Some Operating Specifications for Improving Printing Quality

        If the quality of the printing plate is not qualified, the printing quality cannot be guaranteed. The impact of printing plate quality on printing is obvious. Some Operating Specifications for Improving Printing Quality

       In actual production, there are many problems in the printing quality of PS plate, such as dirty printing plate, plate loss, printing resistance and so on.Some Operating Specifications for Improving Printing Quality

      Which not only affect the printing quality, but also reduce the production efficiency. One of the important reasons for poor printing quality is that the printing operators do not have enough knowledge of plate making, nonstandard operation and unstable printing conditions.Some Operating Specifications for Improving Printing Quality

         PS version is based on 0.5-0.30mm aluminum plate, After sanding (roughening) the surface of the aluminum plate, it is made by coating a light decomposing diazo photosensitive layer. When printing, the positive film is used as the original to expose the PS plate. Some Operating Specifications for Improving Printing Quality

        After exposure, the blank part is decomposed by light, and the sanding layer is dissolved by the developer to be hydrophilic; the photosensitive adhesive layer without light in the figure does not decompose and is lipophilic. The process flow is as follows:Some Operating Specifications for Improving Printing Quality

Plate loading – exposure – Development – water washing – dirt removal – (baking and ink extraction) – glue wiping

Baking plate and ink extraction can be increased or decreased according to production needs.

       In addition to correctly restoring the image and text tone of the original, the printing plate with qualified quality should also ensure good oil and water repellency of the image and text part and hydrophSome Operating Specifications for Improving Printing Qualityilic and oil repellency of the blank part, clean layout, no dirty spots, strong and smooth mesh points, etc. Some Operating Specifications for Improving Printing Quality

       To achieve this goal, in addition to having qualified PS plates, the key is to master the plate making law, correctly select and use plates, standardize plate printing and development operations, control the factors affecting the plate quality in each process link, and ensure the plate printing quality.Some Operating Specifications for Improving Printing Quality

1.correct selection of plate

             The quality of PS plate directly affects the printing quality. Qualified PS plate requires that the plate base should be clean, the sand mesh distribution should be uniform, the thickness and depth should be moderate, and the photosensitive adhesive layer should be uniform and the thickness should be consistent.Some Operating Specifications for Improving Printing Quality

              Although there is little difference in the performance of the plate, the stability of the quality is quite different. Some Operating Specifications for Improving Printing Quality

         The problems such as rough sand mesh, dirty spots and “horseshoe” printing are still common. Therefore, we should choose the PS version with good printing and development performance, good dot reduction, high printing resistance and not easy to get dirty.Some Operating Specifications for Improving Printing Quality

         In addition, during the use of PS version, pay attention to the storage and storage of PS version. It should be stored in a dark, moisture-proof, dry and well ventilated environment to ensure that the plate will not be damaged and the storage period should not be too long.Some Operating Specifications for Improving Printing Quality

2. Standardize printing operation

1) Printing environmental conditions

The stability of printing environmental conditions is the premise to ensure printing quality.

         The printing workshop should be closed to prevent dust. If dust adheres to the front of the printing glass, film or printing plate, it will form dirty spots on the printing plate after printing; if dust adheres to the picture and text, it will even cause the printing plate to be scrapped; Some Operating Specifications for Improving Printing Quality

        And if there are large sand particles between the film and printing plate, it will make the surrounding parts of the sand weak. Therefore, the environment of the printing workshop must be improved Keep clean and try to reduce dust pollution to the printing environment. Some Operating Specifications for Improving Printing Quality

         Before printing, carefully check the film and wipe it with detergent to remove all dust and dirt. Wipe the printing glass with soft fiber articles to avoid scratching the glass surface.Some Operating Specifications for Improving Printing Quality

       The temperature of the plate printing workshop shall be controlled at (23 ± 3) ℃ and the relative humidity shall be controlled at (60 ± 5)%.Some Operating Specifications for Improving Printing Quality

        The yellow safety lamp shall be used as the lighting lamp, and the fluorescent lamp shall not be used as the lighting lamp. If there is a window, it shall be covered with yellow window curtain.Some Operating Specifications for Improving Printing Quality

2) Ensure film quality

(1) The layout of the print film shall be clean, clean, free of scratches and creases.Some Operating Specifications for Improving Printing Quality

(2) The field density of the film is above 3.50, and the haze D is ≤ 0.15. If the film density is insufficient, the dot will turn gray and yellow, which will affect the printing quality.Some Operating Specifications for Improving Printing Quality

