Assembling Electric Vehicle Motors

Engineers are scrambling to find cost-effective ways to mass-produce EV motors.

By John Challen

The shift from the internal combustion engine to batteries and electric motors is, in automotive terms, monumental. But, there is no denying that it’s a challenge that manufacturers and suppliers are tackling head on.

Faced with new regulations to help reduce global carbon emissions, original equipment manufacturers (OEMs) had no choice but to shift focus away from diesel and gasoline to batteries. Almost every OEM has now gone public about their plans for electric vehicles. That paradigm shift has piqued the interest of both traditional motor manufacturers and a handful of startups developing new technology.

Whether it’s an electric car, truck or tractor, traction motors are vital to making wheels spin. That’s why many automakers, such as BMW, Ford, General Motors and Volkswagen plan to assemble motors in-house.

For instance, Ford is spending $150 million to refurbish its 53-year-old Van Dyke Transmission Plant in Sterling Heights, MI, to mass-produce e-motors. General Motors is also taking a vertically integrated approach with its modular Ultium Drive power train family, which consists of three interchangeable motors.

“As with other propulsion systems that are complex, capital intensive and contain a great deal of intellectual property, we’re always better off making them ourselves,” says Adam Kwiatkowski, executive chief engineer for global electrical propulsion at GM.

“Most of the Ultium Drive components, including castings, gears and assemblies, will be built with globally sourced parts at [our] existing global propulsion facilities on shared, flexible assembly lines,” explains Kwiatkowski. “[This will allow us] to more quickly ramp up EV production, achieve economies of scale and adjust [our] production mix to match market demand.”

“Taking over the role of the internal combustion engine in car engineering, e-motors are a fundamental building block of electric cars, together with the battery and power electronics,” adds Henrik Green, chief technology officer at Volvo Cars, which has committed to assembling electric motors at its power train plant in Skövde, Sweden.

“Bringing the development of electric motors in-house will allow [our] engineers to further optimize the entire electric driveline,” explains Green. “This approach will [enable us] to make further gains in terms of energy efficiency and overall performance.”

While there are many different types of e-motor designs, every device has four basic components: a rotor, stator, body assembly and battery control module. And, there are fewer parts overall than with an internal combustion engine (ICE). An e-motor typically has only about 20 moving parts vs. 200 or more in an ICE.

Automated Assembly

As OEMs and suppliers ramp up EV production, more robots will be used to assemble smaller parts and subassemblies, in addition to the entire motor itself. One area that is an ideal candidate for automation is rotor assembly, where close tolerances present numerous challenges.

Rotor and stator assembly applications use robots to pick, wind and shape coils or windings. Robots can also be used for making connections, pressing the rotor shaft, welding and gluing, plus bolting the body together.

“Accurate, automated injection of glue into magnet housings is essential to ensure retention of the magnets, even at very high rotational speeds of 15,000 rpm or more,” says Patrick Matthews, global power train group manager at ABB Robotics. “Test and inspection also is a continuous activity throughout e-motor production, with robots constantly monitoring quality and correct assembly within very tight tolerances.”

Suppliers such as ABB have seen an uptick in business due to the automotive industry’s recent shift to electrification. In particular, they’re producing more automated systems for assembling electric motors. According to Matthews, two themes in the electric motor market are constant change and ongoing product improvements.

“For everyone involved in electric vehicles, the whole race is about producing cars faster and at higher quality,” says Matthews. “To do that, you need to really scale up development, and that is what we see as both a challenge and a new horizon. Through the years, OEMs have found it easy to build at low volumes, but the challenge comes when you need to build thousands of components in a month.”

ABB engineers are developing robotic assembly cells that can help manufacturers achieve those high-volume levels.

“We want to help them get to volumes of 500 to 1,000 units, and then scale up further,” explains Matthews, adding that maintaining high levels of quality is vital. “Electric motors are no longer a niche product; they are going mainstream and they need to be [assembled] right.”

ABB has used its vast experience in traditional body shop and power train applications to develop a more flexible approach to EV motor manufacturing.

“Our serial processes on a standard line mean that all parts come into the station one after the other,” explains Matthews. “We’ve now taken that process apart and are looking at parallel production. With more parallel stations, parts come down the line together so that all the parts for one particular component are [joined] together. Complete assemblies—or major portions—are then completed, before going to the next station.”

According to Matthews, there are four key advantages of parallel vs. serial production for electric motor manufacturers. “The first advantage is that you overcome the ‘one down, all down’ concept, which can slow down or stop series production,” he points out. “In a parallel process, you can continue to run one or two of the cells without closing the whole line down.

“The second advantage is onboarding or [capital equipment spending],” says Matthews. “Volumes of spend are based on a scaled-down volume. With the parallel process, you can scale the cells, so you don’t have to invest capital at the beginning.”

