Numerical Control
Prior to the Second World War, the developments in manufacturing that took place are mostly related to hard automation or what is generally called as Detroit automation. It is characterized by the utilization of automatic machine tools that run on cams and hydraulic attachments and transfer lines. These need a big amount of time for design, manufacturing and setting. But they provide high productivity at low cost. However they are hard to change for any small changes. Therefore these are utilized for mass manufacture only.
After the Second World War, two important things have been encountered by the manufacturing industries which are:
1. The success of aeroplane in providing a decisive control in the war supremacy, and
2. Invention of the digital computer which for the first time allowed a facility for large scale computation;
The first development means that the manufacture requires small batches, but with extremely precise manufacturing needs. The second development helped in taking care of the necessary flexibility in manufacturing for small batches.
Mr. John Parsons of Parsons Corporation as a sub contractor for USAF (United States Air Force), has proposed the proposal of utilising the digital computers which were just been demonstrated to run the milling machines for machining precise contours, which or else requires a extremely skilled machinist. His suggestion is that the co-ordinate points of a complicated three dimensional profile might be calculated by the digital computer which may then be utilised for controlling the milling machine table so that correct jobs could be generated. The USAF agreed and funded the proposal along a contract that was awarded to build up such a machine to the Servomechanism Laboratory of Massachusetts Institute of Technology in the year 1951, who finally demonstrated a working milling machine in the year 1952.
A 28-inch Cincinnati Hyrdro-Tel vertical-spindle contour milling machine was comprehensively modified by retrofitting with servo motors that were associated to a digital computer. The resolution of the machine was equal to 0.0005-inch. A feedback control system including synchros was provided to make sure that the machine was moving to the accurate positions as programmed. The demonstration of this machine was extremely well received by all of the manufacturing industries.