1. Working principle of flat screen printing machine.
1 working cycle program of flat screen printing machine. Take the flat screen type flat-type monochrome semi-automatic hand surface screen printing machine as an example. Its working cycle is: feeding piece → positioning → falling plate → falling to the ink plate, rising back to the ink plate → scraping stroke → rising to ink Plate → return to the ink board → lift the plate → return ink stroke → release the positioning → receive the piece.
In the continuous cycle action, as long as the function can be realized, the time occupied by each action should be as short as possible to shorten the synchronization of each work cycle and improve work efficiency.
3 embossed lines. In the printing process, the ink is pressed against the ink plate and the screen printing plate, so that the screen printing plate forms a contact line with the substrate, which is called an embossing line. This line is at the edge of the squeegee, and numerous embossed lines form the printed surface. Achieving an ideal embossing line is difficult because the printing stroke is a dynamic process.
3 screen printing machine works. Taking the commonly used hand-screen screen printing machine as an example, the working principle of the screen printing machine can be described as follows: the transmission mechanism transmits power, and the squeegee plate squeezes the ink and the screen printing plate during the movement to make the screen The printing plate and the substrate form an embossing line. Since the screen has the tensions N1 and N2, the force F2 is generated on the squeegee plate, and the resilience makes the screen printing plate not contact with the substrate except the embossing line. Under the action of the pressing force F1 of the squeegee, it is leaked from the moving nip to the substrate through the mesh. During the printing process, the screen printing plate and the squeegee plate are moved relative to each other, and the squeezing force F1 and the resilience force F2 are also synchronously moved. Under the action of the resilience force, the screen is timely returned to contact with the substrate, so as to avoid The blot is dirty. That is, the screen is constantly in the process of deformation and rebound during the printing process. After the squeegee finishes unidirectional printing, it is separated from the substrate together with the screen printing plate, and at the same time, returning ink is returned, that is, a printing cycle is completed. The distance between the top of the substrate and the opposite side of the screen printing plate after ink return is called the same plate spacing or mesh distance, and should generally be 2 to 5 mm. When hand-printed, the manipulation and proficiency of the operator directly affects the formation of the embossed line. In practice, silk screen workers have accumulated a lot of valuable experience, which can be summarized as six points, that is, to ensure linearity, uniformity, equiangularity, pressure equalization, centering and vertical edge in the movement of the squeegee. That is to say, when printing, the squeegee should be straight forward, not swaying from side to side; not slow before and after fast, slow or slow before and after; the angle of inclination to the ink board should remain unchanged, pay special attention to gram
The common problem is that the printing angle is gradually increased; the printing pressure should be kept uniform; keep the distance between the squeegee and the inside of the frame equal; the ink plate is perpendicular to the frame.
2. The working principle of flat screen curved screen printing machine. Flat screen curved screen printing is a screen printing on a flat or conical surface with a flat screen.
Under certain conditions, screens such as elliptical surfaces, drum surfaces, and curved surfaces can also be screen printed.
The dry mesh curved screen printing machine is a machine that prints the above curved surface using a flat screen.
The working principle of the flat screen printing machine a-roller bearing b-shaft will support c-inlaid bearing. During printing, the flat screen plate moves with the substrate while the squeegee is stationary. The flat screen printing plate is clamped on the frame by a flat screen curved screen printing machine with a uniform motion, and the substrate placed on the supporting device rotates due to the friction of the screen. The line speed of the curved substrate at the embossing line is consistent with the moving speed of the flat screen printing plate.
In theory, the embossed line should be at the highest busbar of the curved substrate to facilitate the increase of the off-grid angle and ensure the printing quality. For the convenience of adjustment, the squeegee generally adopts a 60°±15° apex angle, which is required to be adjusted for the vertical degree and the upper and lower dimensions. Adjusting to vertical is to ensure that the cutting edge line does not produce lateral displacement when adjusting up and down, always aiming at the highest one of the bus bars A; the squeegee with a apex angle of 60 ° ± 15 ° is to ensure the inclination of the squeegee after vertical installation α. In the actual adjustment, in order to ensure that the flat screen printing plate and the curved surface substrate are separated in time, the embossing line can be appropriately biased a little ahead, especially when the diameter of the substrate is large, the embossing line must be biased to the front, and the supporting device for the curved surface printing is Various forms of special equipment are designed and manufactured by users according to product requirements.
