Decisions you make during the screenmaking stage can have a major impact on the success of the printing process. Learn about the choices you face in frame selection and in securing your mesh to the frame.
By Eric Klein
The act of stretching screens on a drawbar frame usually consists of either turning a series of bolts along the side of the frame or using a special tool on the corners to draw the bar back mechanically. In the first scenario, depending on how much you turn each individual bolt along the frame, you can influence the fabric in that general area to compensate for any inconsistencies in the way the mesh was loaded. In the second situation, the construction of the frame may cause issues because as you tension the mesh, the dimensions of the frame will increase. This is not a problem in some applications, but it’s something to keep in mind if you’re considering this frame type.
Roller frames are clearly the most popular of the retensionable frames. Once again, some skill is required to use these frames, but once they are mastered, roller frames provide a quick and easy method of making a screen. The principle behind the roller frame is that the fabric is locked in the frame with either a plastic strip or two round plastic rods. Then the rollers are turned away from each other to increase the tension. Just like the drawbar frame, the fabric can be retensioned to a degree to compensate for tension lost during printing. Also, pneumatic tensioning systems are offered for roller frames to simplify tensioning even more.
With all retensionable frames, you have to take care when reclaiming and handling due to the fact that there are many pockets in which cleaning chemicals can collect, only to drip out at the worst possible time. The other common issue with these frames is that oily reclaimers and ink washes tend to get trapped in the locking channels and can sometimes lead to the fabric slipping out of the channels. Liquids also can leak into the hollow tubes. This problem is quite common when using a dip tank in the screen-cleaning area. Everything works fine until the frame is placed under vacuum in the exposure unit, which causes chemicals trapped inside the tubes to be pulled out and across the screen, ruining the emulsion.
Strive for superior screenmaking
Whether you use static or retensionable frames, it’s imperative that you strive for consistency and repeatability in your screenmaking procedures. Begin by making sure your frames are structurally sound, clean, and free from defects that could lead to lead to damaged mesh. Take care in stretching the screen fabric and measure the tension level to ensure that it’s high and consistent from screen to screen. If you are attaching the mesh with an adhesive, make certain the glue is compatible with the inks and cleaning chemicals you employ. And on retensionable frames, focus on loading and locking the mesh in place as evenly as possible to ensure that the tension will be consistent across the entire screen surface. By following these steps, you’ll be rewarded with long-lasting screens that deliver top-notch prints.
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