(3) The dot should be smooth without virtual halo, that is, the dot center density should be consistent with the edge density, so as to ensure the tolerance of exposure time and achieve faithful restoration. Some Operating Specifications for Improving Printing Quality

         If the dot center density is high, the surrounding density is low, and there are virtual edges, the small change of print exposure will make the dot on the printing plate change greatly.Some Operating Specifications for Improving Printing Quality

        while if the middle density of the text part is large, the pen will be damaged The low density of fine strokes such as front will lead to the reduction of the font of the printing plate, lack of pen and broken stroke, and affect the text quality.Some Operating Specifications for Improving Printing Quality

3) Exposure control

          Exposure determines the quality of PS plate, which is the main factor affecting the change of printing plate dot and the depth of printing plate. The exposure is too large. Due to the diffraction of light, the photosensitive adhesive layer of the image and text without light can also be decomposed by light,.Some Operating Specifications for Improving Printing Quality

          Resulting in the loss of small dots, the lack of pen and broken lines of fine lines, the overall image and text is shallow, affecting the printing effect, and it is easy to lose the version, Some Operating Specifications for Improving Printing Quality

         And even waste the version in serious cases; If the exposure of the printing plate is too small, the photosensitive adhesive layer in the blank part will be decomposed incompletely, and there will be resin residue after development processing, resulting in the expansion of the dot, resulting in the paste of dark tone small white spots, and it is very easy to get dirty for machine printing, which will also indirectly affect the printing resistance.Some Operating Specifications for Improving Printing Quality

        Since the light source is relatively fixed, the exposure is mainly controlled by adjusting the exposure time. The exposure time must be determined according to the printing suitability conditions of the unit. Some Operating Specifications for Improving Printing Quality

      The exposure time of PS plates of different types and manufacturers is different, and is also affected by various factors such as different originals, light source aging, film quality and so on. Some Operating Specifications for Improving Printing Quality

           Specifically, it should be obtained through the actual test with the printing test strip or gray ladder. Generally, the exposure of 21 gray ladder without inking at the third level and 2% and 98% black-and-white small dots can correspond to the same time is the best, but the exposure time of text and line version can be slightly longer than that of fine dot image version.Some Operating Specifications for Improving Printing Quality

        In order to ensure the stability of exposure quality, pay attention to the following points:Some Operating Specifications for Improving Printing Quality

         The light source for plate printing shall be standard. The spectral characteristics and illuminance of the light source shall meet the requirements for plate printing. Some Operating Specifications for Improving Printing Quality

        A correct and reasonable light source can not only shorten the exposure time, but also improve the resolution of plate and reduce the change of dot.Some Operating Specifications for Improving Printing Quality

              The ideal plate printing light source is iodine gallium lamp (metal halogen lamp), it has a strong ultraviolet spectrum, the spectrum range is 320nm-450nm in the blue purple light area, which matches the spectral sensitivity of PS plate, and the illumination of the lamp tube is uniform.Some Operating Specifications for Improving Printing Quality

        The light has no scattering and less heating, does not produce harmful gas, and has the advantages of cleanness, safety, stability and high efficiency. It is an ideal light source for drying PS plate.Some Operating Specifications for Improving Printing Quality

(2) The printing light source will age, so that the spectral radiation and illuminance will change, and the uniformity of illumination will be affected. If the exposure time is more than 20% longer than normal, it is best to replace it in time.Some Operating Specifications for Improving Printing Quality

(3) When vacuumizing the printing plate, the film and PS plate must be compacted, and there must be no residual air in the middle. In order to ensure the vacuumizing effect, the vacuum degree should be maintained above 20KPa.Some Operating Specifications for Improving Printing Quality

(4) The fluctuation of power supply voltage in the printing workshop should be small to ensure the stable light intensity of printing exposure.Some Operating Specifications for Improving Printing Quality

4) Development control

        Development is to dissolve the photosensitive adhesive layer of the light decomposition part of the printing plate under the action of alkaline developer to expose the hydrophilic sand mesh of the aluminum plate base, and the unexposed part is retained to become the image part of the printing plate, which is lipophilic.Some Operating Specifications for Improving Printing Quality

         Correct exposure should be matched by correct development, so development also has a great impact on the quality of PS plate. The main influencing factors are developer concentration, development temperature, development time, etc. Some Operating Specifications for Improving Printing Quality