The curved surface of the cylindrical container or the conical container can be printed by two pairs of roller bearings, the cover of the cover type and the cup type having a length to diameter ratio of less than 1.5, and the flexible hollow container can be supported by the inflator. The elliptical surface is approximately a part of the cylindrical surface and can be supported by a cylindrical inlay. The principle of printing on the surface of a cone is basically the same as the principle of printing on the surface of a cylinder, the difference being the shape of the screen printing plate and the form of movement of the screen printing plate. When making a screen printing plate for the surface printing of a cone, first draw out the developed surface of the cone surface, and determine the center of the fan shape according to the developed image, and then select the appropriate mesh frame to make the screen printing plate. On the efgh that can completely accommodate the fan-shaped abed, a plate conforming to the fan shape is produced. Fix the right angle rod on the efgh and install it as a fan-shaped version with o as the axis. Then, like the surface printing of the cylinder, the substrate is supported by four rollers under the plate, the blade is fixed, and the frame is moved in a fan shape, and the surface of the cone plate is printed by pressing the blade. During printing, the conical printing is in line contact with the screen printing plate under a certain blade pressure; when the screen printing plate moves horizontally around the axis of the fan-shaped development view, the substrate is synchronously rotated on the supporting device. Movement; the ink is printed on the surface of the substrate after being pressed by the squeegee to complete the printing.
Take the commonly used hand-screen screen printing machine as an example, which can be used for screen printing.
The working principle of the machine is as follows: the power is transmitted through the transmission mechanism, so that the squeegee presses the ink and the screen printing plate during the movement to make the screen printing plate
Digital printing is a brand-new printing production method, which can realize the real-time transmission of digital files and print output according to customers' requirements. The whole process runs through digitalization and networking, so the advantages of digital printing are concentrated in its excellent production process. The process, that is, the realization of information in the process of transition from computer to print, is digital, and the media must be in any intermediary, or even without printing. Below we analyze the digital press and its working principle.
First, digital printing machine and its classification
The digital press is actually a high-speed digital color hard copy output machine that directly accepts digital signals (digital pages) transmitted from the prepress processing system and converts them into black and white/color hard copies (printed matter).
There are many varieties of digital printing machines, which can be classified mainly from four aspects: printing mode, printing form, printing working principle and printing quantity. This article has two types of digital printing machines: layout and non-plate type for comparative analysis.
The digital press has the following features:
◆ Suitable for printing within 5000 copies
◆Flexible and suitable for printing that requires quick completion in a short time. This is because the film and plate are not needed in the printing process, so even if you need to change the graphic before printing, it can be easily completed.
◆The job exchange, the customer can go to the machine room to get 5 to 10 copies, so that the completion time from the receipt to the print is shortened.
◆ Easy to operate.
Second, no version of digital printing machine
The common feature of the non-printing digital printing is that it is possible to print only one sheet, so that variable information printing can be realized, which is simply impossible to realize in conventional printing. The existing plateless printing machines can be classified into several types such as an electrophotographic method and an inkjet method. Mainly using solid toners, but also using liquid toners, such as Indigo's E-print and Ominius series presses, which is a technology that fundamentally changes the traditional printing concept, although its development has not yet reached the traditional printing office. It has the scale, but it must have a bright future.
1. Electrophotographic (solid toner) printing machine. The electrophotographic method is to charge the photoreceptor (OPC) as a whole, and then perform image exposure with a laser to form an electrostatic latent image, and develop the toner to transfer the toner to the paper.
The digital printing machine with solid-state toner type is generally controlled by a RIP (raster image processor) image information control laser, the laser beam emitted by the laser is directed to the organic semiconductor filter cartridge to image, and then the fine toner Adsorbed thereon, a toner image is formed on the drum, and after printing, the toner is fixed on the paper by heating.
Laser scanning method is used to form an electrostatic latent image on the photoconductor, and then the coulombic force generated between the charged toner (the opposite polarity of the electrostatic latent image) and the electrostatic latent image is used for development, and finally the toner is used. Printing can be done by transferring the image to the substrate.
The characteristics of such imaging system digital presses are as follows:
◆It can be imaged on plain paper, and the coloring agent is made of pigment, which can realize black and white or color printing;
◆The number of tone can realize multiple values within a certain range;
◆The comprehensive quality can reach the mid-range offset level;
◆ Printing speed can reach dozens/100 sheets per minute;
◆The price is higher than other imaging systems, and the price depends on the color price.
2. Electrophotographic (liquid toner) printing press. The digital printing machine of the liquid toner type generally adopts the process of receiving the electronic pre-printing system through the network or the magnetic medium to perform the RIP processing on the data, and then forming the optical grid point on the imaging plate by using the laser imaging system. The image, the image is negatively charged, and the inkjet device ejects the positively charged electronic ink onto the imaging plate, rapidly forms an ink image, and then transfers it onto the rubber cloth, and forms the ink 100 on the rubber cloth by imprinting and static electricity. Transfer to paper or other media.
