GOING GREEN: COATED COILS

For OEMs that are serious about protecting the environment, a conversion to coated metal coil can be a major step to a more environmentally-friendly manufacturing operation. Nearly 90 years ago, engineers discovered the benefits of unrolling a coil of aluminum or steel, applying a primer and/or a finish coat and then re-coiling it before shipping it to a processor.

Since those early days of prepainted metal, a myriad of industries have grown alongside the coated coil industry, finding that it makes more sense to form products from prepainted metal than to form products bare and paint them afterwards.

And for companies serious about protecting the environment, coil coated metal could be just the ticket for jump-starting a green initiative. This growth means prepainted steel and aluminum metal processors are seeing a steady increase in the number of coated coils arriving on their docks.

WHO'S USING COATED COIL?

Over 4.5 million tons of coil-coated steel and aluminum are produced and delivered to processors in North America each year. Industry leaders such as GE, Whirlpool, Trane, Mercedes Benz, Nordyne, and Steelcase depend on prepainted metal to meet their manufacturing and quality needs.

Thousands of products, including stoves and refrigerators, agricultural equipment, heating and cooling units, metal roofs, and beverage cans are produced more efficiently with prepainted metal. Throughout the manufacturing processes, prepainted products retain their flawless appearance and durability, a feat often impossible with post-painted metal.

WHY CHANGE TO PREPAINT?

Prepainting metal provides consistent color, texture, thickness and performance, proven by numerous quality control tests during and after the coil coating process. Coil coating lines unroll each coil, clean it and treat it, precisely apply a primer and/or finish coatings using a continuous rolling process.

This extremely efficient process applies high quality finishes to coil up to 72 in wide at speeds of up to 700 fpm. And the beauty of coated coil is not just one-sided: the consistent, high-quality finish is usually applied to both sides of the substrate to meet nearly every finished product specification.

Coated coil can be final slit to a customer's requirements so it can be stamped, drawn or roll formed into thousands of products, from mini-blinds to door jams. Slitting the material to the OEM's exact width requirements also means waste goes down and yield goes up.

By using prepainted metal, companies enjoy other benefits in addition to manufacturing and quality improvements. Prepaint offers advantages of reducing on-site environmental issues, saving money by-eliminating staffing and operation of in-house painting, and decreasing costs and hassles associated with adhering to environmental regulations. Prepainted metal has weathered many storms, and has outperformed post-painted metal in field tests.

Here are the most common inquiries fielded by the National Coal Coating Association (NCCA) around processing coated coil:

Does prepainted metal with cut-edge hold up?

Some manufacturers are concerned with exposed cut-edge on prepainted metal, but research has shown that prepainted cut-edge actually holds up better over time than post-painted surfaces.

What equipment changes are necessary?

Some changes may be required in order to get the most out of converting a post painted application to prepaint technology. The most common changes are die clearances, depending on the product being made. In some cases, tooling may be need to be adjusted to allow for the additional film that exists with paint on both sides of the product. When making a conversion to prepainted metal, it is always good practice to evaluate potential manufacturing changes to streamline the process. In many cases, manufacturing complexity can be reduced by eliminating steps resulting in moving a product through the manufacturing cycle faster subsequently increasing throughput and reducing costs.

Do I have to change my current tooling?

In most cases, you don't have to change tooling, but you may have to make a few adjustments. Dies should be polished and die clearances adjusted to fit prepainted metal. Prepaint serves as a lubricant, and when you use prepaint, you actually get extended tool life. It is recommended that tooling be devoted to prepainted material, or cleaned thoroughly between runs, vs. moving back and forth between bare material and painted material. If the customer processes bare metal, the raw material has not been cleaned and carries roll oils and metal fines that can contaminate the prepainted metal.

How can I handle prepainted metal without damaging the finish?

There is no need to be fearful of handling prepainted metal. Sound traditional manufacturing techniques should prevent damage in normal production. It is important to remember that prepaint is a finished product, and should be handled as any finished product would be handled.

Will prepaint scratch during forming?

It's important to discuss the manufacturing process with your coil coater or service center, so that the appropriate coating for your application can be determined. Once you've got the right coating, sound manufacturing and handling processes make prepainted metal no more susceptible to damage than finished products. It is recommended, however, that tooling be dedicated to prepaint. There are many proven, simple techniques that can be employed to prevent damage.

What about touch ups?

Touch ups are significantly reduced or eliminated. If touch ups are needed, something is wrong in the manufacturing process. Should transit or installation damage occur, repair paints are available from the original coating manufacturer, as there are with postpainted products.

MORE CONSIDERATIONS

Prepainted coils are, in fact, very forgiving, and only minor process changes are required for specifying, handling, storing and setting up for coated coil processing. The following best practices should be implemented to help prevent damage to coils, while guaranteeing your customers receive brilliantly finished materials ready for manufacture:

Specifications: The coil coater can help determine the best specification for your product. It's important to consider the current and proposed manufacturing processes, the lifecycle of the product, and the expectations of the consumer. The coil coating industry works hard to balance all of the market's requirements, which, in many cases, can be contradictory – such as hardness and flexibility.

Handling: Prepainted coils can be shipped on flatbeds and moved with forklifts while still retaining a flawless surface. In the plant, ensure that forklift forks and masts are padded to protect coil edges. Padding on hooks and other handling devices help keep coil in great shape. Always use V-shaped coil cars with a nonmetallic surface. Turnstiles with modular round supports of hardened steel for coil support work best, but felt and previously used conveyor belting also work well. Cushioning materials like feltboard and polyurethane help protect coils while they are moved, placed in inventory, or shipped.

Storing: It's important to leave stocked coils banded until they are needed for processing. Always use extra care when removing bands so they don't snap back on the coil. Make sure clips are on the side of the coils – not the bottom – when setting them down. If possible, storage in a climate controlled weatherproof building is preferable. (It's a myth that galvanized steel can be stored outside) Floor pads or cushioning materials should be used, and protective films may also be applied at slitting or sheeting, if required. Wrapping coils with stretch wrap, coated paper, fiber-based wrap or particleboard helps protect stored coils. Use care not to create an airtight seal; this could create a humidity chamber that could lead to condensation damage. Always protect the coil from direct contact with the ground or transport vehicle.

Processing: Close attention to gauge must be paid when feeding and processing material, as the coating can significantly change material thickness. Attention must also be paid to burrs as they can damage sheets or parts as they flow through the manufacturing cycle. The use of clean equipment and protective films and papers can significantly decrease any manufacturing damage. Your coil coater can help you determine what processes may be right for you.

Set-up and Cleaning: Every point in a coil processing line where finished surfaces touch another surface should be taken into consideration. Be sure to check clearances and alignments – too much clearance can cause burrs and scratch the surface. Add padding for extra protection, or bonding strips of rubber to the faces of sheers, press brakes, punch brakes, carry tables or bench tops. Watch out for rough dies that can gouge or scratch the prepainted surface. 

Cutting and Slitting: Machinery must be cleaned before it is used on coated coils. Some plants use two lines: one for coated and one for bare metal processing. You can also employ dedicated slitting knives that are changed for coated metal. Consider scheduling coated metals to be cut on certain days or shifts to avoid having to clean machinery as often.

When cutting to length some customers may want strippable film applied which will help protect the surface. Always watch for flecking when slitting coated coils. To avoid "friction scratching" when cutting to length, be aware of the need to maintain proper tension.

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National Coil Coating Association (NCCA), 1300 Sumner Avenue, Cleveland, OH 44115, 216-241-7333, Fax: 216-241-0105,www.coilcoatinginstitute.org.