Automotive 3D Printing

Recently I attended the Automotive World show in Tokyo and prepared a white paper to explain our position to potential Japanese auto clients. It was translated to Japanese but I will post the English draft here. The initial reception seemed to be fairly positive but if it converts into action remains to be seen. What is certain is that something must be done or these Japanese auto companies risk falling more behind. When a BYD engineer looks at a 3D printed connecting arm and an engineer from one of the big seven Japanese auto companies looks at the same part and asks if it is the ‘Eiffel tower’ there should be a giant alarm sounding the mind of these automotive executives.

Why 3D Printing is Reducing Weight and
Making Impact in The Automotive Industry.
株式会社3D Printing Corporation
2018

Too much mass?
Generally, the more an automotive vehicle weighs; the lower the performance is, the greater the fuel consumption is, and the more raw input materials required to build it. At scale, the weight of raw materials becomes the largest factor in the cost of production. Meanwhile, performance characteristics, such as vehicle range are desired by consumers. As emission targets become increasingly strict, fuel consumption must become more efficient.

 

 

(The trendlines of weight/fuel efficiency are very clear)
Weight reduction is the obvious solution but there are major challenges:
Safety and regulatory constraints
More expensive materials (magnesium vs. aluminum)
Keeping or improving on product experience
Additive manufacturing, or 3D printing, and it’s salient technological trajectory is the process which is most suitable over the next 20 years of overcoming these challenges and realistically reducing vehicle weight while maintaining safety and minimizing production costs. 3D printing, with its numerous benefits, must become a critical part in an automaker’s long term weight reduction strategy.

What 3D printing actually is

Most automakers are familiar with 3D printing from their prototyping operations. GM for example uses 3D printing on over 20,000 of their parts. (2) But 3D printing is better thought of as a concept of how to manufacture. According to ISO / ASTM52900-15 there are seven distinct 3d printing processes, The following non-exhaustive chart is a better picture of what 3D Printing looks like. (table removed for formatting) (3)

What some automakers are starting to discover is that different 3D printing technologies are suitable for different parts of their businesses. One technology may perform poorly as prototyping tool while having excellent performance for production parts and vice versa. Another 3D Printing system may be a perfect solution for low-cost custom automotive jigs and tooling needed at the manufacturing site but unsuitable for mass production. Understanding the technological map of 3D printing is key for automakers to successfully reap the benefits of this new manufacturing concept.
The number of technologies and machinery in 3D printing is difficult to know entirely but there are some fundamental steps that all 3D printing technologies and systems share:

Data
All 3D printing starts at the data level. If the data in deficient in anyway, no matter the following steps, the end result will inherit this deficiency and perhaps exaggerate it.
3D Printing is currently done on a mesh basis and some new and limited voxel based data. This takes the form of a mesh. A mesh is composed of many small triangles that attempt to form an approximation of the desired shape that was likely designed in a CAD program.
Meshes are difficult to work with for engineering purposes because they are not easily manipulated and are hollow. Part of the challenge for 3D printing in the automotive industry is having the correct tools to smoothly go from CAD -> Mesh Draft -> Mesh repair and correction.

Parameters
All 3D printers require the newly created mesh to be broken into ‘layers’ that the 3D printing system can interpret as machine instructions. Because this is a critical step in transforming the digital data into a real object and because parameters will vary based on the hardware and technology involved; Almost all 3D printing manufacturers provide some solution alongside their systems to solve this problem.
The complexity of 3D Printing parameters increases as the materials and performance specifications become more specific. In the case of a metal automotive component, travel time of a laser on a powder bed fusion system can change the crystal structure and ultimately the end performance characteristics of the automotive component.
Meeting performance goals of parts requires technical skill with the manufacturing hardware as well as theoretical understanding of the technology.

Hardware
There has been a deluge of 3D printing manufacturing systems over the last few years. Some very good and innovative, many more derivative and lacking in real performance. Picking the right 3D printing process is the first step to picking the right hardware. Once an understanding of which process is required, you can look for specific technologies amongst a plethora of manufacturers. For the sake of this paper, there are too many to list.
There is often a very step in trade-off in build size. Build size, is large factor in cost/performance. You can expect that if you want to produce large objects, you will either have to sacrifice performance or pay much more for the larger system.
How does 3D Printing reduce automotive weight?

There are three major ways

  • DFAM
  • Topology Optimization
  • High performance geometries

Design for Additive Manufacturing (DFAM)

While it is partly true that 3D printing can make nearly any shape at the automotive scale. There are limitations and considerations that should be taken into account crystal structure of metal, conductivity, and thermal stress are all major factors that vary greatly from traditional manufacturing methods and must be considered before a part can be used successfully in production. This process is called DFAM and involves experienced technicians, engineers, and designers who understand the technology involved and can alter printing parameters and digital data to achieve the desired results. There are a handful of software that try to address this issue but this is still largely done by hand.

Topology Optimization

There are at least 5 distinct methods of topology optimization and dozens of software for topology optimization. The most widespread being variable density method (VDM) and solid-isotropic material with penalization (SIMP) (4) These processes seeks to find the minimum mass required to satisfy a set of engineering parameters. Much of topology optimization is based off research done in the 80’s that tried to answer the question of why human bones are shaped they way they are. This is the reason that often topologically optimized shapes tend to have an ‘organic’ look to them. The first algorithm was adopted to commercial software in the mid 90’s but didn’t see much use due to the limitation of manufacturing technology. Recently, topology optimization has renewed interest due to advances in 3D printing machines.