The characteristics of such imaging system digital presses are as follows:
◆It can realize black and white and color printing;
◆High resolution, fast printing speed, close to the printing speed of traditional A3 format offset printing machine;
◆Comprehensive quality can reach medium and high grade offset printing level;
◆Diversity of substrates, almost any new material can be printed;
◆ Low operating costs.
3. Electrical cohesion. Electrical agglomeration imaging is a new imaging method with very high imaging speed. The formation time of each pixel is about 4us. The imaging method adopts the principle of electrochemical condensation, which causes the ink to coagulate through the electrochemical reaction between the electrodes. An aqueous reaction ink is converted from a liquid state to a solid state, thereby fixing an image area formed on the surface of the image forming roller, and the ink which does not undergo an electrochemical reaction is still in a liquid state, constitutes a non-image area, and then can be non-image by a mechanical action of a squeegee The liquid ink in the image area is removed, leaving only the fixing ink in the image area. Finally, the ink fixed on the image forming roller can be transferred to the substrate by the action of pressure, thereby realizing image recording and completing the printing process.
Although the current condensing imaging system can only achieve a resolution of 400 dpi, each pixel has a tone of up to 256 steps.
Reproducibility, it can be seen that it still has a high quality, this imaging method has no special requirements for the substrate, and the graphic part of the fixed ink can be transferred to the ordinary substrate.
Digital imaging machines of this type of imaging system have the following characteristics:
◆ can be imaged on plain paper, can use pigments;
◆ The tone value can achieve multiple values in a wide range;
◆The comprehensive quality reaches the mid-range offset level;
◆ Speed can reach hundreds of sheets per minute;
◆ The price is between inkjet imaging and electrostatic imaging systems.
4. Inkjet method. Inkjet imaging is the process of ejecting ink from a fine nozzle onto a substrate at a certain speed, and finally reproducing the ink image through the interaction of the ink with the substrate. Inkjet digital printing generally requires that the solvent and water in the ink can quickly penetrate into the substrate to ensure sufficient drying speed, and the coloring agent is required to be high. To ensure good printing quality, the ink is required to match the substrate.
The inkjet imaging system has the following features:
◆ It is necessary to use a printing material that matches the ink, and the coloring agent has been developed by the pigment of the dye;
◆ The tone can achieve multiple values within a limited range;
◆In addition to the direct digital color proofing system of inkjet imaging mode, its comprehensive quality can only reach the low-grade offset printing level;
◆Speed up to 2000 sheets / hour;
◆The price is low.
5. Magnetic recording method. The digital printing machine adopting the magnetic recording method adopts the same recording principle as the magnetic tape recording technology, that is, the magnetic material relying on the magnetic material is aligned to form a magnetic latent image under the action of an external magnetic field, and then the magnetic toner and the magnetic latent image are utilized. The interaction between the magnetic forces, the development process, and finally the transfer of the magnetic toner onto the substrate to complete the printing process. This method is mainly suitable for black and white printing, and it is difficult to achieve color printing.
At the Drupa2000 exhibition, Xeikon and Nipson launched a magnetic recording imaging system with a resolution of 480 dpi, followed by Nipson.
Introducing a digital printing system for magnetic recording systems, which have the following characteristics:
◆It can be imaged on ordinary substrates, and the pigments are mostly black and white;
◆ The tone can realize multiple values in a narrow range;
◆Comprehensive quality is equivalent to low-grade offset printing, suitable for black and white text or line printing;
◆The speed can reach hundreds of sheets/min;
◆The price is low.
Third, there is a version of digital printing machine
A digital printing press is a printing press that mounts an exposure device on a printing press so that it can directly expose the printing plate on the printing cylinder. Unlike a non-printing digital printing press, a printing plate is required, which can be The types of plates are divided into different modes such as no development and use of the plate solution. Generally, there are two types of digital printing machines that can be divided into two categories: one is to mount an exposure head on a conventional printing plate cylinder; the other is a newly developed new printing machine.
1. There is development - there is water (special model). The use of developed - water-based digital printing press belongs to the first category, its plate can be directly imaged after being mounted on the drum, the upper and lower versions of the printing system are exposed and developed, the whole process of positioning will be It is completed by digital automatic control, and after water-based offset printing, the printing quality can reach the level of traditional offset printing.
The brush system has the following features:
◆ Can print on a variety of substrates;
◆Comprehensive quality makes the printing speed and price close to the traditional offset printing level.
2. No development. This type of machine requires a plate material, and the common use of waterless offset printing plate is mainly to record the image directly on the printing plate of the printing machine by using pre-press digital data. The process of developing is not required, and the waiting time for printing is shortened. The printing speed of such a printing machine is relatively fast and the resolution is quite high.
