Adapting to technological innovations and the public’s demand for high-quality finishes on their personal electronic digital devices has increased the usage of silkscreen finishing technology and these methods have become increasingly popular in a number of industries.
The screen printing process consists of printing the logo or pattern on a screen with a film and then using a squeegee to print the ink onto the surface of the substrate. Once completed, the logo is printed on the surface of the product.
Screen printing definitions:
Screen printing is a relatively new printing technique that uses a mesh to transfer ink onto a substrate (except in areas blocked out by the use of a stencil). A blade or squeegee is then moved across the screen to fill the gaps in the mesh with ink. A reverse stroke may also be used if the ink has not imprinted on the substrate or to increase the intensity of the print colour. Only one color can be printed at a time so several screens can be used to produce a multi-colored image or design.
Pretreatment process of metal silkscreen:
For screen printing on metal surfaces, the surface has to be prepared ahead of the treatment beginning. The pre-treatment process of metal surfaces is also called pre-printing processing. There are many ways to prep the processing metal surfaces, such as degreasing, polishing, wire drawing, oxidation, sand surface treatment, spray painting and more. These processes can be used alone or in combination to achieve the desired effect according to the different requirements of the product and the conditions of the underlying material.
The purpose of the pre-processing is mainly twofold:
- Decorative, which means removing some defects of the aluminium plate material to increase the aesthetics of its surface
- Manufacturability, which means that the surface finish of the material is changed by pre-treatment processes to enhance the adhesion of the printing coating on it.
There are many methods for metal pre-treatments such as:
- Degreasing: Before the degreasing treatment process, to give the metal surface a certain affinity for the coating printing, it is important to remove any oil stains from the surface of the metal material. Generally speaking, the oil contamination of the package can be removed with specialised fine soft powder. The oil contamination during machining can be scrubbed with organic solvents or chemically degreased with alkaline solutions.
- Polishing: Polishing is a common method to overcome surface defects and improve the surface finish. Polishing can be roughly divided into three categories: mechanical, chemical and electrochemical.
- Mechanical polishing – first we rough polish the surface with a cloth wheel polishing machine and polishing paste, then perform a fine polish with a fine cloth wheel, ensuring the material can achieve the desired smooth effect. This method is mostly used for the decorative treatment of anodized dyes signs or for mechanically polished aluminium plates to help obtain desired brightness and good oxidation results.
- Chemical polishing is mostly performed in acidic solutions.
- Electrochemical polishing is a higher surface finishing method, which can help the parts obtain a brighter mirror polishing effect and reduce the surface oxidation of metal materials by the atmosphere.
There are a number of advantages of using silkscreen processing:
1) Wide application area and range of applicable inks
2) After printing, the ink has good adhesion and will remain intact for a long time
3) The screen printing process is not limited by the size of the object
4) Good resistance to sunlight, acids, and alkalis
5) The printing methods are flexible and can be printed either manually or mechanically as the screen printing process is simple and easy
6) The cost of printing beautiful three-dimensional realistic patterns is low compared to alternative methods
7) Can be used to decorate a range of products and is very aesthetically pleasing
8) The ink is safe to use and conducive to environmental protection