The reason topology optimization has not seen faster adoption in the automotive industry seems to primarily be a lack of skill to transform the topology optimized computer solutions into real manufacturable products, as derived solutions often have real-world problems. (5)
Nevertheless, topology optimization + 3D printing is a powerful tool as part of a weight reduction strategy due to the extremely promising initial results. For example, a car front hood was topologically optimized to reduce mass by 12% yet still meet engineering requirements.

Structural optimization of automotive front hood (6)
In practice, we observed similar savings to those often reported inside the industry and scholarly literature. In the case of one bracket for a Japanese automaker, mass savings, while meeting engineering requirements and manufacturability requirements, were an excellent 44%.

 


(basic bracket: 18.35 cm3 optimized bracket: 16.26 cm3 topology optimized: 12.75 cm3 株式会社3D Printing Corporation)

There also also somewhat newer non-density based topology optimization tools that offer many benefits. Built into these design workflows is the manufacturability and the ability to design structures that have multiple properties over the entire part. In this case, as mass reduction on a connecting arm for one Japanese automaker is at 54%.

Design for Additive Manufacturing (DFAM)
While it is partly true that 3D printing can make nearly any shape at the automotive scale. There are limitations and considerations that should be taken into account. Crystallinity of metal, conductivity, and thermal stress are all major factors that vary greatly from traditional manufacturing methods and must be considered before a part can be used successfully in production.(4) This process is called DFAM and requires experienced technicians, engineers, and designers in a collaborative effort to achieve the desired results. (Connecting Rod 株式会社3D Printing Corporation 2017)

As part of a light weighting strategy, DFAM also has two major benefits.

  • Producing complex single part assemblies
  • Innovative/High Performance geometries

When using 3D printing, there is a possibility to combine multiple parts into a single part and eliminate the need for screws or fasteners or otherwise redundant joints. By eliminating these unnecessary parts, the automaker may save weight as simplify the supply chain. The best known example of this is perhaps GE, who, by adopting a 3D printing approach to their aircraft engine, reduced the number of parts by 30%. Meanwhile, they were able increase fuel efficiency by 15% (7)
By increasing individual part performance, automotive designers have a wider range of marginal options, or better trade-offs, to meet performance and safety requirements.

Challenges of adopting 3D printing for Automakers

Speed, cost, and size are the three largest challenges facing automakers. Because of these three factors, it is the opinion of the author that powder bed based systems, while exceptional for prototyping and small batch production, are unlikely the correct solution for automakers looking to adopt 3D printing at a larger scale like medical and aerospace industries have done. Forutently, in the last few years there have been a deluge of technologies that address each of these. Metal sizes are now greater than 1 meter and will likely see further increases in 2019. While, the cost of metal 3D printing has dropped by about 1/10th of what it was compared to 2016, due to newer simpler 3d printing processes that piggyback of existing metal injection moulding technology. Speed is also going up by a factor of 2-5 times compared to previous years with newer technologies like wire arc additive manufacturing (WAAM) and cold-welding 3d printing systems.
If we consider the number of new patents filed for 3D printing over the last several years, it is also reasonable to expect the development of newer 3D printing systems to meet automaker’s demands.

The second largest challenge facing automakers and 3D printing tends to be a lack of trained staff. 3D printing, like other manufacturing technologies, requires skilled technical staff as well as managers who understand the process well enough to solve their current challenges with 3D printing. A plethora of 3D printing solvable challenges in the automotive industry are often ignored simply because teams are not aware of recent developments in 3D printing.
Although there are several economic and personal challenges, automakers looking for a long term weight reduction strategy for their vehicles should consider adopting 3D printing technology in its current state. This has the benefit of strategically preparing their staff and organizations for the inevitability of a digital manufacturing and design process. Secondly, because 3d printing has not been fully explored in the automotive industry, there are numerous easily achievable product and supply chain enhancements for early adopters.

Sources cited
https://www.wired.com/2012/08/fuel-economy-vs-mass/
https://www2.deloitte.com/content/dam/insights/us/articles/additive-manufacturing-3d-opportunity-in-automotive/DUP_707-3D-Opportunity-Auto-Industry_MASTER.pdf
Guo, N. & Leu, M.C. Front. Mech. Eng. (2013) 8: 215. https://doi.org/10.1007/s11465-013-0248-8
Sehmi, M., Christensen, J., Bastien, C. et al. Struct Multidisc Optim (2018). https://doi.org/10.1007/s00158-017-1876-0
Zegard, T. & Paulino, G.H. Struct Multidisc Optim (2016) 53: 175. https://doi.org/10.1007/s00158-015-1274-4
Cavazzuti, Marco & Splendi, Luca & D’Agostino, L & Torricelli, E & Costi, Dario & Baldini, Andrea. (2012). Structural optimization of automotive chassis: theory, set up, design. .
https://www.ge.com/reports/treat-avgeeks-inside-look-ges-3d-printed-aircraft-engine/