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Determining and Maintaining Optimum Screen-Inventory Levels

(November 2006) posted on Mon Dec 18, 2006

Learn how to use mesh and frame management to streamline changeovers and ensure that screens are always ready when needed.

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By Mark A. Coudray

A much better way to select the desired mesh is to consider the percentage of open area at each mesh-count range. For instance, you can select an open area of 36% ±2% for any given mesh count between 160-355 threads/in. By selecting the mesh count that is closest to the same open area, you establish a common open area for fine, medium, and coarse meshes (355, 305, and 230 threads/in., for instance). You've now established the range of meshes that will all pass ink at the same rate, regardless of how many threads per inch.

Frame size

Press requirements and preregistration systems determine frame size. Most presses support multiple frame sizes, but is it wise to go this route? The most common approach is to have multiple frame sizes in inventory in order to conserve mesh—in other words, use the smallest frame suitable for any designated job. But there are flaws in this way of thinking, because rarely does it conserve mesh. Actual yields will vary substantially, and you'll ultimately waste more mesh as selvage unless you choose the frame size that accommodates the width of mesh on the bolt. You'll need to piece together the length and width combinations in order to maximize the yield from the bolt.

Another consideration is the orientation of the mesh (warp vs. weft) on each frame. I am a big believer in consistency. Orienting the warp and weft in the same direction on the frame minimizes registration variations and makes tension more consistent over the life of the screen.

The labor component also plays a part. You can stretch mesh and prepare a small frame in roughly the same amount of time as you could a large frame; therefore, the economy is gone. If you use a static stretch-and-glue system, you'll spend a small amount of additional time and material to glue the larger frame. I'm not sure it's significant enough to worry about.

The goal with a standardized frame size is to reduce the amount of adjustment you have to make between sizes. Keeping the frame the same size dramatically minimizes the time needed to make frame-holder adjustments on press. The savings can be substantial, especially when the press isn't marked in some way to accommodate the various sizes or when you're using a multi-station press.


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