The advantages of flexographic printing in the field of packaging, decorating and printing have been recognized by more and more people in the industry. There are still many printing companies considering the introduction of flexographic printing presses. However, flexo printing presses are different from other types of printing presses. The equipment used to complete certain specific processing functions on the flexographic printing press is configured according to the user's requirements. The decisive factors in selecting the printing format are also different from other kinds of printing presses. different. Therefore, how to select the type and configuration of a flexo press suitable for the respective business conditions has become a topic of great concern. The following is just to discuss some personal opinions on how to choose a unit type narrow-width flexographic printing press.
Before determining the model and configuration, it is necessary to clarify why the flexographic printing method is selected. People choose flexographic printing, nothing more than from the economic or technical point of view, take a look at the advantages of flexographic printing. From an economic point of view, the flexographic printing equipment has a small investment, a small footprint, a small number of workers, and a lower cost of use than other printing methods. Especially group-type narrow-width flexographic printing presses, which can be post-pressed on-line, are more efficient and profitable than other printing methods, and are economically more obvious for some products that are well suited for flexographic printing. . From a technical point of view, the effect of flexographic printing is somewhat inferior to offset printing in some respects, but it has its own unique strengths in the printing of product labels. For example, on-site printing and ink control are superior to offset printing; some non-permeable materials that are not well-printed by offset printing can be printed easily with flexible printing. Compared with gravure printing, flexographic printing machines can print any material that can be printed by a gravure printing machine, but some rough surfaced materials or softer materials that cannot be printed by a gravure printing machine can also be printed on a flexographic printing machine. Of course, as with other printing methods, flexographic printing methods also have their limitations, such as the printing of a gradient color, because an anilox roller can not take into account both the high light part and dark part of the ink supply, the printing effect is significantly inferior to offset printing . Therefore, when purchasing a flexographic printing press, it is necessary to have a fuller understanding of the flexographic printing method in order to avoid weaknesses and give full play to the economic advantages and technical advantages of flexographic printing.
To purchase a flexographic printing press, it is necessary to specify the orientation of the printed product. Before buying a machine, it is necessary to be very clear about what kind of product the flexographic printer is used to print. Because only the products to be printed are clarified, it is decisive to decide how to purchase the models and provide additional configurations. For example, if the same is a printed sticker, if it is only a sticker for printing paper type paper, the corona treatment device is not required, but a sticker for plastic film or aluminum foil is to be printed. Must consider installing corona treatment device. For another example, the same printing folding carton, the printing thin paper box can choose the ordinary type flexo printing machine, and printing the thick paper box should select the cardboard type special printing machine, there are many differences between the design and function. In the case of printing thick paper, large-diameter unwinding or non-stop conjoining units should be selected. For printing thin paper, smaller diameter unwinding and 3-inch mandrels can be selected.
For each of the above issues, it needs to be resolved before the selection.
After the printing product is finalized, the processing technology of the product, including the process route, should also be clearly defined, which is also very important for the reasonable choice of additional configuration. Printing process, number of color groups, die-cutting requirements, and process requirements for glazing, screen printing, and bronzing should all be considered.
Flexographic printing is very different from offset printing and gravure printing only in terms of the number of printing sets. A color can be printed with a color plate in the offset and gravure printing modes, and printing with a flexographic plate may not be possible. If the color has both a large area of ​​color blocks and fine text or thin lines, it must be divided. Two versions to copy. If a large area of ​​color blocks and fine text or thin lines are printed on a single plate, the high number of anilox rollers can be used to ensure that small text will not be affixed to the plate, but the amount of ink in a large area of ​​color blocks will be insufficient. The use of a low number of anilox rollers can meet the demand of large areas of color blocks for large amounts of ink, but small texts can be crushed. Since it is difficult for the same anilox roller to take into consideration the different requirements of large area color patches and fine texts for the transfer of ink, it is necessary to disassemble this color into two plates for printing, and thus two printing units must be occupied.
In foreign countries, three-color and four-color flexographic printing presses are very common, but in our country, most of the printed products are more complex in design (which has both aesthetic and anti-counterfeiting requirements). Therefore, more colors need to be configured. Group, usually more six to eight colors. If equipped with UV coating system, it will also occupy a group of printing units. The eight-color machine can only have 7 color groups for printing. In addition, some models of flexographic printing presses are twin printing units that are designed as a single unit. When selecting such devices, try not to select odd color groups.
After the above issues are resolved, the specific options for specifications, models, configurations, brands, and agents can be selected.
First, select specifications:
The web width of the flexographic printing press is mainly selected based on the printed products that have already been determined. For narrow flexographic printing presses, 7 inch, 10 inch, 13 inch, 16 inch, 17 inch, 18 inch, 20 inch and many other sizes are usually available. It should be noted that we must not use offset printing to understand the issue of flexo printing. Because the width of the offset press signifies efficiency, the breadth of the width increases, except for increased equipment investment, and the cost of use increases only in equal proportions. The efficiency of the flexographic printing press comes from the printing speed. The main factor in selecting the width of the machine is to meet the dimensional requirements of the printed product.
