Seventh, the relationship between the amount of fountain solution and conductivity, PH value
1, ideal for water
Before adding the fountain solution, the conductivity of the water should be 300 us/cm-500 us/cm, the hardness is 5 ã‚š-8 ã‚š, it is soft water, and the pH is between 6.5-7.
2. The relationship between the change of the PH value of the ideal fountain solution and the conductivity
Dilution of the fountain solution, when the pH value changes between 4.5-5.5, the conductivity should be changed in equal proportions between 1200-600us/cm.
When the conductivity exceeds the initial configuration value of 500us/cm, the fountain solution should be replaced. Namely: According to the local water quality, through the printing test, assuming a conductivity of 900us/cm and a PH value of 4.9, the dampening effect is good. When the electrical conductivity reaches 1400us/cm, the water in the water tank has become contaminated and is not suitable for printing. The tank needs to be cleaned and the fountain solution replaced.
Eight, the printing machine fountain solution automatic addition system PH value management requirements
The fountain solution can be classified into two types: "buffer type" (such as liquid B) and "non-buffer type" (such as liquid A). When the concentration of the "buffer type" fountain solution changes, the pH value changes nonlinearly.
At present, the vast majority of presses control the amount of fountain solution by controlling the pH of the fountain solution, requiring a linear change in the concentration of the fountain solution and the pH, that is, a slight change in the concentration of the fountain solution. The pH value should be changed. When there is a slight change in the concentration of the “buffered†fountain solution, the pH value may not change at all, resulting in an uncontrollable concentration of the fountain solution. Therefore, the “buffered†fountain solution is not suitable for automatic machine addition.
The “unbuffered†dampening solution undergoes small changes in concentration, and the pH value changes greatly, making it difficult to control printing. Therefore, what is marketed is basically a "buffer type" fountain solution.
In order to reduce the occurrence of printing failures, the "buffered" dampening solution must be hand-configured and then added to the water tank and equipped with a corresponding measuring cup to control the accurate addition amount.
(to be continued)