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Mesh Matters

(June 2009) posted on Wed Jun 03, 2009

The level of detail you can print, the quantity of ink you lay down during the print stroke, and the ability to reproduce an image accurately and consistently are but a few of the print characteristics that are influenced by your screen. Here you

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The measurement of the woven mesh’s cross section is fabric thickness. It is used to help calculate the theoretical ink volume that each open cell of the fabric will hold, the wet ink-deposit thickness that a mesh can be expected to deliver (Figure 4), and the total volume of ink required for a particular job. Though it might seem logical to assume that the fabric thickness is the sum of the two thread diameters, this is not the case. Weaving and finishing operations affect the total fabric thickness measurement, which is always smaller than the sum of two thread diameters. For example, a 305-thread/in. fabric with 40-micron thread diameter might have a total thickness of 63 microns.


Tensile strength and yield point

A screen fabric’s tensile strength is its ability to be stretched without breaking. Tensile strength usually is measured as the amount of force (N/cm) required to cause thread breakage. Low-elongation mesh fabrics possess higher tensile strength that conventional fabrics.

The yield point is the point at which the polyester becomes deformed and can no longer regain its former tension level. It occurs well before the fabric’s breaking point. Regardless of the amount of tension applied to the fabric, it will not hold tension any longer after its yield point has been reached. The objective of tensioning is to reach the optimum tension level that is below the yield point. Mesh manufacturers will provide you with information about the yield points of their fabrics as well as guidelines for optimizing tension levels.


Fabric behavior under tension

The minute you apply tension to screen fabric, it goes from a static to a dynamic state. As tension increases, the mesh parameters and physical characteristics of the polyester begin to change. Understanding mesh behavior under tension not only will help you to select the right mesh, but it will also influence how you use it.

Once tension is placed on the screen fabric, parameters begin to change. Some change in proportion to the amount of tension, and others are only minimally affected. It is impractical to predict the specific changes that happen in every situation at every tension level, but in general, the following things occur when mesh is tensioned:

• The size of the mesh opening increases.

• The mesh count (threads/in.) decreases.

• The fabric thickness decreases.


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