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G & M Codes

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What Are G & M Codes?

• Operate CNC machines

• Began in the form of punch tape

• Developed into computer chips in the 1970s



G & M Today

• Translates human language to machine language

• Typed into computer or generated by a program



Sample Program Block

N1 M06 T1 ; Change to tool #1

Block Sequence #Miscellaneous code: Tool change

Tool Number

Comment

Comment separator




N02 M03 S1500

Line Number

Miscellaneous code: Turn spindle on

Spindle Speed: 1500 rpm




N03 G90 G01 X.5 Y.5 Z0 F1

Line NumberPrep Code – Absolute

Prep Code – SL Interpol

Y Coordinate

X Coordinate

Z CoordinateFeed Rate (in./min)



More Terminology

Address Character – A letter used in G & M code programming to designate a class of functions

Parameter – Attribute of a feature, such as a dimension, that can be modified

N00 G90 G01 X.5 Y.5 Z0 F1



TerminologyWord – The programming expression formed when a letter (address) is combined with a number

Block – A single line of code in an NC part program

N00 G90 G01 X.5 Y.5 Z0 F1



G Codes – PreparatoryG90 Absolute CoordinatesG91 Relative CoordinatesG00 Rapid Traverse (non-cutting move)G01 Straight Line Interpolation (cutting move)G02 Circular Interpolation (clockwise)G03 Circular Interpolation (c-clockwise)G04 Dwell (wait) – Pause measured in seconds on all

axes between motions (i.e., G04F2.3 is a pause for 2.3 s)

G05 Pause – Wait for user intervention



G Codes – Arcs

Absolute coordinatesExample

N0 G90 ; Absolute coordN5 G01 X1 Y2 ; startN10 G02 X2 Y1 I1 J1

X2Y1

Relative coordinatesExample

N0 G91; Relative coordN05 G01 X1 Y2 ; startN10 G02 X1 Y-1 I0 J-1

X1Y2

I1J1

X1Y-1

X1Y2

I0 J-1

Method 1: Arc with I and J(I and J are center point coordinates)



G Codes – Arcs

Absolute coordinatesExample

N0 G90 ; Absolute coordN5 G01 X1 Y2 ; startN10 G02 X2 Y1 R1

Relative coordinatesExample

N0 G91; Relative coordN05 G01 X1 Y2 ; startN10 G02 X1 Y-1 R1

X1Y-1

X1Y2

R1

X2Y1

X1Y2

R1

Method 2: Arc with R(R is arc radius)



Other Common G Codes

G20 Inch programming unitsG21 Millimeter programming unitsG80 Canned cycle cancelG81 Drilling cycleG82 Drilling cycle with dwell



M Codes – MiscellaneousM00 Pause M01 Optional stopM02 End of programM03 Spindle onM05 Spindle offM06 Tool changeM08 / M09 Accessory # 1 on / offM10 / M11 Accessory # 2 on / offM30 Program end and resetM47 Rewind (used for handshaking operations)



Code Suggestions• Same code not required to be repeated every

block– Machine will use same code until changed– Called modal

• Tab remarks away from code to facilitate troubleshooting program

• Specify absolute or relative coordinates and inch or metric modes at beginning of program

• Always use a tool change command to move tool to safe position away from material; change tool if necessary

• Indicate spindle speed each time turned on



Code Suggestions • Move tool to start position in two lines

– First line moves in X-Y plane, then moves in Z axis

– Prevents ramping or inadvertently cutting a part

• Raise tool out of the stock at end of program• Always move table to safe unload position and

turn spindle off at end of program• Use M02 command to end program



Sample Part – Absolute

A 0.5 0.5B 0.5 1.5C 0.875 1D 1.25 1.5E 1.25 0.5F 1.75 1.5H 1.75 0.5I 1.75 1

AbsoluteCoordinates

Origin



Sample ProgramAbsolute

N0 G90 G20 ; ABSOLUTE COORD & INCH MODEN5 M06 T1 ; TOOL CHANGE – LOAD TOOL 1N10 M03 S3000 ; TURN SPINDLE ON CW TO 3000 RPMN15 G00 X.5 Y.5 ; RAPID TO POINT AN20 G00 Z.1 ; RAPID TO .1 ABOVE PARTN25 G01 Z-.0625 F9 ; PLUNGE 1/16 AT 9 IN./MINN30 G01 X.5 Y1.5 F18 ; STRAIGHT LINE INTERP TO BN35 G01 X.875 Y1 ; STRAIGNT LINE INTERP TO CN40 G01 X1.25 Y1.5 ; STRAIGHT LINE INTERP TO DN45 G01 X1.25 Y.5 ; STRAIGHT LINE INTERP TO E



