Aluminum Extrusion for Lightweighting: Key Factors
for Success

By on August 16, 2017 in BREAKING NEWS

OEMs can replace steel with aluminum extrusions, but often engineering teams are not as familiar with the alloys, the extrusion process, and the tolerances and performance characteristics that can be achieved. Here’s what engineers need to know and what to expect from suppliers.

By Harry Siegel, Vice-President and Mark Butterfield, Magnode

In their drive to shed weight from cars and trucks, original equipment manufacturers (OEMs) and their tier suppliers are turning attention to more potential applications for aluminum extrusions in the vehicle.

Substituting steel for alternatives like aluminum is often proposed as a simple solution, but that’s rarely the case. Automotive engineers are challenged by the fact that while aluminum weighs half as much as steel, it can be twice as expensive, especially when the design of the original steel part is retained. To minimize the potential cost impact of lightweighting, engineers must redesign components to optimize the alternative material being considered and meet the functional requirements.

OEMs can replace steel with aluminum extrusions, but their engineering teams are not as familiar with the alloys, the extrusion process, and the tolerances and performance characteristics that can be achieved. OEMs should seek partnerships with automotive suppliers that produce lightweighting solutions with advanced materials and innovative manufacturing processes. Conversations with these suppliers will assist engineers in developing a design using extruded aluminum that fulfills performance requirements while also saving weight and cost.

Here’s what engineers need to know and what to expect from such suppliers.

Aluminum Is the New Steel

The auto industry shift to lighter and stronger vehicle parts is well underway, so much so that North American extruders added five presses dedicated to automotive customers from 2014 to 2015. That investment can produce more than 110 million pounds of aluminum and aluminum alloy parts a year.1 In 2017 and 2018, at least seven more extrusion presses are planned, adding another 150 million-plus pounds of capacity in North America.2

“Extrusions have been used in various applications for a long time. What you have is an expansion of the use of extrusions into new areas of the vehicle,” says Harry Siegel, vice president of sales and marketing at Magnode Corporation, a Trenton, Ohio-based automotive supplier with decades of experience as an extruder and fabricator.

“In the push to lightweight vehicles, what we’ll often see is a steel or die-cast design that the customer will say, ‘Make it out of an extrusion.’ That’s not using the extrusion to its optimal value. You’re just re-creating the design in a different material,” Siegel says. “To be most cost effective and material efficient, you need to design from the ground up based on extrusions.”

Such a shift in thinking can be difficult in an industry with limited experience in designing aluminum extrusions. That’s where the right supplier will be invaluable. Engineers should look for a partner that helps identify a solution appropriate for the application. Suppliers should help support a detailed analysis of the costs and benefits of the available material options. Ask the supplier to discuss in detail:

  1. Alloy selection
    1. Which aluminum alloys would most efficiently produce the physical performance characteristics required?
    2. Can the alloy chemistry be tweaked to optimize its performance for the specific application?
    3. What are the micro-structure and testing requirements?
  2. Physical performance requirements
    1. What is the application?
    2. How does the part need to perform?
  3. Tolerancing requirements
    1. How does the part mate up to other parts?
    2. What are the secondary operations to be performed and their associated challenges and implications?
  4. Profile design
    1. How can design—features, wall thickness, geometry, mass and size—be optimized to minimize weight and secondary operations while meeting the performance requirements?

How design considerations translate from current material selections to aluminum extrusions is a new topic for many engineers.

“Symmetrical extrusions are easier to manufacture, but often inefficient in application. A key advantage to the extrusion process is putting the mass where it’s required for performance and removing it where no value exists. Compared to a steel structure that originates from a uniform sheet, aluminum extrusions provide a clear advantage on mass placement,” says Mark Butterfield, vice president of engineering and manufacturing at Magnode.

It’s All About Cost of Vehicle Weight

There’s a fundamental question to get out of the way. If aluminum can cost twice as much as steel, why should automotive engineers consider extrusions as an alternative?

“The OEMs are saying, ‘To meet the CAFE [Corporate Average Fuel Economy] requirements, we must take weight out of the vehicle.’ While aluminum is more expensive than steel on a cost-per-pound basis, the value is created from the weight savings aluminum can provide and the value the OEMs place on weight savings. The material cost-per-pound delta is offset by the value the OEMs place on weight savings,” Siegel says.

