10 percent EMR is more common as it provides the stencil just enough relief from the mesh on the substrate side, but still reduces total screen thickness (mesh plus emulsion) so that very fine detail can release from it without bleeding. A measurement of 20 percent EMR (emulsion over mesh ratio) provides enough emulsion build-up on the print side to effectively lift the threads off the surface of the substrate at the shoulder of the print reducing any loss of printed image by allowing the ink to fill the entire image area.Īpplications involving fine detail, multi-color or ultraviolet printing require thinner overall stencil thickness. Stencil thickness should also be periodically inspected with a PosiTector 6000 FS gage, particularly for shops that manually coat their screens.įor general printing of non-ultraviolet ink applications and jobs that do not require extreme detail, an emulsion build up of approximately 20 percent of the mesh thickness usually provides excellent print resolution and edge definition. For process control it is necessary to control mesh and emulsion thickness across the surface of the stencil. The ability to measure the thickness of the mesh and stencil enables the user to predict and control critical elements of the screen printing process. The PosiTector FS has a variable accuracy of 1% and up to a 0.05 mil (1 micron) resolution. The measurement range of the FS is up to 60 mils (1.5 mm). With statistics enabled, the gage automatically calculates a running average of the readings taken. Due to variations in screen mesh thickness, repeatability can be improved using the statistics mode available in selected models. After zeroing the PosiTector 6000 FS probe on the included ferrous base plate, the gage is ready to provide an accurate thickness measurement of any substrate or screen mesh placed flat against the base plate.Īccurate mesh thickness measurements are important as they are a critical factor in formulas used to predict a mesh's wet ink deposit. Since during the tensioning process, the thickness of the mesh changes as compared to the thickness identified by the manufacturer, it is important to determine the mesh thickness on a stretched screen at printing tension. The wide surface of the probe bridges the mesh openings enabling the probe to consistently measure from knuckle to knuckle of the mesh and stencil. The PosiTector 6000 FS (Screen Printing) gage was specifically designed for thickness measurements on fabric and stencils.
The process is repeated as often as required for multi-colored items.
Each item is then heat cured to permanently set the ink. When printing multiple items the squeegee floods the screen again with a return stroke. Ink is placed on the top side of the screen and a rubber squeegee blade is pulled across the top of the screen, pushing the ink through the stencil onto the substrate. The screen is fit to a press and a substrate to be printed is placed under the screen. A jet of water is used to wash from the screen any of the emulsion that has not been hardened by the ultra-violet light, creating a stencil corresponding to the image on the film. The positive film transparency and coated mesh are placed together and then exposed to ultra-violet light.
The image to be printed is output onto a film transparency. The mesh is coated with a light-sensitive emulsion or film that, when dry, blocks the holes in the mesh. The process begins with a fine nylon mesh stretched over a wooden or aluminum frame. Applications include store displays, posters, advertising boards, electronic equipment marking, textiles, clothing and bumper stickers. Today, screen printing is used everywhere. While quality improvements have been made in the equipment and materials used for silk screen printing, little has changed in the actual process. At this time silk screening popularity increased and an industrial printing process for flags, banners and advertising signs in stores began. In 1914 the process was expanded for multicolor printing with a screen process. It involved silk stretched on frames to support hand painted stencils. The modern silk screen printing process was patented in 1907.
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