In electric motor engineering, copper is king, and winding architecture is one of the main levers engineers use to balance power density, efficiency, cooling and manufacturability. Higher copper fill in the stator can reduce winding resistance and improve current loading for a given package size, but only if the design also manages the magnetic, thermal and high-frequency loss penalties that come with pushing performance harder. Traditional motors rely on bundles of round wires, but those circular cross-sections leave large pockets of unused space.

“If you would take such a motor and cut through and count the surface of the copper compared to the area where the wires are, you will get something of the order of 40% of the volume is copper,” Dr. Florian Kassel, co-founder of Germany-based electric motor developer SciMo, told Charged in an interview. “This is very cheap to manufacture, but only allows very small currents, and results in poor performance.”

The copper density in the stator is a key property of an electric motor determining the performance for a given motor size. An increased copper density leads to reduced stator diameter, less motor weight and a reduced rotor diameter, enabling increased rotational speeds. Increasing motor diameter to make room for more copper can create tradeoffs in rotor inertia, mechanical stress and high-speed design. In high-rpm machines, increasing diameter to gain copper area can compromise some of the speed, packaging and rotor-dynamics advantages the designer is trying to preserve.

One solution is the auto industry’s hairpin technology: thick copper bars, roughly 2.5-3 mm across, bent like oversized staples and inserted into the stator slots. On the far side, every protruding end must be precisely aligned and welded to form closed loops.

One tradeoff with large rectangular conductors is higher AC loss at elevated electrical frequencies, especially in high-speed operating regimes. That is a well-known challenge in hairpin-style windings and one reason engineers look for ways to reduce conductor dimensions or otherwise mitigate skin- and proximity-effect losses.

To overcome these limitations, Germany-based SciMo is pursuing a different approach. The company’s pitch is not simply the use of rectangular copper conductors—hairpin motors already use those—but the use of thinner rectangular flat wires in a distributed winding architecture, combined with a manufacturing process designed for automated, lower-volume production. SciMo says this lets it push copper filling factor above 70% while avoiding some of the design-flexibility and AC-loss penalties associated with larger-section hairpin conductors.

SciMo says its winding architecture reaches copper filling factors above 70%. Compared with conventional round-wire distributed windings, which the company lists at around 45%, that represents a major increase in slot fill and can support higher current loading and power density in a given motor package.

The smaller conductor cross-section is intended to reduce the high-frequency losses that can affect larger-section hairpin conductors. The method pairs high copper density with better efficiency at top-end RPMs. “We don’t have these negative effects, so we’re somewhere in between these two worlds and have a really nice tradeoff,” Kassel added.

This winding technique also appears to offer a thermal advantage. SciMo says the geometric placement of its conductors creates a shorter and more uniform thermal path from the winding to the cooled structure of the motor, which can help reduce hot spots and improve continuous current capability.

In traditional round-wire bundles, hundreds of strands may sit buried in the middle of a coil, far from any cooling path. Hairpin motors also introduce thermal-management challenges around large conductors and welded end connections, and some designs use oil cooling to help manage those regions. The precisely arranged flat wires are intended to improve heat extraction from the winding, which can give engineers more thermal headroom before overheating becomes the limiting factor.

The result is unusually high power density—at least in peak terms. SciMo publicly claims peak power densities of up to 17 kW/kg and continuous power densities above 10 kW/kg for some motors. In motorsport applications, SciMo says its lightweight motors can contribute to very high total system outputs in multi-motor setups. The company describes individual motors in the roughly 20–30 kg range, with total system output reaching levels comparable to 2,000 horsepower in some configurations.

Slashing winding costs through full automation

SciMo was founded in 2017 by three PhD students working with the Karlsruhe Institute of Technology (KIT) and supported the students on the university’s formula racing team with electric motors. Every year, about 60 students develop, build and drive a vehicle in the Formula Student Electric international competitions.

“During that time, we realized that these motors were exceptionally good; they had significantly higher power density compared to all the competitors,” Kassel said. “In the following years this team won the World Title of the series and made first places several times—at that point we knew: this technology is really something.”

The SciMo team has grown to 25 people working on the technology full-time, building the business by working with customers directly without backing from outside investors to fund its development.

But producing such stators hasn’t been simple. In the early years, each unit required weeks of painstaking manual work. “We started in the beginning doing it by hand. It was highly expensive. It took three weeks for just one stator.”

Production was limited to small batches, often just three to 30 motors per customer, depending on the project. That limited the business to niche applications willing to absorb high labor costs, such as motorsport or early-stage aerospace customers.

