Worried about Lube Delivery? Just Roll With It

February 1, 2009

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If the substrate is flat, roll coating is an ideal means to apply lubrication prior to stamping. That’s the word from Walter Weiland, vice president of sales for Black Bros. Co., Mendota, IL, in business for more than 125 years providing roll-coating equipment for metalforming and other industries.

“We think the advantages of roll coating over other methods for lubricant delivery,” he says, “relate to the precision and efficiency of the coating delivery system as opposed to spraying, curtain coating, misting, mopping or any of the other methods typically used to apply lube.”

Roll coaters apply a broad range of lubricants, oils and drawing compounds to metallic stock prior to stamping or forming parts.

“Increased attention is being paid to the amount of emissions released into the factory environment,” Weiland continues, “and here roll coating offers benefits. Roll coaters apply only to the substrate, negating overspray issues. Also, as lubricant and coating costs continue to increase, it becomes more important to precisely control lube delivery, and roll-coating machines do that.”

Adjust to Material Thickness

Roll coaters have numbered settings that adjust to the thickness of the material being coated. That allows the use of these machines on a variety of substrates, from thin flexible sheeting to rigid heavy material.

“For example, the feed-gap openings on the roll coaters we manufacture adjust from nearly 0 in. thick to 12 in. thick,” Weiland says, also noting that roll coaters can handle nearly any coil or sheet width. “Stampers often tell us that their parts usually measure, say, 12 by 18 in., but they may have a job that calls for part widths to 68 in. wide. A roll coater does not care if the piece going through is 18 in. wide and the next is 40 in.”

Black Bros., he notes, has built roll coaters for material widths from 14 in. to 14.5 ft.

Other settings control the amount of lubricant applied to the material surface, with Weiland noting that machines provided by his company have been required to apply coatings in thicknesses from 5 to nearly 80 wet mils.

Ideal for Deep Drawing

Roll coaters can be used to apply wet and dry lubricants, making roll coating a viable option in deep drawing, which often utilizes dry lube and where uniform coating to prevent scratching during the draw is a must.

“We have installations in numerous deep-draw-forming facilities, everything from popsicle molds to kitchen sinks,” Weiland says. “Uniformity, efficiency and speed are important to deep drawers, and roll coating addresses each of these issues.”

The ability of roll coaters to consistently apply a set amount of lube removes guesswork, especially given that thickness measurements leave something to be desired. Even something like a weighstrip layout—placing a coupon on the processing line and measuring coating thickness—doesn’t provide a continuous reading of the thickness across the entire coil.

Where stampers paint or mop to apply the coating, such application generally can’t be controlled with much precision. That invites trouble in dry-lube applications, as excess lubricant can cause blanks to stick together or parts to stick to tooling, and compromise lubricant consistency during deep drawing. Other adverse results include reduced washability and accumulation of lube on tooling.

Function Inline or Off to the Side

Roll coaters work on a variety of substrates, including stainless steel, and can adjust for material and coating thickness.

A roll-coating machine can reside in the press line or off to the side. When applying a wet lubricant, the stamper typically would place the roll coater immediately in front of the press with coil or sheet feeding through the roll coater and onward through the forming operation. In dry-lubricant applications, the roll coater typically locates offline, perhaps in a nearby corner where personnel run sheet or coil through and stack it nearby. Then the coil or pallet of prelubed sheets is picked up and transported to the press for stamping.

Roll-coating machines most likely incorporate their own lube reservoirs, with several methods available for lube to be supplied to the machines. Some roll coaters incorporate a 10,000-gal. tank, 55-gal. drum or 250-gal. tote, depending on lube needs. And the machines can automatically request more lube from lube-storage tanks via sensors and controllers on the roll coaters or incorporated into press controls. That means no downtime for lube replacement.

Lube can be reclaimed as well, as some stampers create a fountain where lube pumps into a reservoir on top of the coater, and as the lube is used, excess is captured and pumped back into the reservoir.

Works Best with Proper Lubricant

Of course, a lubricant-application system functions best given the proper lube for a part run and for the method of application. With this in mind, a good application-equipment supplier should work with stampers to match the lube, job and application system.

“Our typical stamping customer will provide a part size, its lube supplier and a desired outcome,” says Weiland. “If we have experience with that particular lubrication vendor, we can be confident that our equipment can apply that lube properly. For a new lubricant or for a formulation on which we don’t have data, we process sample parts at our facility. Then we can go back to the customer and say, ‘Based on your materials, your lube and our roll coater, these are the results you can expect.’”

More than Just Lube Application

Besides lube application, roll coaters can perform other functions in the pressroom, as metalformers also find use for roll coating after forming, according to Weiland.

“Again, roll coating responds best to flat surfaces,” he says. “So preformed or nonflat surfaces usually aren’t good candidates for applying lubricant via roll coating. But you can use roll coaters on formed parts if your intent is to apply a controlled amount of material to a raised surface.

“A good example is a stamped number that goes on a telephone pole,” Weiland continues. “You can stamp it, paint it and then run it through a roll coater to coat the embossed areas, or the numbers. This often is performed in signage manufacture.” MF