High-volume EV motor production is a study in variation control.
A Feintool plant in Vaihingen, Germany, makes rotors and stators for the motors powering BMW electric vehicles. I filmed this video during a visit to the plant. At about 0:21 in the video, you can see a drone’s-eye glimpse of all the production this part producer has ready to ship to its automaker customer.
A rotor or stator is an unusual part. What looks like a solid is really an assembly. The basics of motor operation demand lamination layers with an air gap between each layer. So: Each rotor and stator seen here is a stack of identical stampings, each stamping about 0.3 mm thick, hundreds of stampings high.
And because even small imprecision leads to electromagnetic losses, there is a lot the manufacturer can do to deliver motor performance:
See the tooling used to control stacking. Repeatability here directly translates to lower losses and a more capable motor.
The air gap must be there but it can be small. Feintool does not mechanically join the laminations for these EV motors, but instead uses a precision gluing process the company developed itself. Closer bonding = smaller air gap = more steel per stack = more power output per motor volume.
Even the precision of the assembly hardware does not represent all that can be done to limit variation. To even out any small thickness variation across each individual stamping, the robot rotates lamination substacks as it combines them.
Why this matters:
The advance of electrification means motors will be more and more central to our world.
And with motors, the manufacturing process directly determines how efficient, capable or small the motor can be.
EVs are a beneficiary, yet it’s not just EVs. The sophisitication of motor manufacturing will have a lot to say about how powerful, economical and compact the compressors, robots, heavy equipment, hand tools, and even recreational vehicles of the future can be.
To state the matter another way, the power output, efficiency, or package size of machinery of the future will be shaped by process precision in making motors.
