1.offset Printing
There are two types of offset printing for corrugated cardboard packaging: direct offset printing and conventional offset printing.
Direct offset printing uses corrugated cardboard as the substrate for direct printing with a special offset printing machine. It is suitable for thin corrugated cardboard (such as G-type and F-type microfine corrugated cardboard), and can be used to make packaging boxes and gift boxes for home appliances, toys, food, electronic products, etc., and is likely to become the direction of development for the printing of corrugated cardboard boxes in China.
Conventional offset printing of corrugated cartons uses indirect printing, i.e., printing the carton face paper first and then laminating it to the corrugated, requiring machinery including ordinary offset printing machines and fully-automatic and semi-automatic laminating machines. Offset printing is more suitable for high-quality, smaller quantities of corrugated box packaging.
2.flexographic
Flexo printing, i.e. flexographic printing, belongs to letterpress printing, but the printing plate is soft. The pressure of flexo printing is only l/30 of the pressure of traditional letterpress printing, and the deformation of corrugated cardboard is very small after printing. The water-based ink used in flexo printing is absorbed by the corrugated board when it gently touches the board, and the commonly used flexo plate materials are photopolymerised resin plate and rubber.
Flexo printing is more suitable for corrugated cartons that do not have a high standard of printing precision (e.g., text lines), large quantities, rapid requirements, large areas, and low prices.
3.prepress
Pre-printing means that the corrugated board is printed on its roll face paper before it is produced, the paper is collected into rolls after printing, and then the printed face paper is sent to the corrugated board production machine to be laminated and formed. Pre-printed corrugated is not subjected to printing pressure, so the appearance of the formed corrugated box is ideal.
There are two types of pre-printing: flexo pre-printing and gravure pre-printing. Many foreign corrugated packaging printing companies favour flexo pre-printing. For our country, gravure printing is more mature than flexo printing, so the current corrugated packaging printing efforts in gravure pre-press are more in line with the actual situation in China.
Pre-printing is more suitable for high-quality, high-volume corrugated packaging. If there are many varieties of products, and the printing volume of a single variety is not large, pre-printing will not be cost-effective.
What's the difference between them?
1.print quality
Flexo printing is inferior among the three, offset printing and pre-printing quality are good.
The quality of flexo printing cannot reach the standard of high-grade corrugated box packaging. Firstly, this is due to the water-based ink used in flexo printing for corrugated box packaging, which leads to poor brightness of the printed products; secondly, the number of mesh lines in flexo printing is usually 30-65 LPI, not higher than 150 LPI, which is lower than that in offset printing and pre-pressing; and thirdly, the dot enlargement of flexo printing is more serious, which is not easy to control.
Offset printing in our country has been relatively speaking perfect printing technology, but also the printing industry within the field of printing process advantages more obvious. Therefore, corrugated box packaging offset printing quality is very normal. First, offset printing uses a high resolution PS plate, which is capable of printing very fine patterns, as well as laminating, varnishing, and other surface finishing work. Therefore, at this stage, the vast majority of high-end corrugated carton printing used for sales and packaging in China is offset printing; second, the number of mesh lines added to the offset printing of corrugated carton packaging is able to reach 150 to 200 LPI; third, the expansion of the offset printing network is much lighter than that of flexographic printing, with 50% of the printing points expanding 15 to 2O percent. Thirdly, offset printing dot expansion is much lighter than flexo printing, with 50% at 15% to 2O%; fourthly, corrugated carton packaging offset printing can reproduce a large range of dots, reaching 2% to 98%, or even 1% to 99%.
The printing pressure of pre-printing is uniform and is not affected by the height of the corrugated box, so the printing quality is excellent. Flexo preprinting screen line number can reach 150LPI, 50% dot expansion than the traditional flexo printing lower than 15% to 25%, but the reproduction of the continuous tone of the image when the range of steps can only be between 8% and 85%; gravure preprinting preprinting than the flexo preprinting strong, the screen line can reach 300LPI, the most representative of the gravure printing ink full, strong sense of hierarchy, overprinting precision advantages, gravure preprinting even higher than the effect of offset printing.
2.Cost of printing equipment
The cost of pre-printing machinery and equipment is relatively high, and flexographic printing equipment is low.
Pre-printing process requires web printing equipment, after printing the first rewinding to form a web of printed matter, and then on the corrugated cardboard production line compound corrugated boxes, the current stage of the corrugated cardboard production line is not suitable for pre-printing of cardboard composite, but also need to continue to improve the technology. The introduction of pre-printing printing equipment and transformation costs are very large.
Flexographic printing equipment is simple in construction and low in price. Offset printing equipment (especially direct offset printing machine) is about twice the price of flexographic printing machine.
3.Cost of printing plates and print resistance
Flexo plates are relatively costly and pre-printed plates have high print resistance. Flexographic rubber plate and photopolymer plate cost is relatively high.
Offset printing is usually only hundreds of thousands of prints; flexographic printing rate of 1 million prints or so; flexographic printing plate is very high print resistance, and can be recycled.
4.Printing Ink Performance
Offset printing inks include resin-based and glossy printing inks, and water-based inks can be used for flexographic printing and pre-printing.
Offset printing inks include resin-based and glossy printing inks, which often contain benzene and have certain pollution problems. Flexographic printing and pre-printing can use water-based ink, which is beneficial to the structure of loose corrugated board penetration drying, and has non-toxicity, no smell, no pollution, low price and many other advantages.
5.Printing efficiency
The slower efficiency is offset printing, while the pre-printing efficiency is faster.
Offset printing is only suitable for the use of single-sided corrugators and is not suitable for the use of cardboard linkage production lines, so the work efficiency is lower.
Prepress is faster. Because pre-printing prevents the impact of traditional printing on the cardboard's flat compression strength, the printing efficiency can reach 200-400m/min.
The second is flexo, flexo printing plate printing equipment can be die-cutting, creasing, slotting, gluing, folding, stapling (gluing) box, bundling and other post-press production equipment online continuous operation, efficiency is very good. Because the flexo printing plate printing speed is faster, it is difficult to stabilise, which in turn leads to multi-colour printing overprint precision is not high.
5.print format
Pre-printing can reach a large printing width, flexo printing second, offset printing smaller.
Flexographic printing equipment and pre-printing printing equipment can reach wide-format printing, flexographic printing corrugated cardboard width can reach 2.8m, gravure pre-printing printing equipment can reach a maximum print width of 3.4 m. Offset printing can not be printed in large format.
