Screen Printing Process

Silkscreen printing uses a woven mesh to hold an ink-blocking stencil. The attached stencil forms positive areas of mesh that transfer ink to create an image onto the receiving printing material. A design is imposed on to the screen , with blank areas coated with an impermeable substance . The screen is then placed with the stencil and flooded under UV light to expose the image onto the screen.

In commercial silk screen printing there are six main types of printing presses:

The Flatbed Press : used for printing onto flat materials

The Flatbed Cylinder Press: Much like a letterpress flatbed, a cylinder press is used for longer runs with flat materials.

The Cylinder Press: Used for printing onto round or over objects such as bottles.

Textile Flatbed: T-shirts and other clothing items are printed on such a press bed.

Precision Flatbed: Mainly used for printing onto circuit boards.

The Rotary Press: A high production process that increases the printing run rates. The ink is pumped into the printing cylinder and a squeegee n the inside of the cylinder controls the flow of ink. This process is one of the most common within commercial printing due to the speed of the production.

above are examples of high end mass production rotary screen printing presses. The rotary system of the left is a 12 colour stage process, and the right is a 16 colour two tier printing press. Both are fully automatic and able of being connected to a web or stack feeder if printing onto most flat materials or 3d packaging such as bottles. The t-shirts would however be manual placed and removed from the presses.

The process:

The screen is placed on top of the printing material then ink is placed onto the screen, through either a ink reservoir or added manually. A squeegee or roller is then pulled down either manual or mechanically depending on the press used, which uses down force pressure to pull ink across the screen, through the open gaps on the screen stencil and transferred to the printed material under the screen. Capillary action is used in this processes to control a specific amount of ink onto the printed material.

Due to the simplistic nature of this printing processes over others mean that the equipment costs for screen printing are lower, however the rate of production is much slower.

The benefits of the most commonly used fabrics on the screen include:

Silk: used to be the most common fabric because of its durability, but it is not used as much today because other fabrics, especially synthetics, have proven to be as good or better and are less expensive.

Organdy: is inexpensive and is good for short and medium runs.

Nylon: is the most durable fabric (synthetic or natural). It is a good choice for print applications involving convex or concave surfaces

Polyester: is widely used for its durability and versatility.

Metal Mesh: is made of stainless steel, copper, bronze, or brass and is used when plastic substrates are printed with heated inks.

Screen printing can be used on almost any type of material including paper, glass, fabric, plastic, wood, and metal. Products can be as varied as signs, posters, circuit boards, mugs, clothing, and soft drink bottles, glass bottles, all can be printed using the process. Screen printing is very useful when an image needs to be wrapped around an object or when images need to be printed onto oddly shaped manufactured objects.