The relationship and application of G code and CNC machine tool

G-code  is the most widely used computer numerical control programming language. It is primarily used in computer-aided manufacturing to control automated machine tools and has many variants. G-code instructions are given to the machine controller (industrial computer), which tells the motor where to move, how fast to move, and what path to follow. The two most common cases are that in machine tools such as lathes or mills, the cutting tool is moved according to these instructions, cutting away material through the toolpath, leaving only the finished part and/or the unfinished part precisely positioned around three Any of up to nine axes in three dimensions, relative to the toolpath, and one or both of which can move relative to each other. The same concept extends to non-cutting tools such as forming or polishing tools, additive methods such as photo-drawing, 3D printing, and measuring instruments. All CNC machines rely on G-code to function.

G-code programming is used in conjunction with M-code. M code stands for machine code and controls various functions of CNC machine tools that are not directly related to motion. These functions include commands such as machine loading programs, program pauses and coolant flow.

The Application of G Code in NC Machining

G code is the most widely used CNC programming language, mainly used in computer-aided manufacturing to control automatic machine tools.

G-code plays a vital role in CNC programming. CNC machines cannot understand conversational language. They use a dedicated set of machine language commands. Programmers compile these commands into G-code files that instruct the CNC machine how to operate. G code is an instruction in the NC program, generally called G instruction, using G code can realize fast positioning, reverse circular interpolation, forward circular interpolation, intermediate point circular interpolation, radius programming, and jump processing.

Are all G-codes common in CNC machine tools?

There are more than one hundred G-code commands for CNC programming. Most G-codes are common to every CNC programming operation. However, certain G-codes are specific to types of operations such as milling, turning, drilling, etc. G-code listings may vary between different CNC manufacturers. Not every machine supports all G-codes. Additionally, machines with unique features or multi-axis machining capabilities may have additional G-codes. The manufacturer may provide instructions for G-code for CNC programming in the reference yearbook accompanying the machine tool. The G-code may vary slightly depending on the specific build model you are using, before referring to your machine’s owner’s manual, check your equipment’s CNC programming design for differences.

Knowing G-codes is essential for learning CNC programming and making any part by automating the machining process, there are many different G-codes for different instructions. You can refer to the table below for G-codes to use when working on a CNC programming project.

Commonly used G code types in CNC machine tools
G-code that controls motion and toolpaths in CNC programming
G00	Machine tool moves quickly
G01	Machine tool linear interpolation
G02	Clockwise circular arc interpolation
G03	Counterclockwise circular arc interpolation
G04	stay
G09	precise stop

 

Plane selection G-code program specifies a two-dimensional plane in the X, Y, Z axis Cartesian coordinate system
G17	XY plane selection
G18	XZ plane selection
G19	YZ plane selection
G-code programs for dimensions indicate which units of measure are selected
G20	Change unit measurement to inches
G21	Change unit measurement to mm
Tool compensation codes take into account parameters such as tool length and tool radius. Using these commands increases the precision of the entire CNC operation.
G40	Cancel tool length compensation
G41	Cutter Compensation Left
G42	Cutter Compensation Right
G43	Tool Length Compensation
Workpiece offset, zero offset ensures that the workpiece is in the true zero position
G54	Work Offset 1
G55	Work Offset 2
G56	Work Offset 3
G57	Work Offset 4
G58	Work Offset 5
G59	Work Offset 6

Canned cycle G-code program
G73	High-speed deep hole drilling canned cycle. Chip breaking while drilling
G74	Peck drilling canned cycle, usually used for face grooving. For tapping only.
G75	Quick grooving cycle for CNC lathe
G76	Fine Boring Canned Cycle and Threading Cycle
G81	Standard Drilling Canned Cycle
G82	standard drill with dwell at the bottom of the hole
G83	Deep hole peck drilling cycle, retracts the entire hole
G84	Right-hand tapping cycle for threading into pre-drilled holes
G85	Reaming cycle or Boring cycle
G86	Bore and stop canned cycle; the spindle stops when the tool reaches the bottom of the hole
G87	Boring cycle for enlarging the hole diameter with special tools
G88	boring cycle with P command; P indicates the number of seconds to stay
G89	Back boring cycle with dwell
cancel code		speed and feed
G50	zoom out	G94	Feed per minute mode
G80	Cancels all active canned cycles	G95	Feed mode per revolution
		G96	constant surface speed
		G97	constant spindle speed
Targeting		return command
G90	Use absolute mode for positioning	G98	return to initial plane
G91	Use incremental positioning	G99	return fast plane

 

uncommon G-code
G10	Program Offset Input	G51	Zoom
G22	Store travel limit	G52	Temporarily move the program to zero
G23	Store stroke limit cancel	G53	Return to Machine Zero
G27	Zero Check	G60	one-way movement
G28	Return to Zero	G61	Exact stop check (modal)
G29	return from reference position	G64	normal cutting mode
G30	Second position return to zero	G65	Custom macro call
G31	Jump function	G66	Custom macro modal call
G44	Negative Tool Length Compensation	G67	Cancel custom macro modal call
G45	Single offset increase	G68	coordinate rotation mode
G46	Single Offset Reduction	G69	cancel coordinate rotation mode
G47	Double Offset Increase	G92	Program Work Offset
G48	Double Offset Reduction

Precautions for writing G codes for CNC machine tools

CNC machine tools need to cut different materials, including many materials with high hardness. Therefore, writing errors in G-code may cause safety hazards to machines, operators and work areas. It is a relatively common accident that props are damaged due to collisions. Therefore, factors such as workpiece offset and tool length offset should be considered when writing G codes to ensure that tool damage does not occur.

When writing G code, you need to keep the following points in mind at all times:

1. Be familiar with the functions of the CNC system (such as the g command of the fanuc system);
2. Understand the structural characteristics and performance indicators of machine tools;
3. Master the setting method of processing route and process parameters;
4. Familiar with the types and specifications of the knives used, and choose the knives reasonably
5. Familiar with the use of commonly used measuring tools.
6. Use various measuring tools correctly.
7. Correct use of fixtures.
8. Pay attention to safe and civilized production, and always remember safety first.