The following is a list of frequently asked questions from customers regarding coil coating technology. These questions and answers were obtained with permission from the National Coil Coating Association (www.coilcoatinginstitute.org).
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Q: Why should I consider pre-paint rather than convert to a powder system?
A: To fully answer this question, you must look at powder coating in two ways: 1) as an alternative to pre-paint, 2) using powder in conjunction with pre-paint. As an alternative, powder looks like the most logical step from wet paint to solve environmental problems, but it is limited in its environmental friendliness. Powder solves one environmental problem—the elimination of volatile organic compounds (VOC’s). However, powder leaves open the issue of cleaning, pretreatment and the disposal of sludge. Pre-paint addresses environmental problems, including air, water, solvents and waste disposal. Pre-painted metal is cleaned and treated in the flat, effecting better cleaning and pretreatment, and correspondingly, a higher quality product. Certain applications can benefit from the unique advantages of both pre-paint and powder technologies. The coil coating process can be utilized to clean/pre-treat and prime, providing a superior surface for subsequent powder coating. This combination meets both air and water compliance issues and provides a superior product for corrosion resistance. Technological advantages of both pre-paint and powder.
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Q: What are the costs of an in-house spray operation?
A: There are numerous primary, secondary and hidden costs. Primary costs are materials, people, energy, water and the cost of compliance. Secondary costs are the cost of rework, the time involved in manufacturing the product, the number of manufacturing steps appropriate to produce a product in a spray operation, and, of course, touch-ups. Hidden costs include lack of flexibility, since you can only apply one coat at a time, growth limitations and slower manufacturing cycle time due to a paint line bottleneck.
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Q: How does the overall corrosion resistance of coil coating compare to my current method?
A: Unquestionably, the corrosion resistance is better using pre-painted metal than metal from a typical post-painted product. Due to the superior cleaning and treating of the strip during the coil coating process, the priming of both sides and the painting of both sides, pre-painted metal has better cut edge corrosion resistance than post-painted metal. A fine line of corrosion may develop on the cut edge of pre-painted metal, but the resistance to underfilm corrosion creepage will be much better than with post-painted metal. The corrosion resistance is also better where nicks and scratches occur. The online tutorial, Cutedge: Tougher Than You Think provides helpful information on this matter and can be viewed on NCCA’s web site www.coilcoatinginstitute.org.
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Q: How does the process affect floor space and throughput?
A: When you eliminate a post-finishing operation, you free up floor space. Additionally, since work-in-process inventory is reduced, the demands for additional floor space are correspondingly reduced. Production capabilities can grow without adding exclusive manufacturing space.
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Q: Can the process provide a consistent, uniform coating?
A: The distinct advantage of the coil coating process is its ability to provide a uniform, consistent coating. Painting metal in the flat allows for consistency in film application and color uniformity.
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Q: Can you paint both sides at once?
A: Yes. Coil coaters paint both sides of the coil at once. The coating process on a coil coating line is very flexible, allowing the application of many different types of primers, solid color finishes and top coats.
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Q: Can you put two coats of paint on in one operation?
A: Yes. Actually, you can put four different types of paint on in one operation: primer on both sides of the coil, a finish coat on the top side and a wash coat on the backside. If desired, it is possible to apply two different types of paint in the primer station on the back and top side, cure the first coat, and then apply two completely different paints on the top and backsides.
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Q: What colors are available?
A: There are wide varieties of paints available: polyesters, polyurethanes, zinc-rich coatings, epoxies, fluorocarbons, silicone polyesters and more. A wide range of colors and glosses are available to meet customer needs.
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Q: How do you control the color match from batch to batch?
A: The color control from coil to coil and run to run is one of the distinct advantages of the coil coating process. Metal is coated in the flat, and because of the roll coating process, it is possible to lay down a smooth and uniform film. Laboratories and paint companies that supply coatings have developed ways to maintain film control at a variety of thicknesses that are very reproducible. Line results are very consistent, and coaters have the ability to coordinate lab conditions with line conditions to control the incoming raw materials for consistency.
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Q: Can you bend it?
A: Yes. Since the metal is painted in the flat and rewound into a coil, it is ready to be formed into the ultimate part. You can bend it, shape it, punch it and more.
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Q: What do you do with the bare edge?
A: There are several approaches to answer the question. If it is an aesthetic issue, it can be hidden, folded, roll formed or tucked away so that the bare edge can be kept out of sight. If there is concern about performance (such as fear of corrosion because of bare edge), it can be roll formed to take it out of a corrosive environment. It is important to note, however, that pre-painted material, even with bare edges, has shown better corrosion resistance than post-finished product because of the cleaning and pre-treatment the metal undergoes before painting. For additional information, refer to Tool Kit #5, Cut Edge Protection Using Prepainted Sheet.
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Q: What equipment changes are necessary?
