Compact vibratory screeners are designed to provide efficient throughput with no blinding.

Manufacturers in every field are keeping their processes private, if not secret. After all, most processes are in some ways proprietary, comprising a mix of methods, technologies and operations that ultimately affect a manufacturer's ability to compete successfully. This is certainly not lost on the industrial coatings sector, where both products and processes can be highly proprietary.

One of the best-kept secrets in the manufacturing sphere is a new generation of vibratory compact screeners. Screening is an essential process for many manufacturers and can be especially vital to those involved with applying powder coatings, whose end product and production efficiency depend on getting this step right.

The benefits of using compact vibratory screeners were so significant at a major coatings applicator in the auto industry that management decided not to go on record. Yet an outline of the process and its results might prove helpful for those facing similar challenges.

A Screening Challenge

When the coatings applicator recently won a contract to build mass production primer shops for one of the world's largest automakers, it faced a daunting task.

A standard wet spray primer system was ruled out for cost, performance and environmental reasons. Since overspray occurs with wet paint application, any paint that doesn't adhere to the auto body has to be captured and ends up as costly waste disposal. The plant was given the go-ahead to invest in a more durable, cost-effective, powder-based primer system where overspray can be reused instead of becoming an environmental liability. But to deliver its benefits, the powder application system had to meet rigorous quality and production specifications.

"For proper flow through small orifices, such as applicator guns and valves, the powder must be screened so nothing larger than 105 microns gets through," says an engineer responsible for automotive powder application of the project. "This prevents visible defects on the primer coat after curing."

Screening to these size requirements was complicated by the tendency of the raw virgin powder to clump before delivery to the hoppers for transport to the powder applicators. Screening also had to remove any debris or contaminants from reconditioned powder before reuse.

"To maintain the necessary quality and reliability, the powder must be pharmaceutical-grade clean," explains the engineer. "Any particles above 105 microns can cause blockages of the applicator guns, which could stop production or require pulling a vehicle off-line for spot paint repair and reapplication."

A high-quality powder coating application requires that the powder be screened so that nothing larger than 105 microns gets through the applicator guns and orifices.

A High-Frequency Solution

Though powder primer application got its start in the automotive industry over two decades ago, its full acceptance has been hampered until recently by screening deficiencies requiring undue downtime and production space.

Conventional screeners used in powder primer application required an electronic sensing device to detect whether they were blocked and needed servicing. Such screeners only ran about two hours before having to be removed for cleaning and inspection - a process that stopped production.

Because conventional screeners were large, they presented more surface area for clogging and also occupied more production floor space for installation. These larger installations required bigger, costlier rooms with more environmentally controlled airspace, since the powder used in primer application must be regulated for temperature and humidity.

To avoid these problems, the automotive coating applicator chose a new generation of high-capacity, 36-inch compact screeners with Vibrasonic deblinding systems from Russell Finex of Pineville, N.C. According to the engineer, the compact screeners, developed to maximize cleaning efficiency, are suitable for powder primer application. Due to their efficient throughput, blinding sensors are not required on the screeners used for primer application to auto bodies.

"Unlike standard screeners shaken by an electric motor, the Vibrasonic screeners sonically vibrate at a high frequency in conjunction with the motor harmonics," explains the engineer. "They're engineered to flow oversized particles toward a vacuum pickup, which keeps them clean and extends service life.

"Because of their extended service life, inspection can be done every shift or two, which eliminates production stoppage for screener change out every few hours," he adds. "That's the equivalent of gaining an extra hour of production each day. It also dramatically cuts the capital cost of sending out the screens for professional cleaning."

The engineer also found the Russell compact screener's small size beneficial in maximizing production line real estate. In a separate installation, the plant retrofitted a spray primer system to powder application using a smaller 15-inch unit.

"Everything fights for space on the production floor - from pumps, pipes, filters and automation to electrical controls, fire protection and supervisory space," says the engineer. "Because of the unit's compactness, we were able to locate it below a gravity-fed bulk sack unloader. This eliminated the need for a conveyor and transfer pump, which saved valuable production space and capital."

Expanding Applications

Beyond the production automotive primer shops, the coatings applicator has loftier goals.

"With the Russell compact screeners, we'll offer the ability to apply true color-specific, final-paint color systems with the durability, cost-effectiveness and environmental benefits of powder application," says the engineer. "This will be possible with multiple colors in a small paint booth, without impinging on existing production space."

For an industry challenged on many fronts, the shift from wet spray to powder primer application shows that ingenuity and cooperative vendor support can yield significant benefits in optimizing production, cost efficiency and environmental improvement.

For more information about screening solutions, contact Russell Finex, Inc. at (704) 588-9808, e-mail sales@russellfinex, or visit www.russellfinex

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