CTcP is Computer To conventional Plate of the English acronym, refers to the traditional PS version of the computer direct plate, as a form of CTP process, in fact, CTcP is not a CTP second best solution, but in order to complete the computer direct plate and derived from another new road.
As early as drupa1995 International Printing Expo, the German Bespoke Printing (BasysPrint) company launched the first prototype of the UV-Setter plate making machine, to show the application of UV light source on the traditional PS offset printing plate exposure of the new technology. This can be regarded as the birth year of CTcP, and also in this session of the drupa exhibition, ctp technology also debut in the world.
After more than a decade of development, computerized direct-to-plate technology has been perfected, CTP technology from the outer drum to the inner drum, from the silver salt, thermal to the violet laser, CTcP technology has been developed to the fourth generation of China's printing enterprises to invest in computerized direct-to-plate technology and applicability has not been too much to worry about, and more considerations lie in how to recover the cost of investment more quickly. If in order to enjoy the benefits of computerized direct-to-plate technology, while minimizing the pressure of investment, perhaps in addition to CTP, you can also consider CTcP.
One of the same advantages as CTP
CTcP as a computerized direct-to-plate one of the key technologies, with all the computerized direct-to-plate technology to bring all the advantages.
Improve the quality of printing
The use of computerized direct plate making instead of film tanning after the use of film, due to the non-use of film, the print quality of the printed matter has significantly improved, because the image and dot are not subject to the traditional pre-press process of those quality attenuation. The output of the plate, the quality is better, because the dust, scratches and other influences on the film are no longer present, and the edges of the dots are clean and sharp and faithful to the original.
No need to repair dirt, resulting in improved efficiency
Likewise, because there is no influence of the dust and scuff marks mentioned above, the output plate is very clean, and in particular, there is no formation of tiny dirty spots that are not easily visible to the naked eye but can be detected on the machine. No need to repair the dirty, so that the plate shop, especially the printing press work efficiency increased dramatically, which is most obvious for short-run printing jobs, printing time will often be shortened by half or even more.
Reduce printing debugging time and material loss
Because there is no need to position the plate, the quality of the plate is better, and it will not need to be repositioned due to inaccurate positioning, avoiding the need to spend a lot of time calibrating the plate when it is on the press. With more and more short-run jobs in the entire printing industry, plate changing and on-machine debugging have become regular tasks, reducing printing debugging time can significantly save time and costs. It also reduces the waste of water, paper, ink and other consumables needed for on-machine debugging.
Printing customers are more satisfied
Printing customers are more satisfied with the quality of prints, printing production time is shorter, which means that the delivery is more timely, reducing the cost of factory operations, so that the printing company in the fierce competition in the market to take the lead.
Two, more advantages than CTP
More based on the existing printing conditions for the transformation of computerized direct-to-plate solutions - CTcP, with more advantages than CTP.
PS plates can be used
Although CTP plates have been mass-produced for many years, the price has dropped considerably, but it still can't come down to the price level of PS plates, and the plates used in CTcP plate making are cheap conventional printing plates, that is, the general PS plates used in the process now. In fact, it is more important to note that, because of the use of PS plates, printing companies in the plate inventory, operator training, as well as the development of sets of drugs are able to maintain the previous state, without the need to re-investment, so the subsequent maintenance costs are quite low.
Light source is more durable
In a previous CTP survey done by Kejian.com, more than 60% of the respondents believe that the biggest cost in the use of CTP is the laser head, not only the use of time is shorter, the cost of replacing a laser head is also quite high.
And for CTcP, due to the use of cheap and durable lamps, the maximum annual consumption of roughly 60,000 yuan, with CTP laser head annual consumption of 100,000 yuan / year is quite cost-effective. And it is understood that the new generation of CTcP will use LED replacement lamps, so that its service life is theoretically unlimited.
Simple operation
Can be operated in a bright indoor environment, can be convenient to sun various specifications of the size of the printing plate.