3. Rewritable and sleeve type (dedicated models). The rewritable version of the digital press no longer uses a disposable plate, but instead installs a metal tube of special material on the plate cylinder jacket, a substance on a transfer belt consisting of a thin layer of polymer and a transfer layer. Transfer to this special metal sleeve, make the sleeve have oleophilic and hydrophilic printing characteristics and then print. After printing, wash the sleeve with cleaning solution to prepare for the next imaging. In the printing process, it is necessary to receive digital data from the prepress system, image the surface of the drum with a transfer belt, and then transfer it to the printing surface through the laser transfer belt, and the transferred pixels form a graphic area.
The telescopic digital printing machine mainly adopts ion imaging printing technology, also known as ion charge deposition printing, which transfers the electric charge by special magnetic toner to generate images, which is suitable for monochrome or spot color printing. Currently, this type of digital printing is adopted. Less printing presses,
It adopts laser-induced copper deposition method, which is suitable for printing invoices, reports, manuals, forms, etc. It can also realize variable printing, and is generally used for special printing such as bills, labels, checks, etc.
4. No development - there is water (conventional model). This type of printing press also belongs to the first category.
In general, the printing methods are different depending on the substrate, and the following materials are available:
1, paper: This is the most common printing, the new era of printing is printed on paper or paper and similar materials.
2, plastic printing: more common in the printing of packaging bags.
3. Special materials: refers to printing on glass, metal, wood and other materials.
The types of printing presses are:
1. Offset printing machine: generally used in lithographic printing, mostly used for printing on four-color paper.
2, gravure printing: refers to the use of gravure (usually referred to as steel plate) printing, mostly used for plastic printing.
3, flexographic printing: refers to the use of flexible material version (generally referred to as resin plate, etc.) printing, which is actually letterpress printing, mostly used for large-scale self-adhesive trademark printing.
4, screen printing: can be printed on a variety of materials (especially non-planar materials), mostly used for gifts, containers and other printing.
Second, the structure and principle of sheetfed offset press
With so many presses, in addition to the offset press, other machines are only a general understanding. The offset press is divided into a sheet-fed offset press and a rotary press. A sheetfed offset press means that the printed sheets are printed one by one and tiled into the machine.
Rotary machine refers to a large-scale printing machine that uses paper to print on paper. It is used for printing large batches of books and newspapers.
Both of these printing presses are offset presses, and the principle is the same, except that the way of feeding, transferring, and delivering paper is different. Therefore, let me take the sheet-fed four-color offset press as an example to talk about the structure and principle of the offset press.
1, the transmission part
The so-called transmission is to transfer the movement of the prime mover of the printing press to the printing machine through belts, gears, chains, etc.
In part, the various working parts can be periodically, closely coordinated, and accurately mechanically moved according to the work requirements to complete the printing action. It is equivalent to the bones and joints of our people.
The prime mover of the printing machine is the electric motor. The transmission mode generally has three modes: belt transmission, gear transmission and chain transmission. Among them, the belt drive (with belt drive) has the lowest precision, and the belt drive is used between the prime mover (motor) and the next driven wheel of the general printing machine; the gear transmission has the highest precision, and the paper conveys and inks in the side wall of the printing machine. The roller set, the water roller set and the drum are generally driven by gears; the chain drive (chain drive) is used for the parts with high precision requirements, but it is not convenient to use the gear transmission, and is generally used for the paper feeding part and the delivery part.
We know that the printing precision is extremely high. We require the error of the graphic on the printed matter to be a few filaments (1 wire = 0.01 mm). The accuracy of the printing part is determined by the accuracy of the printing part, and the accuracy of the transmission part depends on Machining accuracy and metal material. Only the high precision of processing is not enough. Many printing machines and new machines are still unsatisfactory, but they can't be used for a while, because of the metal material. In today's world, the printing press manufacturing industry is a benchmark for the level of national machinery manufacturing. So far in our country, the import of famous brand printing presses is still tax-free, but even if the tax is tax-free, the price is still very expensive, because of the level of our national machinery manufacturing industry, which often makes the industry
People are heartbroken.
2. Paper feeding, delivery and delivery
The paper to be printed is placed on the paper table at the front of the printing machine (commonly known as the paper feeding table, note 1 in Figure 2). The printing machine automatically separates the paper into single sheets and loses them one by one.
It is sent to the rule parts (Note 5 in Figure 2). This part is called the paper feeding part (Heidelberg calls it Feida); the paper is positioned at the rule parts, the paper
Zhang wants to "pause" here (this is done in an instant, the Heidelberg printing press used by the New Age Printing, printing speed of 15,200 sheets / hour
, equivalent to 4.22 sheets / sec.), then grab the paper at the front end of the paper by the fangs and feed it into the inside of the press. The structure is the same (the ink is different).