Sample ProgramAbsolute

N50 G01 Z.1 ; RETRACT CUTTING TOOLN55 G00 X1.75 Y1.5 ; RAPID TO POINT FN60 G01 Z-.0625 F9 ; PLUNGE AT 9 IN./MINN65 G01 X1.75 Y.5 F18 ; STRAIGHT LINE INTERP TO HN70 G03 X1.75 Y1.5 I1.75 J1 ; CCW CIRCLE INTERPN75 G01 Z.1 ; RETRACT CUTTING TOOLN80 M05 ; TURN OFF SPINDLEN85 G00 Z2 ; RAPID Z TO SAFE POSITIONN90 G00 X4 Y3 ; MOVE TABLE TO UNLOAD POSITIONN95 M02 ; END OF PROGRAM



Sample Part – Incremental

LABEL X YA 0.5 0.5B 0 1C 0.375 -0.5D 0.375 0.5E 0 -1F 0 1H 0 -1I 0 0.5

IncrementalCoordinates

Origin



Sample ProgramIncremental / Relative

N00 G90 G20 ; ABSOLUTE COORD & INCH MODEN5 M06 T1 ; TOOL CAHNGE – LOAD TOOL 1 N10 M03 S3000 ; TURN SPINDLE ON CW TO 3000 RPMN15 G00 X.5 Y.5 ; RAPID TO POINT AN20 G00 Z.1 ; RAPID TO .1 ABOVE POINT AN25 G91 ; INCREMENTAL COORD & INCH MODEN25 G01 Z-.1625 F9 ; PLUNGE 1/16 AT 9 IN./MINN30 G01 X0 Y1 F16 ; STRAIGHT LINE INTERP TO BN35 G01 X.375 Y-.5 ; STRAIGHT LINE INTERP TO CN40 G01 X.375 Y.5 ; STRAIGHT LINE INTERP TO DN45 G01 X0 Y-1 ; STRAIGHT LINE INTERP TO E



N50 G01 Z.1625 ; RETRACT CUTTING TOOLN55 G00 X.5 Y1 ; RAPID TO POINT FN60 G01 Z-.1625 F9 ; PLUNGE AT 9 IN./MINN65 G01 X0 Y-1 F16 ; STRAIGHT LINE INTERP TO HN70 G03 X0 Y1 I0 J.5 ; CCW CIRCLE INTERPN75 G01 Z.1625 ; RETRACT CUTTING TOOLN80 M05 ; TURN OFF SPINDLEN85 G90 ; CHANGE TO ABSOLUTE COORD N85 G00 Z2 ; RAPID Z TO SAFE POSITIONN90 G00 X4 Y3 ; MOVE TABLE TO UNLOAD POSITIONN95 M02 ; END OF PROGRAM

Sample ProgramIncremental / Relative



Your Turn

What line in the last example uses the arc command?

N70Change the arc command in the last example into the format with R (radius).

N70 G03 X0 Y1 R.5 ; CCW CIRCLE INTERPSee next slide for change in program.



SolutionN50 G01 Z.1625 ; RETRACT CUTTING TOOLN55 G00 X.5 Y1 ; RAPID TO POINT FN60 G01 Z-.1625 F9 ; PLUNGE AT 9 IN./MINN65 G01 X0 Y-1 F16 ; STRAIGHT LINE INTERP TO HN70 G03 X0 Y1 R.5 ; CCW CIRCLE INTERPN75 G01 Z.1625 ; RETRACT CUTTING TOOLN80 M05 ; TURN OFF SPINDLEN85 G90 ; CHANGE TO ABSOLUTE COORD N85 G00 Z2 ; RAPID Z TO SAFE POSITIONN90 G00 X4 Y3 ; MOVE TABLE TO UNLOAD POSITIONN95 M02 ; END OF PROGRAM



Explain the Code

N2 G1 X2.5 Y3 F2

N2G1X2.5Y3F2

Block twoLinear interpolation

2.5 on the X axis

3 on the Y axis

Feed rate = 2 IPM



What’s Wrong with These?1. N1G01G90X2X2; 2. N1G00G01X2Y2; 3. N3G01X.5Y2F1;

N4G01X.5Y3.5F1;4. Changing N6G00X0.500Y1.500; to N6G0X.5Y1.5;5. Changing N2G90Z0.05M00; to N2G9Z.5M;



ReferencesMattson, M. (2010). CNC programming principles and

applications. Oregon City, OR: Delmar.



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