The essence of pulp moulding - three-dimensional papermaking technology
Pulp moulding is a three-dimensional papermaking technology, refers to a certain concentration of wet pulp with the appropriate amount of chemical additives in the molding machine through vacuum or pressure to make the fibers uniformly distributed on the surface of the mold, so as to make the wet paper mold blank, and then further dehydration and demolding, drying and shaping of the products, and made of pulp moulded products of the production technology. Waste paper of different compositions to produce products with different properties.
Pulp moulding as a production process from pulp to packaging products, product structure is diverse, convex and concave changes, and printing format is small, the use of traditional conventional printing process is difficult to meet its requirements, should consider the use of more flexible printing methods, such as pad printing, inkjet printing, screen printing, letterpress offset printing, etc., to complete the paper moulded packaging products to achieve the concave and convex surface of the multicolor fine printing.
A variety of printing methods for pulp moulding
1: Surface screen printing method
Screen printing method is the thick ink on the screen plate, and then use the scraper and screen plate contact and form a certain angle, while the pressure is applied while moving, so that the ink through the screen printing plate leakage printed on the substrate.
Manual screen printing method using a squeegee, with which at the same time to complete the scraping and ink scraping two jobs. Mechanical screen printing must have scraping and scraping ink two scraper, two scraper for alternating back and forth movement, scraping scraper squeezing ink printing, back to scraping scraping scraper lifted off the screen plate. In order to make the scraping scraper again scraping when there is enough printing ink, scraping ink scraper will be printing ink and then scraped back to the initial position of the printing ink, in order to continue printing.
The main characteristics of screen printing:
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Plate making and printing method is simple, less investment in equipment, low cost, suitable for small batch production;
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Not subject to the type of substrate, size, shape restrictions, can be curved surfaces, spherical, fragile printing.
For the structure and shape of more changes in the surface printing of paper-molded packaging products is also more suitable, and it is printed with a thick ink layer, bright colors, three-dimensional sense and strong covering power. Therefore, small screen printing equipment can be used to print on the surface of paper mold packaging products.
2: Surface inkjet printing
Paper mold packaging products in structure on the concave and convex changes more, the use of inkjet printing can also be completed on the surface of the decorative printing. Inkjet printing is a non-contact non-plate imaging printing method, it applies the computer to store information, without having to store the graphic information on the printing plate, the print head does not contact any part of the substrate, can be in the operating conditions of a wide range of changes in the case of the paper mold packaging products in the various concave and convex surfaces, and reliably printed out clear text and patterns.
The principle of inkjet printing is that tiny dots of ink are sprayed from one or more printheads through a gap onto the surface of each paper-molded product located in the production line, forming a matrix of dots to form text and patterns.
The printing machine uses a microprocessor to control the desired text pattern, which is synchronized with the speed of the production line through the action of sensors to ensure that each paper-molded article is correctly printed with the graphic material. The ink is sprayed by pressure or electrostatic force and can be sprayed along the horizontal direction from bottom to top, from top to bottom, or from any angle, which is especially suitable for the surface printing of paper-molded packaging products with many changes in structure and shape.
3: Surface pad printing method
According to the printability of the paper mould material and the structural characteristics of the paper mould products, pad printing technology can be used to complete the surface decoration printing. Pad printing is an indirect printing method, the system uses the silicon rubber cast into a hemispherical pad printing head pressed to the copper or steel intaglio layout, the layout of the graphic ink stained up, and then transferred to the substrate to complete the printing. It can achieve multi-colour printing on irregular concave and convex surfaces.
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