1. Keep the drying device clean The drying device is particularly susceptible to contamination by powder and paper dust via static charge, warm air convection, and stable blowing during paper transport. Therefore, lamps, reflectors and sensors must be cleaned regularly, otherwise, the increase in radiation loss can reach two percent. KBA's recommendation for the VariDry drying device: the UV module should be removed once a week, and the infrared module should be removed from the drying unit at the end of the unit and printing machine once a month, and the lamp should be cleaned with a cloth soaked in petroleum solvent (Fragile!) And reflector (surface is easy to scratch!), Check for mechanical damage and replace as needed. Blower? The filter on the suction system must be cleaned regularly to prevent premature contamination of the radiation device. Dust and ozone must be effectively discharged from the UV dryer. The metal halide spectrum of medium pressure mercury discharge (mercury) lamps. The method of adding indium (In), gallium (Ga) or iron (Fe) can flatten or increase the peak of individual mercury. The wavelength shift from the important but unobtrusive UV-C to UV-A can seriously weaken the curing of UV varnish. There is a loss in the intensity of lamps that are used continuously and turned on and off repeatedly, and thus their efficiency. Therefore, the elapsed time counter on the console must be checked regularly and compared with the manufacturer's regulations. Once the specified service life is reached, it should be replaced even if it can still work. The transparency of quartz glass should also be checked, as the milky white spots that may be generated during UV radiation are impenetrable by radiation. 3. Check the output The effectiveness of the infrared radiator can be checked by measuring the temperature difference of any given energy input with a metal probe and a contact thermometer. If the drying test can be performed regularly with the specific drying device settings and the specified thickness of the aqueous varnish, then a lot of information about the output of the infrared radiator and the "real" age can be revealed. The temperature sensor can only determine the radiant energy, so it is not suitable for obtaining absolute measured values. In addition to certain hardening tests of similar reliability, you can also use a UV dosimeter to directly test the UV lamp, so that you can compare the set radiation level with the actual emitted level. 4. Check the spectrum Infrared radiators have a continuous and peakless radiation curve, with only a single maximum value that gradually rises and falls. When the lamp ages, the curve flattens, that is, the intensity level decreases, but the operating mode remains unchanged. Therefore, aging inspection is sufficient to meet the requirements. The UV mercury lamp has multiple peaks in its metal halide spectrum, and these peaks are cured when curing various substances (varnish, ink, opaque white coating) and during the reaction process (beginning, in-depth influence, thorough curing) Plays a major role. In order to target these substances (the lowest possible absorption when passing through colored or white pigments), or to support specific bonds during the reaction, it may be necessary to replace individual lamps with more suitable special lamps. This is because in lamps with a specific dose (such as lamps used for opaque white paint or cationic photoinitiators), coating the electrode with a metal (indium, gallium, iron) will weaken the destructive peak and enhance it Useful peak. A UV radiometer can be used to determine what kind of UV particles are present and how much. The portable radiometer can only collect a whole measurement value in the range of UV-A, UV-B and UV-C: the position and height of the peak can only be determined by the measurement device in the laboratory. Therefore, it is best to make the portable radiometer used in the printing workshop also have this function, because as the UV lamp gradually ages and loses power, the spectrum of the radiation will also change. More precisely, in the life of the lamp, the spectrum and all its peaks will drift from UV-C to UV-A. Even if the level of radiation is high, this drift in wavelength will seriously affect the film formation in the varnish layer and ink layer. The operator of the printing press must ensure that the UV-C is regularly "updated". Therefore, when replacing the lamp, it is recommended to arrange their position in the drying device at the end of the printing press according to the service life of the UV lamp: the first is the new lamp (because it has the necessary function to start the photoinitiator and cure the varnish High-level UV-C radiation), the second is the lamp originally in the first position, and the last is the lamp originally in the second position.
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All materials have undergone rigorous quality testing.
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2. Aging test
Operation and Maintenance of Drying Device of Sheet-fed Offset Press
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