Color group printing, this process is called the paper transfer process. The paper transfer process is actually a row of dentitions on each of the rollers that cooperate with each other.
The process of mutual transfer. Finally, the already printed paper is placed neatly on the delivery deck, which is called the delivery section.
The so-called cavities are a row of periodically opened and closed steel teeth placed horizontally on the cylinder or chain of the printing press. Of course, its opening and closing is
Need to be very accurate. The paper starts from being separated into a single sheet, and until the final printing is completed, it is placed on the delivery table, except the embossed, the whole process
The middle is "floating" (by blowing and other institutions), it will not produce friction with other mechanisms inside the machine, so as to avoid the smudging of the printed matter, which is generally
The press can't do it.
3, the rules section
- rules, bleeding, bite, front gauge, side gauge (by the body, outside),
Core size, large set, self-turning, large rollover
Even those who have not done printing, but who have done print design, know that
The rule line should be considered when designing the brush.
The rule line form, a complete rule line, with inner rule and outer rule. We cut the inner rule line (see Figure 4
Word line), there is no rule line on the finished print, we get a clean print.
However, the graphic on the printed documents we designed can't be used only for the inner rule, because the cut after printing is error (included here)
The error of the knife when cutting, and the error caused by the pumping up due to printing), we can hardly guarantee that it will be cut across the board, just like on the edge of the picture, such as
If the knife is cut across the picture, it will leave a white line, which will damage the beauty of the printed matter. So we have to do the graphics (generally just the map)
The outer ruled lines are aligned, and the part that exceeds the inner ruled line is called bleeding. Habitually, the bleeding is 3mm, so the distance between the inner ruled line and the outer ruled line is one.
It is also 3mm.
The role of the rule line is not only for cutting, but also the main role of printing. In color printing, blue (C), red (M), yellow (Y
), black (K) four-block version has a rule line, we have to make these four color rule lines completely overlap together, such prints will be bright
Qualified, this is the "registration" of printing. As we mentioned earlier, a piece of paper, fed into the machine by Feida, is transferred many times and printed.
Four-color graphics, so the accuracy of this transfer is very high. Many printing equipments themselves have large errors, and their correction is also very troublesome.
If the brush staff lacks responsibility, the error is even greater. The printed matter that the user gets is the finished product, and the rule line is not seen. In addition, due to the naked eye vision of the person
Discrimination accuracy is limited, you will not feel that the graphics are not registered. However, inaccurate prints will give people a false, foggy feeling.
Of course, some printed matter printed a single eyelid person into a double eyelid, it is not a virtual, foggy feeling, for the new era of printing
That is waste, but for our printing press, even if the first proof after the version is published, this will not happen.
The paper is fed to the ruled parts and will be positioned. The paper will be “paused” here, and then the paper will be held by the fangs.
Inside the press. Why is paper positioned here? This is to make the paper enter the machine in the same state and be printed, so that the front and back print
The printed sheet, the text is in a fixed position on the paper. Imagine that even if the printer passed the paper accurately, we got a clear picture.
The prints, but the prints on the front and back are not in one position, we cut them in a cut, so that the uneven prints are cut out.
Don't you mess around?
The rules organization consists of a front gauge and two left and right side gauges. When the machine is running, the front gauge and one side gauge move, and the other side gauge is closed. before
The gauge is a row of fanned metal flaps in front of the first row of cavities. The paper arrives at the front gauge and is blocked. At this time, a side gauge motion is opened, and the paper is opened.
Pull the paper to the left (or to the right) to bring the paper to a fixed position, and the paper is positioned.
We stood in front of the printing machine and faced the machine. We found that the machine's common operating buttons and operating handles were mostly on the left side of the machine.
The operator is usually active on the left side of the machine, so the left side is called the body, the left rule is called the body rule, and the other side is called the outside and the outside.
rule. The paper is blocked by the front gauge and the side of the fangs is called the mouth. (Relying on the rules, relying on external rules often let some friends faint, we will paper
Put it on, bite on the top, the left side is the body, the right side is the outer side. )
When printing a single-sided print, we can use the rule of the body or the outer rule. As long as the print is made, the cutter presses the print.
After the mouth and side rules are neat and then cut, we can get satisfactory prints. But when you want to print on both sides, you have to change the side when printing the second side.
regulation. This is because we have the error when cutting the base paper into the printing opening surface (commonly known as cutting) before printing.
For example, we want to print a hanging flag for the store. The finished product size is 420×570mm, which is a large 4 open, large 4K base paper size.
It is 440 × 592mm, and the finished product size should be smaller than the original paper size. Because we have already mentioned before, the printing press needs a bite and a rule line.
