Detailed explanation of CTP direct plate making technology

Classification of CTP platesetter

At present, CTP direct plate-making machines are generally divided into inner drum type, outer drum type, flat type, and curve type. Among these four types, the most used are the inner drum and the outer drum type; the flat panel type is mainly used for large format plates such as newspapers; and the curved type is rarely used. According to statistics, of the 58 CTP machines provided by 29 manufacturers in 1997, there were 24 internal drums, 16 external drums, 9 flat plates, and 9 curved lines. In these forms, the external drum gradually shows the mainstream trend.

Loading mode

According to the degree of automation, the loading mode can be divided into manual and automatic. Manually on the version of the machine is cheap, but generally requires a darkroom operation, so the efficiency is lower; and automatic version of the equipment, work efficiency, but the price is more expensive, generally more expensive than the manual model 100,000 US dollars . Moreover, when the automatic device is in the upper version, it must use a full-size plate with a release paper. There is a layer of light protection film on the surface of the plate, so it can be operated in bright room. In the upper version, it is possible to automatically peel off the protective film on the surface of the printing plate by means of a plate feeder so that the plate material can participate in plate making.

The fixing method of the plate material on the drum includes: full adsorption type and middle adsorption, and two types of clamping are fixed at the end and end. There is no limit to the size of the plate for full adsorption, and the size of the plate for the clip type must be fixed. 30% of CTP equipment with punching device, the general punching process after exposure, this can ensure that the printing plate in the printing press precise positioning, reduce the pre-press preparation time for the printing roller adjustment, improve the printing quality and overprint ,positioning accuracy.

Printing size

The printing plates used by CTP machines are generally large-format printing plates with dimensions of 66*84 inches according to the printing format and equipment requirements; large-format printing plates with dimensions of 55*67 inches; medium-format printing plates with sizes of 41 inches. 32-inch, 22-inch three; small format plate, size less than 18 inches. The most used ones are medium format and small format.

Equipment major suppliers

The suppliers of CTP equipment are mostly from the United States, as well as companies established by Germany and Japan in the United States. The suppliers of large-format equipment include Agfa, Barco, Creo, Heidelberg, Gerber, ECRM, Optronics, Saiten U.S. Prepress, U.S. Screen, etc.; medium and small format manufacturers include: PrintWare, DuPont, etc. Many. Providing equipment dedicated to newspapers includes Creo, Krause and others.
The basic working principle of CTP

The CTP plate making machine consists of three parts: precise and complex optical system, circuit system, and mechanical system.

The single-beam original laser generated by the laser is split into multiple beams (usually 200-500 beams) through multiple optical fibers or a complex high-speed rotating optical splitting beam system. Each beam of light is transmitted through an acousto-optic modulator. The bright and dark features of the image information in the computer modulate the light and dark changes of the laser beam to become controlled light beams. After focusing, several hundred micro lasers are directly shot onto the surface of the printing plate to perform engraving work. After scanning and engraving, latent images are formed on the printing plate. After development, the image information on the computer screen is restored on the plate for direct printing by the offset press. The diameter of each micro laser beam and the light intensity distribution of the beam determine the sharpness and resolution of the latent image formed on the plate. The smaller the beam spot, the closer the light intensity distribution of the beam is to the rectangle (ideal case), the higher the clarity of the latent image. The scanning accuracy depends on the mechanical and electronic control parts of the system. The number of laser microbeams determines the length of the scan time. The greater the number of microbeams, the shorter the time for etching one plate. At present, the beam diameter has been developed to 4.6 micrometers, which is equivalent to the printing accuracy of 600lpi. The number of beams can reach 500. The etching time of a pair of printing plates can be completed in 3 minutes. On the other hand, the higher the output power and the energy density of the plate beam (laser energy per unit area, in joules/cm2), the faster the etching rate. However, too high power also has the negative effect of shortening the working life of the laser and reducing the beam distribution quality.

The source of the platemaking machine includes: a gas laser (argon ion laser 488 nm, power: about 20mw); a solid-state laser (FDYAG532nm, 100mw or more); a semiconductor laser (LD, an infrared semiconductor laser among semiconductor lasers has the advantages of low power and long lifetime.)

The plate making system is a comprehensive multidisciplinary technology industry. It includes precision machinery and optical technology, electronic technology, color digital image technology, computer and software technology, new type plate and material technology, automation technology and network technology. The automatic production system is yet another major technological revolution in the contemporary printing industry.

development trend

The CTP wave is surging. From the end of 1990-1996, there were more than 300 patent articles published. In 1996, 55.3% of the 100 largest printing companies in the United States used CTP systems, and 28.8% used color short-run digital printing systems.

Yangcheng Evening News In April 1998, Agfa's flat CTP platesetter and Fang's Optronics Drum CTP were tested in the "New Express" section.

Since 1985, most newspapers and printing factories in mainland China have adopted laser photocopying and offset printing. The next step of technological transformation of these financially powerful newspapers and printing houses is direct plate making, color newspapers, and high-end color printing and packaging printing. Requires scanning of the web to be expanded to the side (740*510), and the printability of the media is from 300,000 to 500,000 impressions.

For newspaper printing, CTP saves manpower, improves quality, and reduces environmental pollution. And refine the optimized process, easy to set up a high degree of automation of the continuous production line. In terms of newspapers, the nationwide national newspaper has a high degree of prepress digitalization and advanced technology and equipment. Compared with foreign newspapers, there is no obvious difference. The domestic newspaper industry is facing fierce competition. The CTP system can save the entire publication stream for 30-50 minutes, so for the publication of evening newspapers in particular, the time for press release can be postponed by 30-50 minutes without changing the printing time. This is important for the news of the day. significance.

CTP system and technology have been taken as a development direction of China's printing and publishing industry, and have been listed in the national "Ninth Five-Year Plan" key scientific and technological projects. It is a typical high-tech, high-growth, high-return technology-intensive industry.

CTP system requirements

When using the CTP system, first of all, it is necessary to pay attention to the interface technology with the front-end system, that is, the data exchange technology between the color prepress processing systems, and the improvement of the data and technology of the back-end devices. For large-capacity files, data exchange speed and data transmission speed are of utmost importance. Secondly, companies are required to establish a complete set of new electronic document management systems, improve data preservation and retrieval technologies, and then apply color management technologies and RIP technologies. The requirements are also very important. Large-capacity files require RIP's powerful processing capabilities to achieve efficient work efficiency. For the consistency of proofing and output, it is necessary to participate in color management technology.

When purchasing CTP, users need to make detailed system argument analysis and make decisions based on their own needs. The new technology system should not be required to match with the old workflow. It should be considered comprehensively: comprehensive benefits, maintenance workload, consumables prices and supply sources; the system must be open, and the technology used may be upgraded.