WHAT ARE FLEXOGRAPHIC PRINTING PLATES?

Flexographic printing plates, often referred to as flexo plates, are a critical component in the flexographic printing process, a popular method used to print on a wide range of substrates such as paper, plastic, metal foil, and non-wovens. These plates are flexible, relief-style printing elements that transfer ink onto the target material, enabling high-speed, high-quality printing for various applications including packaging, labels, and newspapers.  

How They Work

The operation of flexographic printing plates is rooted in the relief printing principle, where the image area of the plate is raised above the non-image area. The process unfolds in several key steps:

1. Ink Application: First, ink is supplied to anilox rolls, which are cylindrical rollers with tiny, evenly spaced cells engraved on their surface. These cells act as reservoirs, holding a precise amount of ink. The anilox roll rotates and picks up ink from the ink fountain, and a doctor blade scrapes off excess ink to ensure only the cells are filled with the correct ink volume.

2. Ink Transfer to Plate: The ink-laden anilox roll then comes into contact with the flexographic printing plate, which is mounted on a plate cylinder. The raised image areas of the plate pick up the ink from the anilox roll's cells, while the non-image (recessed) areas do not receive ink.

3. Image Transfer to Substrate: As the substrate (e.g., a roll of plastic film) moves through the press, it passes between the plate cylinder and an impression cylinder. The impression cylinder applies pressure to the substrate, pressing it against the inked flexo plate. This pressure causes the ink on the raised image areas of the plate to transfer onto the substrate, creating the desired printed image.

Key Characteristics

Flexographic printing plates possess several distinct characteristics that make them suitable for diverse printing needs:

Flexibility: Their flexible nature allows them to conform to the shape of various substrates, including uneven or textured surfaces. This flexibility is particularly advantageous when printing on curved or cylindrical objects, as well as on stretchable materials like plastic films.

Relief Structure: The raised image areas ensure efficient ink transfer, even at high printing speeds. This relief design also minimizes ink smudging, as the non-image areas do not come into contact with the substrate or ink sources.

High Resolution and Detail: Modern flexo plates, especially those made from photopolymer materials, can achieve high levels of resolution and fine detail. This makes them suitable for printing intricate designs, small text, and vibrant graphics, meeting the demanding quality standards of packaging and label industries.

Durability and Longevity: Flexo plates are resistant to wear and tear, chemicals, and UV radiation. Depending on the material and printing conditions, they can withstand thousands to millions of impressions before needing replacement, ensuring cost-effectiveness for large print runs.

Compatibility with Multiple Inks: They work well with a variety of ink types, including water-based, solvent-based, and UV-curable inks. This versatility allows printers to choose the most appropriate ink for the substrate and application, such as water-based inks for eco-friendly packaging.

Prepress, Platemaking, and Press Set Up

1. Prepress:
This stage involves all the digital preparation of the artwork. The design file is processed to separate colors and, most importantly, to compensate for the natural tendency of the flexible plate to distort during printing. Techniques like screening and profiling are used to ensure the final print matches the digital proof. The final approved artwork is output onto a high-resolution negative film (for analog) or directly imaged using a laser.

2. Platemaking:

• Exposure: A sheet of light-sensitive photopolymer is placed in a platemaking system. A UV light source shines through the negative film (or a laser directly ablates a black layer in digital systems), hardening the image areas of the polymer. The non-image areas remain soft and unhardened.

• Washing Out (Development): The plate is then placed in a processor where a solvent or water-based solution washes away the unhardened, non-image polymer, revealing the raised relief image.

• Drying: The plate is dried in a warm air oven to remove any residual solvent or moisture and to shrink it back to its original size.

• Post-Exposure and Finishing: The plate is exposed to UV light again to fully harden and cure the polymer, making it tough and durable. Finally, a final UV exposure eliminates tackiness on the plate's surface, ensuring smooth ink release.

3. Press Set Up:
Once the plates are ready, they are sent to the pressroom. An operator mounts each plate onto its respective plate cylinder, ensuring it is perfectly aligned according to registration marks. This setup process is aided by advanced camera systems that read these marks to ensure each color is perfectly aligned with the next—a critical step for a high-quality, sharp print.

INVESTING IN THE RIGHT FLEXO MACHINE

When you are looking to expand your printing capacity, speak to Rui Ting about the right flexo printing press for you. Expect high quality and consistency, as these two go hand in hand with all the products we offer. Consider what type of printing needs your customers have and then select a press specification that suits your requirements. Flexo remains the leading technology employed in the mass production of printed images. For cost effectiveness and reliability, it is still to be unsurpassed.

RUITING's Flexo Printing Machine has strong compatibility and can print a variety of paper materials. It is the preferred equipment in the packaging and printing industry.

Imported servo motor drive, the fastest speed can reach 150 meters/minute.

Auto color register system with color sensors, make print sample more accuracy.

UV curing technology, can print various of different materials, like plastic film, PP, PVC, Bopp films, aluminum foil, etc.

Conclusion

Flexographic printing plates are the dynamic and versatile heart of the flexo process. Their evolution, particularly with digital platemaking, has dramatically increased print quality, making flexography the dominant force in packaging printing today. When paired with precision-engineered machinery from manufacturers like ruting, these plates enable the production of vibrant, efficient, and high-quality packaging that fills our store shelves every day.