Shedding light on lightweight castings

  • 11-May-2016 11:33 EDT
Grede products.jpg

Example of a typical differential case (top), which is the type of part that’s the focal product of the LIFT thin wall casting project. The steering suspension knuckle (bottom) is an example of a Grede cast iron safety-critical component.

Driven by rising demand for lighter weight components in automotive, heavy-duty trucks and off-highway vehicles, a new wave of technology and operational initiatives is taking center stage in the iron castings industry.

Current and upcoming government regulations covering fuel economy and engine emissions are, in part, instigating the trend toward lightweighting, but economics also are in the forefront.

The results to date are highly encouraging, and the future looks bright as well. Internally there is now closer collaboration at Grede between design and foundry manufacturing personnel to spot problems and opportunities much earlier. Similarly, we are working more closely up front with our customers to optimize the design and materials for the best solutions, more efficiently and at lower cost.

Although aluminum has its place in the lightweight components competition, Grede's high strength ductile and lost foam iron castings have several advantages. Take recycling, for example. We re-melt 220,000 ton (199,500 t) of scrap each year plus yield loss (excess) material from our production processes to produce new components. The re-melted material has the same mechanical properties as virgin iron. Aluminum production, including recycling is more costly and the recycled material properties are not as “pure” as the original material.

One primary focal point in the iron casting industry is to develop thinner-wall castings that, when added together, reduce mass at competitive costs. By bringing our manufacturing group into the picture earlier we’re finding we can achieve 20% to 30% reductions in mass by changing design parameters.

Of course we produce castings to our customer’s specifications, but we want to do more in the advanced stages, and our level of engagement with them is increasing phenomenally as we seek to demonstrate how we can be helpful in providing the best solutions.

So far it has been a huge success, and one customer now even views us as an important extension of its operations in meeting its performance requirements. By working together we can deliver precisely what they want right down to specific component packaging in tight spaces, a shortcoming for aluminum.

Thin-wall technology is an industry game-changer in the battle to trim weight, and it is gaining impetus from LIFT (Lightweight Innovations For Tomorrow), a federal government consortium of businesses and universities working to develop processes and lightweight materials across numerous industries.

I am pleased to lead the LIFT project on thin-wall ferrous castings, which aims to examine manufacturing methods of lightweight structures, thin-wall cast-ability, and performance expectations of lightweight structures. At LIFT we are trying to step out of the box. We want to take an existing production part and examine what is needed to reduce weight and how to test the new structure. We’ve also submitted a paper that explores achieving thin walls of 4 mm (0.16 in) or less in a production-based operation.

As one of the world’s largest suppliers of lost foam castings, Grede also is using this versatile technology to shave component weight while also creating up to 40% lower cost and providing less assembly complexity. As many as 15 to 20 pieces can be combined in a single casting at near-net shape with superior strength, stiffness, balance, durability, quality and performance.

In this process we use foam patterns for complex components such as engine, chassis, suspension and steering applications. Then the molten metal volatizes the foam to form the desired part. Post-processing such as drilling or machining can be eliminated, and there are opportunities for 30% weight savings and a 10% to 30% reduction in material.

There’s also this to consider: Lost foam can reduce production energy by 50%, and we have reduced our solid waste stream, especially sand, by more than 700,000 ton (635,000 t) annually. The molding media is completely recycled, lowering solid waste costs calculated at $31.5 million annually.

In our development work, we also are looking at how lost foam castings might be applied to nearby components. When the customer realizes the potential lost foam can provide, a design activity that focused on a single part that has various surrounding components can be converted to a larger integrated 1-piece casting encompassing multiple components.

Finally, Grede’s proprietary high-strength ductile iron alloy technology we offer in North America also is helping wage the lightweight battle by thinning component cross sections, thus requiring less overall material and saving weight while maintaining strength.

The material is developed and tailored for a wide variety of chassis, powertrain and structural components to achieve lighter weight and cost competitiveness, and is especially applicable to safety critical, high stress and high torque applications.

Overall, when the design is optimized the material can achieve both mass and cost savings.

Ferrous castings remain at the heart of automotive, commercial, off-highway and industrial vehicle componentry. Our job is to take out weight without compromising the integrity of the part while maintaining the numerous essential advantages the iron castings can offer. It’s a task that is already paying big dividends, with very real prospects for further significant gains approaching on the horizon.

Jay Solomond, Vice President, Engineering and Technology, Grede Holdings LLC, wrote this article for Off-Highway Engineering as part of the annual Executive Viewpoints series appearing in the June 2016 issue.

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