Unimate

A machine built for the factory floor

Unimate was an industrial robotic arm. The Henry Ford museum, which holds one of the machines, describes Unimate robots as the world's first successful industrial robots ^[1]. The museum's artifact is dated 1961, weighs 3,000 lbs, and measures 63.25 inches high, 48 inches wide and 59.938 inches deep ^[1]. Those figures describe a piece of production equipment rather than a laboratory demonstration: a heavy, floor-mounted arm built to work inside a real plant.

Where it came from

The idea behind Unimate is usually traced to a patent application. In 1954 George C. Devol applied for a patent for "programmed article transfer" ^[3]. The prototype that followed weighed about 1,200 kg ^[3]. Unimate was designed by Devol together with Joseph F. Engelberger, and the machine was made by Unimation, Inc. of Danbury, Connecticut ^[1].

One account of the early work says the prototype was first put to work in 1959 at a General Motors die-casting plant in Trenton, New Jersey, where it removed hot metal and placed it in coolant ^[3]. Die casting makes a natural first job for such a machine: the part comes out hot, the motion repeats identically every cycle, and the surroundings are unpleasant for people.

What it did on the line

The first Unimate ever installed on an assembly line went to the General Motors plant in Trenton, New Jersey, in 1961, to unload a die-casting press ^[1]. In the same period Unimate entered use in a General Motors production workshop, where it picked up car parts and placed them on a conveyor ^[2]. Both are transfer tasks: take an object from one place, put it in another, and repeat at a steady pace.

What the machine could not do is just as important as what it could. Early industrial robots such as Unimate repeated a fixed programmed action precisely and had no ability to interact with the surrounding environment ^[2]. It did not look at the part or check whether its grip had landed correctly; it replayed a stored sequence of movements. Accuracy came from repetition rather than from sensing, which is why the first jobs were ones where the object always arrived in the same position.

Position in the history of robotics

A report on the period says the Unimate 1900 series became the first mass-produced robotic arm for factory automation in 1961, and that 450 Unimate arms were put to die-casting work ^[3]. Mass production is the significant part: it turned a one-off piece of engineering into a product that plants could order, install and maintain.

The shape Unimate established — a fixed, programmable arm carrying out a narrow, repetitive task, often a hot or heavy one — became a basic template for factory automation. Work of that kind is hard to staff and easy to describe in advance, so it suits a machine that follows instructions exactly and never tires. The same template also defined the limit of the first generation. A robot that cannot perceive its surroundings can only operate in a world arranged for it: parts in known positions, arriving in a known order. Later machines would have to sense the world before they could do more than replay a motion.