Ultrasonic Cleaning Saves Time, Money

Parts cleaning in industrial settings—especially those with demanding quality requirements, such as in the aerospace industry—has traditionally necessitated costly and time-consuming dedicated labor and solvents that can be dangerous for workers and for the environment. Cleaning fluids often require special chemical handling and disposal, and hand cleaning parts is not only labor-intensive but may result in missed soils in part cracks and crevices.

Any missed soils were unacceptable to Boeing Corp. and other customers of Eaton Corporation’s Fluid Conveyance Div. plant in Jackson, MI. The plant’s 350 employees produce custom tubing for conveying air, oil, water and other fluids in aerospace and marine applications.

Eaton has been in business since 1940. Its products are used on a variety of civilian and military aircraft, including the Airbus A380, the F-22 Raptor and the F-35 Joint Strike Fighter. Workers first cut tubing to length, then use CNC tube benders and other equipment to produce more than 10,000 different part numbers, according to senior manufacturing engineer Bud Greener. Work materials include stainless and carbon steels, plus titanium, aluminum and Inconel alloys, and tubing sizes range from about ¼ to 3 in. diameter with a variety of wall thicknesses.

Internal Contamination

Greener explains that keeping the inside diameter of tubes open during bending often requires use of a mandrel. “It’s like a straw,” he explains. If you bend a straw, it will kink. But if you fill it with sand and then bend it, it won’t kink.”

Problems arise because mandrels necessitate use of fluids on the tube ID. Some of the compounds used are water-based. Others are oil-based and very viscous, including one Eaton workers call Heavy Honey.

“If you have a tight radius especially, you want to have a lubricant that can handle extreme pressure,” Greener explains. “That requires one of the heavier lubricants. If we have to use Heavy Honey, we actually flow mineral spirits through the tube first before ultrasonic cleaning.”

Ultrasonic Solution

Using hand cleaning and solvents on a few parts is not so bad compared with the plant’s previous cleaning method, which was hand cleaning of all parts. “Prior to the ultrasonic systems, we cleaned all the tubes manually,” Greener recalls. “Now, we put them into the cleaning system and walk away to do something else while the parts are being cleaned.”

The ultrasonic cleaning system currently used by Eaton was manufactured by Omegasonics (Simi Valley, CA). It was installed after the plant’s initial foray into ultrasonics turned out to be a disappointment. “The first system ran for six months or so, and we started seeing parts coming out not clean and other problems,” Greener says. “Plus, maintenance and service were difficult. Sometimes we literally had to wait months for someone to come out.”

Greener and his supervisor discovered Omegasonics at a trade show, and were impressed not only with the company’s cost estimate but also with its emphasis on service and maintenance. They commissioned Omegasonics to retrofit Eaton’s old ultrasonic system, consisting of two, 300-gal stainless steel tanks, with new generators and other components. The company also supplied components for a couple of smaller ultrasonic systems machines.

Working with Greener, Omegasonics supplied six transducer and generator sets for each tank. Eaton employees installed the retrofit components and built the new control panel. The retrofit features Omegasonics’ Super Pro and Pro Plus single-phase amplifiers, which can deliver up to 4,000 W of ultrasonic power.

The modular design of the retrofit components allows ease of maintenance, according to Greener. “With the old system, it was hard to tell if one of the amplifiers wasn’t working properly,” he recalls. “With this system and our control panel, I can turn on each amplifier separately and make sure it’s working properly.” If one amp is malfunctioning, the tank can be drained and the malfunctioning unit replaced without disturbing the other units. Greener had the in-tank units designed with eyebolts for easy attachment of a hoist and removal.

The large ultrasonic system operates at 140°F in the wash tank and 150°F in the rinse, which also features mechanical agitation via the hoist used to move baskets of parts. The cleaning solution used is specified by Boeing, one of Eaton’s main customers.

“Boeing mandates that we use certain processes and materials, so that they know have a controlled manufacturing process for parts we supply,” Greener says. “You have to stick to the approved process. If you don’t they can shut you down—and they have auditors out on the road every day.”

Smaller ultrasonic units have the same amplifiers and transducers as the larger unit, but they run at a different voltage. “Basically, we vary ultrasonic frequency to handle different parts and different part densities,” Greener says. “We also use ultrasonics to clean our bending tools.”

Multiple Benefits

Ultrasonic cleaning technology provides several benefits for Eaton, according to Greener. For starters, it reduces the amount of hand labor required to make a tube ready for shipment. “Before we went ultrasonic, we cleaned all the tubes manually,” he says. “Now we just put most of them in the ultrasonic unit, adjust the settings, and walk away to do something else while they’re being cleaned.” Greener calculates that ultrasonic cleaning eliminates 5 to 10 minutes of hand labor per tube—conservatively, about 20 hours per week total.

But labor savings in cleaning is not the only benefit. According to Greener, the vast majority—90% or more—most of Eaton’s parts are bent to spec, then cleaned and placed into stock to await completion with welded fittings or other finishing touches. Before being placed into stock, they are chemically cleaned in any of several baths that depend on the work material. Chemical cleaners include nitric and muriatic acids, caustic cleaners for carbon steel tubes, and acetone.

“For example, if a part’s going to be cut and welded later, it needs to be chemically clean,” Greener explains. “If parts go into a chemical cleaning tank and they’re not already clean, they will contaminate the tank. Then we have to drain and recharge it, and that’s costly and time-consuming.

“So parts need to be as clean as we can get them before they go into the chemical cleaning tanks. If we can avoid contaminating those tanks, that’s definitely a cost savings.” The normal schedule for draining and recharging the plant’s chemical cleaning tanks is about every two to four weeks, he adds.