By Andrew Halonen, Mayflower Consulting LLC.
Every business owner would like to have a better understanding of their customer to be sure they are meeting customer needs and are remaining competitive. So, how do they get this insight and feedback? The process is referred to as the voice of the customer (VOC). While this sounds easy, the process is actually more complicated and involves a number of considerations, starting with who to ask.
In the automotive business, there are many stakeholders, many people who influence design and material decisions. For extruded aluminum, it is understood that materials engineers specify and approve material selection. Vehicle architects select what material fits the application and integration strategy. Engineering and simulation teams, referred to as computer-aided engineering (CAE), perform the analysis to ensure materials will meet crash performance and long-term reliability. Meanwhile, design and release engineers may be in charge of a specific system, such as the rocker or the bumper assembly, and generally have their comfort zone regarding their favorite solutions and suppliers. There are other voices, too, such as personnel in supply chain departments who are responsible for long-term pricing and stability. They need to know that the supply base is robust, stable, and able to meet the vehicle program needs through the life of the vehicle.
Prior to the Aluminum Extrusion Technology Seminar & Exposition 2024 (ET ’24), the Aluminum Extruders Council (AEC) requested a VOC investigation regarding the use of extrusions in automotive. The project was conducted by Mayflower Consulting. This article provides an overview of the insights from the VOC interviews, which revealed that the current research and work in the extrusion market is well-aligned with the expressed market needs of the automotive industry.
Obtaining the VOC
When seeking the voice, feedback, and insight of the customer, the questions need to be tailored to the audience. It’s easier to engage with an interviewee when the topic is well understood by the interviewer. For example, the areas of expertise for Mayflower Consulting are in materials and design engineering. Another reality in this line of work is that everyone is busy, short on time, and there are limitations in which they are allowed to comment on behalf of their company. If the questions are brief, focused, and aligned in common areas of expertise, there is a good chance of a rich conversation in a short amount of time.
What are the best questions to ask? The short answer is that there are a wide range of questions, depending on the market and what the supplier is interested in learning from the customer. When the AEC requested the VOC interviews, they wanted to learn from automakers about the kinds of applications for extrusions, the customer’s wish list for extruders, and the potential competitive threats three to four years from now. As a result, a sample of the VOC questionnaire used for this project is presented in Figure 1.
Trends change in any industry, therefore the interests of the customer likewise change. For example, ten years ago in the automotive industry, electric vehicle (EV) battery boxes were not a major topic of conversation in media and engineering circles. Extruders were not anticipating that the protection of these massive and costly systems would be so critical. Battery boxes are a complex system that take advantage of extrusions for protection, heat transfer, fluid flow, and structural integrity. At 2 m in length, these multi-hollow extrusions need to meet increasingly stringent requirements for straightness, weight, and crash protection.1 As the applications change, so do the requirements in alloys, extrusion processing, and final product.
Automotive Market Feedback
The VOC project resulted in good interviews with OEMs, Tier 1 suppliers, and consultants. The insights from these interviews included four main concerns that automakers need to be addressed by extruders, including consistent wall thickness, straightness, integration expertise, and alloys and performance. Note that extrusion customers appreciate and utilize the variety of materials available. It’s important to understand that a winning solution is not just an extrusion, but rather a component that integrates well within the vehicle. OEMs want solutions, not parts.
Wall Thickness Consistency
The competition to aluminum extrusions is often a steel sheet stamping. Steel has the advantage of higher modulus and higher strength, so it will be thinner than an extrusion, and consistent wall thickness across the 8 ft (2.4 m) length of the stamped part. When the automotive engineering team designs an extrusion, they work to optimize the wall thickness to meet the mechanical performance and minimize weight. An OEM engineer described a situation where the CAE engineers had a very thin wall extrusion, yet they were disappointed to learn of a process variation that drove inconsistent wall thicknesses, which resulted in a heavier component.
The aluminum extrusion industry has been aware of this concern for years, as is evidenced by the webinar, “The Power of the Hollow,” presented by Mark Butterfield in 2021.2 However, it can take time to get all of the extruder supply base to deliver on these new targets, which they are working towards.
