The effect of temperature on the quality of printed products during printing
Temperature control of offset press and its effect on print quality
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Most of the drive power of a printing press is used to drive the inking unit. On the inking unit, when the ink is separated, the mechanical rubber becomes heat when the elastic rubber roller is pressed and the ink roller is moved back and forth. Therefore, people try to use the circulating water to keep the ink roller and the ink fountain roller constant, and try to discharge this heat from the source. This circulating water is in the central tank and is also partially adjusted to the required temperature in the lower unit attached to the printing unit. It is best to use full temperature (cooling and heating) to allow the inking unit to reach the standard operating temperature before starting printing.
To date, three options have been implemented for adjusting the temperature of the inking unit.
1) The adjustment amount is the surface temperature of each inking unit.
2) The adjustment amount is the water temperature for the temperature of the ink roller to be injected into each inking unit.
3) The adjustment amount is the water temperature in the central water tank of the thermostat.
·Oil cooling
Although the heat power generated on the transmission mechanism and the bearing on the transmission side of the offset printing machine is relatively small, the possibility of discharge is small, which may cause the side mechanism to generate heat. A high temperature of about 60 to C can be felt where there is no shield-protected drive side member, which adversely affects the temperature uniformity of the entire machine face width. The effect of oil cooling is to keep the temperature of the side parts from being higher than the hand temperature.
·Dampening solution cooling
So-called water film or alcohol wetting devices are usually supplied with a cooled fountain solution at a temperature of about 10 °C. Overall, the dampening solution cooling has little effect on the heat dissipation of the offset press. However, maintaining the low temperature of the dampening solution helps to reduce the evaporation of alcohol in the mixing tank and the water delivery device, and can improve the viscosity of the dampening solution.
· Plate cylinder constant temperature
Waterless offset lacks the cooling effect of dampening solution. For waterless offset presses that do not have a constant temperature of the inking unit, it is preferred to cool the plate cylinder by blowing it. Offset printing with water requires only a constant temperature of the inking unit. The plate cylinder thermostat was not included in the experiments described in this article.
·Infrared (old) temperature sensor
Infrared rays are emitted from the surface of all heating elements. This type of radiation can be measured with a sensitive radiation detector and displayed as a temperature. For absolute measurements you need to calibrate or accurately understand the emission capabilities of the relevant surface. The infrared temperature sensor is used herein to measure the temperature on the inking unit, the measuring unit and the blanket to provide a constant temperature adjustment (Adjustment Method 1).
· Fluctuations in printing
For the increase in solid density and tone value, three adjustment methods can be used to determine by means of the printed sheets, which are extracted from more than 175,000 sheets in high-volume printing. The plates are almost identical. Mainly to determine the standard deviation of the statistics and the range of differences between the maximum and minimum values.