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AM: good for making lightweight metal auto parts, less so for mass production

3D printing helps automakers lightweight cars, but the process doesn’t meet their mass-production needs

metal 3d printing

BMW uses additive manufacturing to mass-produce window guide rails for its i8 Roadster. BMW Automotive Group

The use of metal 3D printing in automotive manufacturing has been limited to date because the relatively slow additive manufacturing process doesn’t meet automakers’ mass-production needs.

Examples of mass-produced metal AM parts exist, including the aluminum bracket on the convertible roof of BMW’s i8 Roadster. It was the first 3D-printed metal component used in a production-series vehicle.

With the emphasis on lightweighting of vehicles to increase fuel efficiency and extend the charging range for electric vehicles, the ability to 3D-print metal parts that weigh less than those currently installed in vehicles is actively being pursued.

Lightening Up

Lightweighting is especially important to the automotive sector, said Jonathan Harris, lead application engineer at nTopology. “Higher performance, better fuel economy, better safety, lower emissions, and the compounding coupling effect that these all have on one another are motivating manufacturers to take lightweighting efforts to new heights.”

nTopology, a New York City software developer, offers a lightweighting toolkit that helps designers reduce the overall weight of parts using several design techniques, including part consolidation, conformal ribbing, lattices, and topology optimization. The latter technique calculates the optimal component design so that the required load is distributed throughout the part, which minimizes the amount of material needed. It also leads to some unusual, organic-looking parts.

Problems can arise, though, when trying to manufacture these complex shapes. And that’s where 3D printing can make a difference.

“With additive, you have much more freedom over geometry, so you can actually build the results of these computational designs rather than having to consider how to fit it into a casting mold or machine it in five axes,” Harris said.

Lightweighting Aids Supply Chain

With fuel economy standards and sustainability goals, weight reduction is “low-hanging fruit versus redevelopment of electric motors or batteries,” said Kyle Adams, lead field application engineer at SLM Solutions, a German builder of powder bed fusion systems that has offices in Wixom, Mich.

3d printing

Bugatti 3D-prints titanium brake calipers for its Chiron sports car. Originally the French company forged the calipers from an aluminum alloy. The Ti6AI4V version weighs about 40% less and is considerably stronger. A force of slightly more than 125 kg can be applied to a square millimeter of the printed caliper without the material rupturing. When the Chiron travels at its top speed of 400 km per hour, the braking system halts the vehicle in nine seconds. The 2.9-kg caliper is produced in approximately 45 hours on an SLM Solutions four-laser model 500 printer. Bugatti

Adams pointed out that in addition to the benefits of lightweighting the end vehicle itself, you also can reduce the weight of transporting individual components to their assembly destinations.

“By reducing four or five components down into a singular component, you’re contracting your supply chain, by either not needing to fabricate the five or six different components into a single part or not needing five or six different sources to manufacture that one component,” he said. “That means you can transport more parts per load or lighten the existing load if you’re carrying the same number of parts.”

AM Drawbacks

Despite its benefits, additively manufacturing metal parts is far from a universal practice within the automotive sector. AM is well-suited for building complex metal parts, but the relative slowness and expense of the process makes its use impractical in an industry reliant on high-volume production.

“The cost of a 3D-printed component is driven by the speed at which it’s made,” said Adams. “So when you’re Toyota and you’re producing 50,000 Camrys a year, the numbers don’t currently make sense for any [3D printing] system on the market. The bottleneck would be the production of the part, even if there is a clear performance gain.”

Another limiting factor is build size. Most components in a vehicle that would be good candidates to print are fairly small, like seatbelt brackets, said Adams, “and you’re not gaining a lot of lightweighting performance with those smaller components.”

The biggest potential weight savings would come from 3D-printing things like wheels, brakes, and suspension components. “Because of the additional power needed to rotate the mass of those wheels, any gram of weight you save there is a huge advantage versus taking a couple pounds out of the body of a vehicle,” Adams noted.

But such large components are usually too big to fit into most traditional additive systems, and if they do, they take too long to print. However, with the advent of larger and more powerful metal 3D printers, automotive manufacturers will begin to print full-size metal components and reap economic rewards.

“With larger-scale, faster printers, build time is now one or two days, and we can get a 30% increase in performance along with a 30% decrease in weight off that component, which starts to tip the scales into value,” Adams said.

Another factor slowing implementation of additive in automotive production is the need for validation of printed parts.

additive manufacturing software

nTopology software was used to lightweight and design an additively manufactured car brake pedal. During the design process, lattice elements were thickened where higher stresses develop. nTopology

“Automotive manufacturers building hundreds of thousands of cars and trucks need repeatability, and they’ve got to have the necessary safety factors relative to variabilities in real production,” said Bruce Colter, vice president and general manager of Spee3D North America, Benton Harbor, Mich.

The Australia-based company makes “cold spray” 3D printers that jet-spray powdered metal at Mach 3 speeds, so that kinetic energy bonds the particles and layers together—a technology originally used for repairing aircraft parts (see sidebar).

“Lots of lightweighting concepts exist for computer-generated designs that remove material in ways that can only be produced by AM,” Colter said. “However, these designs are questionable in the real world for repeatability and having the necessary safety factors for variations in real production and use.”

nTopology’s Harris noted, “If you’re buying metal off the shelf and then machining it, your metal is already characterized to have X strength and Y stiffness to some quality specification. But with additive, you are making the metal as you’re making the part, so the quality is a lot harder to characterize.

“A car company putting a part on a vehicle can’t afford to get it wrong, because a recall costs millions of dollars and chances are people are going to lose trust, which costs the company even more,” Harris said.

Additive’s Auto Future

Many automotive advancements are introduced at the highest levels of automaking: cars made for racing and limited-production vehicles. These improved technologies then trickle down to the consumer market.

“Metal additive and lightweighting are being fully optimized in the top tier right now,” said Adams. “High-end automotive suppliers are starting to utilize the technology, and five or 10 years from now, what’s to say that the technology won’t be in every car?”

Though the 3D printers themselves won’t necessarily be cheaper, their speeds will continue to increase, making the end parts much cheaper, he added.

“In two or three years, [AM] machines are going to be able to produce a ton of small components very quickly or produce larger components in a very short period of time. Whether it be a steering bracket or a small valve that increases efficiency, every car is going to have some [3D-printed] thing on it,” Adams said.

SIDEBAR: Lightweighting electric vehicles

Metal 3D printing may have a significant impact on lightweighting of electric cars, according to Bruce Colter of Spee3D North America.

By printing components using two different materials, combining aluminum with copper, for example, manufacturers can reduce weight and reduce costs at the same time, Colter said.

Spee3D’s cold-spray additive manufacturing (CSAM) system applies powdered materials at Mach 3 speeds, allowing kinetic energy to bond particles and layers together.

Using the technology to “print cooling components like heatsinks, water-cooled busbars, and battery trays improves thermal management,” Colter said. “Built-in cooling channels where the batteries would lay, either on top of or inside the channels, allow the battery to operate cooler, so that it lasts longer and performs better.”

– H. Martin

About the Author

Holly B. Martin

Holly B. Martin is a freelance writer and editor from Winchester, Va., who specializes in science and technology.