The width of the flexo press should not be narrow enough. This point is not understood by many people in the country and needs to be explained. With the increase in the width of the flexographic printing presses, the increase in cost during use is not proportional to the increase in investment in machinery and equipment. Taking a round die cutting die as an example, the price is determined by the length of the drum, the size of the circumference (number of teeth) and the total length of the die cut line. When the width is doubled, it is self-evident that the length of the drum is doubled. However, there is a proportional requirement between the length and the diameter of the drum. In order to meet this technical requirement and ensure die-cut quality, it is possible to increase the number of drums. Diameter, in this way, the total length of the circumference and die-cut line should be increased, so the width is doubled, and the price of the die-cutting roller is more than doubled. In addition, the flexographic plate is adhered to the plate cylinder with double-sided adhesive. The operator's meticulous degree and technical level will affect the register in the process of pasting. When the width of the machine is narrow, the plate cylinder is relatively small, the operation error can be controlled within a small range; and when the machine width is wider, the registration error caused by the same level of operation will increase. . Therefore, the use of a narrower flexo printer can easily eliminate the registration error caused by the paste level. In addition, when the volume of printed products is small, the marginal cost that a narrow-format flexo printing machine brings to each batch of products is always lower than that of a wide-width machine.
In short, the principle of choosing the width of the flexographic printing press is: In the range of the allowable size of the printing product, the application is good, and do not blindly pursue widening. The benefits of a narrow format flexo press are, first of all, less investment, followed by the lower cost of the platen, printing plate, sticker glue, and die cutting tools during use. Of course, the narrowness mentioned here is relatively speaking, it is the first consideration for the printing products.
Second, choose the model
Well-known brands of flexographic printing presses are usually available in the same size, there are several different models or series to choose from, there is a wide range of printing products, machine automation, price and many other differences. The basic principle of choice is practicality. In foreign countries, some of the most basic and practical models are the most popular. In China, many customers tend to pursue unrealistic so-called one-step principles and have entered the blind pursuit of high-grade errors, which should attract attention.
Third, choose the configuration
The greatest feature of flexographic printing presses is that many additional functions can be added by adding related configurations. Understanding the functions and uses of some major configurations is very important for the rational purchase of flexographic printers.
Machine configuration is usually divided into standard configuration and selective configuration.
(-)Standard configuration
The standard configuration of a flexo press should generally include:
1. Unwinding device
The maximum unwinding diameter of the unwinding device is generally 40 inches and also 48 inches or 60 inches. The commonly used gas lift mandrels are available in 3, 6 and 12 inch options. When the maximum unwinding diameter is under 48 inches, a 3-inch or 6-inch spindle can be selected; when the maximum unwinding diameter is 48 inches or more, a 6-inch or 12-inch spindle can be selected; if it is mainly used When printing over 200g/m2 paper, it is recommended to use a 6-inch or longer spindle, a 3-inch spindle, and a 6-inch spindle, so that a 3-inch and 6-inch core can be accommodated. Paper roll. The large-diameter unwinding device can also be equipped with a shaftless type.
The unwinding device not only contains a tension control system, but also a splicing table and an electronic correcting device. When selecting the correcting device, note that when printing opaque materials, photoelectrically corrective control heads can be used. When printing transparent plastic films, ultrasonically induced corrective control heads should be used.
2. Printing unit
The number of printing color groups is determined according to the customer's requirements. The relatively mature design of the printing press has a second-level tension control system in the printing part. The tension measurement roller and the floating tension roller make the printing material in the printing process. Keep a constant tension.
The ability to quickly change jobs affects print production efficiency. Therefore, there should be a quick change of ink system, which can quickly replace the anilox roller, transfer roller, and can quickly change the impression roller.
Due to the different design of the main power transmission system, some models use a 360° adjustable gear box and can achieve 360° radial register adjustment; some models can only achieve phase adjustment within a small range. These two design methods do not affect the accuracy of the registration of the machine, only affect the ease of operation when replacing a new job.
There are 3 ways to register the printing process, namely manual register, electric register and automatic register. The models that do not have a 360° adjustable gearbox can only be adjusted manually, and models with a 360° adjustable gearbox can achieve electrical registration and can be fitted with an automatic register system.
3. Drying system
In general, there are two options, hot air drying and infrared drying. The most common and effective drying method is hot air drying.
4. Die cutting unit
There are usually 3 standard die-cutting stations and 4 die-cutting stations for indentation, embossing, die-cutting, slitting and cross-cutting.
5. Scrap recycling
Used to roll away the waste edge after die cutting. The general rewinding diameter is 24 inches, using a 3 inch gas rising mandrel, and can be equipped with a second waste scrap reel.
6. Winding unit
The general reel diameter will be less than the unwinding diameter, typically 30 inches or 40 inches, and a second set of second rewinding devices may also be added in addition to the standard configuration. If printing adhesive products, double winding is always available. The selection of the mandrel can refer to the section “Unreeling Device†in this article and the process requirements of the printing business. Few people need a winding diameter of more than 40 inches, so a 3-inch mandrel is the most common configuration.
(B) selective configuration
Since flexographic printers are known for their comprehensive processing capabilities, many additional devices can be added to the machine to perform special functions. Common selective configurations include:
1. Non-stop receiving unit
In order to avoid frequent paper change when printing thick paper, an optional non-stop coupling device can be selected to achieve continuous operation, thereby reducing the number of man-hours due to frequent roll change and paper waste due to frequent downtime. When the receiving mode of the printing material is the rewinding mode, after the non-stop receiving device is used, the non-stop rewinding unit needs to be installed.
The non-stop continuation unit usually uses a 60-inch unwinding diameter or 72-inch