Corrugated board printing

introduction

Economic development, fierce market competition, and increased economic affordability and aesthetic awareness have promoted the improvement of product 91 and packaging quality. Landscaping has become a beautification of goods and propaganda. An important means to promote sales. The printing quality of corrugated boxes has been increasingly valued by commodity producers and consumers. Carton printing has been made from rough production, poor printing quality, monotonous printed matter, and the development of colorful and exquisitely printed products.

Corrugated board type and structure

At present, the corrugated paperboard models and concrete heights are mainly Type A (large 4.6-4.9mm), Type C (medium 3.6-3.9mm), Type B (fine 2.6-2.9mm), E-type (1.1 to 1.8mm), K-type (6.6 to 7mm), F-type (0.75mm), G-type (0.5mm ultra-thin and ultra-thin), N-type (ultra-fine ultra-thin 0.46mm), O-type (ultra-thin ultra-thin 0.30mm) and so on. Different models are suitable for different occasions, have different requirements for printing quality, generally high requirements for printing quality, suitable for high-end carton packaging, and relatively coarse corrugated printing quality requirements are relatively low. In the ordinary carton packaging. Even the same model may have a different structure. There are 2 floors, 3 floors, 5 floors, 7 floors and even 1 floor. There are U-shaped, V-shaped and uV-shaped, different structures have different uses, have different strengths, and have different requirements for printing. Corrugated board printing is one of the fastest growing packaging and printing in recent years. Therefore, how to improve the printing quality of corrugated board is a very urgent problem to be solved in packaging and printing cartons.

Corrugated board printing process

At present, the printing of corrugated paperboards is mainly based on flexographic printing processes. It accounts for more than 70% of corrugated board printing in China, and is even higher in Europe and the United States, with more than 85%. The printing process can be mainly divided into two categories: one is the direct printing process, which is to directly print on the already formed corrugated cardboard, and the other is the pre-printing process, which is to print the corrugated cardboard first, and then the printed surface paper Corrugated paper fits into corrugated cardboard.

1. Direct printing process

This kind of printing method is one of the main printing methods of corrugated paperboard, including flexographic printing and offset printing. Among them, flexographic printing is absolutely dominant. The process flow: the production of corrugated cardboard is a cardboard printing die-cutting groove. - Stapler box.

1 Flexographic printing technology uses photosensitive resin with very good elastic deformation properties as a plate material, and uses water-based ink or solvent-based volatile ink to transfer the ink directly from the plate to the printing technology on the substrate.

This kind of printing is the best method for direct printing on corrugated paperboard today. It is very suitable for corrugated board printing and mainly has the following features:

a. Water-based inks: At present, flexo inks printed on corrugated paper basically use water-based inks, which have no toxic volatile gases and are well absorbed. Fast drying, green, especially suitable for food, medicine, cosmetics and other packaging printing.

b. Flexo printing pressure is light. The layout is soft and elastic. Because corrugated cardboard is corrugated and empty in the middle, it cannot bear large printing pressure. At the same time, it will suffer from uneven pressure during imprinting, and it will be subjected to great force at the peak, and it will run through all the problems in a workflow in Silicon Valley. The layout of the same middle equipment and control device is hard, there will be a serious "squeeze board" stripe, at the same time will make the strength of corrugated board worse, or even collapse phenomenon. The flexographic printing pressure is light, the printing plate is soft and elastic, and it can be very good. It prevents mistakes caused by misrepresentation. It is expensive to run or

c. The machine has a simple structure, easy operation, good quality control, high printing speed, and high production efficiency.

d. The printing plate is resistant to printing force. Suitable for mass production, reducing costs.

e. Printing presses can be linked to other processes. Such as slotting machine, creasing machine and other linkage production. Increased production efficiency.

f. The printing accuracy is not high, only suitable for some text lines and field prints, used in some of the less demanding on the packaging box.

g. The strength of corrugated board is reduced to some extent due to the pressure.

2 Offset printing is based on the natural law of immiscibility between oil and water, in the graphic part and blank part on the printing plate almost in the same plane. The graphic part only adsorbs ink. The blank part only adsorbs water. The printing technology of transferring the graphic part of the ink to the substrate via a blanket. Offset due to high pressure. And the use of fountain solution has a great influence on the strength of corrugated board. It has not been suitable for printing on corrugated cardboard. But in recent years, with the development of printing press manufacturing technology and corrugated board technology. 2. Offset printing technology has made a breakthrough in the printing of micro corrugated cardboard. In the field of miniature corrugated board will replace the flexographic printing. Compared with flexographic printing N. Use direct offset printed packaging, with clear and delicate images. Colorful, rich layers. Good visual effect. The formed carton has good strength, light weight, sharp edges, etc. And gradually become the main printing method for high-end commodity packaging. For example, direct offset printing is available on the MAN Roland ROLAND 700, 900 and KBA Rapida 105. However, due to the large printing pressure of offset printing and the use of fountain solution in printing, the pressure and water absorption will reduce the strength of corrugated cardboard. Therefore, direct offset printing can only be printed on micro-corrugated cardboard with high strength and thinness. And to use a special rubber blanket with strong compressibility and good ink-absorbing transfer performance, to prevent the strength of corrugated board from falling and the phenomenon of “pan plate”.

2. Preprinting process

The pattern on the box is getting finer. Rich and delicate layers, delicate network lines, to meet this requirement. Many packaging and printing companies use corrugated board pre-printing process. That is, the first printing paper is then glued into the cardboard, which can solve the problem of low product quality. Pre-printing process flow: printing a printing paper and corrugated paper a die-cut groove -41 - box.