No need to change the current hardware configuration
CTcP can utilize 1bit/tiff format data and can utilize RIP data, can use conventional developers and processing chemicals, does not need to use a special network, and can be networked with existing network environments.
For us, many printing companies have not invested in CTcP for fear that the imaging quality of CTcP is not as good as CTP, but as the purchase of the second CTcP in Beijing, Beijing Caiyunlong Printing Co., Ltd. deputy general manager Qiu Hailong said: We have done special tests, first of all, there is no difference in the quality of the imaging and CTP compared to, and secondly, we use the computerized direct-to-plate The purpose is to achieve a reasonable quality improvement interval, both CTP and CTcP, have reached this interval.
And for many printing companies "one step to" the idea, perhaps CTP more to assume a role of image advocacy, if the same printing quality and efficiency but have different operating costs, how would you choose?
In fact, in the computerized direct-to-plate (CTP) technology is widely used in overseas regions, they often discuss a problem is "CTcP will not be the end of CTP? For China, which has already entered a period of explosion in the application of computer-to-plate technology, our question is: "Why not choose CTcP?"
CTP includes several meanings:
Offline direct plate making (Computer-to-plate)
On the machine direct plate making (Computer-to-plate)
On the machine direct plate making (Computer-to-plate) (Computer-to-press)
Direct printing (Computer-to-paper/print)
Digital proofing (Computer-to-proof)
Common PS version of direct plate technology that is, CTcP (Computer-to-conventional plate)
Conventional PS version of the direct plate technology, that is, CTcP (Computer-to-conventional plate)
Direct plate technology, that is, CTcP (Computer-to-proof)
First of all, it is clear that the CTP system discussed here is offline direct plate making (Computer-to-plate). ctp is from the computer directly to the plate, is a digital plate imaging process. ctp direct plate making machine and the structure of the phototypesetting machine is similar to the principle. Its plate-making equipment are directly controlled by a computer, with laser scanning imaging, and then after the development, fixing generated directly on the printing machine printing plate. Computerized direct plate making is the use of digital workflow, directly to the text, image into digital, direct generation of printing plates, eliminating the material of film, the process of manual collation, semi-automatic or fully automatic tanning process.
CTP can handle a wide range of printing methods, including business forms, manuals, address books, documents, financials, newspapers, labels and packaging. In addition to this, CTP is also suitable for printing sheetfed and brochures. It is particularly suited to closed workflows that tightly integrate the editing and creation part of the front end with the production part of the back end. Therefore, CTP systems are particularly suitable for printers that use data exclusively in digital format, such as forms printing, financial printing, packaging printing and general commercial printing. For newspaper publishing, the use of fully digital editing process, or pure classified ads of the newspaper can be used to CTP.
1-2 Why Computer to Plate Making Technology
Market demand: more and more short-form work, higher quality requirements, shorter delivery time, price competition is becoming more and more intense.
Need of Digital Workflow: In the traditional process, there are many production links and the quality is difficult to control, the traditional printing plate is adjusted on the machine, and the productivity of the printing machine is not high. There is no efficient, high-precision, fully automated prepress system can not realize the digital workflow.
Compared with the traditional printing process, CTP plate making process has been rapidly promoted for the following reasons:
1) Delivery time is greatly shortened: the process steps to reduce a lot of time is not a problem, a variety of short blocks of hardware to cope with.
2) stable and consistent high quality: the production process is reduced, the quality is easy to control, no dot gain, the dot is precise and sharp, the printing density is very high, the fine printing is easy to complete.
3) the efficiency of the printing press to give full play to: the printing plate automatic registration adjustment is very little, the CTP printing plate on the ink very quickly, it is easy to reach the water-ink balance, the print preparation time is greatly reduced to save the overprint paper, ink, reduce the waste, the efficiency of the printing press is greatly improved.
4) labor savings: in the soft film development, manual collodion, plate tanning, plate repair, ink proofing.
5) Consumption of material savings: eliminating the soft film, developing fluid, ink proofing with PS plate, process simplification, reduce the chance of error, to avoid redo waste.
