Transforming Metal Additive Manufacturing for Automotive

General Motors’ Dr. Anil K Sachdev – Global Research & Development, General Motors explores the automotive industry’s challenges with additive manufacturing (AM) and what needs to change for it to become a mainstay technology.

When it comes to the automotive industry, AM is still very much the reserve of prototyping and small volume parts, but we want to change this. Our charter is to take AM into high volume manufacturing, making it an economically viable technology fit for automotive production.

To do this we need product designs that exploit the specific benefits of AM and can also be produced economically in order to extend volumes from a dozen to at least one million per year. Until we can break this million-volume barrier, AM will keep hitting dead ends.

GM worked with Autodesk to produce this proof-of-concept seat bracket

There are five main impediments standing between reality and this goal – three technical issues that speak to the ‘can we make it?’ question and two economic impediments that seek to answer the ‘should we make it?’ dilemma:

Machine size: With most metal AM powder bed machines making a part limited to less than 400 millimetres per side, there are only a few singular parts we can create in their entirety. And for small components, machine size still limits us to perhaps only creating five to ten at a time – that’s a long way from one million considering the very large castings and stampings we make.

Accuracy: The cost of AM is already high – and adding the labour and expense of post-processing makes the price for the technology too dear. Until AM can create accurate parts with minimal need for post-processing, it will not be economically viable for large-scale automotive production.

Materials: Most AM materials are currently geared toward the medical or aerospace industries, where the volume (often singular in the medical field) and cost structure can justify expensive alloying additions.

We need substantial developments in materials to support the high volumes required in automotive. This is the heart of the work I’m doing at General Motors Research & Development – using computation methods to design materials that are lower cost and meet our performance requirements when processed optimally with available AM methods. The alloys currently available are typically those designed for cast or wrought products and don’t necessarily exploit the rapid heating and cooling rates experienced in AM processes.

Throughput: Currently AM is too slow for automotive production, considering the rates relative to competing manufacturing methods. A stamping press can produce a part every six seconds, while additive takes several hours to produce a batch of small parts.

Cost: As a high volume and consumer facing industry, cost is a major factor for automotive. For example, die casting (like AM) can combine many parts, but is almost two orders of magnitude cheaper. AM will have to compete with processes that have been optimised over the past 50 years and provide additional value in order to replace them.

All of these issues cannot be tackled by a single entity – or even one sector alone. While the machine builders are best positioned to continue to address size and throughput, our focus as an automotive entity is currently on materials development and processes. For example, I am researching metal powder development and processing as a function of throughput, which with advanced modelling techniques available, will help us to address – and overcome – AM’s current impediments.

Metal powder is not new to automotive –about 300 metric tonnes of it are used per year in North America and it is recognised as an optimum solution when it comes to creating detailed, complex parts that need almost no post-processing. A 1:1 part substitution will not be sufficient to disrupt this well-established process. The driver to proliferate AM into the automotive sector will be aggressive designs outside the scope of traditional manufacturing that provide a key performance benefit.

 The importance of adding value
The true stumbling block for AM is its value proposition. Even factoring in the increased design capabilities of metal powder bed fusion, the benefits still do not outweigh the cost of AM for medium to large numbers of components. To be adopted as a mainstay in the industry, AM needs to create better value than our current processes. We are trying to find applications for AM that make sense in high volumes – something we’re working toward.

Let’s look at the evolution of the beverage can as an example of how this journey can progress. The original design for this every-day container was a three-piece, steel cylinder. At the time, aluminium—though lighter weight—was too expensive to be considered as an alternative. Looking to improve upon the cans, the beverage industry invested in researching new materials and processes. As technology evolved, they were able to create a lighter, two-piece can using closed-loop recycling. Despite being the more expensive material, aluminium replaced steel, becoming a commonplace consumer material because its properties added value to the process and the product. Its benefits outweighed its cost.

  A collective effort
By overcoming its technical and economic impediments, AM can achieve similar results. Like the beverage can, the AM transformation cannot be achieved by a singular entity – we need collaboration across industries to enable high volume production and continue developing new materials. Suppliers and OEMs all need to be involved as well as automotive businesses, start-ups and research institutions to drive innovation – taking the design, performance modelling, building and finishing stages of the journey all into account.

Collectively, we can transform AM into a more viable technology for the automotive industry. By mapping the elements of this ‘journey’ against the five impediments we need to overcome, we can start to develop a roadmap to take AM from prototyping to high-volume production.

 The need for standards
As we get closer to the solution, the need for standards is beginning to surface. Rather than pre-empting the process and trying to anticipate what may be required, however, standards need to evolve collectively across the industry as a response to what is needed.

For example, we’re already calling for a level of standardisation so powder suppliers can work with multiple machine builders. With the hundreds of millions of parts we require each year, it is not sustainable for every machine builder to have its own unique powder – the automotive industry’s sheer volume requirements won’t permit this.

Powder standards are only the tip of the iceberg – by spreading the word and communicating what is required, the industry can work together to support the evolution of AM and break the all-important one million parts volume barrier.

Sources: The engineer