Last updated on September 8th, 2023 at 08:31 pm
Definition of Screen Printing
Screen printing is becoming increasingly important. The designs are fairly simple to apply and the dimensions of the screens can easily be changed. The pressure which is exerted is also lower than with roller printing. Textured surfaces are not crushed and color development is also better.
Screen printing is comparable to stenciling. A distinction is made between flat screen printing and rotary screen printing. In flat screen printing, rectangular frames (screens) are used with thin gauze fixed to them. Rotary screen printing is done with cylindrical screens. The cylindrical screens contain the color paste and rotate over the fabric to be printed. The dye is forced through the cylindrical screen which is perforated according to a particular design onto the fabric underneath.
The screen properties are very important here. Stable screens are necessary. The frames used for flat screen printing are made of wood, or preferably of metal. The use of strong nylon or polyester gauze threads (hydrophobic material) guarantees a tightly stretched mesh which will not bend under loading (with the color paste). The paste is pushed through the screen by means of squeegees onto the fabric according to a certain design.
Flat Screen Printing Method
There are three types of flat screen printing, such as hand screen printing, semi-automatic flat screen printing and fully-automatic flat screen printing.
Hand screen printing is to be considered a craft rather than a productive working method. The fabric is fixed to a blanket or black grey on a printing table where the screens are put on. Normally, another screen is needed for each color of the eventual drawing. The print paste is spread across the screen by hand with a (rubber) squeegee blade forcing the paste through the screen. The manual method may cause irregularities.
In semi-automatic flat screen printing the squeegee is moved across the screen mechanically, it is impossible to reach a considerable speed of working with this method.
In both hand and semi-automatic screen printing, various colors are applied one after another with intervals for drying (wet-on-dry method). Application with shorter intervals is known as the wet-on-wet method.
Fully-Automatic Flat Screen Printing
Increasing the printing speed can be done by applying (printing) all colors on the fabric simultaneously which leads to a continuous process instead of a batch wise one. In that case the fabric to be printed moves over a distance equal to the width of the repeat between each printing operation. The repeat is that part of a design or pattern which is repeated on equal distances in length and width.
The design or pattern is the whole set of figures which are printed on the material. The material to be printed is gummed to an (endless) printing blanket or conveyor. This blanket can be easily stuck to and removed from the textile to be printed. It is then washed and dried during one working period (so called Buser system). Adhesives can be applied and removed in each cycle, or can remain on the blanket and be active permanently (thermoplastic layer). Some products in the paste, however, may (gradually) affect the adhesive layer.