September, 2024: The coil coating industry is ripe for innovation and differentiation through specialty coil finishes such as pattern coating, digital printing, paint embossing and metal embossing. For over 50 years, Bronx Group has worked to engineer and manufacture coil coating lines, enabling coaters to produce a wide variety of unique and high-quality products. These specialty coil finishes enhance the visual appeal of metal products and imbue them with unique properties, expanding their application potential. Let’s explore some technologies in detail.
PATTERN COATING
Pattern coating involves applying patterned ink over a uniform base color. The Bronx Group uses offset rotogravure printing on its coil coating lines for this purpose. This technique allows for intricate designs, such as wood grains, brick, rock, stars, clouds, slate, marble and numerous others.
TECHNICAL DETAILS
1. Engraving and ink transfer: The pattern is engraved onto a chromeplated steel pickup roll. Ink is applied to this roll, and a doctor blade removes excess ink, leaving it in the engraved areas. The ink is then transferred to a polyurethane applicator roll, which applies it to the base-coated strip with light pressure.
2. Doctor blade application: The angle and pressure of the doctor blade are critical to remove excess ink and prevent defects like hazing. Proper adjustment ensures the correct amount of ink is retained in the engravings.
3. Layer thickness control: The primer layer is typically 5μm, the base coat is 10-15μm, the ink layer is 1-2μm, and the clear protective coat is 10-12μm. These layers must be precisely controlled to ensure durability and visual appeal.
4. Multi-pass process: Depending on the coater head configuration, the coil may need multiple passes through the line. This ensures each layer, from primer to clear coat, is applied correctly. In some setups, the clear coat can be applied wet-on-wet simultaneously with the pattern.
5. Material flexibility: Pattern coating can be used on various materials, including steel and aluminum, and is compatible with multiple base colors and finishes.
DIGITAL PRINTING
Digital printing offers unmatched flexibility and customization for coil coating. This method allows for printing various lengths for the image, from 12 cm (4.72 inches) to 10 meters (32.8 feet), and in any color combination. Instant image changeover reduces scrap losses and enhances production efficiency. Bronx Group’s digital printing systems use modular technology with up to 12 print heads, accommodating specialty inks such as glazes, glues, lusters, metallic inks and more. These systems are equipped with built-in maintenance and purging, ensuring reliable 24/7 operation.
TECHNICAL DETAILS
1. Resolution flexibility: The system can adjust the resolution of images, allowing for ink conservation or high-quality prints. This flexibility helps in managing ink consumption and achieving desired visual effects.
2. Modular technology: Standard delivery includes four heads for CMYK printing, but the system can expand to 12 heads for a broader range of colors and specialty inks. This modularity enhances customization and product differentiation.
3. Maintenance and reliability: The built-in maintenance and purging systems ensure continuous operation, reducing downtime and ensuring high productivity in a 24/7 environment.
4. Integration with existing systems: Digital printing systems can be integrated into various coil coating line configurations, whether dedicated start/ stop lines for digital products or combined lines for standard polyester paints and digital prints.
PAINT EMBOSSING
Paint embossing creates texture on the coated surface by embossing patterns into the paint layer. This technique is often used with plastisols, applied at around 200μm thickness. The process involves using a threeroll head system to apply the thick liquid PVC, followed by embossing with water-cooled rolls while the film is still hot. The embossing ensures a uniform surface with patterns like leather grain, adding visual appeal and improving corrosion resistance.
TECHNICAL DETAILS
1. Application technique: Paint embossing uses a three-roll head system to apply thick liquid (melted) PVC, ensuring uniform surface and film thickness. The V arrangement of the rolls aids in achieving the desired embossing eff etc.
2. Embossing process: The embossing is performed at the exit of a curing oven with water-cooled rolls at around 180 degrees Celsius, ensuring the pattern is embedded into the hot film. This process guarantees a consistent and uniform embossed surface.
3. Emboss depth: The depth of embossing is typically less than half the thickness of the plastisol fi lm, ensuring durability without compromising the visual appeal.
4. Material compatibility: Paint embossing is primarily used on plastisols but can be adapted for other coatings, offering flexibility in design and application.
METAL EMBOSSING
Metal embossing deforms the actual metal substrate to create patterns that enhance strength and stiffness. This process is useful for reducing material thickness while maintaining structural integrity. The Bronx Group’s embossing machines can handle carbon and stainless steels, aluminum and their alloys, making them suitable for a such applications as appliances, building materials, automotive parts, elevator panels and more.
TECHNICAL DETAILS
1. Material deformation: Unlike paint embossing, metal embossing works directly upon the metal substrate, enhancing its strength and stiffness. This allows for lighter gauge materials to be used without sacrificing structural integrity.
2. Material specifications: The process accommodates material thicknesses from 0.005 inch to 0.098 inch and widths from 11.8 inches to 65 inches, offering versatility for a great variety of applications.
3. Embossing patterns: Common patterns include stucco, which reduces reflectivity and adds strength. Coil coaters can choose standard designs or create custom patterns for unique applications.
4. Machine integration: Embossing machines can be incorporated into new or existing coil coating lines or be supplied as a stand-alone unit, offering flexibility for manufacturers looking to expand their product range.
5. Applications: The embossing process is used in various industries, including appliances, building materials, automotive parts and more. It enhances both the visual appeal and functional properties of the metal products.
FORM + FUNCTION
Coil coating offers a wide array of specialty finishes to metal substrates that can significantly enhance the appearance and functionality of end products. Techniques like pattern coating, digital printing, paint embossing and metal embossing provide manufacturers with the tools to create distinctive, high-quality products that meet diverse market demands.
The Bronx Group’s expertise in coil coating technology helps coil coaters and their manufacturing customers unlock the full potential of specialty coil finishes and drive the industry forward. By embracing these advanced finishing techniques, coil coaters can build stronger relationships and ensure the effective use of their coating lines, ultimately securing their place in a competitive market.
The Bronx Group, 708/212-7371, http://thebronxgroup.com/