The company’s turning point arrived in 2022, when it secured roughly €2 million in EIC Accelerator funding from the EU to automate the production process.

Semi-automation followed. Machines supported the technicians in winding the stators, which reduced the production time to one week.

Now the company has achieved fully automated production—an essential step toward scaling the technology beyond today’s niche markets.

“Since founding SciMo, we have always had this target of having fully automated manufacturing of this winding technology,” Kassel said. “This winding takes up 30-35% of the total manufacturing costs of the motor, and now we can drop that to half. And the more volume we produce, the better the margin gets.”

Because the cost per unit improves with volume, the company can now consider markets that were previously out of reach.

Scaling motor innovation with robotic precision

The new winding line relies on robotic systems guided by a sophisticated software stack, rather than the conventional CNC-style machines that dominate the motor industry. These robots execute fine, force-controlled movements to place each fragile rectangular wire into the stator slots with more accuracy than skilled human technicians. “There’s no reduction in precision or performance,” Kassel noted. “With automation, it actually gets better.”

But precision comes at a cost: time. Unlike the automotive industry’s hairpin-wound motors, which can be produced in around 60 seconds per stator, even with full optimization, a single SciMo stator is expected to take roughly six hours to wind. That makes it challenging to scale the technology for mass-market production.

“It’s still very time-consuming to produce motors with our winding technology,” Kassel said. “We will never be a competitor to hairpin technology or anything like that.”

Instead, the robotics-based process offers something equally valuable for certain sectors: flexibility. Because the system relies on software-defined motion paths for precision rather than fixed tooling, engineers can reconfigure the winding setup quickly to accommodate different stator geometries or custom layouts. Producing five units for a research program, 50 for a specialty vehicle maker, or 500 for an electric bus fleet all fall within the company’s sweet spot.

The approach has practical limits. Scaling to 10,000 units a year would require upwards of 20 to 25 winding machines—an investment that would make other technologies more cost-effective. But in the niche markets where high performance matters more than ultra-low manufacturing cost, the company’s robotic system gives it an edge. It can deliver custom, high-performance motors without the rigid tooling and requalification burdens that constrain hairpin or other conventional winding manufacturing technologies.

With the winding process automated, SciMo says it can now target markets with tighter cost constraints while maintaining the precision needed for its motor designs. The main remaining limitation is not performance consistency, but cycle time and scale economics.

Powering motorsports, aviation and the next frontier

Automation enables SciMo to dominate the high-performance, low-volume applications in which precision, adaptability and unconventional engineering pay off.

That includes the high-end automotive sector, where manufacturers of high-performance car brands are willing to pay a premium for increased power density.

“In the motorsport business, where we have batch sizes of 100 to 200 motors per year, we’re a big competitor,” Kassel said, “because you can either have a cheap, non-custom, mass-produced motor or you go to manually produced custom motors that rely heavily on expensive materials and come with astronomical prices. SciMo is exactly in between these two worlds.”

One of the most promising applications is electric aviation, where weight is crucial. One of SciMo’s first customers was a company developing electric people-carrying drones. “You want to have as little weight as possible, and therefore we could sell these motors at high prices.” The sector’s needs align perfectly with the company’s lightweight, high-output motors.

“We are in many different industries at the moment. The main customers come from the motorsports and aviation industries, but we also provide electric motors for rocket engines or as dyno motors in test bench applications,” Kassel said.

Setting the stage for the next leap in electric motor engineering

If SciMo succeeds in scaling, the economic implications could be as transformative as the performance gains. Conventional motors derive around 70% of their cost from materials, especially copper and steel.

By packing copper more efficiently, SciMo argues it can reduce motor size and material demand for a given performance target while preserving the thermal and packaging advantages needed in high-performance applications. The company also sees thermal headroom as a path to future gains, especially if paired with more advanced magnetic materials or lower-loss electrical steels.

“Now if we would say, we need an even higher performance output, we could do this either with advanced magnetic materials for much higher temperature tolerance, or with ultra-thin premium electrical steel to cut stator losses even further,” Kassel said.

Electric motors are fundamentally constrained by heat, because as the temperature rises, the magnets weaken and can be permanently destroyed. But motors built with premium, heat-resistant materials can tolerate much higher operating temperatures.

“For us, there’s still lots of room for improvement; but at the moment, we don’t need it. We are just happy that we have now managed to get this winding technology fully automated and can pass on these savings to our customers,” Kassel said.

“We’re now at a really interesting point in time for the company where we’ll now try to scale up and find new markets, and we’ll see how it goes. But this is the point we’re standing at. So, exciting times ahead.”