Dryer settings in sheetfed offset printing
The IR dryer can be adjusted in steps or stepless. It is important that the operator selects the dryer settings according to the pile temperature recommended by the ink manufacturer. The pile temperature is applicable to the settings of the IR lamps. These settings have to be adjusted accordingly to ink coverage, printing material and printing speed.
Eltosch IR dryers can be used in manual or automatic mode. With use of the automatic mode (ASR) the IR lamp power will be automatically adjusted to reach the preselected pile temperature.
IR/HA dryer settings
In general the dryer settings have to be adjusted to the printing job. A variety of parameters influence the drying results, so it is not possible to give general recommendations for dryer settings.
The operator has the possibility to adjust the following parameter independently of each other.
- Hot air volume:
- Hot air temperature:
- Exhaust volume:
- IR lamp power:
Hot air-/ exhaust volume
- Preselect the maximum possible hot air and exhaust volume. Sheet travel is the only restriction for both the hot air and exhaust volume.
- Hot air volume should not be higher then the exhaust volume.
Hot air temperature adjustment
- Hot air temperature should generally be between 70° - 100°C (158°F - 212°F).
- Adjust the hot air temperature to the coating thickness. Thicker coating applications often need a higher air temperature.
- The operator should slowly touch down to the lower hot air limit to reduce the amount of energy and temperature load of the press.
IR lamp settings
- The IR lamps are mainly applicable for the pile temperature.
- Only preselect the minimum amount of IR lamps necessary. The pile temperature guidelines of the ink-/ coating manufacturer have to be followed up.
- Too high pile temperatures results in set off or blocking.
- The printer can use the dryer in manual or automatic mode. With use of the automatic mode (ASR), the IR lamp power will automatically be adjusted to reach the preselected pile temperature.
UV dryer settings:
In particular cases in the press, it is important that the dryer configuration is adjusted to the print job. Some inks need more UV power because ink components absorb UV radiation. The settings of the dryer power have to be adjusted to the following conditions:
- Inks like opaque white, black, and metallic effect inks need more UV power.
- Thick ink/ varnish layers need more UV power.
- When printing more overlapping inks, it is recommended to use more inter deck dryers.
- Low migration inks and varnishes often needs more UV power then conventional UV inks.
- With higher printing speed, higher UV power is necessary because the UV dose for curing is related to the press speed. Eltosch drying systems are equipped with an automatic mode. With selection of this mode, UV power output is linked to machine speed.
Too much UV power is critical when printing heat sensitive material. This can result in register warping. UV power decreasing can relieve this. If the majority of jobs are printed on heat sensitive materials, it should be considered to use Eltosch modules.