Screen Printing Technology in Textile:
Screen printing has some advantages, which are pointed out in the following:
- It needs relatively cheap equipment.
- It has very few preliminaries.
- This type of printing permits printing on almost any surface.
- Areas of far greater size can be stenciled. Frames 1.27m X 1.52m (50” X 60”) are frequently used for textile printing.
- It is very economical for short runs of suitable subjects and so widely used for posters, show cards etc.
- Surface to be printed need not be flat.
Disadvantages of Screen Printing in Textile:
The major faults of this type of printing are listed in the below:
1. Poor pattern registration.
This arises from inaccurate screen placement or fabric movement, from the fabric slipping on the blanket because of poor adhesion, or from distortion of the screen mesh by the drag of the squeegee. Marks on areas already printed are caused by the frame crushing the paste beneath it while the printing paste is still moist. This is more of a problem in fully automated screen printing where colors are printed one after the other with little time for drying of the deposited paste. For this reason, printing of large areas of color is usually done last.
2. Off-contact printing:
Off-contact printing minimizes squeegee drag and frame marks. For this, the frame is not quite in contact with the fabric. The pressure of the squeegee forces the screen material to stretch slightly so that it touches the fabric and the paste transfers. Splashing of color is caused when the paste beneath the screen initially sticks the screen to the fabric. When the screen is lifted quickly, color is splashed outside the printed zone as the paste on the fabric separates from that on the screen. Gently lifting the screen from one end and then the other avoids this, although it slows down the process.
3. Print repeat size:
Flat screen printing with large screens allows much greater print repeat sizes than is possible using engraved copper rollers or rotary screens. Forcing the paste through the screen openings involves much lower applied pressures than in roller printing, so there is less penetration of paste into the fabric. This results in higher color strength and less crushing of any fabric texture. Flat screen printing is, however, relatively slow and is now only used for materials such as high quality furnishing and fashion fabrics.