A: Minor changes may be required in order to get the most value out of a conversion to pre-paint. The most common changes are die clearances, depending on the product being made. If it is a brake press product, dies might need to be adjusted to allow for the additional film that exists with paint on both sides of the product. It’s also a good time to evaluate potential manufacturing process changes, such as steps that can be eliminated and where time and money can be saved moving a product through the manufacturing cycle faster when utilizing pre-paint.
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Q: Do I have to change my current tooling?
A: 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 pre-painted metal. Pre-paint serves as a lubricant, and when you use pre-paint, you actually get extended tool life. It is recommended that tooling be devoted only to pre-painted material versus moving back and forth between bare material and pre-painted materials. If the customer processes bare metal, the raw material has not been cleaned and carries roll oils and metal fines. Therefore, it is not wise to move bare material and pre-paint on the same equipment.
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Q: How do you fasten pre-painted metal?
A: There are varieties of ways to fasten pre-painted metal. The NCCA developed the booklet, How to on Assembly and Joining, which provides ways to fasten pre-paint, including mechanical fasteners such as screws, bolts, rivets, adhesive bonding, welding, crimping, lock forming, self-forming, piercing rivets, “Tog-Lok” systems and more. The on-line tutorial, How to Join Prepainted Metal also provides helpful information on fastening and can be viewed on NCCA’s web site www.coilcoatinginstitute.org.
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Q: How do I transport, store and handle pre-painted metal?
A: Sound manufacturing techniques make pre-paint no more difficult to transport, store and handle than other material. The NCCA specifically addressed this issue in a report, “Receiving Prepainted Metal Into Your Plant.” Contact NCCA to secure a copy.
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Q: How can I handle pre-painted metal without damaging the finish?
A: There is no need to be fearful of handling pre-painted metal. Sound traditional manufacturing techniques should prevent damage to the product in normal production. It is important to remember that pre-paint is a finished product and should be handled as any finished product would be handled. The on-line tutorial, How to Handle Coil Coated Metals also provides helpful information on handling and can be viewed on NCCA’s web site www.coilcoatinginstitute.org.
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Q: Will pre-paint scratch during forming?
A: Sound manufacturing practices, including proper handling, make pre-painted metal no more susceptible to damage than finished products. It is recommended, however, that tooling be dedicated to pre-paint. The use of bare and pre-painted material on the same tools can cause scratching of the pre-painted metal. There are many proven, simple techniques that can be employed to prevent damage, should it occur. Again, refer to NCCA’s “Receiving Prepainted Metal Into Your Plant” document. The on-line tutorial, How to Form Prepainted Metal also provides helpful information on forming and can be viewed on NCCA’s web site www.coilcoatinginstitute.org.
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Q: Are there cost savings associated with making the change?
A: There are not necessarily cost savings associated with the change, but cost savings enabled by the change that need to be reviewed. In other words, some of the greatest benefits will be derived in other areas of manufacturing. The use of pre-paint solves manufacturing issues by increasing productivity, reducing manufacturing cycle time, providing faster throughput, producing better yields and reducing environmental problems. The NCCA encourages industry professionals to work with its Cost Justification Brochure to analyze all of their processes and associated costs to understand the value of using pre-painted metal.
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Q: But it must be more expensive?
A: To understand costs involved, the customer must look at the big picture and look at the total cost versus just the cost of eliminating in-house painting. Often, the mistake is made to evaluate costs where the paint line begins and ends, instead of the entire manufacturing operation. The paint line is often the bottleneck in the manufacturing process, so you have to look at all the ancillary and supporting costs for the paint line, including time and effort to create materials to be painted at the paint line in order to do a complete cost analysis. The NCCA Cost Justification Brochure is a good starting point to assist the customer in analyzing costs.
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Q: What is the minimum quantity I have to order?
A: Your order depends on your supply source. Typically, truckload orders or truckload quantities would best fit the bill. However, pre-painted metal can be produced to any size order. The larger the order, the lower the cost per pound.
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Q: Can I depend on supply?
A: Yes. The coil coating industry has the capacity to meet ever-growing demand for pre-painted metal.
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Q: How am I going to make this change?
A: You can create a team with the customer organization and work with an NCCA member.
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Q: How long does it take to convert to a pre-paint system?
A: The majority of time is spent developing and understanding the requirements of the painted product. Once the requirements are fully understood and agreed to by all members of the team (which should include the metal supplier, coater, paint supplier and key customer representatives), a small trial run is done to confirm that the system, which includes the metal, paint and treatment, meets customer requirements. Once the qualification process is complete, the conversion to pre-paint can take place, and the current paint system can be eliminated. Depending on requirements, this transition can last anywhere from 60 days to one year.
FAQ’s from Metal Coaters®
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Q: Is technical assistance available?
A: Yes. Metal Coaters is the first choice for assistance when considering converting to the use of pre-painted steel and aluminum coil. As part of the conversion process, Metal Coaters and the entire supply chain team design and develop an engineered coating system that will meet the specific requirements of the end use.
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