The success story most often highlighted is how the Ford Motor Company solved the lightweighting challenge in its F-150 pickup by replacing 95 percent of the truck body with aluminum components that contribute to a vehicle that weighs 700 pounds fewer than the previous model. Stiffness or rigidity results from a combination of stronger aluminum alloys and innovative adhesive and rivet fasteners.3

There Are More Ways to Cut Costs

Some automotive engineers are reluctant to consider aluminum extrusions because they believe tolerances will not meet their requirements. While dimensional tolerances for steel parts typically are tighter, suppliers using advanced extrusion methods can produce components with repeatable tolerances that support the desired application. It is important to engage the extruder upfront in the design of the part or assembly so it is optimized for the extrusion process. This will minimize the total costs and ensure the end result is repeatable.

Another important lesson for OEM engineers accustomed to the grades and standards of the steel industry: “While aluminum has been used in vehicles for decades, the Aluminum Association standards were based on building construction applications. Few of these standards apply to the rapidly increasing automotive applications of aluminum and aluminum alloys,” Butterfield says.

He adds that automotive designs must be efficient and performance bands tightened. The Aluminum Association standards are “just too broad for many automotive applications. For example, advanced suppliers of extruded components will refine alloys and tighten chemistry to get more repeatable characteristics and physical properties optimizing the intent of the extrusion design.”

Controlling the extrusion process and producing required tolerance starts with the die design. The design principles are different for solids versus hollows versus multi-hollows and are influenced by the type of application. “Structural parts require another level of analysis to ensure longitudinal weld integrity,” Butterfield says.

Butterfield finds that many extruders are skilled at producing symmetrical parts that have the same wall thickness, left side to right side, top to bottom. The value of aluminum extrusions is increased when webbed and honeycombed profile designs are created to meet the functional requirements and further reduce weight. “The more intricate the wall structure with variability in the wall thicknesses means a more complex, highly engineered die is needed to control the flow of material during extrusion.”

It should be noted that there are many good extruders providing a wide range of expertise. “However,” Butterfield says, “for automotive applications at this level, the capability of internal die design and engineering is critical to providing structurally high-performing extrusions. Advanced automotive suppliers have more tools and internal design knowledge and capabilities required for extruding the complex geometries OEMs need today. That’s where advanced suppliers apply the greatest resources on die design and process.”

CAD model of complex die design

Ways to Impact Secondary Processes

Aluminum extrusions can help automotive engineers meet functional requirements while also saving weight because of the unique ways alloy chemistry, the extrusion processes and profile design can be customized for each application.

Suppliers with advanced knowledge and techniques will adjust die design, alloy chemistry and quench process to improve tolerances and repeatability of their extrusions. The most skillful extruders also produce increasingly complex geometries that increase strength while reducing weight. Even rarer are suppliers with the expertise to extrude aluminum in ways that also enable OEMs to save time and cost on secondary manufacturing operations.

Put Magnode in that latter group. As an example of its know-how, it produces a part that has a hole through its length that gets bored to a final critical dimension and tolerance for a major Tier 1 supplier. After working with the customer and further development of the extrusion die and process, Magnode improved the design so the time required for boring to finish the part was reduced by 20 seconds. Based on the program volume, this change is expected to save the customer more than 5,000 hours of machining time per year.

Simply converting a steel component to aluminum is almost never cost effective. Therefore, OEMs should collaborate with suppliers such as Magnode to thoroughly explore alternatives among the 537-plus registered aluminum alloys and find the combination of material chemistry, extrusion process, temper and quench to create near-net shapes and achieve the desired component performance. A key consideration: The cost of aluminum extrusion tooling is significantly less than other manufacturing processes and much faster. This yields two benefits:

  1. Prototype parts made from a production intent extrusion die
  2. Die timing quick enough to enable multiple design iterations all within the vehicle-development cycle

Automotive Supplier Producing Extrusions

Magnode, a third-generation family company with more than 200 employees, has focused on the automotive industry for more than 20 years.

“Fundamentally, we’re an automotive supplier that produces aluminum extrusions. The way we look at our business and approach our designs, process controls, production methodology and quality systems is through an automotive-supplier lens,” Siegel says. “How we design dies is different. Our ability to hold tighter tolerances in complex extrusions is different. Our perspective as an automotive supplier is different. These are the attributes that differentiate us from other aluminum extruders.”

The company produces the most difficult and intricate extrusions available to automakers. Magnode also makes products for a variety of industrial applications, the infrastructure market and electronic equipment. On top of the varied extrusion expertise, Magnode is ISO/TS 16949:2009 and ISO 14001 certified. Plans are also in place to achieve the new IATF 16949 certification required by the automotive industry.

Magnode is expanding its automotive reach into crash-management components. The company’s skill set aligns perfectly with the requirements of this product segment. Working with a global OEM, Tier 1 and alloy supplier, Magnode is assisting in the development of the next generation of crash-management system that meets stringent performance, tolerance and weight objectives.

