From the point of view of the direct platemaking equipment used today, there are complete sets of equipment suitable for newspaper printing plants and large-scale printing plants, as well as small-scale platemaking equipment suitable for small and medium-sized enterprises. Because the specific service objects of direct plate-making equipment are different, the requirements for the precision of direct plate-making plates are not the same. Therefore, the characteristics of different types of direct plate making are also different.
The main features of CTP are as follows:
1 completely eliminate the film process and the corresponding materials, greatly simplify the process, significantly shortening the plate-making time;
2 can output a variety of format plates, to meet the press requirements;
3 Plates can be accurately positioned during platemaking to ensure plate registration requirements;
4 high resolution, with output accuracy of 3000~5000dpi;
5 can form 175~300lpi, 256 tone network;
6 plate making speed, can make a printing plate in a few minutes;
7 Four-color printing plate overprinting accuracy, to meet the printing requirements, and can prevent the occurrence of moire phenomenon caused by dot shape, angle;
8 has good operability, can automatically transport, automatic exposure, automatic development, to ensure accurate printing plate production;
9 can produce good economic benefits.
2CTP improves printing quality
Computer direct plate-making records have high-quality dots, small dot changes, and can better record FM network points; high-light and dark-spot network dots have good reproducibility and a large range of tone levels; there is no problem of dust and the edge of the film; plate overprinting is accurate Sex is very good. In all cases, it is superior to the traditional CTF process. Moreover, computer-assisted platemaking has almost no possibility of misoperation of the plate exposure.
3CTP improves production efficiency and economic efficiency
The CTP system has eliminated film and its related process equipment, greatly shortening the time for printing plates and improving the timeliness. Eliminates the need for manual trimming of plates and film edges. Digital imposition replaces the time-consuming film imposition in traditional printing. Compared with traditional plate making, CTP plate making speed can be increased by more than 3 times.
In CTP, exposure and imaging time are the core factors affecting productivity. Imaging time increases with the resolution. At a resolution of 1200 dpi, the shortest imaging time for a 70 cm x 100 cm plate is approximately 2 minutes. Some CTP systems are highly automated. If sufficient data and plate supply are available, they can be run without any operator.
In commercial printing, book printing and newspaper printing, the requirements for plate making productivity are different. In commercial printing, the printing plate is completed in daily working hours, usually 10 sheets/hour, and some CTP systems can reach 20 to 30 sheets/hour. In press printing, a large number of plates must be completed within a short period of time (a few hours), the quality of which is lower than that of commercial printing, and the image resolution of newspaper printing is also low, usually between 800Ã—1400 dpi. Relatively shorten the imaging time. Some newspaper CTP systems can achieve productivity of more than 100 sheets/hour.
Computer direct platemaking has cost advantages. Since the cost of film and its development and processing are eliminated, the amount of trial printing waste paper, ink, fountain solution is reduced, the utilization rate of the printing machine and the postpress processing equipment is improved, and the prepress and printing preparation time are saved. Reduce costs. In particular, with the use of digital ink preset technology, presses can shorten the production, accurate registration and preset ink time according to the printing plate's own situation, save the adjustment time, record repeatability, and make adjustments during the time of printing. short. The CTP system has realized the data exchange from prepress to the printing control system and the unification of its format.
4 Several Problems to Be Noted When Using CTP Process
1) According to product demand, choose CTP process
In the current production, the products are divided into quality-priority commercial plate-making and speed-priority newspaper plate-making. In the quality-priority commercial plate making, the main products are high-quality catalogues, exquisite samples, fashion magazines and other high-quality printed materials. They have high requirements on the color, level, and clarity of the products, especially highlights and shadows. Better than CTF. Sometimes it is necessary to use a variety of screening technologies, such as FM screening and AM screening, so use a slower CTP process. For newspapers with speed priority, the main products are newspapers with emphasis on timeliness and color books with low quality requirements. Their requirements for time are higher than the requirements for quality, and most of them are printed on semi-commercial or newspaper web presses. The tone of the image is short, and the color reproduction requirement is low. The main use is the amplitude modulation screening with a low number of screen lines. Therefore, a fast CTP process can be selected.
2) Quality control is very necessary for the production of printing plates
You must detect exposure errors that result from occasional defects in software and hardware: If you miss some images or text, photos are not corrected. These errors often appear in explanations or postings. Therefore, it is very important to check the printing plate with the digital proofing method. These errors can be detected before printing. The calibration of the production line must also be monitored. In particular, the plate output machine can use the imaging control bar.
The digital plate control bar has many control functions with different functions and can be visually detected by naked eyes or densitometer/magnifier. The control bar is embedded in the document to be output and sent to the output system together with the page and paper parameters, which can be used to find the cause of the quality defect in the output due to the parameter change. Density measurement of the plate provides relative measurements and this method is suitable for routine production control.
The allowable range of temperature and chemical composition in the plate developing tank must be very small. Only in this way can a stable developing effect be obtained. If it deviates from the ideal value, satisfactory printing plate quality, such as unclear dots or dots, will not be obtained. There are some limitations on the accuracy of overprinting for polyester-based printing plates.
3) Precautions when using CTP output in DTP process
1 should pay attention to the interface technology with the front-end system. For large-capacity files, data exchange speed and data transfer speed are of utmost importance.
2 It is necessary to establish a complete set of new electronic document management systems and improve data preservation and retrieval technologies.
3 Color management technology and RIP technology are also very important. Large-capacity files require RIP's powerful processing capabilities to achieve efficient work efficiency.
4 Experience in the use of Postscript electronic prepress systems, which will ensure that prepress technicians are familiar with basic file processing and troubleshooting, and can quickly identify and promptly solve font problems, missing images, and poorly constructed documents.
5 need to have enough plate consumption. To achieve a CTP system requires a certain amount of money, printing plants must consume a certain number of plates in order to obtain a corresponding return on investment.
6 has digital proofing experience.
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