Need light edge after printing, Heidelberg bite generally needs 9mm, the tip light edge needs 3mm, so the upper and lower should stay 9mm+3mm=12mm; left
The right rule line is 6mm each, so the left and right should also leave 6mm × 2 = 12mm. So, when you find the paper in the "Common Paper Startup Schedule"
After opening the size, the size of the inner rule line after the imposition of the printed matter (commonly known as the core size) should be smaller than the original paper size and 12 mm or less.
Such a 4K flag, we use the sky as a bite (print is placed, the top is called "day", the bottom is called "ground"), when printing the front, if we
With the body (left) as the rule, then, no matter how much the error of our cutting, we get all the printed sheets, the front picture is from the bite edge and the left side of the paper
The distance between the edges is always the same. When printing the back side, we turn the paper around and still use the sky as the bite. The original left side is here.
On the right side of the back side, in order to align the regular back rule line, we have to use the right side of the back side (outside) as a rule.
For a piece of print, to print two sides, we use two sets of plates to print the front side separately. This is called a large set. There is only one finished product, which is to be printed.
Brushing the back, the big set is easy to understand. When there are multiple finished products, it is necessary to consider the correspondence between the front and back of each printed matter.
5)), in particular, do not appear printed reversed image of the finished product.
Some prints have a small layout. We can put it on the back of a printed sheet. As long as we match the requirements, we can
To print the front side with a set of plates, this is called a self-reversing version. When we printed the first time, turn the paper left and right and change the side gauge
We print it again, cut it in the middle of the post, and we got two finished products.
If multiple prints are printed on a set of plates, pay attention to the correspondence between the prints.
There is also a case where the finished product is narrow and long, we can't make it to the left and right, then we put it into the front and back.
At this time, the side gauges are unchanged. After printing the first pass, we turn the paper back and forth, change the bite, and print the second time. This is called big
Rollover (commonly known as 驴 rolling), large rollover is a form of self-turning, but also shoulder-to-shoulder, tail-to-tail, head-to-head.
4, the water delivery part
- What is water, ink emulsification, dirty version, water bar?
What needs to be explained here is:
First: the water here is not the water of general significance. It is the water of the clean water to which the fountain solution is added. The so-called fountain solution is a special type of water.
Learn the solution, according to the raw water quality, add the appropriate amount to adjust the water pH, conductivity, hardness and so on. General printing companies do not use Run
The plate solution (because the dampening solution is expensive), it is not to detect the pH value, conductivity, hardness, but to use lithopone or a cheaper dampening solution.
Second: the water roller group has so many rollers, and the texture is different, not only to transfer water, but also need these water rollers to grind in the middle.
The water (the middle part of the roller is tilted left and right) makes the water particles reaching the plate roll extremely small.
Third: the water of the printing press is pumped into a cabinet for circulation, and then returned to the sink. This cabinet has a compressor and filter
There are two main functions: cooling and filtration. The printing machine runs at high speed, between water roller and water roller, between ink roller and ink roller, water roller ink roller and plate roller
The PS plate on the cylinder relies on friction and grinding to work, so a large amount of heat is inevitably generated. A considerable part of this heat is taken away by the cooling water.
Fourth: Anyone who knows the printing press knows that the water roller of the general printing machine is a rubber roller that is covered with a rubber rubber sleeve for adsorption.
Water and water reaching the PS plate are more uniform. Heidelberg now sells presses that do not use water-based velvet, but a rubber roll made of special texture rubber.
It is called water-free rubberized damp. There is no water gelatin, there are two major benefits: First, more accurate water supply; Second, the printing layout is cleaner. Water-filled fabric
Especially, the new water velvet sleeve that has just been changed will lose hair. Especially when printing on the ground, we often see a white silk thread on the ground. This is water plastic velvet.
The falling fluff is caused by the PS plate.
As can be seen from the above, the offset water and water delivery system is extremely particular, so that the pH, conductivity and hardness of the water are kept within the optimal range.
The particles are extremely small, and the proper temperature is maintained in order to make the water reaching the PS plate as small as possible, and to achieve the purpose of cleaning the plate after the ink is applied (ink-inking)
Balance). In many printing houses, we saw that the PS version on the running press was bright and reflective, indicating that the water was big, and the prints of the water printing.
The picture will make people feel imaginary and foggy. If the water is too large, it will cause the paper to be excessively pumped up or even deformed. Due to the large water, the excess water will be PS
The plate is brought to the ink roller. We know that the printing machine is running at high speed. This part of the water will dissolve with the ink. This is the emulsification of the ink. If the water temperature is controlled.
