Lid Top Wine Box prototyping quality control and maintenance

Lid Top Wine Box prototyping quality control and maintenance

Proofing is a very important process in the process of prepress plate-making. Proofing can check the production quality of the previous process, at the same time proofing proof is also a large number of printing color tracking standards. Therefore, proofing plays a connecting role, which is an important part of the quality management and control of each plate making company.

 

There are many factors affecting the quality of proofing, such as: plate composition, printing, development, ink, wipe water, field density, dot increase, maintenance and maintenance of the prototype, temperature and humidity of the environment and so on. Any problem in any of these factors will have a great impact on the final proofing result. Therefore, only standardized, digital management and operation in the proofing process to make the dot copy and restore to meet the requirements, and for the mass printing to provide qualified chase everything. Next, I will discuss with readers how to effectively control the main factors in the process of proofing and relevant data.

 

One, Mosaic, printing and development

A proof block is very different from a printed block. The printing of the large plate must be in accordance with the binding mode in the folding order, and part of the film cross and corner lines have to be cut, so the assembler can only according to the edge of the image on the film or lines and color blocks are easy to identify other places to align and alignment. In the case of proofing, there is no need to consider hand folding, and the crosshair and corner lines on the film are preserved. As long as the cross line and Angle line of various color film can be aligned. Generally speaking, the color order of the proofing determines the color order of the Mosaic. Because it can improve work efficiency. For the first color, the film should be horizontal, not tilted, and the corners should be glued with scotch tape. The other three plates are aligned with it based on this. The standard of alignment is that the eye cannot see the crosshair and Angle of the upper and lower film are offset.

 

The control of printing and developing is realized by UGRA control strip. The UGRA control bar has five functional segments, each with its own role. As shown in the picture:

 

The first stage is used to control the development of the plate and also to evaluate the exposure of the plate. Qualification is graded from level 3 onwards and indistinct classification from Level 9 onwards.

 

Stage II: Micron coils are used to control exposure time. Qualified as clear resolution micron coil starting at 12μm.

 

Section Ⅲ : The dot section is divided into 10 pieces from 10% dot to 100% field, which are used to check exposure and development, and also used as the standard of measurement of printing characteristic curve. Qualified for 2% outlets to appear, 3% outlets clear.

 

Section Ⅳ : Fine network cables along different angles can be checked for dot deformation and double image.

Section Ⅴ : fine dot section positive figure 0.5% to 5% and negative figure 95% to 99.5%, used to check whether the dot in the process of proofing is reduced.

 

Although the exposure and development can be controlled more precisely through the UGRA control bar, the operator still needs to make appropriate adjustments in some subtle places according to experience, so as to make the best reproduction and restoration of the dot. For example, for different thickness of the plate to adjust the pumping time, the temperature and speed of the developer match the adjustment and printing machine glass cleaning and maintenance and so on.

 

Two, proofing

A press is very different from a printing press. The printing press uses the "round press" printing method, and the press machine uses the "round press" printing method. In addition, the printing press ink, alignment of the degree of automation is very high. The prototype is mostly by the operator according to personal experience to adjust the amount of ink, and the various versions of the registration is also carried out by the hand. Although in the proofing process, the operator must rely on the density meter to constantly measure the field density and dot density at 80% and dot increase to adjust the size of the amount of ink and ink balance, but the inking process must be used to shovel the ink onto the press roller. Therefore, the quality of proofing is closely related to the level of operators.

 

Field density value is the most important technical parameter to control dot replication and restoration. Different companies have their own technical indicators and margins of error. This technical index is determined by each company according to its own specific situation. The field density of the general colored version is Y: 1.30, M: 1.45, C: 1.50, K: 1.80. As for the margin of error, the European standard is ±0.07. It is said that the error range of a domestic company is controlled within the range of ±0.05.

 

Like printing, proofing is also very important to control the balance of ink and wash. The principle of printing, in essence, is the principle of oil-water incompatibility: the dot part of the image formed by exposure on the PS plate is oil-friendly rather than water-friendly, and the unexposed blank part is water-friendly rather than oil-friendly. Therefore, it is essential to maintain a good balance of ink and wash. Water wipe too little, will lead to dry version, reflected in the proof is the dark level and level; Water wipe too much, will lead to dot deformation, print on the dot will appear "hollow point". So, how much water should be controlled? In general, the less water you wipe, the better. The measure of mastery is that when the water rolls over, there is no water on the table.

 

The technical parameters of moistening liquid are often neglected factors in the quality control of proofing. The technical parameters of the liquid are mainly conductivity and pH value. Their standards are 800 to 1200 conductivity and 4.8 to 5.2 pH.

