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Eliminating Variables in the Screenroom

(June 2013) posted on Wed Jun 19, 2013

Standardization is a key part of preventing costly quality-control issues on press.

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By Rick Davis

Facilities using the DTS process and keeping a film-processing system in house as a backup can use a dual-purpose exposure system that allows for the use of a glass/vacuum system when the film process is required and can double as a DTS exposure unit where the screen stencil is exposed directly to the exposure source without the need of the glass or vacuum.

Should you have a standalone exposure system, one of the easiest ways to expose screens imaged with a DTS imaging system is to simply lean your screen (within an enclosed area) against a wall and directly expose the screens without an enclosed exposure unit. It is important that you test for proper exposure and ensure that you do not allow light to expose the screen from the ink side.

Screen washout
The screen-washout process is one that I feel is taken far too lightly in most facilities. It is, of course, taken seriously when the screen reaches the press, is set up, and inked only to learn that a screen has to be remade. This is a complete loss of productivity and profit.

In the screen-washout process, there are two critical aspects that ensure that you are going to produce a quality screen. First and foremost is the use of a good, backlit sink (Figure 4). It does you no good to wash out a screen stencil when you cannot properly observe the stencil being washed away.

The second aspect is the use of a water source with the proper pressure needed to process the screen. This requires a hose assembly along with an adjustable nozzle to allow you to alter the concentration of the spray to process your stencil. I have seen facilities that use a small pressure washer, a piece of equipment that typically produces negative results as the pressure of the water is not determined by how close the nozzle is to the screen.

The screen-washout area is the one part of the screenmaking process that does not have to be in the screenmaking area itself, although it is a good idea to keep the washout area as close to the screen-exposure area as possible for expediency and productivity.

Once this final process is complete and the screen is dried, the screen should be ready for any touchup of potential pinholes and prepped for the press with tape and any additional prepress procedures you may have.

Screen reclaiming
Two things to remember: The location of the reclaiming sink to the entrance to the darkroom is designed to minimize handling and moving of the screens from one area to another. The second aspect is that a sink being used in the process should also be backlit to allow for easy inspection of the mesh while the screen is being reclaimed/degreased.

I also recommend the use of a minimum of 2500 psi for washout. A unit of that size allows for maximum productivity with relative ease of removal of the stencil from the screen. The high pressure also helps maximize the removal of the ghost image that resides in the knuckles of the mesh. Lower pressures are not as efficient at removing these images. In such cases, haze removers are required. Low-tension screens will also contribute to issues here.

It is critical to ensure that the screens going into the screen department for coating are completely free of debris and any type of mesh obstructions. This simply helps guarantee a quality screen for the next applied graphic.

The primary key to ensuring a quality screen is to establish and use standardized procedures, quality equipment and supplies, and a properly planned workflow to allow for maximum efficiency in your screenmaking routine.

Rick Davis has more than 30 years of experience in the textile-manufacturing and screen-printing industries. He currently serves as the southeastern regional sales manager for Triangle Ink Co. Davis has published more than 200 pieces on all aspects of the industry and printing processes, and he’s a member of the Academy of Screen Printing Technology.


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