The system is not good (many presses do not have a water circulation system, some equipment circulation systems are very simple), and the ink is easier to emulsify. After the ink is emulsified, it is printed out
The things that come are also imaginary and foggy. If you print a general book, black and white, the water is slightly larger, but the beautifully printed work is ten thousand.
Maybe you will say that since the water is big, is it a little smaller? It depends on the quality of the printing press. Many printing presses, when the water is open, the water is big, off
A little bit of water is too small, and it is difficult to balance ink. The water is small, the PS version will be stained with ink, and the local dots will be enlarged. This is called
Make a dirty version.
When printing the field and the net, we often find that there is a horizontal bar at a certain distance from the bite. This bar is more than the upper and lower plates.
The color is slightly lighter, this is the water bar. The water bar is because the water roller and plate cylinder of the printing machine are running one week a week, and the PS plate is rolled on the plate.
The tube is not a 360-degree complete package, and there is a part of the gap, so the resulting water bar will be on the printed sheet.
a fixed position,
And the four colors are all in the same position. When printing a monochrome proof, the water bar may not be obvious, but when the four colors are added together, the water bar
More obvious. When printing multi-color superimposed solid or flat nets, the water bar is inevitable, and the three-color overlay is often encountered in printing, but there are very few
Color overlay of the field and peace net (because the four-color overlay is often meaningless, it should also be avoided in the design, replacing it with other similar colors of lesser colors
, small piece of field and peace net for Heidelberg even if the four colors are no problem), two colors superimposed, for most printing machines, even monochrome solid or flat net
It is all trouble.
5, the ink part
- What is paste, twilight, ghost, ink? Why color cast
The ink is the first from the ink tank
The roller is given (this roller is called the ink roller), after passing, grinding, and finally reaching the roller of the ink roller, the ink is applied to the PS plate by the roller of the ink roller.
on. The ink roller of the printing press generally has 1 to 4 rolls, and the Heidelberg printing machine has 4 pieces. The number of rollers of the ink roller and the ink roller is large, so that the ink is very
Good grinding, while the amount of ink stored is also large, to ensure that the printing requires a large amount of ink on the ground, there is enough ink to make the color of the print saturated
One of the major tasks in printing is to make the amount of ink given to the ink roller equal to the amount of ink carried by the printing paper, creating a balance. So give the ink control to the off
important. Under the ink feed roller of the Heidelberg press, there is a set of inking control devices that are automated and controlled in the control center. If you have been to print
Factory, you often see some printing mills on the machine climb up and down to adjust the amount of ink, because their printing machine's ink control is
Manual, relying on experience to adjust. The amount of ink is too small, the prints will be imaginary, and the ink is not enough (the cause of the lack of ink is also the quality of the PS version, system
Version quality, etc.). If the amount of ink is too large, the dots will expand, and even the blanks will be inked. This is called paste.
In some printing presses, the ink of the first color set will be brought to the second color set by the paper, and the second color set ink will be brought to the third color set... thus making the back
The color group is mixed with the color of the front color group. This is called the color. Twilight can distort the color of the print. The color of the enamel is also related to the quality of the ink and the quality of the paper.
When printing the same prints, you will find that what is printed in many printers will be
Below the figure in the middle of the print there will be a shadow corresponding to the figure, which is called ghosting. The reason for the ghosting is that the original design of the print
There is a "window" of light color, and the rest of the layout is in the field with a large amount of ink. When the plate roller is pressed over the "window", there will be ink remaining.
So that the remaining ink leaves a shadow under the "window".
When printing the field and the net, we often find that there is a horizontal bar at a certain distance from the bite. This bar is more than the upper and lower plates.
The color is slightly darker, this is the ink bar. The production of the ink bar is similar to that of the water bar, also because the ink roller and plate cylinder of the printing press are one week a week, periodic.
In operation, the PS plate is not completely wrapped in the 360 degree on the plate cylinder, and there is a part of the gap, so the generated ink bar will be a solid in the printed sheet.
Positioned, and all four colors are in the same position (but generally at a certain distance from the water bar position). When printing a monochrome proof, the ink bar is not
Obvious, but when the four colors are added together, the ink bar is more obvious. When printing multi-color overlays on the ground or flat
In the case of the net, the ink bar is inevitable, but the ink bar of the Heidelberg press is also very slight.
When we see the color distortion of a print, if it is not the negligence of the original school color correction, it is a color cast. Such as portraits on photos
The face is too red...
The reason for the color cast is:
First, the ink is not accurate. Generally, the ink supply of the printing machine is manual, and the inking device is simple, so it is difficult to grasp.
. Second, caused by imposition printing. The inking unit of the printing press actually divides the ink supply roller into a number of areas.