Straightness
As applications evolve, new requirements can be expected. Bumper beams and crush cans were difficult to produce at inception, yet the mystery has now been solved and these applications are well understood. The new frontier is protection from side impact, but with a focus on long parts for EV battery boxes and rockers (also referred to as sills). As noted previously, the length can be as much as 8 ft. Straightness along this full length is critical, because the multi-hollow extrusions are difficult to assemble if they are bent or twisted. The point of a multi-hollow profile is to prevent deflection, yet a part that is not straight at assembly needs to be manipulated to meet adjacent components for assembly via fasteners or welding. Inconsistencies in bow or twist may require machining to minimize gaps that could cause leak paths for corrosion. These gaps need to be addressed with additional sealers, which increases the cost, manufacturing time, and complexity of assembly.
Straightness is a recognized challenge by extrusion technology professionals, as reflected by at least two papers at ET ’24. A team from Hydro Aluminium Metal wrote on the use of calibration to manage twist and bow with the conclusion that stretching is the best method,3 yet there are situations where more complex solutions are required.
Straightness can be improved post-extrusion, too.4 First, the extrusion is inspected for dimensional accuracy, and those that are out of specification proceed to the straightening equipment. This technology originated in large, thin-wall structural aluminum castings and is now finding application to meet the precision requirements of automotive extrusions.
Profile Integration
Extruders produce the finish profile according to the customer specifications and often assume their job is done. While this is technically true, there is more to the equation. When one considers extrusions’ main competitor steel, it’s important to remember that most automakers are already familiar with steel. Since human beings are often reluctant to learn new things, extruders need to bring more to the table to facilitate a successful product. This includes providing value-added capabilities, such as fabrication and considering the integration requirements of the part, such as joining (Figure 2).
Each successful product builds momentum to the next success story. However, the reverse is also true, and bad news travels faster. If the integration of a perfectly produced extrusion into a vehicle goes wrong, then extrusions as a whole look bad.
One automotive interviewee with 40 years of automotive experience, mostly in sheet metal, was surprised to learn how difficult it was to integrate extrusions together into an assembly. He noted that the challenge involved the amount of sealing required to fill the gaps caused by twisting and bowing in the profile, which required special equipment to make the assembly of the extrusions into the vehicle system possible. In that case, the extruder was little help to the OEM, leaving the automaker’s integration team to figure it out. This engineer strongly recommends that extruders get more proactive on integration technologies, suggesting that extruders offer workshops to OEM engineers to share best practices.
In a similar conversation on high pressure die cast shock towers, an integration engineer who was accustomed to steel shock towers commented, “We put it in there for assembly, and it was an inch from the frame rail, and it didn’t budge.” Extrusions are like structural castings in that they are inflexible, so they need to be produced to a tight tolerance for ease of assembly.
Alloys and Performance
Speaking to engineers, it’s easy to begin the conversation on material selection and popularity. The 6000 series alloys are by far most popular, with one OEM calling 6082 their “bread and butter” alloy, meaning their favorite. In addition, automakers often use 6063 for crush cans and 6005A for easier components.
Each OEM was asked about the use of 7000 series alloys, and the list of pros and cons was presented. The pros of 7000 series alloys include the fact that the use of stronger alloys lead to thinner walls, lower weight, and ability to fit the profile into a tight package space. There is also the possibility of a slight improvement in crash performance over 6082 alloy or similar.
However the cons for 7000 series alloys include the high cost and challenging supply chain due to its small supply base and slow extrusion rates (though the addition of scandium may improve extrudability). These alloys are also difficult to recycle due to the presence of zinc, which is considered a contaminant in 6000 series alloys (used in the vast majority of extrusions) and is difficult to keep out of the recycling stream. In addition, there is a concern of strength reduction in 7000 series alloys in the paint bake cycle. The Cadillac CT6 rocker was over designed to accommodate this issue.
As application requirements become more stringent, engineers need to get down to the fundamentals of physics and metallurgy. In bumper beams, the failure mechanism is bending, whereas in a rocker, it is rupture due to side impact. In the latter, the Verband der Automobilindustrie (VDA) bend test is a critical metric, as is grain structure. One interviewee commented that grain structure is more important than strength in a rocker application.