Another advantage is the ability to add more products into the mix while keeping production online. In addition, Matthews claims that the parallel production system is more flexible.

“We’ve had customers who have taken cells from one plant and moved them to another plant because the volumes were going down in one [facility] but increasing in another,” notes Matthews. “They took the cell, moved it to the plant, installed it in a week and got production back by the end of the week.

“There are tangible advantages of the new approaches,” says Matthews. “We see there is a 5 percent to 10 percent efficiency improvement using these flexible methods. A lot depends on how the plant is structured—whether it was brownfield or greenfield—but there are definitely scalability and savings to be made over the traditional series production process.”

An assembly line for electric motors has much different processes than an ICE line, Matthews points out. For instance, there is much less metal cutting and machining involved.

“There are no longer big banks of machine centers, and there’s less drilling, tapping and milling,” explains Matthews. “We’re seeing more assembly, molding machines, and ovens for heating and curing. There’s also a lot more wire winding.”

Small, Lightweight Beginnings

Many entrepreneurs and start-up companies are scrambling to develop innovative EV motor technology. One of them is Saietta Group, a UK-based firm pinning its hopes on a new motor that is suitable to a wide range of electric vehicle applications.

Its Axial Flux Traction (AFT) motor is modular, lightweight and affordable. The unique design features a dual-rotor, axial-flux permanent magnet combined with distributed windings and a yokeless stator. Saietta’s first commercial offering, the AFT140, is designed for use in midsized motorcycles and final-mile delivery vehicles. But, the company claims that other versions of the AFT motor can be used in other types of EVs.

Thanks to a grant from the UK’s Advanced Propulsion Centre, the company is in discussion with a variety of automakers and Tier 1 suppliers. The grant enables production to be ramped up to 150,000 units a year at a pilot plant in Oxfordshire. But, Saietta’s long-range plan is to mass-produce millions of motors annually. To help achieve that goal, the company is collaborating with Brandauer and AEV Group.

“Brandauer specializes in stamping, and it is helping us scale up the cutting and packaging of grain-oriented steel,” says Wicher Kist, CEO of Saietta. “AEV specializes in potting electric components, which need to be conductive for heat rejection, but insulated from an electrical point of view.”

According to Kist, the unique design of the motor’s coil will affect how the AFT is mass-produced.

“Around 99 percent of electric motors have a steel structure, which is used as a bobbin to coil the copper around,” explains Kist. “But, we’ve created a discrete coil, which is similar to the coil of an antenna.

“With that, we kink it to make sure the current on one side is aligned with one magnet and aligned on the other side to make a circuit.” Kist points out. “We’ve done that 96 times, [then inserted] six busbars on each side to create the circle.

“The coils are then laid in a circle and arranged in a spiral,” adds Kist. “The assembly, at that point, is designed to be automated as we ramp into mass production, as opposed to hand built, which is the initial phase.”

Next, the individual discrete coils go down a conveyor belt and are paired up—to get the current in and out—before being dropped into a stator ring, potted in a curing machine and placed back onto the assembly line.

“One of the companies we’ve worked with is Royal Enfield, which makes motorcycles in India,” explains Kist. “However, it wants to make the motor slightly bigger and glue two together. The have also expressed an interest in keeping motor manufacturing in-house.”

To Infinitum and Beyond

Another fresh approach has been developed by engineers at Infinitum Electric, which has created an electric motor that uses a printed circuit board (PCB) stator. The company has developed a device for household appliances called the IEh series that is 50 percent lighter, 30 percent quieter and 10 percent more efficient than traditional electric motors. It also recently agreed to provide its IEm series motors to a North American supplier that is involved in the development of a hybrid vehicle.

“[We] pull out the iron and copper windings from the stator of every motor and etch copper conductors into a circuit board”, says Ben Schuler, CEO and founder. “The removal of the iron makes for a [much more efficient], smaller, lighter, quieter and more durable motor.

“Our contract with an automotive supplier is for R&D and applying oil-cooling techniques to the stator,” explains Schuler. “We’ve found throughout the process we can increase power density and performance of the stator by applying oil to cool the motor instead of air, like we do on other products.”

“We build the whole motor, but the IEm Series—unlike [our] general purpose product—is not a standard product line, because we don’t have a standard mobility offering,” he explains. “Although we design products to our customer’s needs, there are a lot of off-the-shelf solutions. A lot of the cars are different, so they have different power and voltage requirements.”

Schuler says the long-term goal for his company is to become an e-motor supplier to large automotive OEMs. He’s confident vehicles equipped with Infinitum motors will be on the road in the next two to three years.

