Numerical Control I NC Numerical Control - Software control of manufacturing processes. NC - Numerical Control - Software control of manufacturing processes. Based on a code of letters, numbers & special characters called a program. CNC - Computerized Numerical Control – NC machine with the addition of an on-board computer referred to as a machine control unit or MCU NC History 1725-Knitting machine controlled by sheets of punched cardboard 1725-Knitting machine controlled by sheets of punched cardboard 1863-Player piano introduced 1863-Player piano introduced 1947-John Parsons of Parsons Corp. in Traverse City, Michigan coupled a computer to a jig borer 1947-John Parsons of Parsons Corp. in Traverse City, Michigan coupled a computer to a jig borer 1952-MIT coins phrase “Numerical Control” & demonstrates vertical mill with special control unit 1952-MIT coins phrase “Numerical Control” & demonstrates vertical mill with special control unit 1955-National Machine Tool Show, commercially available NC machines were displayed 1955-National Machine Tool Show, commercially available NC machines were displayed Improvements in electronics & solid-state devices reduced size of control units and increased capabilities

Numerical Control I Applications of NC Chip producing machines: Drills, Mills, Lathes, Bores, Saws, Etc. Chipless machining: Flame Cutting, Punches, Wire EDM, Welding, Non machining: Paint Spraying, Tube Bending, Assembly, Etc. NC used to 1) Position cutter (move table) 2) Change tooling 3) Adjust coolant flow (flood/mist-on/off) 4) Adjust spindle speeds 5) Perform operations at a point (plunge, tap, bore, etc.)

Numerical Control I STEPS INVOLVED ON GENERAL PURPOSE MACHINE: Operation Off Machine On Machine Plan operation sequenceX Select toolsX Set and change toolsX Select feeds and speedsX * Set feeds and speedsX * Position workX * Start and stop machine operationsX * Control path between work & toolX during cutting Rapid position tool for next cut orX part unloading * * Performed via Numerical Control software

Numerical Control I Circumstances best suited to NC  Mass production quantities  Complex geometries  Tight tolerances  Replacement parts  Parts subject to modification

Numerical Control I Advantages of Numerical Control  Greater operator efficiency  Greater operator safety  Reduction of scrap  Reduced lead time for production  Fewer chances for human error  Maximal accuracy and interchangeability of parts  Lower tooling costs  Increased productivity  Minimal spare parts inventory  Greater machine tool safety  Fewer man hours for inspection  Greater machine utilization

Numerical Control I Role of the Operator  Execute Machine Control Unit (MCU) or Console Setups  Start and Stop Machines  Load and Unload Workpieces  Maintain High- Level Machine Tool Performance Standards  Change NC Inputs as Necessary (Per Engineering)  “Feedback” Information to Programmer/Engineer

Programming methods for NC  MANUAL (#4)  COMPUTER ASSISTED A)Language (#5A) B)Graphic (#5B) Numerical Control I

Two ways information is fed into an NC machine.  Auxiliary Operations : Tool change, spindle reversal, tool on/off, coolant on/off, spindle speeds (RPM), spindle feeds (IPM)  Geometrical Machine Movements: a)Translation – X, Y, Z b)Rotation – about X, Y, Z axis

Numerical Control I Any movement under control of NC input is called an axis. (ie)  2 axis machine: X,Y control (usually lathe)  3 axis machine: X,Y,Z control  4 axis machine: X,Y,Z, one rotational control  5 axis machine: X,Y,Z, two rotational control *often called machining centers and include tool changes… Toshiba – 9 axis mill for sub propellers

Numerical Control I To specify coordinate points to a machine tool, there are two positioning point reference systems. (#7)  Absolute: all measurements are taken from a fixed origin (X=0,Y=0,Z=0) *helpful to have part prints with baseline dimensioning*  Incremental: all measurements for the next position are made from the last or previous position