 

The quality control of proofing also involves the adjustment of the proofing machine. The content of adjustment mainly includes the following:

① The pressure of the rubber drum is ±0.03mm (measured once per rotation of 120°, take the average value), that is, the thickness of the rubber blanket + the thickness of the liner = (2.286±0.03) mm.

 

(2) The plate pressure (including PS plate thickness) is +0.12mm ~ +0.15mm, that is, the PS plate surface is higher than the height of the guide rail.

 

③ The pressure of the paper table (including the thickness of the paper) is +0.15mm ~ +0.18mm, that is, the height of the paper surface is higher than the guide rail.

 

The two sides of the movable frame are respectively provided with two rollers. When the frame is moved to one side of the ink leveling system and the machine is not pressurized, the pressure between the roller and the lower guide surface should be just enough to rotate by hand. Too tight and too loose need to be adjusted.

 

⑤ Ink leveling system: the width of the ink bar of the inking roller on the plate and the width of the ink bar on the paper table should be uniform. [next]

 

Three, the maintenance and maintenance of the prototype

In the process of proofing, the operation of the prototype is the most important, of course, the prototype in what kind of working state, is also very important. Only make the press in the best working state, in order to ensure that the dot in the transfer process to maintain good quality, finally get qualified proof. Because the maintenance and maintenance of the proof machine is a continuous process, it is necessary to establish a set of practical maintenance procedures, and make its standardization and standardization.

 

(1) Maintenance of ink rollers

The dot of the proof will change with the hardening of the press roller and become bad. The hardening of the roller refers to the roller used for a long time, its surface will become smooth and hard until the formation of a "crystalline layer". When the surface crystallization of the roller is serious, its ink transfer performance will be affected, the balance of ink and wash in the process of proofing is difficult to maintain. Especially magenta ink, due to the decrease of water absorption, will cause dot hollow phenomenon. The dot area on the proof sheet will be smaller than the dot area on the film, and the color will be lighter. That's a drop in saturation. In some cases, when there is a change in the dot of one color, it will cause the tone of the proof to deviate from the expected effect, and the tone change of multi-color overprint will be greater. This shows how important it is to maintain the roller. In addition to the daily and weekly cleaning routine, there should be specific maintenance measures. That is, every two weeks, take down the ink roll of the prototype and take a "rest", and replace it with a spare ink roll. In this way, the ink roller can maintain good working condition, so as to obtain satisfactory dot reduction quality.

 

② The maintenance of rubber blanket

The blanket is the medium that transfers the dot from the plate to the paper. Its performance directly affects the transmission quality of dot. After long use, there will be chemical residue attached to its surface, making the rubber cloth less elastic. This will make the dot edges transferred to the paper not sharp enough. Therefore, after a period of time in the rubber blanket work also want to let it down "rest", so as not to make it too tired.

 

(3) Daily maintenance and maintenance of the prototype itself

Generally speaking, the proof machine is composed of mechanical part and electrical part. For the mechanical part, lubricating oil needs to be added regularly in each fixed oil hole and the transmission part of the surface (such as the chain) to avoid excessive wear; For the electrical part, it is mainly to check and ensure the patency of the gas path, and keep the surface of the panel clean and so on. In the process of proofing, the ink should be changed when the ink roller and rubber blanket on the oil black cleaning and then add other colors of ink, not at will. Otherwise the residual ink will be mixed with the ink and affect the quality of proofing. In addition, the table and rules near the dust and paper powder should also be wiped off on time, because the accumulation of too much will affect the accuracy of the set.

 

Four, environmental factors

The main environmental factors affecting the quality of proofing are temperature and relative humidity. The temperature is too high or too low, will make the water on the PS plate evaporation too fast or too slow, thus destroying the balance of ink and wash. The relative humidity of the environment is too large or too small will also destroy the ink balance, and even produce ink emulsion phenomenon resulting in the production of hollow dot. In addition, the more serious is that the instability of temperature and humidity will make the paper deformation, resulting in lower accuracy. Therefore, it is very important to maintain constant temperature and humidity in the proofing workshop. Generally speaking, the ambient temperature should be 22℃ ~ 23℃, and the relative humidity is about 50%.

 

V. Concluding remarks

There are many factors that need to be controlled to improve the proofing quality. The above is just a simple analysis and introduction of some main control means and empirical data. There are many subtle factors that are not listed one by one. In the proofing process, often a small error may lead to the production of waste products. Therefore, a complete and feasible management system and operating procedure should be developed according to the specific situation of the company or the department, so as to standardize and digitize the proofing track. Only in this way can the quality of proofing be stable on the basis of high level.