CNC, Machinery,

Many of the commands for the experimental parts were programmed "by hand" to produce the punch tapes that were used as input. While the system was being experimented with, John Runyon made a number of subroutines on the famous Whirlwind to produce these tapes under computer control. Users could input a list of points and speeds, and the program would generate the punch tape. In one instance, this process reduced the time required to produce the instruction list and mill the part from 8 hours to 15 minutes. This led to a proposal to the Air Force to produce a generalized "programming" language for numerical control, which was accepted in June 1956.





Starting in September Ross and Pople outlined a language for machine control that was based on points and lines, developing this over several years into the APT programming language. In 1957 the Aircraft Industries Association (AIA) and Air Material Command at the Wright-Patterson Air Force Base joined with MIT to standardize this work and produce a fully computer-conrolled NC system. On 25 February 1959 the combined team held a press conference showing the results, including a 3D machined aluminum ash tray that was handed out in the press kit.

Meanwhile, Patrick Hanratty was making similar developments at GE as part of their partnership with G&L on the Numericord. His language, PRONTO, beat APT into commercial use when it was "released" in 1958. Hanratty then went on to develop MICR magnetic ink characters that were used in cheque processing, before moving to General Motors to work on the groundbreaking DAC-1 CAD system.

APT soon extended to include "real" curves in 2D-APT-II. With its release, MIT reduced its focus on CNC as it moved into CAD experiments. APT development was picked up with the AIA in San Diego, and in 1962, to Illinois Institute of Technology Research. Work on making APT an international standard started in 1963 under USASI X3.4.7, but many manufacturers of CNC machines had their own one-off additions (like PRONTO), so standardization was not completed until 1968, when there were 25 optional add-ins to the basic system.

Just as APT was being released in the early 1960s, a second generation of lower-cost transistorized computers was hitting the market that were able to process much larger volumes of information in production settings. This so lowered the cost of implementing a NC system that by the mid 1960s, APT runs accounted for a third of all computer time at large aviation firms.

Enter MIT

This was not an impossible problem to solve, but would require some sort of feedback system, like a selsyn, to directly measure how far the controls had actually turned. Faced with the daunting task of building such a system, in the spring of 1949 Parsons turned to the MIT Servomechanisms Laboratory, a world leader in mechanical computing and feedback systems. During the war the Lab had built a number of complex motor-driven devices like the motorized gun turret systems for the B-29 and the automatic tracking system for the SCR-584 radar. They were naturally suited to building a prototype of Parsons' automated "by-the-numbers" machine.

The MIT team was led by William Pease assisted by James McDonough. They quickly concluded that Parsons' design could be greatly improved; if the machine did not simply cut at points A and B, but instead moved smoothly between the points, then not only would it make a perfectly smooth cut, but could do so with many fewer points - the mill could cut lines directly instead of having to define a large number of cutting points to "simulate" it. A three-way agreement was arranged between Parsons', MIT and the Air Force, and the project officially ran from July 1949 to June 1950. The contract called for the construction of two "Card-a-matic Milling Machine"s, a prototype and a production system. Both to be handed to Parsons for attachment to one of their mills in order to develop a deliverable system for cutting stringers.

Instead, in 1950 MIT bought a surplus Cincinnati Milling Machine Company "Hydro-Tel" mill of their own and arranged a new contract directly with the Air Force that froze Parsons out of further development. Parsons would later comment that he " never dreamed that anybody as reputable as MIT would deliberately go ahead and take over my project." In spite of the development being handed to MIT, Parsons filed for a patent on "Motor Controlled Apparatus for Positioning Machine Tool" on 5 May 1952, sparking a filing by MIT for a "Numerical Control Servo-System" on 14 August 1952. Parsons' received US Patent 2,820,187 on 14 January 1958, and the company sold an exclusive license to Bendix. IBM, Fujitsu and General Electric all took sub-licenses after having already started development of their own devices.

Servos and Selsyns

One barrier to complete automation was the required tolerances of the machining process, which are routinely on the order of hundredths of an inch. Although it would be relatively easy to connect some sort of control to a storage device like punch cards, ensuring that the controls were moved to the correct position with the required accuracy was another issue. The movement of the tool resulted in varying forces on the controls that would mean a linear output would not result in linear motion of the tool. The key development in this area was the introduction of the servo, which produced highly accurate measurement information. Attaching two servos together produced a selsyn, where a remote servo's motions was accurately matched by another. Using a variety of mechanical or electrical systems, the output of the selsyns could be read to ensure proper movement had occurred.

The first serious suggestion that selsyns could be used for machining control was made by Ernst F. W. Alexanderson, a Swedish immigrant to the U.S. working at General Electric (GE). Alexanderson had worked on the problem of torque amplification that allowed the small output of a mechanical computer to drive very large motors, which GE used as part of a larger gun laying system for US Navy ships. Like machining, gun laying requires very high accuracies, less than a degree, and the motion of the gun turrets was non-linear. In November 1931 Alexanderson suggested to the Industrial Engineering Department that the same systems could be used to drive the inputs of machine tools, allowing it to follow the outline of a template without the strong physical contact needed by existing tools like the Keller Machine. He stated that it was a "matter of straight engineering development." However, the concept was ahead of its time from a business development perspective, and GE did not take the matter seriously until years later, when others had pioneered the field.

cnc machine shop specializing in precision CNC Machining. Complete CAD/ CAM design and manufacture of precision machined parts, milling,

Used CNC Machines For Sale, CNC Lathe Machines, CNC Milling Machines, CNC vertical, CNC horizontal, Used CNC Machine Shops for Sale, CNC Machine Shop for Sale, Machine Shops Businesses for Sale & Existing Machine Shops Biz Sales, How to Buy and Sell Machine Shops

CNC Machines provides complete information about types of cnc machines, cnc manufacturers, cnc marketplace, cnc automatic and cnc lathe

largest CNC machine tool builder in the Western World, Haas Automation manufactures a full line of CNC vertical machining centers(VMC), CNC horizontal ...

Go C.N.C. Search

Custom Search

Thenk you For Use Search