The screen printing process

Screen printing process is the simplest, yet one of the most versatile printing techniques. All that’s needed to create a print is a screen, ink, squeegee and a table. The screen, expertly referred to as screen printing form, is made of finely woven fabric called mesh stretched over wooden or metal frame. Some areas of the mesh are blocked off with a non-permeable material to form a stencil, which is a negative of the image to be printed. A rubber blade called squeegee is then run over the screen to force the ink through the mesh directly onto the substrate, thus creating a print.

Blocking some areas of the mesh to create a stencil is done either by cutting in special masking foils or, more commonly, through a photochemical process called exposing the screen, which we’ll describe in detail in a separate article. In short, a photosensitive emulsion is scooped across the mesh and then exposed to a source of light. In contact with UV radiation the emulsion hardens and blocks some areas of the mesh permanently. Unexposed areas of the screen are washed out of emlusion leaving open mesh in the shape identical to the image to be printed.

Screen printing can and very often is done using manual presses, however high quality and high volume printing, as well as printing on non-planar surfaces is most often done using semi-automated or fully automated presses. Types of screen printing presses vary depending on multiple factors like type and shape of screen, type of substrate, type of squeegee action, or the way ink is supplied.

Flat-bed screen printing

The principle of flat-bed screen printing is illustrated in the figures below. The screen is mounted to the table with a hinge, allowing for lifting the screen to put a substrate beneath. In the printing process the screen remains stationary and the squeegee moves on top of it forcing ink into the mesh opening and making it contact the substrate. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate leaving the ink upon the substrate surface.

Screen printing process

Image: Harry Wad

 A – ink, B – squeegee, C – open mesh, D – blocked mesh, E – frame, F – image that will be printed after squeegee pass

Flat-bed screen printing

Flat-bed screen printing

A – frame with a clean mesh; B – screen printing form (frame + mesh with stencil); C – screen printing form mounted on a table; D – printing process; E – printed substrate

1 – frame; 2 – threads of the mesh; 3 – blocked mesh (screen printing stencil); 4 – frame support; 5 – table top; 6 – substrate; 7 – screen fastening / hinge; 8 – ink; 9 – squeegee

Cylindrical screen printing

In the cylindrical screen printing process the flat screen moves simultaneously with the material being printed on which is placed on a rotating cylinder. The squeegee is mounted stationary.

Cylindrical screen printing

Cylindrical screen printing

Screen printing on round and oval objects

Screens for printing on round and oval objects can either be flat or in a shape matching the object. In the printing process the screen moves along with the object, while the squeegee remains stationary.

 

Screen printing on round objects

Screen printing on round objects

Rotary screen printing

The screen printing form is thimble-shaped and the squeegee and ink are placed inside it. In the printing process the form revolves and the squeegee pushes the ink onto the substrate which moves between the form and platen roller. Sometimes magnetic squeegees can be used.

Rotary screen printing

Rotary screen printing

One Comment

  1. Ameet jain says:

    The most simplest and useful information on screen printing, I read all the articles . Thanks a ton for posting them

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