Then determine the amount of ink according to the graphic situation of the corresponding area on the PS plate, if we print imprinted on a set of plates
The printed sheets are red and yellow in the upper part of the 6-12 ink zone, so the red and yellow color groups have a larger amount of ink in this area, and the photos below are also
In the same ink zone, the red and yellow of the photo are inevitably too large. Because it is also ground by the ink roller during the ink transfer process, 5, 4
The red and yellow of the 3 ink zone and the 13th, 14th, and 15th ink zones will also be affected. In the schematic diagram, the picture of the person in the lower right corner is a normal color, 6 to 12 ink areas.
The picture of the character is the most serious, and the pictures of the characters in the 12~17 ink area are slightly biased. Of course, this picture is specially made by me, for the sake of explanation.
The title intentionally exaggerated the color cast phenomenon, the actual printing will not have such a large color cast (I don't dare to assert other printing houses).
Therefore, if the color requirements of the printed matter are high, you should pay attention to the imposition. If it is a book, the color and style of the inner page will be relatively close, but
The cover and the back cover often use a large area of the field. Sometimes, due to the P number and other reasons, in order to save printing costs, the customer will ask for the cover and several
The inner pages are printed on a set of plates. At this time, these inner pages are affected by the color of the front cover and the back cover.
6, the roller part
- Why is it called offset printing?
Water and ink first reach the PS plate. This fixed PS plate is called
Plate cylinder; the rubber cylinder under the plate cylinder, the rubber roller is named after wrapping a piece of rubber on the drum;
Imprint cylinder. The paper is printed between the blanket cylinder and the impression cylinder.
That is to say, the PS version first prints the graphic on the rubber of the blanket cylinder, and the rubber relies on the pressure between it and the impression cylinder to print the graphic.
On the paper between them through. Here the rubber has played the role of transferring graphics. Because it is transferred by rubber, it is called offset printing.
Called transfer printing. We know that the graphic on the PS plate is positive, and the print on the rubber is reversed, and the rubber is printed on the paper and becomes positive.
Why use rubber to transfer? Here the elasticity of the rubber is utilized. Probably in the first half of the last century, when the lithography machine was not
The blanket cylinder, the printing plate is directly in contact with the paper, and the graphic is printed on the paper. An engineer in the United States, in order to make the text printed clearly,
A piece of rubber was attached to the impression cylinder as a liner. When printing, the machine emptied a circle (no paper feed), but the back piece of paper passed.
He found that the graphic pressed on the back of the paper was clearer than the front, so he invented the offset press.
Of course, the rollers of the current offset press are extremely precise, and it is impossible for the printer to easily bind the rubber. Like the new era of printing, even the oak
The selection of the rubber on the leather drum is also extremely elegant.
Generally, the offset printing machine needs a cushion under the rubber cover (similar to the woolen coat, but there is a difference, the thickness of the printed fabric is relatively uniform)
This is called soft lining. The disadvantage of the soft lining is that the printing dot will be deformed (because it is relatively soft and elastic), and the effect is to compensate for the accuracy of the printing press.
Not high defects. The rubber of the Heidelberg press is directly wrapped on the blanket cylinder. There is no padding. This is called hard padding.
7, control center
The control center is the result of the rapid development of computers and the perfect integration of mechanical and electrical manufacturing. If you said that the front is the body of the printing press
In the body, the control center is the brain of the printing press. The general printing press has no control center and there is no brain - its brain is the operator.
Third, the printing staff workflow
When the plate making workshop delivers a set of finished glass and a PS version of the hole to the printing shop, the printing shop will do the following:
The first step, the captain operation: the PS plate is placed in a fixed position on the control center table, and the control center determines the inks on each color group according to the graphic on the PS plate.
The amount of ink given to the area. This step is generally not available to the printing house. Instead, after the PS version is hung on the machine, the captain manually adjusts the amount of ink in the ink tank.
The second step, hanging version: the assistant inserts the PS version into the slot of the corresponding color group, and the Heidelberg printing machine automatically hangs the PS version onto the plate cylinder, and before
After clamping. In this step, the general printing factory uses the wrench to open the plate holder and manually hangs and clamps the PS plate. One assistant is hanging at the same time, another
The assistant puts the paper on the paper feeding end of the printing machine, which is commonly called paper.
The third step is to print a sample.
The fourth step is to put the sample on the console, fine-tune the rules and infuse the ink and water according to the sample. General printing factory, if the rules are not allowed, you need to use
The wrench removes the PS version and re-hangs the plate; the ink is transferred and the water is adjusted, and the machine must be climbed.
In the fifth step, repeat the third and fourth steps. If the customer looks at the machine, make a judgment and tell the captain that the captain will answer or adjust until it is printed.
The sixth step, official printing