Common problems and solutions of the hottest packa

Common problems and solutions of packaging offset printing characteristic technology of packaging offset printing

② from the perspective of overprint accuracy, due to the small deformation of the paper at the mouth edge and the large deformation of the paper at the trailing edge, the side with high overprint requirements on the original should be used as the mouth edge

③ from the perspective of saving paper, because the 1cm wide position of its mouth edge cannot be printed, sometimes the paper size is very tight, and it is necessary to make full use of this part of the white edge, then the white edge over the finished product or the tongue edge of the paste box should be used as its mouth edge

④ from the perspective of post press processing, the selection of its mouth edge should be conducive to die cutting processing

how to determine the width of the mouth edge of the printing plate when loading

during plate loading, the distance between the image of the original plate and the mouth edge of the printing plate is required to be within a certain range. Suppose that the distance between the image on the original plate and the mouth edge of the printing plate is C, the distance between the image on the original plate and the mouth edge of the paper is a, and the distance between the mouth edge of the paper and the mouth edge of the printing additive is tested according to the standards of the American Society for testing materials, and the distance between the mouth edge of the test plate is B, then there is c=a+b. The size of B is determined by the position of the printing plate cylinder relative to the embossing cylinder and the number of teeth and papers held by the front gauge. The influence of adjusting the front gauge on B is very small. The position adjustment of the printing plate cylinder relative to the embossing cylinder of different machines is different, generally about 5cm

when C has been determined, adjusting the size of B can change the front and back position of the printed image on the paper, commonly known as "borrowing roller". However, if you need to rely on the "borrowing drum" to adjust the position of the image on the paper during printing, it will obviously affect the production efficiency. It is more reasonable to choose a roughly centered B0 value for a certain type of printer. If you want the image to be printed on the paper at a distance from its mouth edge, then determine the distance C from the image to its mouth edge of the printing plate when printing according to c=a + B0. Every time we use this method to determine the position of the original plate relative to the mouth edge of the printing plate when printing, there is no need to "borrow the drum" when printing. If there is a corner line on the original, it is usually used as a reference to determine the distance between the original and the mouth edge of the printing plate

what is a printing positioning system

from the original to the printed matter, it needs to be separated, made up and copied. Plate printing, printing and other production processes In order to ensure that the color separation image can be overprinted accurately in the quickest way in the production of each process, the matching of the positioning pin and the positioning hole can be used to achieve the purpose through a series of operations. This system is called the printing positioning system. Since desktop system is widely used for layout making, which can automatically output accurate color separation negatives, the positioning system is mainly used in the process of plate printing and printing

what is the composition of the positioning system

the positioning system is mainly composed of printing plates. The negative punching machine is composed of a locating pin and a locating pin on the plate cylinder

what are the benefits of using a positioning system

① the time of installing and adjusting the version is greatly shortened. If you can reasonably arrange the position of the original relative to the printing plate when printing With the correct use of the positioning system, the printing machine can achieve the purpose of registration basically without adjusting the version between the color groups, which greatly improves the production efficiency

② the printing plate no longer needs to be pulled repeatedly, which reduces the inaccurate overprint caused by the stretching deformation of the printing plate and improves the printing quality of the product

how to use the positioning system correctly

at present, the multicolor printing and printing positioning system is adopted in China, and its correct use method is as follows:

① cut the polyester film base, the width should be less than the distance between the image on the original plate and the mouth of the printing plate, and punch the polyester film base with a punch

② take the perforated edge of the polyester film base as the benchmark of the mouth edge of the printing plate, and take the oblong hole in the middle of the polyester film base as the center line of the printing plate, and fix the negative of the first color plate on the film base. Note that the film base should be attached to the non film surface of the negative

③ put the polyester film base of the first color version with fixed number on the locating pin, and align the negative of the second color version with the negative of the first color version At the same time, put the second polyester film base on the positioning pin, and fix the negative of the second color plate and the second polyester film base together when the negative of the second and first color plates are aligned. Process the remaining negatives of other color plates by processing the negatives of the second color plate

④ punch holes for each printing plate to be exposed to the sun, put the negative film and the positioning hole of the printing plate that are characterized and maintained by the gold assay spring fatigue testing machine of each color plate into alignment with the positioning pin, and then print the plate

⑤ when loading the plate, first make the plate clamp at the mouth of the plate cylinder of each unit retreat to the same reference position, hang the two U-shaped holes on the plate on the locating pin, and make the U-shaped holes closely connected with the locating pin Then tighten the version clip at the trailing edge first, and then tighten the version clip at the mouth

what are the requirements for exposure light source for drying PS version

① the spectrum of the light source of the plate printer should be consistent with that of the PS plate photosensitizer. The photosensitive spectrum of PS version is about 350-450nm, and the light source is required to have a high-energy peak in this wavelength range to shorten the exposure time and achieve good exposure effect

② the illuminance of the light source should be uniform. The illuminance of the central and peripheral points of the plate printing table can be detected with an illuminance meter, and the illuminance unevenness of each point of the plate is required to be less than 15%

