PRINCIPLES OF SCREEN PRINTING

The process is known as screen printing. Silk screen printing is a name first used when the mesh or screen was made of natural silk. Nowadays screen mesh is either made from polyester, stainless steel or nylon.

The basic items of equipment required to carry out screen printing are:

STENCIL: This consists of a frame onto which a mesh is attached under tension. The mesh is coated or covered with a photosensitive material. The image to be printed is created photographically on the stencil leaving open areas of mesh through which ink passes. The stencil is also known as “The screen”.

SQUEEGEE: A flexible polyurethane blade (sometimes rubber) held in a rigid mount or handle.

INK: Can take the form of a wide range of solids or dyes suspended in a fluid.

SUBSTRATE: This is a general term for the surface that is to be printed. The surfaces can range from bread to bio-medical sensors.

MACHINE BASE: The base provides a surface for the substrate to be printed and the upper section secures the screen.

FUNCTION OF THE SQUEEGEE

In conventional screen-printing the squeegee carries out two functions. It deflects the stencil and brings it into contact with the substrate. The squeegee is held at an angle of typically 75 degrees to the horizontal.

During the printing action the squeegee is moved across the stencil, creating a pressure wave in the ink. The actual point of flow is where the leading edge of the squeegee is in contact with the stencil. This is known as the “Flow Point.”

PRESS TYPES

Press types can be split as follows:

• Flat bed press. (Further split into hand bench, semi automatic and fully automatic)
• Cylinder press
• Rotary screen press
• Container (cylindrical) printer
• Carousel textile press

Click thumbnail to see larger images
4 Colour Automatic Flat Bed Screen Printer Courtesy of Registerprint Limited	Automatic Cylinder Screen Printer Courtesy of Trumax Limited	Adelco Carousel Textile Printer Courtesy of Adelco Limited
Container Screen Printer (Cylindrical) Courtesy of Mascoprint Developments Limited	Hand Bench Screen Printer Courtesy of Natgraph Limited	Semi Automatic Flat Bed Screen Printer Courtesy of HG Kippax & Sons Limited

APPLICATIONS FOR SCREEN PRINTING

What makes screen printing so popular is the ability to lay down a film of a wide range of materials on a vast range of substrates. Everywhere you look are examples of the process and many places that are hidden.

Applications include: Posters and point of sale displays, gaskets, watch dials, key pads, transfers, electronic circuits, car windscreens, road signs, architectural glass, tableware, nameplates, labels, ceramic tiles, vehicle instrumentation, mouse mats, office equipment, membrane switches, estate agents boards, textiles, fuel cells, pzt, containers, electronic circuitry, playing cards, scratch cards, heating elements, footballs, baseball bats, cricket bats, tennis rackets, golf clubs, clocks, fine art limited editions, laptops, plasma screen televisions. These are just a selection.

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