Hot Air Dryers for Sheet-Fed Flexographic Printing Machines
Hot-Air Drying for direct printing on corrugated board, designed for high production output, high energy efficiency, and compact integration into the printing press.
When is hot-air drying recommended for sheetfed machines?
In direct printing on corrugated board, hot-air drying has been the proven method for decades for maximizing the printing press’s full speed, even on coated papers. Our systems have undergone continuous development: Thanks to modern frequency converters, air management is controlled with such precision that virtually no heat escapes into the sensitive environment of the printing unit. This protects your machine and optimizes the drying result.
Technical Operating Principle in Sheetfed Printing Machines
Hot-air dryers for sheeting machines operate using precisely directed process air that is heated and evenly distributed over the printed sheet via air nozzles. The hot air absorbs the evaporated moisture and is extracted from the process chamber via a specially designed exhaust system.
Warm air is applied to the corrugated sheet at high air velocities of approximately 60–70 m/min via a specially manufactured aluminum nozzle. The initial air stream breaks through the laminar airflow carried by the sheet. This allows the air from the subsequent nozzles to penetrate unimpeded to the ink or varnish and absorb the water.
The supplied hot air is extracted at the inlet and outlet and recirculated. This creates a cycle to which up to 20% fresh air is regularly added to prevent air saturation. The advantage of this is that the installed heating capacity is only required for heating at the start of the process. Once the system has stabilized, only 40–60% of the installed capacity is required, depending on the set temperature.
The extraction also prevents warm air from escaping into the press chamber, as this prevents the inks and coatings from drying out. The following diagram illustrates the principle.
The hot air temperature for water-based coatings should be between 100 and 110 °C; for paint drying, 60 to 80 °C is usually sufficient. Dryer performance is controlled by temperature, airflow, and, in the case of Duo technology, also by the working width.
Today’s modern systems use demand-based airflow control and speed-controlled fans to adapt energy consumption to changing production conditions.
Advantages of a Hot-Air Dryer
- Maximum productivity: Full machine speed without the risk of ghosting or marks.
- Extreme cost efficiency: Intelligent width shutdown saves you up to 30% on energy costs.
- Safe operation: No fire risk.
- Flexible primary energy sources: Steam, natural gas, biogas, biomethane, hydrogen, thermal oil, hot water, or optimized combinations.
- Compact integration: Also suitable for tight installation spaces between printing units.
Typical Applications in Sheetfed Printing
- Direct printing on corrugated board: Highest quality with water-based inks.
- Inline drying: As an intermediate or final dryer in sheetfed printing presses.
- Finishing: Drying of dispersion coatings at maximum production speed.
- Retrofit: Modernization of existing sheetfed lines to increase capacity.
Technical Specifications for Sheet-Fed Machines
Criterion | Specifications |
|---|---|
| Working Widths | 350 – 3600 mm |
| Types | End dryers / intermediate dryers |
| Air nozzles | 1–9 with slot widths of 2 or 3 mm |
| Air volume control | Frequency-controlled drives and motorized dampers |
| Output control 1 | Temperature control 60–120 °C |
| 2Output control 2 | Stepwise width adjustment |
| Energy sources | Steam, natural gas, biogas, biomethane, hydrogen, thermal oil, hot water |
Frequently Asked Questions About Hot-Air Dryers for Sheet-Feeding Machines
Why is warm air particularly important in flexographic printing?
In flexographic printing, large amounts of moisture must be reliably removed to prevent ghosting, trapping, and marks.
Is the dryer suitable for retrofitting?
Yes, many hot-air systems can be integrated into existing sheetfed printing presses and connected to existing energy sources.
How is energy consumption optimized?
Through coordinated airflow control, speed-controlled fans, width-specific shutdown, and intelligent control concepts.