In 2014, Shaoxing Daily Press Printing Co., LTD., where the author works, officially purchased a Kray UV-CTP equipment and a Kodak Quansheng 800CTP equipment, completely eliminated the phototypesetting equipment, and officially opened the road to the application of CTP. Here, the author combed through some problems encountered in the process of using CTP equipment and solutions to share with readers.

Equipment maintenance "pit"

1. Punching machine transmission gear wear

Once the equipment in normal use, suddenly produced a burning smell. After inspection, it was found that the butter and oil in the transmission gear parts of the punching machine had been exhausted, and the whole transmission gear parts of the punching machine were seriously worn, resulting in the smell of burning.

In view of this problem, our company specifically makes relevant provisions, requiring operators to open the cover of the punching machine every half a year, adding butter and oil, to prevent transmission gear wear.

2. Double sheet printing

In the initial phase of use of UV-CTP equipment, the problem of double expansion often occurs. After careful observation, it is found that there is a double sensor between the plate supplier and the CTP host. Some dust will be generated when the laser is exposed to the plate. After a period of time, the dust accumulation will reduce the sensitivity of the double sensor. At this point, if the two plates are installed on the plate head clip of the CTP host at the same time, the double sensor will not be able to sense signals in time, which is easy to lead to the plate cannot be clamped, and it is easy to cause damage to the equipment when the equipment is running at high speed.

In view of this problem, the company requires plate making personnel to do a good job of equipment maintenance work, regularly wipe the equipment, for the location of the wipe, need to use air gun dust. Since then, there have been no more problems with the device's double advance version.

3. Production environment is not suitable

CTP equipment has a high requirement on ambient temperature and humidity. In winter and summer, air conditioning is needed to keep the working temperature constant in the workshop. In previous work, the CTP device cannot be properly prepared due to the low ambient temperature.

In addition, CTP equipment has high requirements on air source. Dry and clean air can improve the performance of equipment and extend the service life of equipment. Conditions permit, it is best to special gas. Our company is located in the Jiangnan zone, the air humidity is high, therefore, the company requires plate making personnel to exclude the water in the air compressor and condenser every week, in order to meet the requirements of CTP equipment for air source.

Now, our company attaches great importance to the maintenance of CTP equipment. We not only attach great importance to the daily maintenance of equipment, but also invite professional engineers to maintain the laser head, screw and other key parts of the equipment every six months.

"Understand" the linearized curve

In order to ensure the quality and data of the printing plate, our company specially purchased a printing plate dot measuring instrument, and produced a measurement and control strip in the dragging part of the printing plate. The first printing plate production is completed, immediately measured 3%, 50%, 100% color block dot value. Because the linearization curve has been set, but the conditions of the device is constantly changing, judge whether the printing plate is in line with the requirements, it is necessary to measure the color block data to achieve. For our company, the actual measured value of 3%, 50%, 100% color block is 1.5%, 45.0%, 97.0% or so, the printing plate dot reduction, printing resistance rate is in the best state.

Solve two big platemaking problems

1. Grinding plate

Traditional PS version by iodine gallium lamp full exposure, printing resistance is relatively high, can reach more than 100,000 copies. The maximum print capacity of the newspaper printed by my company is 70 thousand copies. When the CTP is used initially, it will appear different degrees of grinding when it is printed to about 50 thousand copies.

After many attempts, we finally solved this problem with the following methods: First, by adjusting the drum pressure and lining thickness to reduce the printing pressure, so as to improve the printing resistance of the plate; Then, after adjusting the press to the best state, adjust the platemaking parameters, and then improve the quality of the plate. Through constant exploration, we finally make the CTP printing plate printing power stable at 70,000 copies.

2. The printing plate is dirty

There are many reasons for the printing plate dirty, such as weak laser, low developer concentration, low temperature setting. The practice found that the most effective way to detect the plate fouling is to drop a drop of anhydrous acetone in the blank part of the plate, when the anhydrous acetone volatilized, check whether the droplet on the surface of the plate left traces. If so, it is likely to stain during printing. For the printing plate dirty, can be enhanced by laser intensity, improve the developer concentration, prolong the printing time, if necessary, can be the printing plate in the printing machine to quickly go again to solve. Nowadays, anhydrous acetone belongs to the goods strictly controlled by the public security department, and can be replaced by anhydrous alcohol, but the detection effect is much worse.

Not to be underestimated in the rehydration link

Due to a small amount of daily plate, my company replacement developer cycle is generally half a month. But in the early stages of using CTP devices, the developer used less than a week, the printed plate will appear dirty. By measuring the conductivity of the developer, it is found that the conductivity of the new developer is about 75μs. After a week of use, only about 65μs, the conductivity decreases, that is, the developer concentration decreases. After analysis: developer is actually a strong alkali, after a period of time, alkaline decline, and distribution of the supplementary solution and developer concentration, so the supplementary developer alkaline still can not be restored to the normal level, will cause the printing plate dirty.

To solve this problem, we asked the plate supplier about the ratio of developer and supplement solution. The result was the same as our analysis, they did not pay attention to the ratio of developer and supplement solution, and provided 1∶4 developer and supplement solution. Later, our company asked the supplier to increase the concentration of supplement solution to 1∶3, which greatly extended the service life of developer solution.