Haas Certification Video 1.3 - Introduction G and M Codes

Summary

John introduces how a CNC milling machine is positioned and how G- and M-code programs tell it what to do.

Machine movement and coordinates

A basic milling machine moves along three axes:

• X: Side to side
• Y: Front to back
• Z: Up and down

The machine coordinate system measures axis positions from the machine’s home position. On the VF3 shown:

• X and Y home at the front-left corner. Moving away from home makes their readings more negative.
• Z homes at the top of its travel. Moving down toward the table is negative, while moving up is positive.

The work coordinate system locates the workpiece within the machine coordinate system. Work offsets establish the part’s starting point, much like identifying a location on a map.

Tool offsets tell the control how far the tool tip is from the spindle face. The control combines work and tool offsets to determine the tool tip’s position relative to the workpiece.

The program coordinates display shows position relative to the workpiece, with zero set at the workpiece’s defined starting point.

G-codes, M-codes, and address letters

A G-code program is a sequence of instructions that can specify tools, spindle speed, movement speed, and cutting locations.

• G-codes generally describe machine behavior or motion.
• M-codes act more like switches for machine functions.

Address letters and values provide additional information required by a command. For example:

• M03 S1000 turns the spindle clockwise at 1,000 RPM.
• M06 T2 changes tools and loads tool number 2.

In a sample sequence:

• G00 commands rapid movement to a position. The example moves the Z axis to 2 inches above the part.
• G43 H2 relates to applying a tool-length offset. The video notes that this topic is more complex and postpones further explanation.
• M03 S2000 starts the spindle clockwise at 2,000 RPM.
• G01 commands straight-line movement at a specified feed rate. In the example, X1 Y1 F20 moves toward those coordinates at 20 inches per minute.

The video highlights three common motion codes:

• G01: Straight-line motion
• G02: Clockwise circular motion
• G03: Counterclockwise circular motion

These motion commands can be combined to create complex shapes.

Finding code explanations

The Haas control has roughly 200 G- and M-codes combined, so the lesson is only an introduction.

To look up codes on the control, press Help in Memory mode, scroll to the G-code or M-code heading, and press Enter. The operator’s manual also contains the code list and explanations.

Speaker and sources

• Speaker: John, the presenter
• Sources referenced: The Haas control’s built-in G- and M-code help; the operator’s manual