Screen printing is by far the most common technology today. Two types exist: rotary screen printing and flat (bed) screen printing. A blade (squeegee) squeezes the printing paste through openings in the screen onto the fabric.
Flatbed screen printing can be considered an automated version of the older hand-operated silkscreen printing process used on t-shirts, sweatshirts, and other printed items. For each color in the print design, a separate screen must be constructed or engraved. If the design has four colors, then four separate screens must be engraved. The modern flatbed screen printing machine consists of an infeed device, a glue trough, a rotating continuous flat rubber blanket, flat bed print table harness to lift and lower the flat screens, and a squeegee.
The infeed device allows for precise straight feeding of the fabric onto the rubber blanket, as the cloth is fed to the machine it is lightly glued to the blanket to prevent any shifting of the fabric or distortion during the printing process. The blanket carries the fabric under the screens which are in the raised position. Once under the screens, the fabric stops. The screens are lowered and then the automatic squeegee moves across each screen pushing print paste through the design or open areas through the screens. The screens are raised, the blanket precisely moves the fabric to the next color and the process is repeated. Once each color has been applied the fabric is removed from the blanket. The fabric moves through the required fixation process. The rubber blanket is continuously washed, dried, and rotated back to the fabric infeed area.
The flatbed screen process is a semi-continuous, start-stop operation. From a productivity standpoint, the process is slow with production speeds in the range of 15-25 yards per minute. Flatbed screen printing also has design limits. The design repeat size is limited to the width and length dimensions of the flat screen, no continuous patterns such as linear stripes are possible with this method. However, flatbed printing offers a number of advantages. Very wide machines can be constructed to accommodate fabrics such as sheets, blankets flags, carpets, or upholstery. Flatbed printing also allows multiple passes or strokes of the squeegee so that large amounts of print paste can be applied to penetrate pile fabrics such as blankets or towels.
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