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Information Needed by a CNC Machine

CNC Programming
Lecture 25 Engineering 475 Automated Production Systems

1. Preparatory Information: units, incremental or absolute positioning 2. Coordinates: X,Y,Z, RX,RY,RZ 3. Machining Parameters: Feed rate and spindle speed 4. Coolant Control: On/Off, Flood, Mist 5. Tool Control: Tool and tool parameters 6. Cycle Functions: Type of action required 7.Miscellaneous Control: Spindle on/off, direction of rotation, stops for part movement This information is conveyed to the machine through a set of instructions arranged in a desired sequence – Program.

Cartesian Coordinate Systems

Right Hand Rule

Z Y

X Consists of three axes positioned 90 degrees from each other.
Chang, Fig. 10.1

The right hand rule is used to define the positivedirection of the coordinate axes.
Nanfara, Fig. 2.1

Standard Lathe Coordinate System

Gantry Mill Coordinate System

Nanfara, Fig. 2-4

Nanfara, Fig. 2-3

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Vertical Mill or Drill Coordinate System

Milling Tool Coordinate System

Chang, Fig. 10.3

Nanfaro, Fig. 2-6(b)

Cartesian Coordinate System Planes
X-Y Plane

Absolute Coordinates

X-Z Plane

x

Y-Z PlaneNanfaro, Fig. 2-7 Nanfaro, Fig. 2-10

Incremental Coordinates

Coordinate System Exercise

Nanfaro, Fig. 2-11

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Letter Codes
Example CNC Program N5 G90 G20 N10 M06 T3 N15 M03 S1250 N20 G00 X1 Y1 N25 Z0.1 N30 G01 Z-0.125 F5 N35 X3 Y2 F10 N40 G00 Z1 N45 X0 Y0 N50 M05 N55 M30 • Each instruction to the machine consists of a letter followed by a number. • Each letter is associated with aspecific type of action or piece of information needed by the machine. Letters used in Codes N,G,X,Y,Z,A,B,C,I,J,K,F,S,T,R,M N5 G90 G20 N10 M06 T3 N15 M03 S1250 N20 G00 X1 Y1 N25 Z0.1 N30 G01 Z-0.125 F5 N35 X3 Y2 F10 N40 G00 Z1 N45 X0 Y0 N50 M05 N55 M30

Letter Codes
(G and M Codes) Example CNC Program •G-codes: Preparatory Functions – involve actual tool moves. •M-codes: Miscellaneous Functions –involve actions necessary for machining (i.e. spindle on/off, coolant on/off).

Letter Codes
(G Codes)
G00 G01 G02 G03 G04 G08 G09 G17 G18 G19 G20 G21 Rapid traverse Linear interpolation Circular interpolation, CW Circular interpolation, CCW Dwell Acceleration Deceleration X-Y Plane Z-X Plane Y-Z Plane Inch Units (G70) Metric Units (G71)

Letter Codes
(M Codes) M00 M01 M02 M03 M04 M05 M06M08 M09 M10 M11 M30 Program stop Optional program stop Program end Spindle on clockwise Spindle on counterclockwise Spindle stop Tool change Coolant on Coolant off Clamps on Clamps off Program stop, reset to start

G40 Cutter compensation – cancel G41 Cutter compensation – left G42 Cutter compensation- right G70 Inch format G71 Metric format G74 Full-circle programming off G75 Full-circleprogramming on G80 Fixed-cycle cancel G81-G89 Fixed cycles G90 Absolute dimensions G91 Incremental dimensions

Letter Codes
(N Codes) Example CNC Program N5 G90 G20 N10 M06 T3 N15 M03 S1250 N20 G00 X1 Y1 N25 Z0.1 N30 G01 Z-0.125 F5 N35 X3 Y2 F10 N40 G00 Z1 N45 X0 Y0 N50 M05 N55 M30 •N-codes: Gives an identifying number for each block of information. It is generally good practice to increment eachblock number by 5 or 10 to allow additional blocks to be inserted if future changes are required.

Letter Codes
(X,Y, and Z Codes) Example CNC Program • X, Y, and Z codes are used to N5 G90 G20 specify the coordinate axis. N10 M06 T3 • Number following the code N15 M03 S1250 defines the coordinate at the end N20 G00 X1 Y1 of the move relative to an N25 Z0.1 incremental or absolute N30 G01 Z-0.125F5 reference point. N35 X3 Y2 F10 N40 G00 Z1 • The number may require that a N45 X0 Y0 specific format be used (i.e. 3.4 N50 M05 means three numbers before N55 M30 the decimal and four numbers after the decimal).

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Letter Codes
(I,J, and K Codes) Example CNC Program N5 G90 G20 N10 M06 T3 N15 M03 S1250 N20 G00 X1 Y1 N25 Z0.1 N30 G01 Z-0.125 F5 N35 X3 Y2 F10 N40 G00 Z1 N45 X0 Y0 N50 M05...
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