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The Proper Coat of Oil PUBLIC ACCESS

Controlling The Lubricant Spray Keeps Presses Running Cleaner and Longer In Die Stamping Shops.

[+] Author Notes

Senior Editor.

Mechanical Engineering 122(01), 62-64 (Jan 01, 2000) (3 pages) doi:10.1115/1.2000-JAN-6

This article illustrates that controlling the lubricant spray keeps presses running cleaner and longer in die stamping shops. The MicroCoat system enabled Warwick, Rhode Island-based ETCO Inc.’s Engineered Products division to minimize oil mist in its press room, reduce maintenance downtime, improve the quality of finished parts, and increase the throughput of it. After installing MicroCoat on all 10 of its Bruderer presses, ETCO has increased the number of hits between sharpenings by 50 percent, or 500,000 strokes per press with much less tool damage. The 2.5-inch-high MicroCoat spray valves use low-volume, low-pressure air to apply die stamping lubricant in fine, even films without producing waste, mist, or overspray. The transparent reservoir of the MicroCoat System feeds metered amounts of lubricant to the compact spray valves mounted inside this Bruderer die press between the metal feed stock and the tool.

High-speed metal stamping enables manufacturers to turn out thousands of parts in a few minutes. However, the fluid dispensing systems, which apply lubricants to part stock before it is stamped to protect tooling from dulling and overheating, and to ensure quality, have not kept pace.

Some spray and roller systems tend to apply too much lubricant, which spills on shop floors or enters the air as a fine mist. Oil mist cannot be present above 5 milligrams per cubic meter according to the U.S. Occupational Safety and Health Administration in Washington, in a rule intended to prevent respiratory and eye irritation.

On the other hand, applying too little lubricant increases tooling wear and harms part quality.

EFD Inc. of East Providence, R.I., a major manufacturer of fluid dispensing systems, designed its MicroCoat system to apply precise films of stamping lubricant. The MicroCoat system enabled Warwick, R.I.-based ETCO Inc.’s Engineered Products division to minimize oil mist in its press room, reduce maintenance downtime, improve the quality of finished parts, and increase the throughput of its stamping presses by 50 percent between sharpenings.

EFD began developing the MicroCoat system in 1994. “Our Model 780S precision spray valve found its way into the metal stamping business in 1991,” recalled Bob Tourigny, manager of technical service at EFD. The 780S uses low-volume, low-pressure air to apply fluids without mist or overspray, making it ideal for many stamping applications.

After installing MicroCoat on all 10 of its Bruderer presses, ETCO has increased the number of hits between sharpenings by 50 percent, or 500,000 strokes per press with much less tool damage.

Grahic Jump LocationAfter installing MicroCoat on all 10 of its Bruderer presses, ETCO has increased the number of hits between sharpenings by 50 percent, or 500,000 strokes per press with much less tool damage.

However, its 4-inch length made it difficult to install in high-speed presses, which typically have only 4 to 5 inches of clearance. “You need a good 2 inches between the valve nozzle and the stock surface to coat it properly,” he said. “As a result, metal stampers would mount the valves outside of the press, lubricating the stock before it was fed into the press. Ideally, the lubricant should be applied to the stock in the press, just before it enters the die.”

Tourigny and his colleagues replaced the air-actuated piston on the 780S with a Teflon-coated Viton diaphragm 0.02 inch thick to develop the new MC785 spray valve, measuring 2.5 inches long. The compact MC785 spray valve fits inside the press between the stock feed and die. The new valve gives metal stampers the option of lubricating the stock from above, from below, or from both directions. The valve bodies are made of anodized aluminum, and the nozzles are of 303 stainless steel.

The 2.5-inch-high MicroCoat spray valves use low-volume, low-pressure air to apply die stamping lubricant in fine, even films without producing waste, mist, or overspray.

Grahic Jump LocationThe 2.5-inch-high MicroCoat spray valves use low-volume, low-pressure air to apply die stamping lubricant in fine, even films without producing waste, mist, or overspray.

Lubricating oil for the MC785 valves is supplied from a one- or two-gallon transparent acrylic reservoir that enables the press operator to see the oil level. A three-way air solenoid connects the MicroCoat spray system to the stamping press and controls on/off operation.

Oil is delivered to the valves under pressure, then mixed with nozzle air outside the valve to transfer it efficiently onto the stock’s surface. Air pressure at the nozzle is kept between 2 and 3.5 psi, and the volume of air is kept between 1 and 1.5 cubic feet per minute, to ensure that a fine, consistent oil film will be applied.

EFD also developed the MC4000 controller to give the metal die stamper complete control over the amount of oil applied to the stock by as many as four MC785 valves. The controller stands next to the stamping press, either mounted on a frame that EFD can supply or bolted directly onto the stamping press enclosure. After turning on the system pressure switch, operators use two sets of gauges and regulators—one set to adjust the pressure that delivers lubricating oil to the controller and the other tor the air delivered to the valve nozzles. Individual flow control knobs enable operators to regulate the amount of oil applied by each valve, and adjust coverage for different types of metal stock.

The MC4000 controller is connected to the stamping machine s clutch circuit so when the press starts the solenoid is energized. This sends air to the controller and the valves begin to spray. Conversely, shutting off the press de-energizes the solenoid and shuts down the controller so that no oil will be sprayed.

As a fail-safe measure, a float switch in the oil tank activates when the tank nears empty. The float switch is tied in series to a pressure sensor in the MC4000 controller that is activated when pressure there falls below 10 psi.

