Camila Domonoske / NPR
Robots have revolutionized auto manufacturing, making plants safer and products more reliable – and reducing the number of people involved in the process. But go into a modern car plant and you will soon realize that robots have hardly replaced the human touch – at least not in some areas.
Volvo's car factory in Ridgeville, SC, opened last year, provides an object lesson. The plant produces S60, a luxury sedan, both in the US market and for export.
The beginning of production is highly automated; in the first of three large buildings, robots reach over 300 to 200 people. But the process is dominated by people.
Let's start with the robots. Behind a safety fence, half a dozen robot arms move in coordination, as they spot-weld a car body together and swear softly. The lights in this part of the massive building are subdued because the robots do not require much light to complete their work.
Robots are undoubtedly better than people in some tasks. They are precise and consistent, and they are distinguished by repeating an identical movement over and over again.
Jeff Moore, Volvo's vice president of manufacturing in America, says that when deciding which jobs to be assigned to a robot, the company starts by focusing on monotonous, physically demanding work – especially all that carries security issues.
"With all the heat and sparks and high currents and things like that associated with welding, it's a natural place to look at where you can more automate," he says.
But on other parts of the line, "the human touch has many benefits," says Moore.  Or as Tesla CEO Elon Musk put it last year, "People are undervalued."
He admitted that Tesla was miscalculated by turning to heavy automation at his Fremont, Calif. After the production problems were installed, the electric car manufacturer returned the course and began giving back jobs to people.
So how exactly do people still hit robots? Follow the car's body down Volvo's assembly line, and eventually the lights become bright while people put hood, trunk, fenders and bumpers.
Logan Cyrus / Bloomberg via Getty Images
Then comes quality control. Robots with sensors test the spot welds, and people run their hands over the surface of the metal body, feeling imperfections. The literal human touch still can't be beaten here.
The car body passes through a skybridge to another building where it is painted – another task where robots excel. Then it travels to a third building for final assembly, where thousands of parts from all over the world come together to form the finished car. Here again people reign.
People are better than robots to manipulate complex shapes and thread them together – exactly the skills needed to attach engine parts.
These workers also handle various kinds of engines – gas or hybrid, full wheel drive or front wheel drive, with or without turbo and in the future even electric motors. People can easily switch between different tasks and even pick up new ones on the run; robots not so much.
When Tremaine Smalls puts drive shafts for engines and a radio reporter sometimes gets in the way, he pushes the complications of working with different engine types.
"It's a bit of the same process, just different drive shafts," he says, showing how he checks part numbers against a piece of paper to confirm that each engine is properly set up.
Gary Coleman / Courtesy of Volvo Cars America
Jason Dodgins, who worked on the same line, used to be a team leader for a rental producer. There he says that his job was to run a computer-controlled machine.
"The machine did a lot of the actual work area," he says. "You basically did the inspection." Working on this auto assembly line, in contrast, "has much more manual labor for it," he says.
As the engine moves along the line, people and machines share the work. Kayla James, just two weeks into this job, uses a mechanical elevator to install an exhaust system; It takes away the physical burden of the task. Later, a large machine makes dozens of bolts at the same time – but between each cacophonous volley, Brandon Marshall puts the various bolts in place.
People edge out robots on these tasks, even when everything goes smoothly, but they have a special advantage when things go wrong.
In modern car factories – inspired by Toyota's revolutionary production philosophy – workers are encouraged to stop the line when there is any problem, big or small. (On plants like this Volvo facility, workers draw a string and music game – another song for each location signals where a problem has come up.)
Robots can also identify certain errors that come into the queue, but people have a definite advantage when it comes to solving these problems.
Consider Volvo's radiators. At a key point in the line, the car's body – waiting in an elevated conveyor – falls on the engine, transmission, axles and anything else that makes the car move. They come together at the "place of marriage."
"If this radiator is not pushed back far enough, it will go down into the body," says Trey Yonce, who helped set up the marriage point line.
The original production process required the rubber bands to hold the radiator in place for the key moment, but a laser sensor would often find that the radiator was not in the right place. Machines could mark the problem to be solved.
But humans, unlike robots, get annoyed by repeated problems.
"They just got tired of doing it, and a guy came up with an idea and it worked." Yonce says. He points to a small yellow piece of plastic that more effectively holds the radiator in place – an improvement of the process.
Moore, the Volvo Vice President, says the company has already applied for more patents based on ideas that came from workers at this new facility.
People have strengths compared to robots in every possible workplace – not just auto plants.
And generally, people and robots work best together, with robots that handle dangerous, monotonous jobs and precision work, while people handle tactile work, switch between tasks, make decisions – and create creative ideas for improving things.
There is a philosophical lesson here in a way.
"People often think of the production of workers as actually a bad substitute for a robot," says Susan Helper, economist at Case Western Reserve University. As a machine that complains, gets tired and makes mistakes.
And historically, some factories have tried to treat their workers as robots, separating "brain" work from "hand" work and pushing assembly line workers to do repetitive tasks without thinking. In this setup, a robot is an upgrade from a human worker: It will not complain or get tired.
"But in practice these things are very difficult, and the fitter leader makes many judgments." Helper says. "And it turns out that when you take that person away, you end up with some problems that are difficult to solve."
This means that the best thing robots can do for manufacturing is not replacing people – but releasing them to work as good people.