“The advantage of the VDA-238:100 bend test is it more accurately measures a material’s resistance to damage and, in effect, its ability to absorb energy. This data can be directly correlated to CAE simulations or component tests,” noted Victor, J., et al., in their ET ’24 paper.5 This is well stated by the authors, but unfortunately, not all extruders are on the same page.
One OEM interviewee complained that extruders still talk in terms of elongation, yet VDA is a far more accurate representation of the crash management system. The ET ’24 paper, “The Journey to Supply Automotive Grade Extrusions: Challenges and Solutions,” by Fourmann, J., et al., expands on common 6000 series alloys and the value of the VDA test.6 In addition, VDA was discussed in the Q&A following the presentation, showing that the test is clearly on many extruder’s minds, but the challenge is to get all of the suppliers to this level of understanding.
Both in the VOC interviews and at ET, there was also a fair amount of discussion on recycled alloys. Based on these discussions, it was learned that the requirements regarding recycled content are inconsistent across OEMs and regions. BMW was mentioned most often, and it was stated that extrusions need at least 55% recycled content. This does not seem difficult for an extrusion, but perhaps it is more challenging for hard alloys than soft.
One VOC interviewee asked if the extrusion market will ever have an alloy like cast A380 that is 100% secondary material? In a conversation at ET, it was said that if the scrap stream could be limited to automotive materials, this is a possibility.
The Future is in Extruders Hands
Automotive VOC interviewees are optimistic on the future of aluminum extrusions. When asked about potential competition to extrusions, one OEM engineer does not see a replacement to aluminum profiles. Rather, extrusions are getting better and more competitive. Even steel-intensive vehicles use extrusions because they are capable of geometries that steel can’t do, such as the bumper beams on the Ford Mustang Mach-E and the rocker on the electric Hummer that is comprised of steel with an extrusion on the inside for energy absorption.
Extruders understand the need for continuous improvement and in the product, this comes via straightness, consistent wall thickness, and mechanical properties. The bumper beam is becoming a commodity, and the multi-hollow rocker is a highly engineered solution that delivers safety-critical protection in a tight package space, such as the Tesla Model S rocker extrusion (Figure 3).
The future of automotive extrusion can be summed up in the concept of precision. Extruders can leave nothing to chance. They need to achieve precision in grain structure, wall thickness, straightness, and a deep understanding of vehicle architecture integration.
References
- “Electric Vehicle Battery Box,” AEC.
- Butterfield, M., “The Power of the Hollow: Using Hollow Aluminum Extrusions to Meet Vehicle Engineering Challenges” (webinar), Auto Beat, 2021.
- Moretro, J., U. Tundal, S. Tjoetta, and F. Paulsen, “Use of Collaboration to Achieve Tight Tolerances in High-Strength and Ductile Automotive Profiles,” ET ‘24 Proceedings, May 2024, Orlando, FL.
- Meinikmann, N., P. Hettich, and M. Hartlieb, “Measuring and Correcting Distortion in Extrusions,” ET ‘24 Proceedings, May 2024, Orlando, FL.
- Victor, J., A. Poznak, L. Itchue, and M. Tozier, “Overview of Methods to Evaluate Extruded Profile Ductility as It Relates to Automotive Profiles,” ET ‘24 Proceedings, May 2024, Orlando, FL.
- Fourmann, J., J-F. Beland, P. Rometsch, and N. Parson, “The Journey to Supply Automotive Grade Extrusions: Challenges and Solutions,” ET ‘24 Proceedings, May 2024, Orlando, FL.
- “Front Cradle and Suspension | Tesla Model S Plaid Teardown” (video), Munro & Associates, 2022.
Andrew Halonen is president of Mayflower Consulting, LLC, a lightweighting consultancy that provides sales, marketing, and market research for high tech clients. Halonen works with castings, extrusions, artificial intelligence, and machine learning. He earned a BS Mechanical Engineering degree from Michigan Tech University. Contact him at: www.lightweighting.co.
Editor’s Note: This article first appeared in the June 2024 issue of Light Metal Age. To receive the current issue, please subscribe.