Use the following tips to control the variables most commonly encountered in garment screen printing.
Screen printing is next to impossible to control without proper and consistent screen tension. To deal with tension at all, you need to use a calibrated tensionmeter as part of a daily routine of managing tension on screens. Tension should be measured on every screen every time you stretch, retension, or pick out a screen to enter into the production cycle.
Higher tension levels produce better print results, improve registration, and increase production speeds. Appropriate tension levels for a particular mesh count and thread diameter vary based on the fabric strength, frame type, and—in some cases—stretching device. Most meshes used for garment printing can be tensioned easily to 25 N/cm and higher. Tension should not be considered a goal unto itself. Choose tensions that that can be consistently achieved and maintained given your shop’s conditions.
High-tension screens have less resistance to knocks and pokes and will break more easily, and therefore need to be handled with more care. Off-contact distances must be reduced when higher screen tensions are introduced to the press. Failure to lower off-contact accordingly can result in the mesh breaking on press. When raising tension levels, it is a good idea to increase operating tension gradually, and establish timely communication with the pressroom so appropriate adjustments are made.
Screen-tension uniformity refers to consistent tension within one screen. Maintaining tension uniformity is important for preventing image distortion and registration problems. Uneven warp and weft tension can create inconsistent registration, unpredictable ink deposit, and destructive moiré. For best results, variations should be within ±1.0 N/cm.
Tension measurements should be taken in at least five places on the screen. This is known as a five-point measurement method. To establish your measurement locations, divide the screen into four equal quadrants, each with a corner joining at the center (Figure 1). Measurements are taken in the center of the four quadrants and in the center of the screen. Warp and weft measurements should be taken in all five points.
For multicolor prints, selecting screens with similar tensions will help ensure consistent printing results. This issue is especially important when printing four-color-process work or on any job where the quality requirements are high. Tension differences screen to screen can result in inaccurate registration, as well as different printing effects on the image. As a rule of thumb, variations of no more than 1.5 N/cm screen to screen will help ensure registration and print quality on multicolor work.
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