Offset production ink balance control solution

At present, the formulation of dampening solution is usually quantitatively proportioned, that is, the container is fixed in size, the amount of water is fixed, the amount of dampening solution additive is fixed, and the amount of isopropyl alcohol is fixed. It should be noted that the first time this method is used, the amount of water, dampening solution additive and isopropyl alcohol should be accurately measured. When mixing, it must be stirred evenly to make it fully mixed. After standing for about 20 minutes, use downtime. It is added to the dampbox. The pH of the suitable dampening solution should be controlled between 4.8 and 5.5, the temperature should be maintained between 8 and 15 ° C, and the conductivity should be controlled between 800 and 1500 μS/cm.

In order to reduce the possible failures in offset printing , it is recommended to use a measuring instrument to detect the pH value and conductivity of the dampening solution every week, and to clean the filter sponge of the dampening box to reduce the influence of external impurities such as ink and paper on the conductivity of the dampening solution. It is recommended to clean the damp box every half month.

Guarantee plate quality

Strictly control the quality of the printing plate, and choose a photosensitive resin plate with fine and uniform sand and a certain mechanical strength.

After exposure and development of the photosensitive resin sheet, the operator should measure the dot reduction rate and the solid density on the surface of the printing plate, so that the printing plate has a solid graphic basis and a blank foundation.

Correct adjustment of the ink roller pressure

Under normal circumstances, the pressure of the ink roller should be adjusted under the condition that the ink roller is warm. If it is carried out under cold conditions, the pressure between the roller and the roller should be appropriately increased. The principle of adjusting the pressure of the ink roller is: from the inside to the outside, first adjust the pressure between the ink roller and the ink (water) roller, then adjust the pressure between the ink roller and the plate cylinder, and the ink roller and the ink (water) The pressure between the rolls is slightly greater than the pressure between the plates. When adjusting the pressure of the ink roller, the more accurate measurement method is to let the ink roller stop for 10s after the plate is pressed, and then remove the ink roller to observe the length of the ink mark on the plate cylinder. When adjusting the pressure, it is necessary to use a light-colored ink (such as yellow ink) for observation. It is recommended to use a transparent film ruler when measuring. The paper can be used to indent the paper and measure the length of the ink mark on the paper. The measurement results require ink marks on both sides. The length is as uniform as possible, and the error is less than ±0.5mm. It should be noted that the pressure of the ink roller must be adjusted according to the manufacturer's recommendations and the specific requirements of the machine.

In addition, the pressure of the ink roller should be checked periodically to ensure good condition according to the use of the offset press.

Well controlled workshop temperature

Printing machines and materials are very sensitive to changes in temperature and humidity, the temperature is lowered, the ink thickens, increase the viscosity, drying speed slows down, galling easily lead sheet, or even tear; humidity decreases, the paper side of the phenomenon will be tight, so that Lead to unevenness and static electricity, affecting paper feeding. When the temperature rises, the ink becomes thinner, the viscosity decreases, the drying speed increases, the image reproducibility deteriorates; the humidity rises, the ink drying speed slows down, and the paper is prone to flounces, curls, etc., resulting in failure to feed paper.

Humidifiers, air conditioners, etc. should be installed in the offset printing workshop. The suitable temperature and humidity of the workshop are: temperature (23 ± 5) ° C, relative humidity (65 ± 15)% (generally not less than 35%).

Preset water volume and ink volume

The thickness of the ink film on the surface of the ink roller during pre-printing of the pre-press is controlled to ensure the formation of the flowing ink layer. When adjusting the amount of ink on the printing plate, the overall or partial water volume and ink volume should be preset by visually measuring the dot size and image area of ​​the printing plate according to the printing suitability of different papers, thereby avoiding four states of ink imbalance. This process requires a high level of experience and is generally done by the printer captain.

Identify and control the amount of water in the layout

The identification and control of the amount of water in the layout is an important factor in maintaining the balance of ink and water. Typically, the operator can stand on one side of the machine and observe the state of the water on the surface of the plate during printing with natural light or light. Generally speaking, when the amount of water is large, the plate reflection light is strong and the side view is brighter; on the contrary, the plate reflection light is weak and the side view is dark. When the blanket is checked for maintenance, if water droplets appear on the back end, it indicates that the water volume of the layout is too large and should be adjusted in time.