Doing its level best

More than ever manufacturers depend on high-quality blanked and stamped parts to reduce production costs, speed up assembly time, and eliminate secondary processing requirements.

The automotive market in particular is focused on consistently achieving uniform and accurately dimensioned parts. Automotive blanking and stamping supplier SET Enterprises needed to eliminate shape defects caused by the mill strip production process for ferrous and nonferrous coils.

These shape defects vary considerably from coil to coil and within a coil. Regardless of the origin of a defect, product variability or inconsistency causes production delays and costs processors potential income because of material-related shape problems during downstream processing.

Some mills try to correct these defects by installing tension leveling systems in some of their upstream processing equipment. However, SET still had to deal with material shape defects from upstream, intermediate processing equipment. A correction needed to be made to eliminate unwanted shape anomalies.

The stamper was experiencing edge wave, loose centers, and some coil set that caused length measurement problems for SET and, more important, problems with the production of laser-welded blanks for its customers. Material defects slowed down the laser welding process or resulted in scrap when blanks with edge wave were matched and welded to blanks that had no defects.

A Need for Flatness

Over the past several years, SET experienced extraordinary growth thanks to its flat-rolled metal processing services to the automotive industry. As a result, the supplier recently won a significant amount of blanking business for select DaimlerChrysler plants to produce side panel blanks for minivans, including the Dodge Caravan®, Grand Caravan®, and the Town and Country®.

"More and more automotive manufacturers require a higher degree of flatness," said Jim Smith, director of machinery and equipment for SET Enterprises. "We must provide high-quality blanks that can be laser-welded and are flat where manufacturers and laser welders need them to be flat."

To provide both standard and laser-welded automotive blanks, the stamper needed to install a precision leveler to provide consistent, uniform, and accurately dimensioned parts (see Figure 1). A precision roller leveler, installed between the coil payoff reel and the press equipment, would allow an operator to stretch the edges when necessary to compensate for loose centers or stretch the center to compensate for loose edges before the blanking operation.

Figure 1 To provide both standard and laser-welded automotive blanks, the stamper needed to install a precision leveler to provide consistent, uniform, and accurately dimensioned parts.

After researching several precision levelers, SET chose a 1.75-inch Herr-Voss Stamco Precision Leveler Plus, which was installed in late 2005 along with coil feeding, washing, and oiling equipment ahead of the blanking press.

"Custom-designed ball screw actuators provide the precise adjustment we need for repeatable calibration and repeatable machine operation," Smith said. "This ease of operation allows an easy coil setup and processing, which make the blank more predictable and consistent."

Steel is fed through the leveler, across a looping pit, and through an electrostatic oiler using the leveler drive. The strip eventually reaches the adjustable-height feed rolls that hold the strip while the pit is filled, and then the feed rolls power the strip into the press and die.

A carryover table also was designed and built with the leveler to give SET the ability to check flatness before the steel enters the press. The leveler can run at 200 feet per minute.

A washer was included in the line for special applications. For example, the stamper now has the ability to wash coils and apply draw-quality oils with a GFG oiler. The washer traverses in and out of the line to prevent the material that must be dry from coming in contact with the washer.

"For some welding applications, one of our core customers is reporting that flatness issues have dropped more than 30 percent, and another customer is reporting that flatness issues have been eliminated," said Smith. "We are making more than 25 parts and they must be within an extremely flat tolerance to be accepted by our automotive partners."

SET's facility now can slit, blank, and stay in close contact with its laser welding partners and ship panel-flat steel faster. "Our investment in the Macedonia [Ohio] plant requires we deliver accurate parts, which is why we are depending on the Precision Leveler Plus to provide us with the quality our customers have come to expect," Smith said.

As the automotive industry continues to demand higher-quality products, it will continue to lean on both equipment manufacturers and blankers to help them consistently achieve uniform and accurately dimensioned parts.