History of numerical control

May. 13, 2024

68 0 0

History of Numerical Control

Are you interested in learning more about high precision double head cnc lathe? Contact us today to secure an expert consultation!

The history of numerical control (NC) began when the automation of machine tools first incorporated concepts of abstractly programmable logic, continuing today with the ongoing evolution of computer numerical control (CNC) technology.

The first NC machines were developed in the 1940s and 1950s, using existing tools modified with motors that moved the controls to follow points on punched tape. These early servomechanisms were quickly enhanced with analog and digital computers, resulting in the modern CNC machine tools that revolutionized machining processes.

Earlier Forms of Automation

Cams

The automation of machine tool control began in the 19th century with cams, which functioned similarly to how cams had been used in musical boxes or elaborate cuckoo clocks. Thomas Blanchard's gun-copying lathes (1820s–30s) and Christopher Miner Spencer's turret lathes developed into the screw machine in the 1870s. By World War I, cam-based automation had reached a highly advanced state.

However, automation via cams fundamentally differs from numerical control as it cannot be abstractly programmed. Cams encode information, but translating design intent into the cam is a manual process. Numerical control, in contrast, allows for transferring design information to machine control using abstractions like numbers and programming languages.

Various forms of abstractly programmable control existed in the 19th century, including the Jacquard loom, player pianos, and mechanical computers pioneered by Charles Babbage. However, convergence with machine tool automation occurred many decades later.

Tracer Control

The application of hydraulics to cam-based automation resulted in tracing machines that used a stylus to trace a template, such as Pratt & Whitney's massive "Keller Machine," which could copy large templates. General Motors' "record and playback" system in the 1950s was another approach, recording a human machinist's movements for later playback. These systems weren't numerically programmable and required an experienced machinist at some point as the "programming" was physical rather than numerical.

Servos and Synchros

One barrier to complete automation was the required machining tolerances, often in thousandths of an inch. Ensuring that controls moved with the needed accuracy was challenging. The servomechanism, which produced powerful, controlled movements with highly accurate measurements, was key. Connecting two servos created a synchro, accurately matching motions remotely, forming a closed-loop control system.

Ernst F. W. Alexanderson of General Electric suggested using synchros for machining control in 1931, envisioning a system where machine inputs followed a template without directly contacting it. GE didn't pursue the idea seriously until much later, allowing others to pioneer the field.

Parsons Corp. and Sikorsky

John T. Parsons and Frank L. Stulen of Parsons Corp. in Traverse City, Michigan, are credited with the birth of numerical control. They were awarded the National Medal of Technology in 1985 for revolutionizing the production of cars and airplanes with numerical controls.

In 1942, Parsons began working with Sikorsky Aircraft, using punched cards for automated calculations. This led to a new method of producing helicopter rotor blades and the development of stamped metal stringers, which were stronger and easier to make. Parsons hired Frank L. Stulen to help with these innovations, leading to automated stress calculations and the "by-the-numbers method" prototype of today's 2.5-axis machining.

Punch Cards and First Tries at NC

Parsons conceived of a fully automated machine tool, removing manual errors and delays by directly driving machine inputs from a card reader. Lack of funds delayed development until the U.S. Air Force funded Parsons to build his machines in 1949. Early attempts with Snyder Machine & Tool Corp highlighted the need for a feedback system to ensure accurate cuts.

First Commercial Numerically Controlled Machine

In 1952, Arma Corporation announced the first commercial numerically controlled lathe, developed by Dr. F. W. Cunningham. Arma had built its first automated lathe in 1948, leading to the 1950 announcement.

Parsons Corp. and MIT

The task of building a closed-loop system led Parsons to MIT's Servomechanisms Laboratory in 1949. MIT's team, led by William Pease and James McDonough, improved on Parsons's design, creating a system that moved smoothly between points, requiring fewer points to generate cuts. MIT and Parsons developed two "Card-a-matic Milling Machines" under a contract with the Air Force, but MIT continued development independently, leading to patent disputes and licensing to Bendix and other companies.

MIT's Machine

MIT fitted gears to handwheel inputs of a milling machine, driven by motors and controlled by a large, complex setup of cabinets housing motor controllers and digital reading systems. The system used punch tape for input, with registers and pulse outputs controlling motor speed and movement. The system demonstrated in September 1952 was technically successful but complex and expensive.

Proliferation of NC

NC development continued at various companies, leading to the introduction of commercial NC controllers like Numericalord. Monarch Machine Tool and others demonstrated NC machines at the 1955 Chicago Machine Tool Show. Despite initial slow uptake, NC proved to reduce costs, lead times, and errors while improving productivity.

The Army had to build 120 NC machines and lease them to manufacturers to popularize its use.

CNC Arrives

Many commands for experimental parts were programmed manually, producing punch tapes as input. MIT's Whirlwind project automated this process, leading to the proposal for a generalized programming language, APT, for numerical control. APT enabled precision programming, automated by computers, revolutionizing CNC.

CADCAM Meets CNC

MIT initiated the Computer-Aided Design Project in 1959, exploring computerized design, leading to the development of APT and, later, CAD/CNC systems. General Motors' DAC-1 project demonstrated end-to-end digital design-to-production. Ivan Sutherland's Sketchpad at MIT further advanced interactive graphics and CAD concepts, inspiring subsequent systems like Lockheed's Digigraphics for production parts.

Proliferation of CNC

With advances in minicomputers and microprocessors, CNC machines became more affordable and widespread. CNC automation improved consistency and quality, reduced human errors, and increased production flexibility. By the 1980s, CNC systems were dominated by German and Japanese manufacturers, who targeted lower-cost markets more effectively than U.S. companies focused on high-end applications.

Researchers noted that U.S. companies' focus on high-end markets left them uncompetitive in downturns, while German and Japanese manufacturers' national efforts supported their successful expansion, coordinated by entities like MITI. This led to U.S. programs aimed at transferring know-how to domestic tool makers.

Direct numerical control (DNC) evolved alongside CNC, with developments influenced by trends in data collection, automated exchange, and data mining, fostering business intelligence and workflow automation in manufacturing. Efforts like MTConnect aimed to standardize these advancements.

DIY, Hobby, and Personal CNC

Developments in small-scale CNC were enabled by the Enhanced Machine Controller project (1989) from the National Institute of Standards and Technology (NIST). This led to LinuxCNC and proprietary low-cost PC-based programs like TurboCNC and Mach3. DIY CNC and personal CNC systems emerged, with hardware designs enabling hobbyists and manufacturers to produce lightweight, desktop milling machines and larger commercial machinery.

Art Fenerty's Mach3 software made complex parts accessible to home and prototype users. Personal CNC evolved to replace larger conventional equipment, characterized by affordability, size, and capability.

Today

Tape readers are still found in some CNC facilities, supplemented by diskettes, USB drives, and direct computer connections. G-code remains the prevalent programming language, though there's a push towards STEP-NC, designed specifically for CNC. Proprietary conversational programming methods like Mazatrol, IGF, and dialog systems simplify programming and setup for certain manufacturers.

Parametric programming, or macro programming, incorporates logical commands and control language, allowing extensive freedom within a program. It enables the creation of a product line or scalable part size using logic and math.

Efforts continue to unite CNC with new IT trends, integrating greater data collection, automated exchange, and data mining for enhanced business intelligence and workflow automation. MTConnect leads efforts to standardize such advancements.