Corrugated paper preprints include offset printing, flexographic printing, and gravure preprinting.

1 Offset printing

Offset preprinting generally uses a sheetfed offset press to print corrugated cardboard. Get a beautiful pattern. Then use a stand-alone rehearsal corrugated. This process can achieve good results in carton printing quality. The print is very fine, with up to 200 lines/inch. Plate making is easy. And can be printed surface after processing such as laminating, polishing and so on. The printing quality is stable and easy to control. However, there are other problems such as complicated process, long production time, unsuitable for linkage production, low production efficiency, limited printing materials, limited size, high production cost, low carton strength, and high reject rate. The disadvantages of high labor intensity and large production sites require a large number of packaging cartons, especially packaging for export products, which cannot meet the needs. This kind of printing is used less and less in foreign countries. However, due to the low labor cost in China, the use of sheet-fed offset printing presses is very common, offset printing technology is relatively mature, so there are many places in high-grade corrugated cartons used for sales and packaging.

2 flexographic printing preprints

Flexographic preprinting is the use of a flexographic printing press to print on a web. And harvest web form. The corrugated cardboard production line on the printed paper is then made into a corrugated cardboard and then cut into boxes. There are three methods for flexo preprinting:

a. Unit type flexo printing machine

This printing press is similar to the arrangement of multi-color offset presses. Each color group is arranged in a line in order, each color group is independent of each other. The number of colors can be arbitrarily combined because of the large distance between color and color. It is good for drying. Printing speed is fast, but overprint accuracy is not as good as satellite.

b. Satellite type flexo printing machine

This type of press has a common large impression cylinder in the center. Various color plate cylinders are around. Due to the high accuracy of the common impression cylinder overprinting, satellite type Up to ±0.05mm. Wide range of printing materials. Can be used from 30 to 700g/m2 paper and cardboard, printing adjustment time is short. Less material loss is currently the most preprinted method.

c. Laminated flexo printing machine

This type of printing press is assembled by layering each individual printing unit up and down. Each color group is independent of the drying time, fast printing, small footprint, easy to cooperate with other processes, the scope of application and overprint accuracy is not as good as satellite.

d. Preprinted features of flexographic printing

Flexo printing has developed very fast in recent years due to the dryness

fast. Printing speed is fast. Green. The low cost is particularly suitable for the printing of corrugated cardboard in large quantities. Specifically has the following characteristics:

â—† Use water-based ink. The main solvent of water-based ink is water-free volatile organics. Non-toxic, non-polluting is a green ink ink with good printability. Imprinted water resistance, wear resistance is good. It is an ideal printing ink.

â—† Wide range of printing materials. Can print 30 ~ 700g/m2 of paper and cardboard.

â—† Can print large-format, multi-color high-quality prints. At present, the maximum size of the latest foreign machines has reached 2.4m. Up to 8 colors can be used.

â—† EpB0 product fine picture. Consistency is good. Colorful.

â—† The carton produced has great compressive strength and impact resistance.

◆ EpB, J speed. High Yield. Speed ​​up to 250 ~ 400m/min. ◆ The machine structure is easy to operate. Quality control. Low printing costs.

â—† High-light and dark-tone networks are easy to lose for 8% to 85% of the tone area.

â—† Can't copy too small text. line. Due to the small deformation of text lines in the flexographic printing, the text lines are easily deformed, enlarged, and stuck together.

â—† The emergence of digital direct plate-making technology and plate sleeve technology has enabled the printing quality and printing speed to be further improved to basically print any product.

3 gravure printing preprint

The gravure printing machine is used to print on a web and take the form of a web, and then the printed web is used as a corrugated paperboard production line to make a corrugated cardboard and die-cut into a box.

At present, there are two major organic and satellite types. The roller arrangement is similar to the unit type and satellite type of the flexographic printing press, but the layout of the unit type in the gravure printing machine is more reasonable and the technology level is higher. It is currently the main type of the gravure printing. Specific features include:

a. The print quality is best and most stable in all kinds of printing.

b. The use of electronically engraved plate-making plates has a high level of graphics and graphics.

c. Green water-based ink.

d. Plate printing and high printing force up to 300 ~ 40 million printing is particularly suitable for long live printing.

e. The continuous pattern printing plate cylinder can be seamlessly spliced, that is, the sleeve technology makes the image continuous.

f. Higher impact strength.

g. Printing speed (up to 1 50 ~ 2OOm/min). high productivity.

h. Platemaking complex. Long period. It takes 5 to 10 days.

i. The entire process is complicated and costly. The gravure plate is 8 to 10 times the cost of the flexographic plate.

Comparison between direct printing and preprinting

Although direct printing on corrugated cardboard is still one of the main printing methods for corrugated boxes at home and abroad, it is not as good as preprinting except for the simple packaging printing process, high speed, and short cycle time. Mainly in:

1. Preprinting for better print quality

Preprinting is printing on smooth paper. The direct printing is printed on the corrugated corrugated board. The quality is naturally different.

2. Preprinted to obtain greater strength of corrugated cardboard

As direct printing is performed on corrugated cardboard. Each embossing will deform the flutes. The intensity is reduced and the preprint is printed on the tissue. Does not affect the intensity of the corrugated. There will also be no phenomenon of a washboard.

therefore. In the high-end delicate. It is better to use pre-printing on large-scale carton printing.