“We’re not a company with four or five plants filled with presses, but we are large enough to have a wide range of capabilities that allows us to produce just about any size profile that is utilized in a car,” Butterfield says. “A lot of extruders can supply automotive parts. The value Magnode provides is that we are more technically advanced and able to produce parts with a much more controlled method. The end results are more stable and predictive. That’s what the OEMs are after.”

9-void multi-hollow automotive structure component

 

 

 

 

 

 

 

This is what a deformed crush can developed by Magnode looks like following a required compression test.

Lighter and Stronger Crush Cans

Crush cans are not a new technology, but they’ve become a growing area of lightweighting—and for good reason.

Automakers want components for collision management systems (CMS) that absorb more energy in less space and at a lower weight than current designs. These requirements prompted Magnode to begin development on new approaches to crush cans about a year ago.

To meet the changing performance requirements of crash cans, Magnode evaluated various alloys and potential chemistry tweaks to provide the optimum mechanical properties. The OEM requirements are extremely challenging to deliver. There is a tight range on the yield, which is typically difficult to hold, and the wall thickness tolerances are extremely tight. The entire manufacturing process from billet production through the aging process must be tightly controlled.

“Had they [the OEM] said they just needed a minimum of 210 MPa, that obviously opens the program up to a number of extruders that can achieve that,” Butterfield says. “Putting a tight band on the mechanical requirements fits Magnode well.”

Magnode joined with its longtime raw-material supplier, Hydro Aluminum, a global aluminum producer, to refine an existing alloy specifically for the crush-can project. The new recipe remains confidential, but Butterfield explains that Magnode and Hydro changed the mix of magnesium and other elements to improve the way the material deforms during a collision. That change led Magnode to collaborate with its customer and OEM engineers on the geometry of the components to tighten tolerances and improve the crash-performance repeatability.

“If we can hold wall-thickness tolerances 50-percent tighter than other versions of the crush can, realized performance during a collision will be in a much tighter band and allow for better predictability. The geometry and tolerances achieved reduced downstream costs relative to how the extruded cans fit during welding and assembly,” Butterfield says.

Collaboration Among Three Partners

Magnode built the extrusion die and ported it specifically to meet the OEM’s crush requirement. The location of welds within the extrusion die, and the depth and volumes of the weld chambers and bearing surfaces were all adjusted based on extensive testing and data analysis of the extrusion, quenching and aging processes.

The crush-can development is an ideal program for Hydro Aluminum and Magnode to work on together for three specific reasons:

  • Hydro is a full-service, raw-material supplier and has the technical staff necessary to support aluminum-chemistry innovation.
  • Magnode has extensive experience producing complex extrusions with tight tolerances and minimal variances.
  • The Tier 1 customer is well positioned with leading metallurgists and engineers driven by research and development.

The partners extensively tested material and crush-can prototypes for chemical and mechanical properties, bendability, microstructure, intergranular corrosion and long-term thermal stability.

“When you put those three together, you’ve got a perfect mix to be able to support an advanced crash-management system or for that matter, any structural component for an OEM. The OEM ends up being the beneficiary of such a partnership,” Siegel says.

Sources

1Butterfield, Mark, “Utilizing the Attributes of Aluminum Extrusion for Effective Automotive Solutions,” Aluminum Extruders Council, 2016.

2Ibid.

3 Isenstadt, Aaron and John German (ICCT); Piyush Bubna and Marc Wiseman (Ricardo Strategic Consulting); Umamaheswaran Venkatakrishnan and Lenar Abbasov (SABIC); Pedro Guillen and Nick Moroz (Detroit Materials); Doug Richman (Aluminum (Aluminum Association); Greg Kolwich (FEV), ”Lightweighting Technology Development and Trends In U.S. Passenger Vehicles,” International Council on Clean Transportation, Dec. 14, 2016.

ABOUT THE AUTHORS

Harry Siegel is Senior Vice President of Sales and Marketing Magnode Corporation. He has more than 25 years of experience in sales, marketing and business development in the automotive industry with the last nine focused on aluminum extrusions. He has also held senior positions in international business development, manufacturing and marketing. Mr. Siegel holds a B.S. in engineering from Michigan State University and an MBA from the University of Michigan.

Mark Butterfield is Vice President of Engineering and Manufacturing at Magnode Corporation. He has 27 years of experience in automotive structural and non-structural 6000 series extrusions. Mr. Butterfield’s background includes profile design and development, extrusion tool design, aluminum casting, extrusion process and equipment, 6000 series metallurgy and CNC fabrication. Mr. Butterfield manages all corporate engineering, extrusion and fabrication operations. He also serves on several AEC committees.

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