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 OFTHE 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