Of course, CTP to 2014 there are many shortcomings, such as CTP system costs are relatively high, and most of the plates need to be introduced, so it is more expensive, medium-sized and small printing companies can not accept. Computer to plate system digital process is not yet mature, especially digital proofing can not fully simulate the printing.
Based on the many shortcomings of the traditional process and the advantages of CTP direct plate making, the use of computerized direct plate making technology is necessary.
1-3 CTP system classification
From the exposure system, can be divided into: internal drum, external drum, flat, curved four categories. In these four types, the most used is the inner drum type and outer drum type; flat plate type is mainly used in newspapers and other large format plates; curve type is rarely used. According to statistics, in 1997, of the 58 types of CTP machines supplied by 29 manufacturers, there were 24 types of internal drum type, 16 types of external drum type, 9 types of flatbed type, and 9 types of curved type. Among these forms, the external drum type is gradually showing a mainstream trend.
From the varieties of plates, it can be divided into: silver salt plate, thermal plate (ablative thermal plate, non-ablative thermal plate), photopolymer resin plate and polyester plate (non-metallic plate base), etc.;
From the technical aspect, it can be divided into: thermal technology (ordinary laser imaging), violet laser technology, UV light source technology;
From the degree of automation, it can be divided into: manual stand-alone machine, semi-automatic type, fully automatic type and hybrid type (CTF-computer to film and CTP-computer to plate).
From the fixation of the printing plate on the drum, it can be divided into: full adsorption type and the middle adsorption, the first and last with the card clip fixed two kinds. Full adsorption of the size of the plate has no limitations, while the clip type must be fixed size of the width of the plate used.
From the application, can be divided into: commercial CTP system and newspaper CTP system.
1-4 CTP system development status
CTP (Computer-To-Plate) technology appeared in the 1980s. This period is the early stage of the research of direct plate making technology. Therefore, during this period, both the technical aspects and the quality of plate making are not very mature. In the nineties, the close collaboration between equipment manufacturers and printers accelerated the pace of research and development of this technology, which reached a level of maturity and industrialization during this period. In the 1995 Drupa printing exhibition, 42 kinds of CTP system on display. In Drupa 2000, from around the world, more than 90 direct-to-plate systems and materials manufacturers exhibited nearly 100 kinds of products. 96 years of the largest 100 printing companies in the United States has been 55.3% of the CTP system, 28.8% of the use of color short-run digital printing system. China's use of CTP technology is much later than abroad, the Yangcheng Evening News in April 1998, Agfa's flat CTP plate making machine and Fang's Optronics external drum CTP in the "New Express" part of the trial area.
China's first CTP computerized plate making system without film was successfully developed by Shenyang Boji Science and Technology Research Institute. This is the Institute of science and technology after more than a year of hard work and launch of a high-tech achievements, it fills a gap in China's printing plate industry.
CTP plate making machine with a similar structural principle of phototypesetting machine is no longer an obstacle to the development of CTP, one of the reasons why it can not be earlier and rapid development of the process with which it is compatible with the past period of time can not meet the needs. Digital proofing, automatic imposition is a CTP system applications must go through, if these technologies are not really solved, CTP system can not talk about the development. That is to say, CTP system depends on the development of not CTP plate making machine itself, but the process. A complete set of printing digital process from typesetting to output control is the basis of the CTP system.
The key to the successful realization of the CTP system is:
1. To have more than two years of experience in the use of PostScript electronic prepress system, this experience ensures that the prepress technician is familiar with the basic file handling and troubleshooting, can quickly identify and solve font problems, lack of images and poorly constructed documents.
2. More than half of the work is in PostScript or PostScript-compatible files.
3. Sufficient print consumption: the realization of the CTP system requires a certain amount of money. Printers must consume a certain number of plates to get the appropriate return on investment.
