— Reprinted with permission from Metalforming Magazine, January 2004.
Faced with excessive lube use and slowed production of drawn parts, this manufacturer turned to tool coating. The result: smooth workflow and drastically reduced lube usage.
Beam Industries, looking to cut production time on a challenging drawn part, found that excessive lube was the problem. Labor required to lube every fourth or fifth part, coupled with the need to rinse all that lube off prior to painting, caused an expensive bottleneck.What to do? After an extensive investigation, the company sent the tooling out for thermal-diffusion vanadium-carbide coating via the TD Center.With the tooling coated, Beam experiences high part production with lube use just a tiny fraction of what it was.
Founded in 1957, Beam Industries manufactures and markets a full line of central vacuum systems consisting of four major brands, Beam, Eureka, Frigidaire and Electrolux, as well as many other private labels. With 160 employees and a 107,800-sq.-ft. manufacturing facility in Webster City, IA, Beam, owned by AB Electrolux of Sweden, produces central vacuum systems for residential, commercial and recreational markets in more than 45 countries.
Beam Industries forms this part, (bottom left), from this blank (bottom right) and uses it in this central-vacuum unit (top). To cut lube use and related labor for the part, which brought production slowdowns, Beam opted to send the tooling out to be coated. As a result, instead of having to lube every fourth or fifth part, the company only has to treat about every thousandth.
“Our processes include metal stamping, forming and painting to produce the metal bodies on our central vacuum power units,” explains Larry Hartley, Beam marketing director. “We also specialize in assembly-light manufacturing, and kitting work to produce the complete central vacuum system – including power brushes and hose and attachment kits in addition to the central power units.”
“In addition, we perform product design engineering, and our inhouse engineering supports our manufacturing processes and tool engineering for a number of metal fabrication and stamping procedures,” adds Dave Strang, senior designer and toolmaker.
According to Strang, Beam had looked for ways to take as much of the lubrication process as possible out of parts it now lubes prior to forming.
“We're trying to achieve just-in-time production scheduling,” Strang explains. “and in combination, we're trying to reduce our piece rate so that we can turn it over more rapidly.”
With one part in particular, Beam had trouble meeting production requirements.
“The blank, depending upon that part, is either 14 or 12 in. in diameter,” says Strang. “We run two different parts for different-sized units, of deep-draw quality cold-rolled steel. Though not a deep-draw application, the blank does not have any centers cut out, so the die actually draws the material down an inch or more in different areas.”
Problems arose in the amount of labor required to apply lubricant to every fourth or fifth part, leading to low throughput. That process could not keep up with production. The company considered switching to a higher grade of steel to make the parts, which would reduce the scrap rate and allow greater throughput with less lube. But that would have brought substantially higher material costs.
Beam Opts for Tool Coating
After discounting that and other alternatives, Strang had the tooling coated with a thermal-diffusion (TD) vanadium-carbide coating, supplied by TD Center, Columbus, IN. The coating reportedly increases hardness, wear resistance and lubricity of tooling surfaces. The TD hardening process diffuses a vanadium-carbide layer (0.0002 to 0.0003 in. thick) into and onto the surface of steel and cemented carbide substrates. Treated materials exhibit surface hardness ranging from 3200 to 3800 on the Vickers hardness scale.
In the process, tooling immerses in a salt bath at temperatures between 1600 and 1900°F for one to eight hours. Vanadium dispersed in the salt bath combines with carbon atoms in the tooling substrate to form the layer. This layer expands due to a continuing reaction between the supply of carbon atoms available in the substrate, and the carbide-forming elements of vanadium from the bath. The substrate must contain a carbon content of 0.3 percent or greater for the reaction to occur.
The high-temperature TD process can result in dimensional changes due to phase transitions in heat treatment of the base steel, and formation of the carbide layer. To minimize such effects, TD Center advises that tooling be hardened and finish-ground prior to treatment. Because cemented carbide does not harden in the process, dimensional changes there are negligible.
Less Lube, More Throughput
“I think we have realized at least four key benefits by coating the tooling,” Strang reports. “It reduced scrap, increased our throughput, almost eliminated the need for lubricant and eliminated the need for us to employ a higher grade of steel.”
Another benefit: Since applying the vanadium-carbide coating to the die, Beam experienced improved throughput in other processes downstream through reduction of the amount of lube that must be washed off of the parts prior to painting.
“We must thoroughly wash each part before it goes into the paint department,” Strang explains. “Whenever we use lube, we spend extra time washing. When we have to lube each part, it takes longer to place the lube on the part. Our time studies show that it takes so many seconds to do each operation. Whenever we can take an operation out of the process, we save money in the long run.”
Strang points out that Beam uses a new lubricant that works very well.
“It's a soy lube, totally biodegradable,” he says. “The viscosity makes it so slick that a little bit goes a long way.”
Without the TD coating on the tooling, forming required a lot of lube to reduce drag, reports Strang.
“After having the dies coated,” he continues, “we now lube every thousandth part instead of every fourth or fifth part.”
The coating works very well, says Strang, in any drawing operation, especially deep draws or in critical situations such as where galling has been a problem.
“Our parts show galling, it wears on blocks, and parts start sticking in the die,” he explains. “Once we install the coating on a tool, we don't have any problem with galling.”
Beam has used the coated die for a year to produce that particular part, and has dies producing other parts coated, too.Also, Beam has begun to implement the coating into new tooling as it is designed.