What Is a Screen Printing Machinery?
Screen printing machinery is a type of stencil printing machine that uses a mesh material screen as the plate for printing.
Among the mesh material’s grid, areas not needed for printing are solidified with emulsion to create a mask. Printing is then done using a plate that has been created to allow ink to pass through specific areas while blocking others. In the past, silk was used, and it was known as silk screen printing. However, nowadays, synthetic fibers such as polyester and nylon are mainly used.
This technique is based on a stencil, where dye is applied over a pattern-cut template. Unlike offset printing, a method that transfers ink to the plate, screen printing allows for a thicker application of ink.
Uses of Screen Printing Machinery
Screen printing machinery can be used on various materials, including paper, glass, plastic, synthetic resin, metal, fabric, and more. This is because it operates on the principle of pushing ink through the mesh. One significant feature is its ability to print not only on flat surfaces but also on cylindrical, conical, and even curved surfaces like bottles and cups.
There are various types of ink available for different weather resistance and special applications. It is used in visual printing materials such as advertisements. While it finds applications in many fields, including industrial products, daily necessities, and commercial purposes, below are some specific examples of printed materials.
1. General Applications
- Tableware such as cups and glasses (glass and ceramics)
- Clothing items like T-shirts
- Miscellaneous goods like toys and stationery
- Various packages and containers
- Printing on food items (chocolates on candies, for example)
- Woodwork
- CD/DVD printing
- Injection-molded products
- Pressed parts
- Semiconductor packages
- Instrumentation in automobiles and other vehicles
- Electrical components (printing heaters on the rear window of a car, for example)
- LCD displays
- Printed circuits
- Posters, signs, POP displays
- Stickers and signs
2. Printed Electronics
Printed electronics involve forming electrical circuits using printing technology, with screen printing being one of the methods employed. It is considered effective in terms of high productivity, low cost, and low environmental impact. This technology is utilized in various electronic devices, particularly in components for smartphones and sensors. Specific applications include:
- Thin film coating for the slimming down and internal density of electronic devices
- Thick film coating to improve the insulation of circuits
- Application of high-viscosity materials in extremely fine line widths
In particular, printed electronics are used in devices such as stacked ceramic capacitors, stacked inductors, chip resistors, solder paste printing, touch panel sensors, and flexible devices.
Principles of Screen Printing Machinery
Screen printing machinery is a type of stencil printing that involves opening holes in the plate itself and rubbing ink onto it. Gravure printing and stenciling are also types of stencil printing. The screen printing process begins with the preparation of the printing screen in a step called “plate making.”
1. Plate Making
The general plate-making process for screen printing is as follows. In recent times, digital screen plate-making machines have simplified these steps:
1. Frame Preparation
Determine the size of the frame (aluminum frame, cast frame, wooden frame, etc.) based on the size of the printed material. Choose the material and mesh count for the screen mesh.
2. Mesh Stretching
Use a mesh stretching machine to stretch the screen mesh onto the frame. During this process, use a dedicated cleaner and a plate cleaning machine to remove dust and debris from the stencil, enhancing the efficiency of the subsequent emulsion application.
3. Emulsion Coating
Apply a liquid photosensitive resin directly (direct method) or attach a film with photosensitive emulsion to the plate (indirect method) to coat with emulsion. Allow it to dry thoroughly.
4. Exposure and Development
Attach a positive film to the emulsion-coated plate and expose it. After exposure, develop it with water and let it dry.
5. Inspection and Pinhole Correction
Inspect for the presence of pinholes and repair them with a photosensitive agent.
2. Printing
In the printing process of screen printing, use a tool called a squeegee to push the ink accumulated in the screen’s patterned (hole) area from the edge of the plate onto the printed material. The squeegee, typically made of rubber or polyurethane, comes in various shapes such as flat, sword-shaped, and angular. The angle and pressure setting of the squeegee are crucial elements in printing.
During printing, align the position of the printing area and use a scraper to flow ink onto the screen’s patterned (hole) area. Conduct a test print with the subject in place to check for issues like ink smudging. After confirming no problems, proceed with the actual printing.
Types of Screen Printing Machinery
There are various types of inks that can be used with screen printing machinery. In addition to regular water-based and oil-based inks, examples include UV-curable inks, powders (gold, silver, pearl), and functional inks (fragrance, phosphorescent, mirror, color-changing), among others. The mesh used in screen printing also varies in mesh thickness and mesh count depending on the application.
In the printing process, the outcome is influenced by the shape, angle, and pressure of the squeegee. It is crucial to select the right combination based on the desired print result.