How to control point expansion through specific operations
point expansion does have a negative impact on offset printing, so how to control point expansion? We will talk about the specific operation measures from the following aspects
1. master the exposure time of offset printing
controlling the ratio of exposure time, development time, developer humidity and concentration is one of the ways to reduce point expansion. The color separated four-color film transfers the image and text points to the printing plate by printing. It is required to expand the points as little as possible, 3% - 5% points are not lost, 5% points are not expanded, 95% - 98% points are not pasted, the points are solid, the particles of the points are round and neat, the points are free of white dots and burrs, and the level of gradation is rich and clear in the first November of this year. This requires the accurate preparation of PS plate developer, according to the formula proportion of the manual, the exposure time is controlled by gray scale and plate printing signal strip. After the printing plate is exposed, use a magnifying glass to check the loss of paste and dot expansion at the scale and signal strip level
2. Reasonable selection of lining materials and printing pressure
offset printing is an indirect printing method, which requires the middle of the rubber drum. 8. The elastomer that can operate 24 hours a day can transfer the image and text points of the printing plate to the paper surface. The rubber blanket and its lining are the intermediate media for image and text transfer, and there is no printing pressure without lining. By adjusting the lining thickness of the offset press, the best printing pressure can be obtained, and the uniformity of ink intensity and dot clarity of printing products can be enhanced. For the occurrence of the above errors, the printing pressure is obtained by adjusting the lining thickness and the center distance of the drum. The pressure should be based on the premise that the print is a little solid, the graphics and texts are clear, the colors are bright and the shades are appropriate, and the smaller the amount applied, the better. The control point expands the deformation, and it is very critical to adjust the accurate printing pressure. In the work, accurately calculate and measure the thickness of the rubber drum lining with a micrometer, adjust the center distance between the two rollers, and evenly use the most self-healing polyurethane elastomer materials within the allowable range of point expansion. New progress has been made in the research of small printing pressure
3. Control the reduction point of ink balance and expand it.
only by controlling the ink balance can the quality of printing products be improved. It is advocated to use as little moisture as possible on the premise of not dirty version and paste version. Ink balance is also a standard to measure the skill of offset printing operators. Only when ink balance is achieved, the paper has small telescopic deformation, high overprint accuracy, bright colors, hues and hues can meet the requirements of a batch of samples. The ink color is the same, and the printed dots are round and solid. During offset printing, avoid the dot expansion phenomenon of large water and ink, and the ink layer is too thick to spread outward. Control 3% ~ 5% of the small dots in the bright tone area not to be lost, 5% of the middle tone points not to be expanded and expanded, and 95% - 97% of the large dots in the dark tone area not to be pasted. The control standard of ink volume is: on the premise of strong and clear graphic dots and accurate color phase of the imprinted ink, use as little ink volume as possible