③ the power of the light source should be about 3000W, and the voltage fluctuation value is required to be less than 10%. Before printing exposure, the light source should be preheated to ensure the stability of light intensity during exposure

how to determine the exposure time of PS version

the test method is as follows: select the transmission gray scale with a continuous density adjustment level difference of 0.15 and the Bruner or other similar test strips with positive dots and thin lines, use two kinds of test strips to gradually increase the exposure time on the PS plate for exposure, record the corresponding exposure time of each piece, observe with a magnifying glass after development, and check each test strip exposed, The exposure time corresponding to the qualified test strip can be used as the normal printing time. When drying ordinary eye-catching products, the first 4 levels of the gray scale are required to be dried out; 1% 6 points are exposed to the sun, and 2% points are neat; eleven μ M-wide thin line reserved, 8 μ The thin thread with a width of M is exposed to the sun

how to adjust the exposure time of PS version according to specific conditions

① there are no dots, only thick text. Lines and field originals can increase the exposure time and dry out small dirt spots and dirt marks to reduce the time of dirt removal

② if the negative is stored for too long, the blank part turns yellow, or after manual patchwork, there are two or three layers of blank film base superimposed together, which can slightly increase the exposure time; If the density of the field part is not high enough, the exposure time can be reduced

③ the pressure of the proofing machine is less than that of the printing machine, so the increase of the proofing point is less than that of the printing point, so the exposure time of the proofing plate should be less than that of the printing plate. Generally, 0.5% of the points of the proofing version are exposed and 1% of the points are retained

why do I need to pump air when printing and exposing

take the production of positive PS plate as an example. When printing, if the film surface of the negative is not closely connected with the photosensitive coating of PS plate There is a gap in the middle, and light will be slanted from the edge of the blank part of the negative to the photosensitive coating directly below the graphic part, causing the edge of the graphic part to see light and decompose Make the image faint Dots become smaller, and dots and thin lines are lost

because one side of the printing frame is transparent glass, and the other side is a rubber pad When the vacuum pump pulls out the air in the print frame, the air pressure inside is low, and the rubber pad will release the PS version under the action of the external atmospheric pressure. The original negative is against the glass and closely connected

nowadays, whether at home or abroad, packaging offset printing has been very active. With the development of economy and the improvement of people's living standards, people have an increasing demand for packaging, and the requirements for packaging are also higher and higher. On the one hand, the demand for offset printing in the packaging market has increased; On the other hand, the development of offset printing technology also makes it more suitable for packaging printing

in addition to the characteristics of general printing, packaging printing also has a wide range of printing, usually requiring spot color printing, anti-counterfeiting printing, hot stamping and polishing. The packaging materials of paper products are thick, and the specifications of printed products change a lot. Many printed products need die cutting, indentation, windowing and numbering

in order to meet these needs of packaging printing, both sheet fed offset printing machines and web offset printing machines have many innovations and breakthroughs in technology. Many connecting devices that were only used in web offset printing machines in the past have been applied in sheet fed offset printing machines

1. Corona treatment technology

in order to solve the problem of poor surface adhesion of special materials (such as plastic sheets, etc.), surface treatment can be carried out first. For example, gaobao rapida 74, rapida

105 and other models install a corona unit in front of the first printing unit to conduct high-voltage discharge treatment on the surface of special materials to improve the adhesion of ink on the surface of materials, so as to improve the quality and speed of printing

2. The film covering device

roland

700 can film the printing materials before the start of color printing. The first printing unit prints viscose on the substrate, and the rubber drum of the second printing unit is wrapped with film. When the printing material passes, the corresponding part is covered with film. This process is completed at room temperature, completely avoiding the influence of temperature on printing materials such as film

3. Cold hot stamping system

configuration of line cold hot stamping sheet is an important feature of packaging offset printing machine. Wire cold stamping is an innovative technology first introduced and patented by MAN Roland, and has won the pia/gatf

INTERTECH Technology Award in 2006. The line cold hot stamping sheet can be installed at any position of the offset press according to the cold hot stamping position, and the original unit can print normally without hot stamping; Printing and hot stamping can be completed at one time, which can realize accurate overprint; It can also be reprinted on aluminum foil to form arbitrary graphics and special color effects

4. Corrugated board printing

in order to adapt to the characteristics of thick packaging materials, many sheet fed offset printing machines have been improved, such as the use of large paper transfer rollers, large impression rollers, seven o'clock arrangement of rollers, etc., the maximum thickness of the printing materials can reach 1.6mm, and many offset printing machines have added the function of direct printing corrugated board. Because printing pictures and texts directly on corrugated board requires less printing pressure and is more difficult, in the past, only flexographic printing machines can print, or offset printing machines can print face paper first and then paste it on corrugated board, which can be completed through two processes. Now the offset press has the function of printing corrugated board directly, which not only reduces the process, but also greatly improves the efficiency

offset printing

uv offset printing can not only enhance the decoration of printed matter