Mesh tension is a very important factor in stencil performance and thus print results. This is one of those technical aspects of screen printing that many beginners and even experienced screen printers often overlook or misunderstand.
The tension of your mesh will directly affect many aspects of the actual printing. Definition and detail are related to mesh tension. Stencil wear, ink flow and performance, as well as registration can be affected in a negative way with poor mesh tension.
As the screen printing fabric expands with increased tension the mesh geometry changes. Mesh count decreases with higher tension while mesh opening increases with higher mesh tensions. This will directly affect ink flow and performance. It is also important to remember tension should be equal in both warp, (long ways), and weft, (crossways), directions to keep mesh openings uniform in their physical shape; extremely important when printing fine lines, halftones, duo tones, and four-color process work.
A “tension meter” is used to measure the tension of stretched mesh in units of Newtons. This is a measurement of resistance and the meter readings show how much the mesh deflects under a specific weight, usually being the weight of the meter itself.
Higher off contact distances are required which will cause the manual printer to have to push harder to print. This can cause premature fatigue over longer print runs.
Poorly tensioned screens pose coating problems for emulsion. Proper mesh tension during coating will give better results.
Flexing of the stencil on under tensioned screens during printing will also cause premature stencil wear. Cracks and pinholes through which ink may pass can form easily with low mesh tension.
Poor tension in your mesh will give you registration problems in addition to the above mentioned difficulties. This is a good reason alone to use a nicely made screen. With lower tensions stencil drag is exaggerated due to the higher pressures needed to print.
Often the stencil will move excessively in the direction of the stroke. This can cause severe blurring and the increased off contact needed for low tension stencils will also produce significant registration problems.
A tight screen will produce better print quality. Combined with proper off contact, proper tension will also improve the flow characteristics of the ink therebye reducing ink consumption. Good tensions will provide for a smooth working surface for squeegee and flood bar. Tight registration will be easier to achieve with less mesh deflection. Proper mesh tension will assist in the achievement of sharp, clean prints that you and your customers will appreciate.