4. High-quality plate operation: the printer must ensure the continuity of plate quality.
5. No more than 4 colors on the main job and print screens below 175 lpi.
6. 6-12 months digital proofing experience: Digital proofing is one of the most controversial techniques in the CTP workflow because of the impact it has on both the customer and the pressroom. Training in various digital proofing techniques is required for both the client and the print operator.
In addition to this, the success of printing is also related to the company's technicians, whose skill level and learning ability directly affects the degree of rapidity of the introduction of CTP, and the company needs to provide the necessary training for such technicians. When the server to deal with the workload is very heavy, in order to ensure that the server and the network can operate normally, increase the system administrator is very important. Because the CTP system affects the entire printing company, all departments involved will need to undergo a series of adjustments and training.
Plate making machine:
From the plate making equipment, after several years of development, manufacturers have introduced a mature technology, can automatically on the plate, can handle different specifications and different types of plates, plate making speed greatly increased in a variety of direct-to-plate system.
such as the prestigious Quan Sheng 3244 series, there have been thousands of Quan Sheng series of computerized direct plate making machine in all parts of the country to run successfully. It utilizes a new 20-watt thermal laser head and the unique SQUARESPOT square photo imaging technology. Winner of the American Printing Technology Foundation's GATF Technology Award five times, it is renowned in the field of computerized platesetting and is rapidly expanding into the field of digital offset printing. Built-in laser cooling system as well as a debris collection unit (for ablative, process-free plates, the tried-and-true external drum design, with the drum rotating at a constant speed during exposure, ensures stable and consistent imaging. For precise registration, a unique temperature compensation system is used, which adjusts and compensates for the thermal rise and contraction of the printing plate due to changes in ambient temperature during the imaging process, ensuring that the same machine can accurately register the same printing plate at different times, and even different printing plates, and that the exposure is stable and consistent and repeatable.
CTP Plate:
The key point of the technology of computerized direct-to-plate (CTP) is that the plate and the imaging system should be matched.
Silver Salt Plates:
High sensitivity, high resolution, high print resistance, must be operated under a safelight, and silver salt exclusions from the process must be properly disposed of.
Photopolymerized resin plates: similar to ordinary plates, they must be handled in aqueous chemistry. However, the sensitivity, resolution, and print resistance of photopolymer plates are low compared to silver-salt plates. By utilizing new high sensitivity resin emulsions, product consistency and graphic solidity can be guaranteed? This is the most important consideration when selecting a plate.
Mixed plate: In the ordinary photographic emulsion added to the exposure process of low sensitivity silver halide montage layer, so that you can get the advantages of the two substances after the compromise. However, this mixture requires a very long platemaking line and two fee exclusion channels, as well as more complex manufacturing processes.
Thermal plates: can be operated in daylight, high-resolution reproduction, accurate imaging, the potential to simplify the process, the plate, film, proofing can be imaged on the same instrument. Just thermal technology is not as mature as the visible laser system, so the thermal option is very limited, thermal technology still has the potential to dig.
Chapter II of the computerized direct-to-plate (CTP) process
The CTP talked about here refers to the CTP system, rather than a simple CTP plate making machine. The realization of any new technology is a complex issue, a CTP system, not only means to install a plate making machine, but also includes a number of additional devices and equipment to enable the operation of the digital workflow. ctp technology, including the plate, the corresponding output device and the corresponding workflow.
CTP platemaking process is:
Computer digital files - CTP workstations - make-up white (Trapping)/color management/OPI/electronic imposition - digital proofing - CTP plate - printing (CIP3).
Traditional Laser Phototypesetting Process:
Computer typesetting-phototypesetting machine output plate film-film through the film processor-development-fixing-drying-artificial film splicing in the PS plate-vacuum suction solid sunshine PS plate-development processing-retouching-plate-printing.
