วันศุกร์ที่ 3 กุมภาพันธ์ พ.ศ. 2555

CAD meet CNC

CAD meets CNC
CAD CNC example.
     While the Servomechanisms Lab was in the process of developing their first mill, in 1953, MIT's Mechanical Engineering Department dropped the requirement that undergraduates take courses in drawing. The instructors formerly teaching these programs were merged into the Design Division, where an informal discussion of computerized design started. Meanwhile the Electronic Systems Laboratory, the newly rechristened Servomechanisms Laboratory, had been discussing whether or not design would ever start with paper diagrams in the future.[13]

      In January 1959, an informal meeting was held involving individuals from both the Electronic Systems Laboratory and the Mechanical Engineering Department's Design Division. Formal meetings followed in April and May, which resulted in the "Computer-Aided Design Project". In December 1959, the Air Force issued a one year contract to ESL for $223,000 to fund the project, including $20,800 earmarked for 104 hours of computer time at $200 per hour.[14] This proved to be far too little for the ambitious program they had in mind, although their engineering calculation system, AED, was released in March 1965.

      In 1959, General Motors started an experimental project to digitize, store and print the many design sketches being generated in the various GM design departments. When the basic concept demonstrated that it could work, they started the DAC-1 project with IBM to develop a production version. One part of the DAC project was the direct conversion of paper diagrams into 3D models, which were then converted into APT commands and cut on milling machines. In November 1963 a design for the lid of a trunk moved from 2D paper sketch to 3D clay prototype for the first time.[15] With the exception of the initial sketch, the design-to-production loop had been closed.

Meanwhile, MIT's offsite Lincoln Labs was building computers to test new transistorized designs. The ultimate goal was essentially a transistorized Whirlwind known as TX-2, but in order to test various circuit designs a smaller version known as TX-0 was built first. When construction of TX-2 started, time in TX-0 freed up and this led to a number of experiments involving interactive input and use of the machine's CRT display for graphics. Further development of these concepts led to Ivan Sutherland's groundbreaking Sketchpad program on the TX-2.

     Sutherland moved to the University of Utah after his Sketchpad work, but it inspired other MIT graduates to attempt the first true CAD system. It was Electronic Drafting Machine (EDM), sold to Control Data and known as "Digigraphics", which Lockheed used to build production parts for the C-5 Galaxy, the first example of an end-to-end CAD/CNC production system.

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