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Quality never takes a tumble at a finishing shop: known for its quality tumble finishes, a company found that it had to design its own finishing line to maintain its reputation.

Quality isn't a passed-buck for Rapid Tumbles Finish, Eaton Rapids, MI. As its name implies, the company specializes in putting the right finish on customer parts. Quality starts before parts enter the facility.


"It begins at the beginning," Loren Cowles, company president, said, "not in-process or after processing. We determine exactly what we're receiving, including what is on the components when they arrive. Not only is it an important step in getting the job done right the first time, but it also protects our chemistry."

The company provides tumble finishing, vibratory deburring, parts cleaning, burnishing, microfinishing, media blasting, and coatings for parts from OEMs, tier one manufacturers, and job shops.

At the beginning of 2006, Rapid Tumbles Finish--RTF--expanded into black oxide and zinc phosphate coating processes. To maintain a grip on quality, RTF designs and builds its own equipment, such as parts dumpers, wheelabrator loaders, quality gauges, and rust-inhibiting equipment.

The company's quality measures, such as being certified to ISO and QSB standards, provide credentials to customers, according to Cowles. So, when RTF searched for ways to expand into the coatings processes, it demanded products with a performance history showing stability, simplicity, and easy waste treatment. The company found that combination in products from Heatbath Corp., Springfield, MA, Cowles said.

"The goal was to provide a coating that rivaled the quality of our deburring," he said.

Some providers RTF investigated didn't offer the flexibility for which the company was searching.

"They were not very good at listening," Cowles said. After considering a number of configurations, RTF created its own preliminary drawings. "We opted for a layout featuring parallel process lines where parts could be cleaned together as they headed toward different processes."

Heatbath worked with RTF to determine the size and scope of the equipment needed.

Critical Chemistry

Chemistry was also critical since the company processes both ferrous and nonferrous products. Compounds are custom-blended for precise results.

The equipment provides five finishing options: pickle and oil, black oxide, heavy zinc phosphate, black zinc phosphate, and calcium-modified phosphate.

There are four topcoat options: water-displacing oil for corrosion protection, water-displacing oil for dry-to-the-touch, water-soluble oil, and water-based rust inhibitor.

The system used by RTF offers rack or barrel parts processing. Gas dryers are used for racked parts and barrel-processed parts are dried in spin dryers. Barrels are designed to accommodate separation chambers workers can empty independently, so two different parts can be run simultaneously.

The line accommodates a standard maximum barrel size. Parts arrive in tubs that equal a barrel. Barrels have a capacity of about 2,000 lb, but the line can accommodate exceptions, such as muffler caps.

The system runs standard and custom process cycles using computerized chemical analysis and process control. With each load, the line generates a process sheet detailing the process cycle used, tank temperatures, and chemical parameters.

RTF's selection of products was guided by cost, process repeatability, tech support, and waste treatment.


Keeping Green

Because of the company's location in EPA Region 5 and Eaton County, effluents such as strong alkalis, corrosive solids, and oxidizing agents are restricted. The cost of regulation compliance was also a deciding factor in the processes and chemistries chosen.


The cleaner chosen by the company was Uni Kleen 1293, a caustic, heavy-duty soak cleaner that eliminates solvent pre-cleaning in electrocoating operations. The cleaner is effective for the complex shapes RTF often processes, and removes polishing, buffing, and forming compounds.

"We focus on high-value parts--particularly ones with complex shapes," Cowles said. "We turn them around fast, and build customer loyalty. Customers more often call on us to solve problems--such as dimensional repair or the resurfacing of rusted parts made in Asia--than to just provide a service.

"Processing that requires us taking 20 microns down to 4 or 5 is an excellent fit for us. We're geared to a 0.0002" standard."

RTF works with OEM customers about specifications, telling them how much the firm's processes will add or remove and how the suppliers should adjust their specifications.

"While this isn't the norm," he said, "it's proven effective in producing large volumes of parts that are exceptionally consistent in dimensions and microfinish."

In a Pickle

The acid pickle stage uses Rust Remover 4, a liquid acid pretreatment for pickling and descaling ferrous metals. It's used at ambient temperature, and contains an inhibitor to prevent base metal attack where long immersion is needed--such as with the parts made in Asia--to remove heavy scale.

The black oxide technology chosen by RTF is Pentrate Ultra L, a "deep black" formula that produces a minimal build-up of colloidal iron in the working bath, eliminating the risk of superficial red, brown, or green films. Of particular importance to RTF was the incorporation of a wetting agent that reduced chemical loss due to drag-out, and minimized the cost of both product and waste treatment. RTF included automatic chemical feed and automatic water additions for this tank.

On the phosphate side, the Black Pre-Dip stage uses Heat-bath Phos Dip BZP-4, a pre-phosphate coating that can be followed by zinc or manganese phosphate.

The heavy zinc phosphate--2,000 mg/[ft.sup.2]--chosen for the automotive, off-highway, machinery, and other heavy-service components RTF processes is Phos Dip 1263, a product with a high tolerance for iron in solution. This coating produces high uniformity of parts coverage and minimal sludge formation in the bath.

For micro zinc phosphating, RTF uses a calcium-modified process that deposits a microcrystalline base and is ideal for pre-paint.

One of several topcoat options for use over phosphate coatings is Rust Inhibitor 1438, a water-based product developed for in-plant rust protection of steel products. Its nitrite-free, solvent-free formula makes it waste-treatment friendly.

Heatbath Lab Oil 100 is a water-soluble, emulsion-type rust preventative that provides high levels of corrosion protection, excellent emulsification characteristics and low toxicity. It is barium-free, and dry to the touch when applied over phosphate or black oxide. In other facilities, it is also used for electroplated parts.

Where maximum corrosion protection is needed, Rapids chose a thin film rust preventative, Pen Dip Super. This solvent-based rust inhibiting oil has excellent water displacing properties. It was developed for black oxide and phosphate-coated components and is also used to protect highly finished parts during manufacture. The other option for water-displacing oil selected by RTF is Pen Dip A, which produces an extremely dry film and allows immediate shipping. Heatbath Corp.

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Title Annotation:COATINGS
Publication:Modern Applications News
Date:Dec 1, 2007
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