This article is part of the FLEXO FLAW FIXING series
In flexo printing, high dot gain not only compromises image clarity, but also affects overall print quality, resulting in printed products that differ significantly from their digital proofs. This article examines how to detect high dot gain, explains its common causes, and offers detailed solutions to address this pervasive problem.
Effective identification of high dot gain relies on careful visual inspection and accurate dimensional measurements. Anomalies in the print, where dots appear larger or more spread out than intended, signal high dot gain. This aberration, if left unaddressed, will distort text clarity and image detail, affecting the print’s fidelity to the original design.
Detailed Causes and Solutions
Dot Gain Calculation
- Cause: Inaccurate expectations of dot gain based on faulty calculations can lead to incorrect prepress adjustments.
- Solution: Revisiting and refining dot gain curves with actual print data in mind will help achieve prints that closely match original proofs.
Plate, Tape and/or Substrate Thickness
- Cause: Variations in plate and tape thickness can affect ink transfer dynamics, resulting in high dot gain.
- Solution: Choose plates and tapes with tight thickness tolerance specifications to ensure accurate ink transfer and reduce dot gain.
Plate, Tape and/or Substrate Hardness
- Cause: The hardness of printing plates or adhesive tapes can lead to improper ink application, contributing to high dot gain.
- Solution: Selecting materials with appropriate hardness based on the specific printing requirements can significantly reduce the likelihood of dot gain.
Pressure Settings
- Cause: Overly aggressive pressure settings between the plate cylinder and the substrate can cause excessive dot gain.
- Solution: Adjusting the press pressure settings to the optimum level will improve dot placement accuracy and minimise dot gain.
Temperature Control
- Cause: Inconsistent centre cylinder temperatures can affect ink viscosity and exacerbate dot gain.
- Solution: Maintaining cylinder temperatures within optimal ranges ensures consistent ink flow and reduces unwanted dot gain.
Plate Alignment
- Cause: Incorrect plate alignment can result in uneven ink transfer.
- Solution: Regularly checking and adjusting plate alignment can prevent uneven ink transfer and reduce high dot gain.
Ink Maintenance
- Cause: The use of old or improperly mixed inks, coupled with poor plate maintenance, results in unpredictable dot gain.
- Solution: Strict adherence to ink quality protocols and regular plate maintenance ensure that dot gain is kept in check and the integrity of print quality is maintained.
Advanced Preventive Strategies
The use of advanced solutions such as high-quality digital plates that offer greater control over dot size and innovative ink formulations can further reduce the risk of high dot gain. The integration of UV curing systems and the use of desiccants ensure rapid ink setting, reducing smudging and spread. Preventive maintenance, combined with continuous monitoring and adjustment of press operations, is the cornerstone of sustained high quality flexo printing.
Conclusion
Recognising and managing high dot gain in flexo printing is critical to producing prints that are true to their digital designs. By understanding the causes and implementing effective solutions, print professionals can significantly improve print accuracy and ensure that the final product meets the highest standards of quality and fidelity. Continual learning and adaptation to new technologies remain key to overcoming the challenges of high dot gain.
