The starting point: machines read tape
By the 1960s, numerically controlled machine tools were a recognized technology in aerospace and some other heavy industries. A typical machine had a control unit that read a punched paper tape, which carried coded positions and commands. The machine followed the tape without a human guiding the cutter by hand.
Tape-driven control had real advantages: repeatable results and the ability to cut shapes that were difficult for a person to follow by hand. It also had awkward features. Making a tape required a part programmer, often using a computer program to calculate the tool path. If a tape was wrong, the error might show up only on the machine, perhaps after material was wasted. Changing a program often meant making a new tape, and tapes were fragile and bulky to store.
Putting computers on the shop floor
In the late 1960s and 1970s, the arrival of smaller and cheaper computers began to alter this arrangement. Two ideas stand out.
Direct numerical control. A central computer stored many part programs and sent them over wires to several machines, removing the need to carry tapes. This was sometimes called DNC, and it reduced handling errors and made it easier to keep track of which version of a program was in use.
Computer numerical control. Machine tools received their own small computers as control units, a change made practical by minicomputers and, later in the 1970s, microprocessors. Programs could be stored in memory, edited at the machine and reused. This was usually abbreviated as CNC, and it became the standard form of machine tool control in later decades.
Machine builders and control makers competed on features, and details varied by country and company. Dates for the spread of CNC differ by industry, but the general decade of change is the 1970s into the 1980s.
Linking to design files
The second major shift was connecting manufacturing software to design data. In the earlier tape workflow, the link between design and manufacturing was a paper drawing that a programmer interpreted. As CAD systems began storing precise geometry in a computer, it became possible for manufacturing software to read that geometry directly, select edges or surfaces, and generate tool paths from them.
This idea, often described as CAD/CAM, developed over the 1970s and 1980s. It reduced the need to re-enter geometry and cut down on transcription mistakes. A change in the design could, in principle, flow through to a new tool path without a programmer redrawing the part. In practice, the link was imperfect for many years, as different programs stored geometry in different ways and translations between them could lose detail.
Software also became more graphical. Instead of writing text commands only, programmers could see the tool path drawn over the part on screen, spot a collision or a gouge, and correct it before cutting. Showing this on a screen was a step toward catching errors earlier and was helped by improving computer graphics hardware.
What the software does
Much of what CAM programs do is conceptually simple but laborious to do by hand.
- Choose cutting tools and speeds suitable for the material.
- Generate paths that rough out most of the material, then finish surfaces more precisely.
- Account for the shape and size of the cutter, so the finished part matches the design.
- Output machine-specific code through post-processing, since different controllers expect different formats.
As personal computers became capable enough in the 1980s, smaller shops could run such programs too. Over time, programs also added features such as simulation of the cutting process, which let programmers check a program before it reached the machine.
Effects on factory work
The effect on workers is a topic where simple stories mislead.
Some skilled machinists feared that automation would devalue their craft, and in certain settings routine operator roles did shrink. At the same time, new jobs appeared: CNC programmers, setup specialists and maintenance technicians. Many machinists learned programming, and some shops combined the roles, with operators editing programs at the machine. Other shops separated them, with programming done in an office, and the operator mainly loading parts and monitoring.
There were management questions too. Who should control a program, the programmer or the operator? Studies and anecdotes from the period suggest that arrangements varied widely, and historians continue to debate how far automation reduced or reshaped skill. A cautious summary is that the change was real but uneven, depending heavily on company policy, training and the type of products being made.
Industrial automation also affected small-batch production. Because a stored program could be reused and changed quickly, a CNC machine could switch between part types more easily than a fixed-purpose machine, which helped smaller production runs, although setup and fixturing still took time.
A continuing development
By the 1980s, CAM had become a normal part of manufacturing in many sectors, and it continued to evolve as machines gained more axes and software grew more capable. The core idea established in this early period has held up: describe the part digitally, derive the machine instructions from that description, and check the result on screen before cutting metal.