The role of thread diameter on a variety of printing characteristics
By Art Dobie
Figure 5 displays two stainless-steel wire screens, both coated and imaged identically with the exact same stencil system, artwork, equipment and procedures. The 18-micron wire mesh shown in Figure 5 has 42% open area, while the 16-micron wire mesh has 60% open area. The weave profile of the smaller diameter/higher open area mesh is lower, while the larger diameter/lower open area mesh has a higher weave profile. This higher weave profile of the larger diameter wire size resulted in irregularities along the edge of the screen image due to reflection of UV light off the taller wire profile during screen exposure. This phenomenon is much less apparent with smaller wire diameter, higher open area wire cloth.
Filament diameter vs. mesh tension
We know when mesh thread diameter becomes smaller while maintaining similar mesh count, the open area of that same mesh increases. Higher open area percentage advises that there is lower mesh content within the mesh area. When the amount of mesh content within a fixed area is reduced, the tension capability of that mesh type is also reduced when all else remains equal.
Historically, lower tension capability was one of the main drawbacks to smaller diameter/higher open area mesh types. Screen tension is vital in achieving proper ink transfer in the screen-printing process. Ink transfer in screen printing is different from most other printing processes. Offset, gravure, and letterpress printing all carry the ink on the outer surface of what comprises the printing plate compo-nent of those respective imaging methods. These printing methods involve intimate contact between the printing plate and the substrate. The ink transfer doesn’t actually occur until the moment the printing plate and the substrate separate from each other. Inkjet printing does not use direct contact with the substrate, instead incorporating a print head to propel ink droplets onto the substrate surface.
The screen is the printing plate of the screen-printing process. The ink is applied to the surface of the screen furthest from the substrate and must then pass through patterned openings in the printing plate in order to make contact in those areas with the substrate.
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