CNC G Code & M Code Programming for CNC Machining

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CNC G Code & M Code Programming for CNC Machining CNC G Code for CNC Programming A strong knowledge CNC G Code & M Code is helpful for CNC Machining CNC Machining programs can be written by hand or with a CAM system

Carlson Manufacturing, Inc. has decades of experience in cnc machining. We offer the following as an intro to cnc machining and CNC G code programming.

This is not meant to be an all-inclusive explanation of CNC Machining, or CNC G code programming. It is meant to be a very basic primer. A first step to get you started on a pathway to a better understanding of CNC programming.

The most popular Cam programs in use today are Mastercam, and Gibbscam. A Cam (Computer Aided Manufacturing) package price can range anywhere from $10,000 to $15,000 for a single seat of software.

Not every company is going to be able to purchase an expensive Cam software package to generate CNC G Code for CNC machining. However, even if a company has a Cam package, it will benefit from possessing a good general knowledge of CNC G Code and M Code programming language. The knowledge will help understand what is going on in the machine you are operating. This knowledge may help to keep you safe, make you

more productive, (and thereby more valuable and highly paid) or it may help you get a better job.

CNC Machining programs can consist of anywhere from a few lines of G code for a simple job, to thousands of lines of CNC G code for a larger job. In this article we will focus on the simple, and shorter version.

CNC Machining programs usually will have N words at the beginning of lines in the program. N words may be at the beginning of every line, or they may be at the N1 N2 N3 Sometimes you will see them as N2 N4 N6 Or N10 N20 N30 In every case, the purpose of the N word is simply to number the line or block of code. It is meant to help identify a specific line of G code or a block of code. This can be important! Imagine trying to track down an error in a huge program of several thousand lines of code if you had no numbering system to go by!

Other than identifying a line‌the N words are ignored by the CNC machine control. Their only purpose is to be a method of identifying where you are at in the program. Think of N words as being similar to the page numbers of a book.

Often you may see a G00 or G0 (G Zero) used interchangeably. In most cases, when using a G number such as G00, G01, G02, G03, G04, etc., on up to G09, one would be able to use the single digit version of the command. Examples would be: G0, G1, G2, G3, G4, etc.. Almost all machines today will accept either this single digit version or the 2 digit version of this code. In the extremely rare case where an error is caused by a single digit version, or when in doubt, use the standard 2 digit version.

Example G00.

What follows is a basic list of the most common G Code for CNC machining with a brief explanation of it’s use/purpose. It is not meant to be a complete list. This is also not meant to be complete description of each individual G code’s use. When a G word offer’s more than one use, The most commonly used purpose to that G code. In some cases a G word has a different use for lathe or mill. Again, the most commonly used G words are: G00 Rapid Transverse Motion G01 Motion by a feed rate G02 Motion in an arc clockwise G03 Motion in an arc counter clockwise G04 Dwell G17 XY Plane selection G18 XZ Plane selection G19 YZ Plane selection G28 Return to Machine zero for axis selected G40 Cutter compensation Cancel G41 2D Cutter compensation Left G42 2D Cutter compensation Right G43 Tool length compensation + (add to tool length offset) G44 Tool length compensation – (subtract tool length offset) G49 Cancels G43 G44 G50 Sets a speed limit for Constant surface speed (lathe) G52 Set Work Coordinate system G54 Work coordinate system #1 G55 Work coordinate system #2 G56 Work coordinate system #3 G57 Work coordinate system #4 G58 Work coordinate system #5 G59 Work coordinate system #6 G65 Macro Subroutine call G70 Bolt Hole Circle G71 Holt Hole Arc G72 Bolt holes along an Angle G73 High Speed Peck Drilling G74 Reverse Tapping G80 Turns off all canned cycles G81 Drilling

G82 Spot Drilling G83 Peck drilling G84 Tapping cycle G90 Calls up an absolute Co-ordinate grid system Positioning G91 Calls up an incremental Co-ordinate grid system Positioning G92 Set Work Coordinate system shift value -(grid shift) G94 Feed per minute mode G95 Feed per spindle revolution mode G96 turns on Constant Surface Speed (lathe) G97 Turns off Constant Surface Speed (lathe) G98 Canned cycle initial point return G99 Canned cycle R Plande return M00 Program stop – Tells the CNC machine to stop in the middle of a program.

M01 Optional Program Stop – Tells the CNC machine to stop ONLY if the optional stop switch is active M02 Program end M03 Turns the Spindle on in a Clockwise direction M04 Turns the Spindle on in a Counter-Clockwise direction M05 Turns the Spindle off M06 Tool change M07 Optional coolant is not available on all machine configurations M08 Turns flood coolant on M09 Turns flood coolant off M10 Normally used to turn 4th Axis brake on (mill) M11 Normally used to turn 4th Axis brake off (mill) M19 Spindle Orientation M30 Program end and reset M31 Chip conveyor on (forward) M33 Chip conveyor off M88 Turns through the spindle coolant on M89 Turns through the spindle coolant off M97 Calls up sub program for local program M98 Sub Program Call M99 Loop or return to rerun a sub program

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