Printing chemical damage
The chemicals used in the printing plate are mainly ink, plate cleaning solution, fountain solution, and protective glue. Different printing plates have different resistance to these chemicals. Some plates are very sensitive to the plate cleaning solution, and the photosensitive adhesive layer on the surface of the printing plate is easily damaged. You should know the chemical resistance of the printing plate used. You can learn from the supplier/manufacturer or through a 5-minute chemical test to preliminarily judge the resistance of the printing plate. Try to use chemicals that are mild to the printing plate.
Even mild chemicals should be used rationally. For example, after wiping the plate with the plate cleaning solution, it is best to use a sponge dampened with water to remove the residue of the plate cleaning solution and start printing as soon as possible to avoid excess plate cleaning solution remaining on the plate for a long time, otherwise, the photosensitive adhesive layer will be easily damaged and affect the printing volume. Excessive cleaning can also significantly reduce print yields, especially for high-resolution AM and FM print jobs.
Regular brand dampening solutions generally have a less obvious impact on the printing volume, and some individual dampening solutions may not be suitable for individual plates and the printing volume is relatively low, which is rare. Mistakes in the preparation of fountain solution or the use of additives such as IPA of poor quality or adding too much will significantly reduce the printing volume, so attention should be paid to daily measurement and monitoring.
Ink is also a chemical that affects the printing volume, especially some specific inks such as white ink, metallic ink, spot color ink, etc. The printing volume is generally lower than that of ordinary inks. Most of the ordinary inks have similar printing volumes, and some printing volumes are indeed worse.
The exposure of the CTP plate also has an impact on the printing volume, especially for the negative plate of the exposure image. For the negative plate, the exposure energy and the correct setting of the exposure focal length must be guaranteed, otherwise, the exposure energy density will be insufficient, resulting in crosslinking strength. Not enough, affect the printing volume.
Different plate-making machines have different laser performances. In general-resolution AM screen printing, the impact on the printing volume is not obvious, but in high-resolution AM and FM screen printing, there is a significant difference.
different paper quality
Undoubtedly, the printing volume of different paper quality will be quite different. For some poor paper quality, it is necessary to pay attention to the standard setting and use of the printing machine in order to have a reasonable printing volume.
The above are some of the more common and obvious influencing factors, and some less prominent factors will also affect the printing volume.
Maintenance and running status of the printing press:
The maintenance and smooth operation of the printing machine are very important. Some printing machine roller pillows are rusty and dirty, and the operation is not smooth enough to impact the plate; the rubber or printing plate cylinder is rusted, resulting in premature wear of the printing plate; some printing machines The cylinder of the machine printing plate is movable, but it is not set strictly according to the standard. The two sides are unbalanced, and one side wears quickly; some cylinders are aging and the hardness is too high;
Blankets have different properties. Choosing a blanket with good quality, moderate hardness (generally around 75-80 Shore A), less likely to accumulate debris, and timely replacement of aged and hardened blankets are beneficial to the printing volume. The installation of the blanket is best to follow the standard torque and steps to keep the blanket setting standard and stable.
Dusting reduces print volume.
The positive plate is exposed to sunlight.
Cleaning and gluing of reserved plates, similar to chemical problems. Pay attention to the strength of the cleaning and the residue of the cleaning solution, and pay attention to the uniform thickness of the glue.
There are some other factors not listed here. In short, strict implementation of printing press settings and operating standards, and strict use of printing plates in accordance with the standard operating specifications of printing plates can generally obtain reasonable printing results.
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