a 260 or 280 or even a 300 with similar percentage of open area would get away from the moire issue that develops when mesh and line count near the 4.5 multiple. I also like elliptical dot vs. round inorder to span the mesh knuckles to allow some of the dot to print. Spot moire is also a product of the quality of mesh. Is the moire over the entire image or just in some areas of the image, particularly tonal percentages below 50%? The squareness of the mesh opening as it is tensioned is crucial. If warp and weft thread are not elongating similarly you will wind up with a rectangular opening which can lead to spot moire. Balanced warp and weft thread combined with low elongation thread yield a better "squareness" to the edge of the frame, and also affects critical registration of dot to dot during the print cycle. I'm curious as to why you chose a 50 line halftone ruling? 45 in this case might show less moire. My favorite line count and angles: 45 @ 7.5 on 200S mesh. 55 @ 7.5, 22.5, 60 on 280 mesh 55 @ 7 on 200S 65 a 22.5, 60 on 305T or S. All elliptical dots, round works well for 4/c proces, square for sim process to achieve some sharpening. Another trick I learned from a great separator, Ron Webb, is to add Pi to the decimal part of the line count. 50.1754 for the halftone ruling at 7, 7.5, 22.5, 60. In using screens off the shelf a mesh reader will tell you mesh but it won't tell you if it at an angle. Shurlock does a good job of capturing the mesh and softening the corners so I don't think it is their technique but possibly unbalanced warp and weft thread causing rectangular openings than square. In setting up a tight 4/c or sim process it may pay to send shurlock a bolt of high quality mesh and have panels made. Superior print quality begins with superior mesh. ____________________ Alan Buffington | ||
  
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