“That sensor circuit is tied to the emergency stop circuit on the press to automatically prevent the press from running without oil,” said Tourigny.

Since 1947, ETCO has manufactured a wide variety of electrical terminals, as well as the equipment used to crimp terminals to wires. The company, at its Warwick, R.I., factory, die-stamps brass, steel, beryllium copper, and dozens of other alloys to manufacture standard and customized electrical terminals for cars, trucks, appliances, and power tools.

ETCO uses 10 high-speed metal stampers made by Brud-erer Inc. of Huntsville, Ala. Three stampers have a capacity of 22 tons; six, 30 tons, and one, 60 tons.

Bruderer Inc. is the U.S. subsidiary of Bruderer of Fras-nacht, Switzerland. Among the companies that use its stamping machines are AT&T, Coors, General Electric, Gillette, and Texas Instruments. The presses are used to make a variety of products, including razor blades, electrical connectors, floppy disk components, and beer can tops.

Continuous lengths of metal stock are fed from a stand into the stampers at 60 to 70 feet per minute. Each machine makes parts by die stamping them at speeds ranging from 600 to 1,800 strokes per minute. The machines produce various parts ranging from under 2 inches to 4 inches in width, and from 0.01 inch to 0.04 inch in thickness from different metal stock. Each stock requires a different thickness of lubricant.

“At our high press speeds, the tooling heats up very quickly,” noted George Brennan, second shift supervisor at ETCO. “If we can’t apply the right amount of lubricant, it’s very easy to break a punch or pull a guide pilot when the tooling dries out. We also have to spend more time on sharpening the die. Maintenance for just one tool can cost us anywhere from one to four hours of lost production time.”

The amount of lubricant applied also makes all the difference to the finished part, added Brennan. Insufficient lubricant means that parts do not form properly. Conversely, if excess oil remains on the parts after stamping, a customer can reject an entire order.

In 1994 and 1995, ETCO relied on the roller systems used in slower stamping operations to apply lubricant to its metal stock. “For us, the results with rollers were hit and miss,” according to Dennis Herdegen, vice president of manufacturing at ETCO. “If we wanted more lubrication, we had to increase the flow of oil to the roller to become saturated. If we wanted less lubricant, we had to back off the flow and wait for the roller to dry out.”

Because the amount of lubricant changed with the stamping job, too much lubricant spilled onto the floor. “At other times there would be too little, and we’d see spots with no lubrication at all,” said Herdegen.

ETCO tried spraying systems in 1995, but again, there was no guarantee that the appropriate amount of lubricant would be applied. In addition, the impact of the dies on the lubricant virtually vaporized it, creating a mist that exposed workers to oil in the air. ETCO soon returned to rollers, but sought a better system.

No-Muss, No-Fuss Lubrication

In 1996, Brennan and maintenance supervisor Rolland Blom spoke to Rhode Island neighbor EFD about a precision lubrication dispensing system. The fluid equipment manufacturer suggested that ETCO test its new MicroCoat lubrication system.

ETCO says that using MicroCoat has significantly improved the quality of the electrical terminals that the manufacturer die stamps for cars, trucks, and power tools.

Grahic Jump LocationETCO says that using MicroCoat has significantly improved the quality of the electrical terminals that the manufacturer die stamps for cars, trucks, and power tools.

ETCO mounted two of the MC785 precision valves above the stock and two below on one of ETCO s presses in early 1996. When they are lubricating stock between 2 and 4 inches wide, all four valves are employed. When the stock width is 2 inches or less, operators turn off two of the valves. Based on its successful performance, ETCO had EFD install MicroCoat systems on its remaining nine presses through the spring of 1997.

The transparent reservoir of the MicroCoat System (left) feeds metered amounts of lubricant to the compact spray valves mounted inside this Bruderer die press between the metal feed stock and the tool.

Grahic Jump LocationThe transparent reservoir of the MicroCoat System (left) feeds metered amounts of lubricant to the compact spray valves mounted inside this Bruderer die press between the metal feed stock and the tool.

“Now that we can control the amount of oil, we just start out with each valve’s flow control set at ‘1’ (settings range from 1 to 10), observe the results and fine-tune the coverage to exactly where we want it, without stopping the press,” said Blom. “Being able to achieve consistent lubrication lets us do an extra 500,000 strokes between sharpenings on each press, with much less tool damage.”

There also has been a significant reduction of cleaning, waste, and disposal costs since ETCO installed MicroCoat, according to Brennan. “With the other systems we tried, many times we had to wash the finished parts to remove excess oil, sometimes in response to specific customer requests, but more often to avoid potential complaints,” he explained. Now ETCO is examining whether such cleaning is justified.

“Since we’re applying less oil to the stock, there’s less oil going into the wash tanks, so our cleaning solution lasts longer,” noted Brennan. There is less sludge, too. “We used to produce as many as 10 drums of sludge every month, but have lowered that to perhaps one,” he said. Reduced oil use and sludge generation saves ETCO a few thousand dollars per year in oil purchases and disposal costs.

A recent air quality study taken in the Warwick press room by an independent testing organization found that the oil mist is less than 0.2 percent of OSHA’s permissible exposure limit.

EFD has sold MicroCoat systems to hundreds of metal stamping companies, and has made inroads in other industrial applications that require consistent lubrication coverage. “One manufacturer uses MicroCoat to spray a light coating of oil on welded steel tubing to protect it against rust,” said Tourigny. “A wire maker sprays its product continuously as it is cold drawn to protect the extruder tooling, and a medical equipment firm sprays silicone oil onto tubing used to make catheters.”

Copyright © 2000 by ASME
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