Drafting before computers
For most of the twentieth century, engineering designs lived on paper. Drafters worked at drawing boards with T-squares, triangles and pencils, then inked or copied the results onto film. Changing a design often meant erasing and redrawing, and every view of a part (top, side, section) had to be kept consistent by hand. A large product such as an aircraft or an automobile could involve thousands of separate drawings.
Some work was even more laborious. Shipbuilders and aircraft makers drew smooth curved surfaces at full size on large floors or sheets, a practice usually called lofting. These pressures, plus the growing complexity of products, are part of why industry showed interest when computers with graphic displays appeared.
Research in the late 1950s and 1960s
The idea of using a computer as a partner in design took shape in the late 1950s and 1960s. Groups at universities, aircraft makers, automakers and computer companies explored the idea at about the same time, so the field has no single founder. The phrase computer-aided design was in use at research groups at the Massachusetts Institute of Technology by the early 1960s, and a researcher at Boeing is often credited with popularizing the term computer graphics around the same period.
The best-known research landmark is Sketchpad, a doctoral project by Ivan Sutherland at MIT in the early 1960s. Using a light pen and a display, a user could draw lines and circles directly on the screen, and the program could keep geometric relationships such as parallel lines or equal lengths. It also let a drawing be defined once and reused many times. Sketchpad ran on a research computer and was not a product, but it shaped how people thought about interactive graphics for decades afterward.
Industry experiments ran in parallel. General Motors worked with IBM on a system for car design, and several aerospace firms built internal tools. These systems were expensive, ran on large mainframe computers and were used mainly by organizations with deep pockets.
Turnkey systems in the 1970s
During the 1970s, CAD began to leave the research setting. Companies started selling turnkey systems, meaning a package of a computer, one or more graphics terminals, a plotter and drafting software, ready to use. Aerospace and automotive firms continued to build in-house systems, and some of those were later offered commercially.
Most of this software focused on 2D drafting. Its main promise was productivity on repetitive work: once a part or symbol was drawn, it could be copied, scaled or revised without redrawing. Printed output came from pen plotters, and the displays were typically early CRT displays, sometimes showing only lines rather than filled shapes. Costs were high enough that a single workstation was often shared among several operators.
From wireframes to solids
Three-dimensional modeling developed in stages, and each stage had different strengths.
- Wireframe models describe an object with edges and points. They are simple, but can be ambiguous, because the same set of lines may be read as more than one shape.
- Surface models describe the outer skin of an object, which suits car bodies, ship hulls and aircraft. Mathematical curve and surface methods developed by engineers at French automakers in the 1960s, often linked to the names Bézier and de Casteljau, became an important foundation.
- Solid models describe an object as a volume, so software can tell inside from outside. Research on solid modeling grew through the 1970s and led to commercial systems in the following decade.
Solid models matter because they allow calculations such as volume and mass, and they provide a better starting point for engineering simulation and for generating tool paths in manufacturing.
The desktop arrives
The microprocessors of the 1970s and the personal computers of the early 1980s changed who could afford CAD. A well-known milestone is AutoCAD, released in 1982 for microcomputers, which brought 2D drafting to small firms that could never have bought a turnkey system. Engineering workstations of the 1980s, more powerful than typical desktop machines, handled larger 3D models.
Early desktop CAD was limited by memory, screen resolution and processing speed, and many users still printed drawings and checked them on paper. Even so, the price drop widened the market from a few large manufacturers to architects, surveyors, machine shops and small design offices. The spread of the graphical user interface and pointing devices in the late 1980s and 1990s made the software easier to learn, though professional CAD programs have always had a reputation for steep learning curves.
Parametric and feature-based modeling
In the late 1980s, parametric modeling became prominent. Instead of storing only final shapes, these programs record how a part was built (a sketch, an extrusion, a hole of a given diameter) and a list of dimensions that control it. Change a dimension and the model rebuilds. This approach, often called feature-based design, made it practical to produce families of similar parts and to revise designs without starting over.
Parametric systems also tightened the link between design and manufacturing. A 3D model could feed numerical control programming for machine tools, and analysis tools in computer-aided engineering could use the same geometry. The fuller story of that connection belongs to the history of manufacturing software, but the shared model became one of CAD’s lasting contributions.
Sharing data and changing work
As more companies adopted CAD, a practical problem appeared: files from one system were hard to open in another. Neutral exchange formats, with IGES (developed in the early 1980s) as an early example, tried to bridge the gap, with mixed success. Translating between systems still sometimes loses detail today.
CAD also changed jobs. Many traditional drafters retrained as CAD operators or designers, while others found their work reduced. Designers could try more alternatives, but the ease of copying drawings also made errors easier to spread. Historians and engineers still debate how much real productivity CAD added, since the answer varies by industry and task, and records from the early period are patchy.
A continuing story
Later decades added 3D printing links, cloud-based collaboration and tools that propose design variations automatically. The details of those developments are better left to specialist sources. What the history shows is a steady shift from the drawing as the main product toward the digital model as the thing that is designed, analyzed and built from.