Open Source CNC

The open – and sometimes free – world of Computer Aided Design and Manufacture and Computer Numerical Controlled machines.

by Dean Meier

Computer Aided Design, the use of software to build prototypes and the specifications of parts virtually, and Computer Aided Manufacturing, the use of software and computer-controlled machinery to automate a manufacturing process, has become increasingly important in all industries. Fortunately for gunsmiths in even the smallest shops, the cost of entry has gotten more affordable.

Any manufacturing process needs three components for a CAM system to function: Software that tells a machine how to make an item by generating toolpaths, machinery that can turn convert software instructions in machine steps to transform raw material into a finished product, and post processing converts toolpaths into a language machines can understand. CAD focuses on the design of parts and products while CAM converts the design into steps toward construction.


Machine-controlled manufacture is older than many realize. In 1839 French weaver Michel-Marie Carquillat wove a 2×3′ silk portrait of Joseph-Marie Jacquard. Done by hand, this large and detailed image would have taken several workers many months to complete. Instead, the image with caption and Carquillat’s name was woven on a Jacquard machine, an automated loom using 24,000 Jacquard cards, each of which had over 1,000 hole positions. Once all the programming was completed, the process of weaving the image with the punched cards could be done in about eight hours with a single weaver operating the Jacquard loom.

The Jacquard loom did no computation, unlike digital machines that would be created over a century later, however, storing and using information via punched holes in a card was an important conceptual step in the history of computing. Charles Babbage used the same idea for data and program input and output and storage in his general purpose programmable computer, the Analytical Engine described in 1837 and programmed by Countess Ada Lovelace, widely considered the world’s first programmer in the modern sense. In the late 1800s, German inventor Herman Hollerith made use of punch cards in his Hollerith Electric Tabulating System, marketed by the Tabulating Machine Company. Hollerith would reorganize under a holding company called the Computing-Tabulating-Recording Company. In 1924, the Computing-Tabulating-Recording Company was renamed “International Business Machines”.

Stacks of punch cards were programs in the modern sense of the word, though the word “program” did not have that meaning until after the development of electronic computers after World War II. John Parsons first introduced Computer Numeric Controlled machining in the 1950s using punch cards to program and automate machinery. In 1949 the United States Air Force funded Parsons to build an automated machine that could outperform manual machines. With some help from Massachusetts Institute of Technology, Parsons developed the first prototype.

Between the mid-1940s and 1950s, various developments were made in computer software. Some of these developments include servo-motors controlled by generated pulse, a digital computer with built-in operations to compute and coordinate radar-related vectors, and the graphic mathematical process of forming a shape with a digital machine.

In 1953, MIT researcher Douglas Ross saw the interactive display equipment being used at SAGE (Semi-Automatic Ground Environment) radar stations. Ross and his MIT Lincoln Laboratory colleagues started using it on workstations to instant display of date. This helped programmers to use and debug software in real time rather that via a batch-processed stack of cards or print out. Ross coined the term “Computer Aided Design” in 1959.

The invention of the 3D CAD/CAM is attributed to French engineer Pierre Bézier at Renault. Between 1966 and 1968, based on his mathematical work with computing surfaces, Bézier developed UNISURF, a pioneering surface CAD/CAM system to assist with car body design and tooling. UNISURF became the working base for the following generations of CAD software. Those of you familiar with computer graphics recognize his namesake Bézier curve, the use of Bernstein polynomials in vector graphics.

CAD implementations have evolved dramatically since this early development. In the 1970s, CAD with three dimensions was typically limited to producing drawings similar to hand-drafted drawings. Advances in programming and computer hardware in the 1980s saw solid modeling, allowing more versatile applications of computers in design activities. In 1981, solid modeling packages such as Romulus (ShapeData) and Uni-Solid (Unigraphics) were offered.

Autodesk, Inc. was founded in 1982 by John Walker who co-authored the two-dimensional design system AutoCAD which is widely used by architects, engineers, and structural designers to design, draft, and model buildings and other structures. AutoCAD is a commercial software product is also noteworthy for being a desktop app running on microcomputers with internal graphics controllers. Prior to Autodesk, most commercial CAD programs ran on expensive mainframe computers or minicomputers with each CAD user working at a separate graphics terminal.

Through the 1980s and 1990s CAD/CAM was increasingly available on personal computers. PC computers using inexpensive commodity hardware affordable for individuals become powerful enough to run design software and control machines, completely revolutionizing how manufacturing is approached. The earliest CAD and CAM jobs were reserved for expensive automotive and aerospace applications, often with government funding, but the cost of software and hardware run it has gotten much cheaper.

CAD/CAM Process

Read more in the July 2021 issue.

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