“[Our unique attribute is something] that no one else has done on the EV side of the market,” claims Schuler. “That’s removing the iron and using a circuit board that is already in the car. With that, we can get higher efficiency and remove the core losses.”

Another advantage is in raw material savings. “Our electric motors are smaller and lighter than most others, which is important, as the whole movement to electric vehicles is built around climate change and being more efficient,” says Schuler. “Transportation of raw materials is a massive contributor to climate change and something that we want to reduce.”

According to Schuler, the biggest challenge to EV motor manufacturing is the long development times. “It’s more about OEM development cycles and less about motor [production], although you still have to create and approve the motor,” he points out.

“We have a proprietary design software platform where we can input the specifications of the user, hit enter and our design file can then be sent to PCB shops all over the world,” explains Schuler. “We can create samples in days or weeks, as opposed to months or years, which some products take.”

Another advantage of Infinitum Electric’s innovative design is that is doesn’t need the traditional capital investment required for a traditional motor assembly line.

“They go through a lot of different production stages, but ours is a simple PCB and we can print out thousands of them very easily,” claims Schuler. “It is a drastically streamlined production process.

“Our process is fabless,” says Schuler. “Much like some of the models of some semiconductor manufacturers, we’re ordering off-the-shelf components, and the only capital costs are the molds and castings for the housing. And, if a customer wants us to use their housing, we’ll do that.

“We’re really only aggregating the components, testing them and shipping to the customer, as opposed to a traditional electric motor manufacturer that has to stamp the laminations, wind the windings and everything else,’” adds Schuler. “Their way is much more labor-intensive.”

Infinitum Electric’s production is currently around 5,000 units, but through a combination of scaling up its own facility and also using contract manufacturing partnerships, Schuler says the company will reach “hundreds of thousands of units a year” by 2023.

“Electric motors consume more than 53 percent of electricity globally every year,” claims Schuler. “That number is only going to increase as electrification of everything takes over. But, if all those motors were ours, we’d be able to reduce CO2 emissions by almost a gigaton every year and save up to 1.2-trillion kilowatt-hours.

“I know those numbers are pie in the sky, but it shows the difference that using lighter, more efficient motors can make,” argues Schuler.

Back to the Future?

Draper Laboratory Inc. is also developing a new family of electric motors that promises to be more powerful, efficient, lighter weight and less expensive to manufacture than traditional EV motors. Among other things, they do not require rare earth materials.

“Electric vehicles require ever-increasing performance from electric motors, but are limited by the weight and cost of materials needed to make a conventional motor—steel, copper coils and rare earth magnets,” says Sabrina Mansur, automotive business development manager at Draper. “[Our] recently patented approach to electric motors replaces those materials with thin, light and widely available materials.

“Almost all electric motors use magnetism to generate torque,” explains Mansur. “For centuries, engineers have known that forces from electric fields can also be harnessed to build motors, but these so-called electrostatic motors were considered too weak to compete with their electromagnetic cousins.

“By leveraging state-of-the-art materials, novel designs and decades of fabrication expertise, [we are] developing powerful new electric motors that break the torque barrier suffered by previous electrostatic motors,” claims Mansur.

“Our e-motors use thin electrodes and electrets which reduce weight by 80 percent or more compared to conventional motors,” Mansur points out. “This translates to a range extension of up to 25 percent for electric vehicles (and up to 40 percent for drones), based on our simulations.”

Bentley R&D Project to Study Electric Motor Recycling

Bentley Motors Ltd. is embarking on a three-year R&D study that aims to revolutionize the sustainability of electric motors. It is part of the luxury automaker’s initiative to only produce hybrid and electric vehicles by 2026.

The goal of the RaRE (Rare-earth Recycling for E-machines) project is to use recycled rare-earth magnets in e-motors. Bentley engineers hope to build on work completed at the University of Birmingham in devising a method of extracting magnets from waste electronics.

Adding to the sustainability benefits that RaRE will provide, the bespoke motors created through this method promise to minimize complexity through manufacture while supporting the development of the UK supply chain for both mass production and low-volume components,” says Matthias Rabe, Ph.D., a member of the board for engineering at Bentley Motors.

As we accelerate our journey to electrification, offering only hybrid or electric vehicles by 2026, and full electric by 2030, it is important that we focus on every aspect of vehicle sustainability, including sustainable methods of sourcing materials and components,” explains Rabe.

RaRE promises a step-change in electrical recyclability, providing a source of low-voltage motors for a number of different applications, and we are confident the results will provide a basis for fully sustainable electric drives,” notes Rabe.

This study will run in parallel to [our] OCTOPUS research program that aims to deliver a breakthrough in electric power trains, utilizing a fully integrated, free from rare-earth magnet e-axle that supports EV architectures,” adds Rabe.

Read the full article at Assembly.