Printing has existed for over 5,000 years, from proto-Elamite and Sumerian civilizations that used cylinder seals in 3500 BC to Chinese engravings of woodblocks for printing in the 7th century AD to the invention of the first printer in Germany in the 15th century AD. As a result of the development of printing, various cultures have been exchanged and spread throughout the world. It is now widely recognized that printing is a very mature technology and has given rise to a variety of printing methods based on different principles. What are the most common printing methods used in the packaging industry? I will discuss several of the most commonly used printing methods in the packaging industry in the following post.
1. Offset printing
Offset printing is a printing method commonly used for packaging boxes. Based on the principle that oil and water do not dissolve, the part of the printing plate that has graphics is coated with oil, which can absorb the ink, and the blank part is coated with water, which prevents the ink from adhering. After the printing plate absorbs the ink, it applies a certain amount of pressure to make full contact with the paper, thus printing the graphics on it. In general, offset presses are fast, print patterns beautifully, and reproduce pictures with a high level of accuracy. Furthermore, offset printing uses light and cheap plates, and the process of making plates is also simple and convenient, making it suitable for printing a variety of food, medicine, cosmetics, and other packaging materials.
2. Gravure printing
Gravure printing is particularly suitable for large quantities of long-term products and is very competitive in high-quality and quantity markets. It involves engraving graphics on a printing plate, filling the depressions with ink, and then contacting the paper, so that the graphics are printed. A gravure printing process is characterized by fewer variation factors, stable printing quality, a high printing speed, a durable printing plate, a thick ink layer, and a strong texture of the print. The finished product often has a raised texture as a result of the ink filling the depressions on the printing plate. Gravure printing plates are complicated, expensive, and take a long time to manufacture. In this regard, Gravure printing is not suitable for a small number of diverse printings. Currently, it is mainly used for securities, currency, and other items of high value. This printing method will also be used in the packaging industry for high-end products such as tobacco and wine.
3. Flexographic printing
Historically, letterpress printing has been used for more than a century. Flexographic printing is a type of letterpress printing. Flexographic printing process involves the use of flexible printing plates and ink transfer through an anilox ink transfer roller.
There are several distinctive characteristics of flexographic printing:
- Low investment in equipment, rapid results, and high efficiency.
- It is easy to operate and maintain.
- High printing speed, its printing speed is generally 1.5-2 times that of offset and gravure presses.
- There are a wide variety of printing applications, including books, business forms, corrugated paper, trademarks, film packaging, paper flexible packaging, paper bags, plastic bags, and many others.
- The use of water-based and solvent-free ink in flexographic printing is in full compliance with the requirements of green environmental protection, primarily for food packaging.
4. Screen printing
Screen printing involves coating photopolymer onto a printing plate with mesh, covering the part to be printed with black film, and then curing the plate with light. The part covered by the film will be able to penetrate ink after cleaning. In practice, the ink is poured into the printing plate from one end, then transferred to the substrate through the mesh of the screen plate under the pressure of the squeegee.
Screen printing has the following characteristics:
- strong adaptability: the print can be used on flat, curved, spherical, concave, or convex substrates, regardless of the substrate.
- Thick ink layer, strong three-dimensional sense: offset and letterpress ink layers are generally about 5 um, gravure printing about 12 um, flexo printing about 10 um, whereas the screen ink layer is approximately 30 um thicker, exceeding the thickness of the above ink layer.
- With strong light resistance and bright colors, can use a variety of inks and coatings. Typically, screen printing is used for the partial decoration of folding cartons for cosmetic products.
5. Digital printing
It refers to the process of printing computer files using a laser printer or an inkjet printer. There is no need to make plates and the printing process takes a short amount of time. However, it does not adhere well to ink, and the cost of mass production is high. Therefore, this printing method is more suitable for small-batch printing or proofing purposes. At present, to meet the need for anti-counterfeiting, the use of one product and one code on the packaging, through a combination of software and printing equipment, digital printing is a more appropriate printing method to print variable information such as barcodes and 2D barcodes on the packaging.
There are five mainstream printing methods mentioned above, each of which has its advantages and disadvantages, depending on the situation. We may also choose one or a combination of several printing methods for printing according to the design of the packaging and the needs of the client. Hopefully, you have gained a better understanding of printing from the above article. If you have any comments or suggestions, please leave them in the comments section.