Through the above comparison of the two plate-making process can be seen, CTP plate fast, simple, to achieve 100% of the transfer of printing, the whole process is all automated, generally only 8 minutes; and laser phototypesetting a process to 55 minutes. In addition, because the CTP plate making machine adopts the fully automatic integrated solution, avoiding the distortion phenomenon of manual collation and plate repair in the laser phototypesetting, and improving the quality of plate making. Secondly, it omits the investment of many equipments and the consumption of raw materials. For example, laser phototypesetting machine, developing machine, plate making machine, developing machine and plate receiving machine, as well as film, chemicals and so on. Again is the CTP machine can be through the satellite digital signals and computer networks, the realization of long-distance transmission of data directly plate, greatly reducing the time and space gap. For example, the application of the newspaper industry, due to the fierce competition in the current newspaper market, the publication of newspapers require fast time, high quality, and with the development trend of color newspaper printing, so that the CTP platemaking become effective in achieving the above objectives of the best means.
The main differences between the process of computerized direct plate making and the traditional printing process are:
CTP technology plates without Film.
Use of CIP3 print production format.
Digital proofing.
Digital imposition of large plates.
Graduation design internship is located in the CTP output center of Jiaxinda Printing Company Limited, the CTP system used is Heidelberg (Heidelberg) Detla Drict system.
The Heidelberg Detla Drict system as an example of computerized direct-to-plate technology - CTP process flow in Figure 1:
The equipment used is as follows:
1) Heidelberg CTP - All Win 3244 computerized direct-to-plate system, including: Heidelberg CREO Trendsetter Heidelberg CREO Trendsetter, HeidelbergDelta Tower, Signastation software, host Preserver, control of the platesetter Trendsetter and control of digital proofing Proofstation. Heidelberg CTP series of platesetter for the external drum structure, the use of thermal imaging technology and a unique square light spot technology, with 240 laser diodes as the light source.
2) Digital Proofer EPSON Stylus PRO 9000.
3) Kodak Polychrome Graphics' Thermal Printing Plate and Kodak Polychrome Punching System.
4) Four-color presses such as the Heidelberg SM74 press.
Requirements of the CTP system:
When using the CTP system, first of all, pay attention to the interface technology with the front-end system, that is: the data exchange technology between the color pre-press processing system, as well as the back-end equipment for the refinement of the data opinion technology. For large-volume documents, data exchange speed and data transfer speed is critical; secondly, the requirements of the enterprise to establish a new set of electronic document management system, improve data preservation and retrieval technology; and then, the color management technology and RIP technology requirements are also very important. Large-capacity documents require RIP to have a strong processing capacity in order to achieve efficient work efficiency. For the consistency of proofing and output, color management technology is required.
Figure 1 Computer to plate technology - CTP process
Chapter 3 CTP pre-press plate making process
3-1 pre-press plate making process program
Computer to plate working program in Figure 2:
Figure 2 computer to plate working program
To shorten the distance between the original, the proof and the printed material
To shorten the distance between the original and the print, Heidelberg's Coloropen software can be used to deal with the image. Coloropen with the ICC profile can be operated under the maximum color space to modify the image file, simulating different system colors and printing modes, once set up, whether it is scanning the input or image library images can be output on the digital proofing machine, and close to the printing results of the proofing. Specific programs are as follows:
Image scanning output: the use of ColorOpen software to set up ICC profile to ensure that the scanned image can be output according to customer requirements. And suitable for different output devices.
Image processing: High-resolution images are stored in the mainframe and only low-resolution images are provided to Signastation for imposition. Before output, the pages are sent to the Preserver for RIP processing.
Panelization: Low-resolution images are used for panelization in Signastation. RIP processing is done in Preserver. High-resolution images are placed in the layout just before output, and can be replaced on a separate page without re-RIPing the entire layout.
Proofing: The Epson stylus PRO9000 outputs color-accurate proofs.
Plate making: The Heidelberg CREO Trendsetter can output print-ready plates with Delta tower control.
3-2 performance parameters
CTP performance parameters are as follows:
The unity of the production software supported: Adobe photoshop, Adobe Pagemaker, Adobe Illustrator, CorelDraw, Freehand, QuarkXpress, etc., in the Mac/Pc workstation.
