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. Alexanderson, a Swedish immigrant to the U.S. The first serious suggestion that synchros could be used for machining control was made by Ernst F. Using a variety of mechanical or electrical systems, the output of the synchros could be read to ensure proper movement had occurred (in other words, forming a closed-loop control system). Attaching two servos together produced a synchro, where a remote servo's motions were accurately matched by another. The key development in this area was the introduction of the servomechanism, which produced powerful, controlled movement, with highly accurate measurement information. In other words, a control such as that of the Jacquard loom could not work on machine tools because its movements were not strong enough the metal being cut "fought back" against it with more force than the control could properly counteract. The movement of the tool resulted in varying forces on the controls that would mean a linear input would not result in linear tool motion. Although connecting some sort of control to a storage device like punched cards was easy, ensuring that the controls were moved to the correct position with the required accuracy was another issue. One barrier to complete automation was the required tolerances of the machining process, which are routinely on the order of thousandths of an inch. None of these were numerically programmable, however, and required an experienced machinist at some point in the process, because the "programming" was physical rather than numerical. Analogous systems are common even today, notably the "teaching lathe" which gives new machinists a hands-on feel for the process. Another approach was "record and playback", pioneered at General Motors (GM) in the 1950s, which used a storage system to record the movements of a human machinist, and then play them back on demand. The application of hydraulics to cam-based automation resulted in tracing machines that used a stylus to trace a template, such as the enormous Pratt & Whitney "Keller Machine", which could copy templates several feet across. These developments had the potential for convergence with the automation of machine tool control starting in that century, but the convergence did not happen until many decades later. Various forms of abstractly programmable control had existed during the 19th century: those of the Jacquard loom, player pianos, and mechanical computers pioneered by Charles Babbage and others. In contrast, numerical control allows information to be transferred from design intent to machine control using abstractions such as numbers and programming languages. Cams can encode information, but getting the information from the abstract level ( engineering drawing, CAD model, or other design intent) into the cam is a manual process that requires machining or filing. However, automation via cams is fundamentally different from numerical control because it cannot be abstractly programmed. Cam-based automation had already reached a highly advanced state by World War I (1910s). Thomas Blanchard built his gun-copying lathes (1820s–30s), and the work of people such as Christopher Miner Spencer developed the turret lathe into the screw machine (1870s). The automation of machine tool control began in the 19th century with cams that "played" a machine tool in the way that cams had long been playing musical boxes or operating elaborate cuckoo clocks. These early servomechanisms were rapidly augmented with analog and digital computers, creating the modern CNC machine tools that have revolutionized the machining processes.Įarlier forms of automation Cams Siemens CNC panel. The first NC machines were built in the 1940s and 1950s, based on existing tools that were modified with motors that moved the controls to follow points fed into the system on punched tape. The history of numerical control (NC) began when the automation of machine tools first incorporated concepts of abstractly programmable logic, and it continues today with the ongoing evolution of computer numerical control (CNC) technology. Please consider expanding the lead to provide an accessible overview of all important aspects of the article. This article's lead section may be too short to adequately summarize the key points.
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