The past, present and future of the assembly line

Posted: July 14, 2025

The assembly line is synonymous with modern manufacturing. We all have a mental image of it: an identical car chassis, for instance, being transported along a conveyor belt past workers who each add a specific part or perform a specific task, perfectly in sync, until eventually a road-ready vehicle appears.

Most widely associated with Henry Ford, the introduction of the assembly line in the early 20th century changed manufacturing for good. With the division of labor, the use of precision machinery to create interchangeable parts and the automatic movement of an item between specialized workstations, this approach allowed for efficiency gains across a wide array of applications, from the Model T Ford to the McDonald’s hamburger and beyond.

Since the assembly line became widespread, technical developments have continued to change the way products get made. From automation and robotics to AI and customized factory production, the assembly line finds itself changing—piece by piece.

The origins of assembly-line production

Many of the principles underlying the 20th-century assembly line have a long history. One such principle is the division of labor: the separation of a work process into a set of discrete, repeatable tasks, each performed by a dedicated person or team.

During the First Industrial Revolution, traditional manufacturing methods—whereby skilled craftspeople created individual objects from start to finish—gave way to techniques of mass production that used the division of labor to increase productivity. Manufacturing was transformed by technological innovations like the steam engine and the spinning jenny as well as the shift to a factory-style organization of workers, including the division of labor.

In 1776, Adam Smith described the advantages of dividing work processes into separate tasks after visiting a pin factory. Only ten men were employed there, he wrote, and some only “performed two or three distinct operations,” yet thanks to the subdivision of tasks they were able to produce vastly more than if each were working on entire pins separately.

By the 1800s, manufacturers also began adopting interchangeability—a principle often associated with Eli Whitney and his Connecticut firearms factory. Previously, a musket would be made by a single skilled workman, part by part. But interchangeability promised a more efficient distribution of effort. While historians doubt that Whitney did succeed in manufacturing individual interchangeable parts, it is true that he and some contemporaries aspired to create a system in which any given worker was making only one specific part, each of which could fit into a musket of the correct design. Since interchangeability requires high standards of precision, however, it took several decades to become cost-effective (or even possible) in many industries.

The sequential aspect of assembly-line production—with objects being moved automatically from one stage to the next—did not take hold until the 20th century. But an important historical forebear came in the form of the Venice Arsenal, which mass-produced ships in sequential fashion as early as the 16th century. Instead of building ships and keeping them at the harbor, the Arsenal managed a stockpile of mast-less hulls and prefabricated parts, which were rapidly assembled in time of war.

A Spanish traveler once watched this assembly process taking place, with hulls moving past sequential warehouses that each added another component: “I know not how to describe what I saw there, whether in the manner of its construction or in the management of the workpeople, and I do not think there is anything finer in the world.”

Nowadays we do know how to describe that system: it was essentially an assembly line.

Ford progress: the 20th-century assembly line

In the early 1900s, all the components of the modern assembly line came together. Using electric power and precision-oriented machine tools, manufacturers could send a product along a mechanized conveyor belt past sequential manned workstations, each dedicated to one specific process or component addition. (In many cases, these stations would themselves be at the end of an assembly or production line, requiring a high level of synchronization to work correctly.)

The car-maker Ransom Olds introduced a progressive assembly line around the turn of the 20th century; Chicago slaughterhouses were using “disassembly lines” for dismembering and processing hog carcasses. Yet the spectacular breakthrough came with Henry Ford in Detroit. His factory system combined the principle of interchangeability with the continuous flow of products, massively ramping up the output of his Model T cars in the 1910s and 1920s while capturing the public’s imagination.

At the Ford factory, a strict division of labor into subtasks meant workers required minimal training and could be swiftly reassigned if overall efficiency demanded it. Electrified tools worked on interchangeable parts; machines were grouped, not by type, but according to the optimal sequence of tasks. Conveyor belts and gravity slides brought the work to the worker—and minimized the distance an item had to travel.

This system involved standardization: Ford quipped that customers could have the Model T in any color they wanted so long as it was black. Standardization increased productivity and reduced labor costs; it also enabled new levels of managerial visibility and quality control.

Assembly-line production spread rapidly from automotive to other industries. By the middle of the century, the assembly line had become synonymous with mass production. Even food would be transformed, with Ray Kroc—the man who made McDonald’s a global franchise—allegedly boasting that he had “put the hamburger on the assembly line.”

The assembly line today: an uncertain future

Since Ford’s day, the assembly line has been widely transformed by the rise of automation. In the wake of the Second World War, firms in the U.S., Europe and Japan sought to increase productivity by automating simple, repetitive tasks; more and more automation technologies reached maturity. Assembly lines remained—but workstations were increasingly manned by robotic arms, not humans.

Now, in many industries, assembly lines can be mostly (or completely) automated through the use of self-regulating equipment. Advances in industrial robotics have enabled the automation of more—and more complex tasks—than earlier thought possible.

Industry 4.0 and its associated software allow for enhanced visibility and monitoring of production as well as the detailed coordination of human labor with machine functionality. AI can be deployed for predictive maintenance and worker safety on assembly lines. The door has opened for smart manufacturing to reap the benefits of AI and new data sources for optimizing operations.

In China, companies like Xiaomi and Nio have recently been publicly showcasing factories with extremely high levels of automation: one Xiaomi EV factory, which is open to tours by the public, boasts an automation rate of 91% overall. The Chinese government has even been promoting the idea of totally automated “lights-out factories” that can operate without lighting since robots, unlike humans, are able to work in the dark.

Another major shift in assembly-line manufacturing has been the turn toward customization. As consumer demand for personalized products has grown, some manufacturers have been able to integrate variation into the assembly line process, thus departing from the ultra-standardization espoused by Ford’s all-black Model T range.

This turn does not mean the end of the line for Fordism, however—just one more station in its ongoing transformation.