Fonts: most PS fonts and all True type fonts; full set of English fonts, 100 Han Yi fonts. 87 Wendi, 88 Founder and some special fonts.
CTP Output:
Maximum size: 749×1030mm
Resolution: 2400dpi/1600dpi/1200dpi
Dot type: FM 21um, round square, round, square, ellipse, etc.
Blast speed: 4min(2400dpi)
Plate: Folio: 770 × 1030 mm0.3mm
Quad: 605 × 745 mm 0.3mm
Octavo: 400 × 510 mm0.15mm
Proofing: Maximum size: width 1090mm, length unlimited
Resolution: 360dpi (blue paper), 720dpi
Paper: Epson special matte photo paper, high-gloss photo paper
Thermal printing plate:
Extremely stable printing plate: full daylight operation without fogging, stable quality of the printing plate to preserve a long time.
More accurate dots: light dots are similar to binary charts either there or not.
High print resistance: 200,000 prints without baking, up to one million prints after baking.
Precise registration: repeatability of the plate ±5um (eight plates exposed by the same machine)
Absolute accuracy <20um (plates exposed by different machines)
Registration accuracy ±15um (image and plate edges).Advantages of Heidelberg External Drum Platemaker:
Automatic focus, Drum speed 150 rpm.
Printing drum-like structure, short optical path, no vibration, stable thermal and mechanical properties.
Square laser dot technology:
Dot edges are very sharp and can accurately reproduce 1%-99% of the dot.
Extremely high printing density, C-1.9D, M-2.0D, Y-1.5D, K-2.75D.
FM mesh output is very easy.
Detailed levels are perfectly displayed.
3-3 Platemaker Color Separation Plate Output Setup Output setup steps are as follows:
If the user's publication includes a PageMaker component to make up the whiteout (a.k.a. trapping), select the "Utilities? No Whiteout" option. Click "Make Publication Whiteout Effective," set the whiteout options, and click OK.
Select "File? Print.
Select a Platesetter PPD for the user's printer type.
Tap "Color" and then tap "Separate Color Printing".
The following is for each color to decide to add the screen angle and add the number of lines, the general rules are briefly described as follows:
a) For spot colors, usually in the PPD for the "custom color" specified screen angle to print, usually 45 °.
b) for the primary colors, select the name of the primary colors, and then the PPD's "optimization" screen to check its value, it is recommended to use the optimization screen settings.
6) Select the name of each color you want to print and tap "Print this color". Alternatively, the user can tap on the name of each color they want to print. To select the colors used, tap "Print All Colors".
7) Select the "Mirror" and "Plate" options as desired.
8) Tap "Paper" to check that the user's publication is adjusted to the selected paper size, and select the printer mark and page information.
9) Tap Print.
3-4 Checking the Quality of Output Plates
1. General Checking Method. This method is commonly used in output centers and design companies, and its main equipment is a plate reader and a densitometer. Densitometer is the key equipment to test the printing plate, its basic function is to read out the mesh tone of the order of the tone percentage, so as to determine the plate making machine to generate the mesh tone dot size is correct. For example, in the original figure, 40% of the order of the tone, corresponding to the measured density on the printing plate is 40%. The following are the main aspects of the general check and what they mean:
a) A test of the dot scale attached to the plate to determine if the individual steps of the plate are correct. This is done to check that the plate development process and its parameters (such as development speed, temperature and time, and developer concentration) are correct, and may also include problems with the plate making machine itself, such as good or bad linearization.
b) Observe the quality of the plate: this includes whether the exposure is even and checking whether the plate is scratched.
c) Check for PostScript errors: used to check whether the PostScript interpreter's interpretation of the file misses the content, mainly observing whether there is a lack of output on each printing plate. For color separations, in addition to single-sheet observation, but also four color separations together to observe the image of the tone and concentration of the normal, whether the registration is correct.
2. Proofing system check. CTP output centers generally use color digital proofing before the printing plate, if problems are found, then modify the electronic file. Successful proofing of color samples will become the standard sample of color printing. This is different from the traditional out of film, and then generate printing plates with a proofing machine for proofing, but also CTP to solve, improve the problem.
