Offset press acceptance
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The price of offset printing machine is expensive. The price of domestically produced machine is several hundred thousand yuan to several million yuan, and the price of imported machine is over ten million yuan. A factory enters such a expensive equipment, and its quality performance can not be a little bit. In case of mistakes, when the new equipment enters the factory, the factory must organize technical force to assist the printing machine manufacturer's technicians in the installation and commissioning work, and carry out the acceptance. After the acceptance is passed, the factory can be put into production. Then, after the completion of the machine debugging, how to accept the machine equipment, this is a very important thing, can not be sloppy, can be carried out from the following aspects.
First, the appearance inspection paint is evenly applied, the plating parts are not bright, and the shield does not leak oil.
Second, the idling test
1. Manually shake the machine, shaking forward and shaking in the opposite direction to make the drum move for one cycle. The force should feel evenly balanced, and there is no blocking force at a certain position.
2. The positive and negative points are stable and there is no abnormal sound.
3. Run at low speed for a few minutes. If there is rainy lubrication, you should see the oil pump to send oil to each lubrication point, carefully check the lubrication of each lubrication part, there is no problem of oil eye blockage and no injection; safety device should Reliable and effective; the ink roller and roller clutch parts work in place; the other parts of the machine are free of abnormalities.
4. The components work accurately and smoothly during operation, and the digital display is accurate on the electrical instrument; after the constant speed, the speed regulation is effective, and the machine speed can be operated between the zero speed and the highest speed provided by the printing manufacturer's technicians. The speed of the machine is stable, no vibration and abnormal sound. After running for a period of time, the temperature rise of the lower roller bearing should be touched, and there should be no overheating.
Third, printing test
1. Paper feeding: The thinnest and thickest paper marked on the machine manual should be used. The paper feeding test should be carried out at high speed. The paper conveying should be smooth, the receiving paper should be neatly collected, and a knife paper should be opened to open the mouth. Check the edge of the paper and there should be no obvious biting and tearing.
2. Imprint: Generally, the method we use is: use the largest open paper, the first is to overprint accurately, it is the most basic condition of color printing, use a magnifying glass to inspect the crosshairs and corners in detail (crosshairs and corners) The line should be as fine as possible. The registration level is consistent. In particular, attention should be paid to the registration of the corner line. There should be no fan-shaped expansion. When registering the test, we should use different speeds to see the shifting situation. Under the machine, the registration stability of the machine, and the pull on the body and the outer side of both sides should be tested. The second is to test the 50% network cable version, which is mainly used to check the uniformity of ink color, the degree of solidity of the dot, the presence or absence of ghosting, bars and so on. Once again, the full version is checked to check whether the ink is evenly saturated, whether the ink stick and each of the rollers are bitten, the biting force of the receiving teeth is sufficient and uniform, and whether the paper wrinkles and tears are caused by the increase of the peeling tension.
The general acceptance test is the embossing test method of the above steps, but I think it is still slightly rough. It separates the 50% network version from the field version. In fact, in the actual production process, the mesh is adjusted to the field. In the same layout, the offset master knows that if the light is in the field, the amount of ink can be increased, so that the printed ink layer is very thick. If it is a mesh, we will consider more of the toned reduction, not because of the pursuit. The thickness of the ink layer spreads the dots, making the white chalk no paste. Nowadays, many printing houses have imported printing machines, and its performance stability is unquestionable. However, for the ability to reflect the color, the light is not enough to explain the problem through the above tests. It should pass standardized testing tools (such as GATF color). Copy the test chart to test the machine.
The following is a brief introduction to the GATF color copy test chart, which is divided into six test areas.
1. Simple color wheel diagram: It is superimposed by the dot color blocks of yellow, yellow and blue inks. Each color version has six levels, which are 5%, 15%, 25%, 50%, 75%, 90 respectively. %. A stack of 216 patches is used to identify the color and detect the restoration of the color.
2. Contact copy control standard section, there are 6 contents: 1 development and exposure time check chart. A density gauge having a density ranging from 0.05 to 2.00 is placed in a blank strip for detecting changes in development conditions and calculating a new exposure time. The 2-point area scale standard ruler is used to detect the amount of change in the line image during the contact copy process. 3 outlet points, from 1% to 99% of the network level is divided into two sections. Each level of 23, the upper section is from 1% to 56% of the outlets, said the positive, the lower section is from 44% to 99% of the outlets, said negative. 56% of the outlets in the upper section correspond to 44% of the outlets in the lower section. The graph can show the situation where the positive point begins to gradually transition to the negative point to check the copy dot change. 4 Yin and Yang cross lines to check whether the cross line of the copy process is thick. A signal that changes in image quality is given by a thickening of the male line or a negative line. 5 black and white intersecting intersecting marks, under normal circumstances, the ink color area is just equal to the blank area, and can be embedded in each other. 6 Mixed mark, which consists of three square figures, where two corners intersect and the other two corners are disengaged to detect image quality with changes in intersection or disengagement.
3. Comparison of the number of dots. A matching reference for selecting the number of screen lines and paper suitability, and also reflecting whether the reproduction of each color tone is normal. From top to bottom from 150l/in to 65L/in has a total of seven screen lines, from left to right, 5% to 90% of a total of 10 levels of outlets.
4. The three primary color neutral gray balance control chart is a color bar composed of 26 blocks, consisting of twenty-two color blocks and four stars, and 1~7 blocks form a set of primary and intermediate colors, 8~13 The block forms a gray to black achromatic color, 14~19 blocks calculate the relative gamma of printing, 20~22 forms a color system, and finally 4 four-color stars.
5. Gray balance map, find the ratio of yellow, fine and green of gray balance from the figure.
6. Proof control bar.
From the GATF test chart test function, we can know that by copying the figure (using the brand ink and a certain paper commonly used in the factory), we can measure the solid block yellow (Y) and the product from the color wheel chart with a colorimeter. (M), cyan (C), red (Y+M), green (Y+C), blue (C+M), synthetic black (Y+M+C), black (K) and tristimulus of paper used The value XYZ, then use the formula x=X/(X+Y+Z) and y=Y/(X+Y+Z) to calculate the chromaticity coordinates x and y, respectively, where Y is the brightness coordinate, and the value range is 0~ 100, x, y value range is 0 ~ 1; from the dot ladder can measure the expansion rate of the 50% network points and other network points and the ability to restore the tone; from the gray balance card can be seen the gray balance of the ink used . The results of testing these data can further explain whether the printing performance of our printing press is excellent, and the data can be transmitted to the prepress department as a reference for design and production.
If there is no GATF test chart, we can make solid block yellow (Y), product (M), cyan (C), red (Y+M), green (Y+C), blue (C+M) in PHOTOSHOP. , synthetic black (Y + M + C), black (K) and yellow, yellow, black, black, 1% ~ 100% grade difference of 1% of the grid ladder, after the trial printing 50% flat net, and then put Printing, you can also measure the basic data of color synthesis and the reduction ability of yellow, fine, green and black tone, and measure 2%, 4%, 6%, 8%, 10%~100% of the cascade points. The expansion rate (required in the curve mode in PHOTOSHOP), of course, the final version is still to be tested, although the raw materials are more wasteful and the test is cumbersome, but for a device that invests tens of millions It is worthwhile to spend some money and energy to do such a test.