Tracing the history of computer numerical control demonstrates not only its importance but also the accelerating pace of change in manufacturing. Early attempts at automation began with camshafts designed with ridges placed in particular points to control machine tools. The cam would turn, and the pre-arranged grooves would trigger machine controls, similar to the way a player piano operates.
CNC machining uses the abstract language of numbers to allow programmable designs that can be refined or completely altered. Cams, by contrast, must be machined and are not easily altered. John T. In addition, novel forms of machining have been developed. These and others are often selected depending on the material used in the mass-production process.
Also common are laser, oxy-fuel, water-jet, and plasma cutting machines. The perspective of rapid prototyping has changed over the years, but the concept was applied from the very first punched tape, numerical control systems. Before then, all parts were machined by hand; even punched tape systems revolutionized the process. Nowadays, there are many prototyping options to choose from depending on the material used, economics, and the complexity of CNC parts.
The available tools and axes of rotation still make CNC machines appealing and extremely useful. With the advent of 3D printing, these advantages have begun to show their limitations. A 3D printer can produce complex parts, including their internal components. Depending on the application, material choices may be limited, so CNC systems remain the preferred choice, especially for prototype development.
The role of traditional machinists is quickly fading. In the 21 st century, the demand for CNC specialists has been growing. Metalworking and fabrication was performed by numerical controlled or NC machines before the invention of CNC machining.
These NC machines were created in the late s by John T. Parsons, who worked closely with the Massachusetts Institute of Technology. The product being developed by them was commissioned by the United States Air Force. The goal of this work was to find a more cost effective way to manufacture aircraft parts that had intricate geometries. During this time period NC became the industry standard. It was not till that the idea of computer-controlled machining started to circulate.
They were invented by Rudolph Boehm in Texas in and are a considerable improvement over the simpler, and frankly cheaper, Acme lead screws used on manual machine tools.
Image Credit: Barnes Industries. The genius of the ball screw is that it provides very low friction and high repeatable accuracy when mounted on a precision screwshaft. So as the shaft is turned by a motor or hand crank, the screw and anything mounted to it is pulled along its length very quickly. When protected by flexible dust covers they are also notoriously reliable and low-maintenance. Like so many other inventions their development was greatly spurred on by the demands of World War II, in this case used to guide radar and anti-aircraft gun placements.
Servo motors work by converting rotational movement into linear distance. They use encoders that send electrical signals that give exact readings of their rotational position. When mated up with the screw shaft on a CNC machine, this means that if the servo motor turns a fraction of a degree, the ball screw will have moved along one axis an exact linear distance and the encoder will display this as a readout.
This is an essential interface in translating digital information into physical motion. All CNC machines rely on such motors to control their positions on each axis. APT was a computer program credited to Douglas T. Ross and his team at MIT.
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