Chapter IV CTP system printing and post-press process
Computer Direct Plate Printing and post-press with the traditional process is not much different from the main, but the CTP technology using CIP3-pre-press (Pre-Press), printing (Press), post-press (Post-press) digitalization and integration of the technology, with CPC32, CPC24 etc. to control the ink zone, thus enabling better control of printing quality. Post-press is the same as the traditional process.
4-1Printing Pressure
Printing pressure is the basis for the design of the printing press and the transfer of ink to the surface of the substrate. Printing pressure is not only a fundamental guarantee for the realization of the printing process, but also largely determines the quality of printing.
Printing pressure generally refers to the ink transfer process of the embossed body in the embossed surface of the pressure, that is, refers to the normal direction along the embossed surface, pointing to the embossed surface of the pressure.
The surface of the imprinted body is rough and uneven, manufacturing, assembly process is inevitable error, only under the action of printing pressure, the imprinted body surface may be in full contact with the transfer of ink. So fundamentally speaking, the function of printing pressure is to force the imprinted body to fully contact, in order to facilitate the transfer of ink. But the printing pressure is not the greater the better, but to moderate. Printing pressure is too large, will intensify the wear and tear of the printing plate, increase the load of the printing machine. Printing pressure is too small, will cause poor contact between the substrate material and ink, the transfer of ink is insufficient, the printed ink is light and unclear.
Factors affecting printing pressure:
The composition of the package liner and its soft should be nature.
Printing speed in printing conditions.
The smoothness of the paper in the printing suitability of the paper.
Method of printing.
The quantity of printing.
Printing content.
So the printing pressure is very important, a lot of influence on the printing quality of the parameters of the change, such as the density of the ground, the relative contrast, the percentage of dots, overprint rate, etc., are due to the printing pressure is too large or too small caused. So the printing pressure must be adjusted according to the print to moderate. Printing with CTP plates, adjusting the printing pressure and traditional printing the same adjustment, are adjusted according to the thickness of the paper.
4-2 offset printing in the ink and water balance
Lithographic printing methods, has its own characteristics. Printing plate on the blank part of the ink and ink the graphic part of the same in a plane, the blank part of the hydrophilic and oleophobic, the graphic part of the oleophilic and hydrophobic. Printing, the first to the printing plate on the water, so that the blank part of the formation of a water film to resist ink, and then to the printing plate on the ink, so that the graphic part of the ink attached to the surface of the substrate by the rubber cylinder transfer, it will be completed a printing.
Lithographic printing in most of the water can not be no, but too much or too little moisture on the printing plate will directly affect the quality of printing and the smooth progress of production. If the offset press operation to change the supply of wetting solution, the following problems will occur:
When the moisture is too large, the print appears white phenomenon, the field part of the so-called "water stains", so that the print is false, the ink color is uneven. At the same time, the deformation of the paper increases, the graphic overprinting is not allowed, but also wet the drum liner to make the drum shell rust.
Moisture is too small, first in the blank part of the print ink stains, causing dirty plate. With the extension of the printing time, the ink gradually blocked the non-inking part, there is a "paste", located in the field above the dot area of the shallow underline gradually blocked by the ink.
Therefore, lithographic printing, the supply of wetting liquid must be moderate. General requirements, without causing the layout rubbed dirty under the premise of the use of the minimum amount of water, to achieve a balance between the amount of water and the amount of ink. Printing with CTP plates, the same attention should be paid to the water-ink balance.
Printing (HeidelbergSM74 press, for example) parameters are as follows:
Printing speed: VMAX for 1500 rpm.
Printing pressure: according to the paper thickness, such as 157g coated paper, paper thickness of 0.13mm, the printing pressure is 13 lines.
Color sequence: generally K-C-M-Y.
Temperature: 20℃-26℃, the best is 22℃.
Humidity: 42°-75°, best at 70°.