Screen printing

Screen printing, formerly also called "serigraphy", is a printing process which uses a wiper-like tool called a squeegee to force the printing ink through a finely-woven fabric (mesh) onto the material to be printed (see picture below). At those places of the fabric where according to the picture motive no color should be printed the mesh openings of the fabric have been made color-impervious by a stencil.

In the silk screen procedure it is possible to print many different materials, flattens (folios, plates etc) as well as formed (bottles, device cases etc). In addition special printing inks are used according to material. Principally paper reports, plastics, textiles, ceramics, metal, wood and glass are printed. The print format can amount to several meters in the extreme case. One advantage of screen printing is the variety of the color application by various mesh finenesses so that one can obtain high coating thicknesses. The printing form of the silk screen exists of a frame which is covered with a fabric. On the fabric a stencil is raised photographically (at artistic works sometimes also by hand). The stencil prevents ink to be applied to areas, where no ink is supposed to be on the print image. In a printing machine, the printing plate is placed atop the material to be printed. Then, the printing ink is applied onto the fabric and painted onto the print substrate through the open areas of the stencil using a rubber squeegee. During this process, the ink is printed through the meshes of the fabric and applied onto the surface of the print substrate.

Exposure

Exposure

A strong light with a high UV amount is used. The exposure time depends on the fabric fineness, the used screen emulsion and the thickness of the coating. As a copy template a transparent film is required on which the image is illustrated in a very good coverage (opaque blackening). The image must be right-reading (not mirror-inverted) and positive. The films can be produced by us according to the customer's templates in a reprographic process. Before exposing the film is laid on the printing side of the covered screen. The film layer must be in contact with the emulsion side of the screen, so that no under-exposure of fine details happens. Now, the screen is laid into a special copying machine (exposure unit) which presses by vacuum the screen with the film firmly onto a pane of glass. Through the pane of glass the screen is illuminated. Due to the illumination the emulsion becomes water-proof; those places of the emulsion which are protected from the light by the covering film remain, however, water soluble.

Washing out of the copy emulsion

Washing out the emulsions

After exposing the screen is moistened on both sides with a hand shower and lukewarm water and the image is washed out. Here, all places of the emulsion that haven't been illuminated are washed out. The washing-out can occur also with a pressure equipment, but not with a too powerful water jet. The water drains off and afterwards the screen is dried.

The printing process

The printing process

The printable screen is installed in the printing machine. This can be a manual imprinter, a semiautomatic, three-quarter-automatic or all-automatic silk screen printing machine. The printed sheets must always be at the exactly same position under the screen, so that when working with various colors the colors lay accurately to one-another. Therefore serve the locators installed into the printing plate or positioning marks made of self adhesive foil sticked onto the printing plate.

The printing process

Now, the printed sheet is put against the marks and after this the color is transmitted through the open screen holes onto the sheet by the squeegee. During the printing process the printed sheets are fixed by vacuum to the printing table so that they neither move nor stick to the screen.

Foil keyboards consist of a foil, which is printed on the back side with the graphic image of the keyboard by screen printing. Behind this graphically designed user interface are, seperated by spacer layers, conducting paths and electrical contact points, which are screen printed, too (see our pictures).   

Screen printing process
Screen printing process
In the screen printing procedure an enclosure is printed manually. The color is spread on the screen with a squeegee and pressed through the mesh web.
In the screen printing procedure an enclosure is printed manually. The color is spread on the screen with a squeegee and pressed through the mesh web.
Screen printing procedure
Screen printing process
Screen printing process

The two pictures show the enclosure before and after printing.

 


We also printing glass

Customized colors and forms

With a high-quality screen printing process, multicolored designs as well as small and large numbers are possible. To avoid any problems with abrasion and nice depth effect, we usually print on the back of the glass pane readable on the front.

More you can finde here ->

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