Introduction To CNC Compute Integrated Project Lead The Way

NC/CNC History of NC Definitions Advantages of CNC Disadvantages of CNC Resources

History Of Machine Tools Single items produced by craftspeople Eli Whitney (Cotton Gin) - Interchangeable Parts Engineer designed parts for production (tolerances). WW II - development of servo motors (electrically aimed guns) Servo motors applied to machine tools

History Development of G codes - Punch tape input (Cartesian Coordinate System) 1970’s Development of computer chips Cheaper processing power Smaller computers More reliable

Definitions NC - A method of accurately controlling the operation of a machine tool by a series of coded instructions, consisting of numbers, letters of the alphabet, and symbols that the machine control unit can understand MCU - Machine Control Unit - decodes NC codes to drive and monitor servo motor movements.

Definition CNC - Computer Numeric Control - computer provides machine codes to the MCU. Control Systems Open loop system - servo motor driven by pulses without feed back encoders. Closed loop system - servo motor is driven by electrical pulses. An encoder provides feedback to verify machine movements.

Advantages Of CNC Increased productivity after programming is completed Reliability - reduces human error Often eliminates need for special jigs and fixtures Reduces location of part features Makes possible the machining of complex shapes requiring simultaneous 3 axis motion

Advantages Single part and production runs can be programmed and machined with minimum effort and cost. Programs can readily be altered and re-run Reduced inspection costs (more reliable) Once programming, setup and verified the equipment can be operated by a less skilled operator.

Disadvantages Initial cost of CNC machine tools Servicing of equipment Larger machines require more space Personnel must be trained in the programming and operation of this equipment.

Resources Fitzpatrick, Mike, Computer Numerical Control Simplified, 1989 Glenco Publishing Company. ISBN Powers, John Jr., Computer Automated Manufacturing, 1987 McGraw- Hill Book Company. ISBN Groover, Mikell P. and Zimmers, Emory W., CAD/CAM, Computer Aided Design and Manufacturing, 1984 Prentice -Hall Inc. ISBN Luggen, William W., Fundamentals of Computer Numeric Control, Third Edition, 1988 Delmar Publishers. ISBN CNC Workshop (CD-Rom), Torcomp Publisher. Cost $39.95 – Contact TorComp at