October 2007 Edition

CAD/CAM

Putting Manhole Covers on a Diet Saved Half a Million Bucks

Faced with soaring material costs, LeBaron Foundry streamlined designs, lightening manhole covers and frames by as much as 50 lb

Manhole covers are an invisible part of the environment, they're everywhere, but no one sees them since they're so common. But, for a company that makes them – trapped in fixed-price contracts – manholes were of prime importance.

LeBaron Foundry, Brockton, MA, is a major supplier of cast-iron products to New England's construction market. The 150-year-old company pours 100 tons of iron each day to supply the region with nearly all of its manhole covers and sewer grates.

Although LeBaron's products seem low-tech, the company used high technology to solve a challenge.

In late 2003, scrap-metal prices tripled, skyrocketing the cost of raw material going into LeBaron's manhole covers and sewer grate sets. The company had no way to pass along these costs, since it was locked into long-term contracts with many municipalities. Although those contracts were mutually beneficial when signed, LeBaron was on the hook to deliver products at a fixed price even as its costs soared.

Steve Clinch, LeBaron company president, holds a mechanical engineering degree, and invested in 3D CAD software in hopes of updating the company's manual testing processes. If less metal could be used in casting the manhole covers and sewer grates without sacrificing strength, it was a way out of his company's dilemma.

Beefed Up

In the past, when greater strength was required in manhole covers, LeBaron simply beefed them up.

"For years, whenever we needed a stronger product, we made them thicker," Clinch said. "They were more than strong enough, but they eventually became over-engineered, which wasn't a problem until material costs escalated. We didn't have the tools to address this problem until we had the right software."

The CAD/CAM system Clinch purchased let the company put its products on a diet.

Strength testing required applying up to 60 tons of force to a product via a 9"×9" steel-reinforced, hard rubber square. The force represents one wheel of a vehicle rolling over the product, and the 9"×9" square simulates the vehicle's tire patch. LeBaron conducts tests under the conservative assumption that one tire is carrying the weight, even though it's likely to be a pair.

The most commonly-accepted criteria for highway loading comes from Standard Specifications for Highways and Bridges published by the American Association of State Highway and Transportation Officials – AASHTO. The specification defines the heavy-duty loading condition as a two-axle load of 32,000 lb or 16,000 lb for each set of dual wheels.

AASHTO recommends that these loads be increased by a factor of 1.3 to account for the impact of the wheel hitting the cover or grate when a vehicle rolls over it. All LeBaron heavy-duty castings meet, or exceed, this loading criteria by a minimum safety factor of 2.5. In fact, most have safety factors in the 3 to 5 range.

Physical Iterative Testing Cost Time and Money

Manual testing is time consuming and expensive. To test a new design, the company builds a new pattern, makes the castings, puts them in the press, applies force, and notes the breaking point. If the product proved strong enough, designers left it alone, instead of spending time and money optimizing it through prototype trial and error.

With raw material costs rising, LeBaron was forced to rethink its approach. The 3D CAD software Clinch purchased was SolidWorks Office Premium, which came with integrated design analysis software, COSMOSWorks Designer.

"We're saving more than $500,000 annually by designing better products."

Clinch set up simulations in COSMOSWorks Designer that paralleled the application of forces that LeBaron had been performing manually. With COSMOSWorks Designer, product testing became affordable. A design team could refine and test a design digitally, creating and testing hundreds of designs in the time it would take to create physical prototypes for manual testing.

Clinch and his design team went through the entire LeBaron product line, modeling products in SolidWorks software, tweaking designs to reduce materials, and analyzing them in COSMOSWorks Designer.

When he and his team created designs the software indicated were optimal, Clinch built prototypes in the resulting geometries and tested them against real-world conditions to establish the validity of his findings. Tests confirmed the software simulations – many of LeBaron's best-selling products were over-designed and thicker than needed.

"We're saving more than $500,000 annually by designing better products," Clinch said. "We're redesigning them in a way that reduces material, while still getting the job done."

50 lb Weight Drop

Using SolidWorks and COSMOSWorks Designer, Clinch and his team shaved weight, paring as much as 50 lb of material from a typical manhole cover, a savings of as much as 25 percent by weight. There was no sacrifice in safety in the newer lightweight designs. Physical tests confirmed the software's conclusions. The company avoided the projected shortfall from rising prices and fulfillment of fixed-price contracts, an estimated savings of more than $500,000 in the first year.

"We could have done all this without COSMOS," Clinch said. "We could have built a pattern, made castings, noted when they broke, made a leaner pattern, and repeated the cycle ad nauseum, until we ran out of time and money.

"It would have been a horrendously time-consuming and expensive process. With COSMOSWorks Designer, we were able to iterate six different models in two afternoons until we came up with streamlined designs that had more than adequate strength. Our work was simplified by a relatively-inexpensive finite element analysis product combined with a 3D CAD package."

LeBaron uses SolidWorks and COSMOSWorks Designer to expand the custom configuration manhole business. The company has more than 5,000 standard manhole cover patterns that it can customize at a nominal charge. Many cities and towns are customizing their manhole covers by incorporating town seals.

LeBaron also uses the software to design and manufacture extra-heavy-duty products to withstand concentrated loads, such as fully-loaded airliners.

"You'd think that after 15 decades there would be nothing more to say about manhole covers," Clinch said. "We learned that prudent use of powerful tools yields better products, and sometimes these improvements yield extraordinary benefits." SolidWorks Corp.

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