Comparing Flexo on EPDM Elastomer vs traditional Photopolymer

Direct Laser Engraving: Fundamentals, Advantages, and Future Prospects

At the turn of the century, innovative laser technologies began to emerge. YAG and diode lasers initially gained traction in the plate-making process, first in mask ablation and subsequently in direct laser engraving (DLE).

Numerous engraving system manufacturers adopted these technologies, incorporating them into their systems. Direct laser engraving technology for flexography eliminates the expensive investment in multiple processing stages and equipment typically required by traditional photopolymer sleeve/plate making methods.

Flexographic engraving systems utilize one or more high-powered CO2 or fiber lasers to directly engrave continuous sleeves or plates in a single step. The laser selectively removes the non-print areas of an elastomer plate or sleeve, creating a print-ready surface without the need for exposures or chemicals.

The Compounds and Workflow

For optimal workflow using laser-engraved plates, it is most effective to engrave them when they are mounted on the printing sleeve. This approach eliminates the need for plate mounting and ensures excellent registration.

Rubber has long been crucial in the flexographic industry. Historically, elastomer was predominantly used in sleeve form for printing background colors in flexible packaging and for decorative printing on items like tissue and wallpaper.

Elastomer didn't significantly penetrate the traditional flexible packaging and label markets until recently due to earlier limitations in elastomer compounds and laser technology, which restricted engraved elastomer plates and sleeves to line work and relatively coarse linescreens up to 85 lpi.

However, with the concurrent development of high-performance elastomers and advanced laser technologies, new levels of quality are now achievable. Modern engraving technologies enable resolutions of 4,000 dpi and higher (e.g., 5,080 dpi in printed electronics), with screen values of 200 lpi now common in everyday production across elastomer plate and sleeve producers worldwide.

Material Properties

Today's high-performance elastomers offer more than just improved engraving capabilities. Most current elastomer printing forms are made from EPDM (ethylene propylene diene monomer), a non-polar synthetic rubber compound highly resistant to UV light and ozone. Due to its polarity properties, EPDM is also compatible with ketones, esters, and alcohols, making it ideal for flexographic printing with solvent-based, UV, and water-based ink systems.

A direct laser engraving workflow involves fewer stages, reducing the potential for errors. By eliminating steps and variables, the process becomes more consistent.

Since EPDM-based printing forms do not swell with normal flexo ink systems and are extremely abrasion-resistant, they are well-suited for challenging printing environments, such as plastic cups, tubes, aluminum cans, corrugated materials, and nonwoven applications. Their surface properties, including roughness, surface tension, and compressibility, are designed to neutralize feeding characteristics that often cause halo effects or mottling. These compounds are also optimized to control ink pickup and release, minimizing buildup.

Advantages of Elastomer Plates over Polymer Plates in Flexography

Elastomer plates offer several distinct advantages compared to polymer plates in flexographic printing, making them a preferred choice in certain applications and environments. Here are the key advantages:

Enhanced Durability

Longer Lifespan: Elastomer plates are significantly more durable than polymer plates. They can withstand longer print runs and more rigorous printing conditions, which reduces the frequency of plate replacements.

Resistance to Wear and Tear: Elastomer plates are less prone to damage from abrasion and mechanical stress, ensuring consistent print quality over time.

Superior Chemical Resistance

Solvent Compatibility: Elastomer plates, particularly those made from EPDM (ethylene propylene diene monomer), exhibit excellent resistance to various solvents, including those in solvent-based, UV, and water-based inks. This makes them suitable for a broader range of printing applications.

Minimal Swelling: Unlike polymer plates, which can swell and degrade when exposed to certain chemicals, elastomer plates maintain their dimensional stability and print integrity.

Consistency and Quality

Stable Print Quality: Due to their durability and resistance to chemical degradation, elastomer plates provide more consistent print quality throughout long production runs.

Enhanced Image Detail: Modern elastomer plates can achieve high resolutions (e.g., 4,000 dpi or higher) and fine screen values (e.g., 200 lpi), resulting in high-quality prints suitable for various applications, including those requiring fine details.

Cost Efficiency

Reduced Plate Replacement Costs: The extended lifespan of elastomer plates means fewer replacements are needed, leading to cost savings over time. Printers can avoid the repetitive costs associated with frequently changing polymer plates.

Elimination of Cushion Adapters: Elastomer plates eliminate the need for expensive cushion adapters, further reducing costs.

Versatility in Applications

Tough Printing Environments: Elastomer plates excel in challenging printing conditions, such as printing on plastic cups, tubes, aluminum cans, corrugated materials, and nonwoven substrates.

Surface Property Control: Elastomer plates are designed to neutralize feeding issues, reducing common printing defects like halo effects and mottling. Their surface properties also help control ink pickup and release, minimizing buildup and maintaining print quality.

Environmental and Workflow Benefits

Streamlined Workflow: The direct laser engraving process used for elastomer plates involves fewer stages compared to the traditional photopolymer plate-making process, reducing the potential for errors and making the workflow more efficient.

Reduced Chemical Usage: Elastomer plate-making processes are often more environmentally friendly, as they require fewer chemicals and less processing compared to polymer plates, which involve multiple exposure and development stages.

Performance in High-Volume and High-Speed Printing

High-Speed Compatibility: Elastomer plates are well-suited for high-speed printing operations due to their durability and ability to maintain registration and quality at fast printing speeds.

High-Volume Production: Their robust nature makes elastomer plates ideal for high-volume production environments, where long runs and consistent quality are critical.

Elastomer Sleeves vs. Polymer Sleeves

Cost concerns, perceived supply chain issues, and limited inventories have hindered the adoption of elastomer sleeves in America. However, new advancements in imaging and manufacturing are highlighting their advantages to printers.

Elastomer sleeves are thicker and more durable, capable of lasting two to four times longer than polymer sleeves. This longevity reduces the need to purchase multiple plates or polymer sleeves for long runs and frequent short runs that require numerous cleanings and press cylinder mountings, resulting in both cost savings and cost predictability. Printers who have transitioned from polymer to elastomer sleeves often comment, "Elastomer usually costs less than polymer, and we’re only buying one set instead of two—so the savings are great, and our print results are more consistent."

Further cost savings arise because elastomer sleeves eliminate the need for expensive cushion adapters and their eventual replacements.

Conclusion

While both elastomer and polymer plates have their respective advantages, elastomer plates stand out in terms of durability, chemical resistance, consistent quality, cost efficiency, and versatility. These benefits make elastomer plates a preferred choice for many flexographic printing applications, particularly those involving high-volume, high-speed, and challenging printing conditions.

Antonio de Llamas - June 2024