Easier Glaze Spraying

August 1, 2005
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A new automatic spray gun can help reduce maintenance and increase quality and efficiency in ceramic glaze and porcelain enamel applications.

The new spray gun is designed to minimize maintenance requirements in harsh applications. Photo courtesy of American Trim's Erie Division, Erie, Pa.
Manufacturers that apply ceramic glazes and porcelain enamels to their products through spraying are well aware of the drawbacks that often accompany conventional spraying equipment. The high-humidity spray environment is corrosive, and the abrasiveness of glaze and enamel materials can accelerate equipment wear. Additionally, the equipment is susceptible to contamination and must be cleaned frequently, and excessive overspray and dust contamination are common problems. All of these issues add up to high costs for excessive downtime, maintenance and repair parts.

Recently, a new automatic air spray gun* has been developed specifically to address these challenges. Designed with increased durability and fewer wear parts, the new equipment is making it easier and more affordable to apply ceramic glazes and porcelain enamels by spraying.

*The RHINO(tm), supplied by Binks, Glendale Heights, Ill.

A Tough Environment

Ceramic glazes and porcelain enamels are inorganic coatings that are applied to a substrate and fused at temperatures above 800°F. They are typically composed of clays, which contain hydrous silicate particles less than 4 mm in diameter; talcs, which are a hydrated magnesium silicate mineral; and/or flint, which is a hard, sedimentary cryptocrystalline silica rock; along with proprietary compounds and water.

The silicate and silica materials are highly abrasive and can wreak havoc on conventional spraying equipment. Frequent downtime for cleaning and maintenance is common, and companies usually have to keep a significant number of replacement parts on hand for the inevitable equipment failures. Corrosion and contamination due to humidity and dust in the spray area can cause quality problems on the products being coated, and clogging due to poor fluid flow through the gun is also frequently encountered.

These problems are enough to drive many manufacturers to search for an alternative, but knowing what to look for in new spray equipment can be difficult. When evaluating spray guns, manufacturers must first consider the gun's atomization performance, which affects the finished quality of the coating. The spray gun should have the ability to break up highly viscous, high-solids-content materials into particles small enough to produce a uniform coating distribution, and should also homogeneously mix the fluid and air. A uniform fan pattern is also important, and some spray guns also provide the ability to adjust the fan pattern from small to large (approximately 3 to 12 in.) to target specific areas on the substrate.

Another important consideration for spray guns is the air consumption of the system and the cost of the compressed air needed for operation. Air consumption is directly related to the design of the gun's air passages and air cap. The air passages must allow for efficient airflow through the gun with a minimum pressure drop, and the air cap should allow a minimum flow of air through the air cap holes to efficiently break up the coating.

Other parameters include the durability of the equipment; maintenance requirements; the ease and speed with which maintenance can be performed; and any specific production requirements, such as an extremely low defect rate and/or a high level of versatility.

Manufacturers also need to keep in mind that costs for items such as the fluid nozzle and needle, atomizing air cap and number of spray guns, along with the durability of the equipment components, the labor rate to service the guns, and the amount of time required to service the guns, all affect the return on investment (ROI) of the system being purchased. A spray gun that minimizes corrosion and maintenance while maximizing quality and efficiency can provide a quick ROI and an improved bottom line.

A New Spraying Solution

The new automatic spray gun was developed precisely to provide these benefits. The gun is completely sealed and can be cleaned by immersing it in a water container and washing it with a wet rag and/or scrubbing brush, or by spraying it with a water hose. To minimize corrosion and prolong the life of the gun parts, cemented tungsten carbide alloys with cobalt additives are used in all high-abrasion areas of the spray gun, and stainless steel alloys are used in the flow-through areas. ASTM Abrasion Tests conducted to assess the spray gun parts have shown that the typical life expectancy is four to seven times longer than parts made with conventional alloys.

The method of material flow through the gun is optimized to provide a smooth flow with no plugging. Fewer internal parts are used to minimize maintenance requirements, and the piston assembly is completely sealed to eliminate internal contamination. The gun's wash-down surface coating is designed to facilitate cleaning and prevent corrosion. Additionally, a removable gun mounting bracket attachment minimizes downtime by facilitating change outs to accommodate a different coating or color, and by ensuring that the gun position stays the same when the guns are changed out.

The gun can be used as a conventional or high-volume low-pressure (HVLP) spray gun, and is designed to provide higher transfer efficiencies along with reduced overspray and bounceback. Typical applications include glazing sanitaryware, floor and wall tiles and ceramic cookware, or applying porcelain enamel coatings to washers, dryers, stovetops and hot water heaters.

For manufacturers seeking to improve the quality, efficiency and reliability of their glaze or porcelain enamel spraying operation, the new spray gun can provide a solution.

For more information about the new spray gun, contact Binks at 195 International Blvd., Glendale Heights, IL 60139; (630) 237-5000; fax (630) 237-5011; or visit http://www.binks.com.

American Trim's Erie Division uses the new spray guns to coat metal products such as this stovetop burner bowl with porcelain enamel coatings. Photo courtesy of American Trim's Erie Division, Erie, Pa.

SIDEBAR: Case Study

New Spray Guns Solve Maintenance Issues for Metal Trim Company

American Trim, headquartered in Lima, Ohio, provides services such as product design, tooling and process development, metal forming, metal finishing, and product/component assembly for the home appliance, transportation, building products and consumer products industries. Applying porcelain enamel coatings is among the company's metal finishing processes.

American Trim's Erie Division in Erie, Pa., had been using conventional paint guns with components designed for high-wear applications. However, according to Joe Bricher, process engineer, the old-style guns required a significant amount of maintenance.

"The gun components wore out quickly due to the abrasive nature of the porcelain enamel. We had to replace the guns a couple of times per week on average. We also had trouble with clogging, which required additional maintenance and created some product quality issues," Bricher says.

In August 2004, American Trim's Erie Division became a beta site for testing the new automatic air spray gun, and Bricher was immediately impressed with the results. After just three months of testing, the company began to replace all of its conventional spray guns with the new model. "Matt Kapsar and Mike Maliszewski, local Binks reps, and Chris Strong, the spray gun designer, were instrumental in resolving some early issues and helping us understand the spray gun's potential," says Bricher.

The new spray gun addressed all of the issues that previously caused American Trim to lose production time. "With the new guns, the wear on the components is minimal, and our uptime has increased significantly. A maintenance issue will come up every once in awhile, but we've basically gone from changing out our spray guns biweekly to once a month based on a predictive maintenance schedule," Bricher says.

While Bricher admits that the new spray guns are more expensive (the wear-resistant design costs more to produce), he believes the savings in maintenance alone is worth the extra upfront cost. For American Trim, the payback on the initial investment of 15 spray guns was realized in just a few weeks. Bricher also points out that the new spray guns offer increased control of the fluid volume and atomizing pattern-both notable benefits in an era where companies are seeking to continuously increase production flexibility and product quality.

Overall, Bricher is thrilled with the performance of the new spray guns.

"Our maintenance requirements have dropped to almost nothing. It's been an outstanding product for us," he says.

For more information about American Trim, visit http://www.amtrim.com.

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