G14 CNC Code | Understanding G14 on CNC

[Hakan]

G14 on CNC Lathes and Mills: The Definitive Guide (and Why You Probably Don’t Need It)

If you’re researching CNC G-codes, you might have encountered information suggesting that G14 is used for:

• Selecting a “secondary coordinate system.”
• Activating “imaginary axis interpolation.”
• Performing polar coordinate interpolation.
• Managing multiple coordinate systems.

This information is generally incorrect for modern, mainstream CNC lathes and machining centers from major manufacturers like Fanuc, Siemens, and Haas. G14 is not a standard, universally recognized G-code for any of these functions.

This article sets the record straight. We’ll cover:

• Why G14 is not the command you’re likely looking for.
• The correct G-codes for managing work offsets (the actual way to handle multiple “coordinate systems”).
• The correct ways to perform polar and cylindrical interpolation (if supported by your control).
• Brief notes on Mazak and Mitsubishi controls.
• Why CAM software is often the best solution.
• Troubleshooting tips.
• An FAQ.

Crucial Point: Before using any G-code, always consult the programming manuals for your specific CNC control system and machine tool. Never assume a G-code’s function without verification.

1. The Myth of G14 and the Reality of Work Offsets

The articles you provided likely intended to describe the functionality of work offsets, but incorrectly attributed it to G14. Work offsets are the standard and correct way to manage different part zero locations on both CNC lathes and mills.

• Machine Zero: A fixed point on the machine.
• Work Offset (G54-G59, etc.): An offset from machine zero to the part zero (the origin of your part program). You can have multiple work offsets, allowing you to easily switch between setups or parts.

Standard G-Codes for Work Offset Selection:

• G54 - G59: These are the standard G-codes for selecting the first six work offsets. Most controls have at least these.
• Extended Work Offsets: Many controls offer extended work offsets (e.g., G54.1 P1, G54.1 P2, or other numbering schemes).

Example (Lathe and Mill - Selecting G55):

G55 ; Select work offset #2
G00 X0 Y0 Z0 ; Rapid to the part zero defined by G55
; ... machining operations ...

This is how you switch between different “coordinate systems” (in reality, different offset locations). You do not use G14.

2. Setting Work Offsets: G10 (and Manual Entry)

You can set the values of work offsets (G54-G59, etc.) in two ways:

• Manually: Through the control panel’s offset pages.
• Programmatically (using G10): The G10 command allows you to set offset values within your part program. (See the dedicated G10 article for a complete explanation.)

Example (G10 to set G54 - Lathe):

G90 ; Absolute mode
G10 L10 P1 X-20.0 Z-50.0 ; Set work offset G54 (P1 = G54)
G11 ; Cancel data input mode
G54 ; Select work offset G54
; ... rest of program ...

3. G14 on Specific Control Systems: What Does it Actually Do?

Since G14 is not a standard command for coordinate system selection, what does it do (if anything)? It depends on the control system.

• Fanuc (Lathes and Mills): On most modern Fanuc lathe and mill controls, G14 has no standard, documented function. It is not used for selecting work offsets, defining secondary coordinate systems, or general-purpose polar/cylindrical interpolation. It might be:
  • Unused: Simply an unassigned G-code.
  • Assigned to a Custom Macro: The machine tool builder (MTB) could have assigned G14 to a custom macro function.
  • Used for a Very Specific, Optional Feature: There’s a small possibility it’s used for a niche function on some Fanuc control/machine combinations, but this is not common.
  • On some Fanuc controls, Polar Coordinate Interpolation is turned on with G12.1 or G13.1, and turned off by G12 or G12.1.
• Siemens (Lathes and Mills): Siemens controls do not typically use G14 for coordinate system selection or the functions described in the provided articles. Siemens uses G54-G59 (and related commands) for work offsets, and other functions for coordinate transformations.
• Haas (Lathes and Mills): Haas controls do not have a standard G14 for coordinate system manipulation. They use G54-G59 for work offsets.
• Mazak:
  • Mazatrol: Mazak’s conversational programming language handles coordinate systems and offsets through its menu-driven interface, not typically with G-codes like G14.
  • EIA/ISO (G-code): Even in G-code programming on a Mazak, G14 is unlikely to be a standard command for coordinate system selection. Consult the specific Mazak machine and control documentation.
• Mitsubishi:
  • MELDAS: The function of G14 (if any) will depend on the specific MELDAS control series (M800, M80, M700, M70, etc.). It is not a standard command for coordinate system selection. Consult the appropriate Mitsubishi MELDAS programming manual.
• Other Controls: Always consult your documentation.

4. Polar and Cylindrical Interpolation: The Right Way

The original articles might have been attempting to describe polar or cylindrical interpolation (incorrectly using G14). Here’s a reminder of these features and how they are actually implemented:

• Polar Coordinate Interpolation: Defines positions using a radius and an angle. On some Fanuc controls, this is enabled with G12.1 (or G13.1) and often canceled with G12 or G12.1. Siemens and Haas use different methods. This is typically used for milling on the face of a turned part (lathe with live tooling).
• Cylindrical Interpolation: “Unwraps” a cylinder, allowing you to program as if it were a flat plane. On some Fanuc controls, this is enabled with G07.1. Siemens uses TRANSMIT/TRACYL. Haas often uses G107. This is used for milling features on the circumference of a cylindrical part.

5. CAM Software: The Best Approach for Complex Geometries

For any complex machining operation, including those that might conceptually involve “secondary coordinate systems” or polar/cylindrical interpolation, CAM (Computer-Aided Manufacturing) software is the strongly recommended approach. CAM software:

• Handles all the complex calculations automatically.
• Generates optimized toolpaths.
• Uses the correct G-codes for your specific machine and control system.
• Provides simulation for verification.

6. Examples (Using Correct G-Codes)

These examples demonstrate how to achieve the intended results of the original articles, using the correct G-codes:

Example 1: Machining Two Different Parts (Lathe or Mill - Using Work Offsets):

; Part 1 (using G54)
G54 ; Select work offset G54
; ... (Machining operations for Part 1) ...

; Part 2 (using G55)
G55 ; Select work offset G55
; ... (Machining operations for Part 2) ...

M30 ; Program end

Example 2: Setting Work Offsets with G10 (Fanuc - Lathe or Mill):

G90 ; Absolute mode
G10 L10 P1 X-20.0 Z-50.0 ; Set work offset G54 (P1 = G54) - Lathe Example
G10 L10 P1 X-20.0 Y-50.0 Z-10 ; Set work offset G54 (P1=G54) - Mill Example
G11 ; Cancel data input mode
G54 ; Select work offset G54
; ... rest of program ...

Example 3: Polar Coordinate Interpolation (Conceptual - If Supported, e.g., Fanuc G12.1 on a Lathe):

; Milling a slot on the *face* of a turned part (using live tooling)
; Assume workpiece zero is at the center of the face.
G28 U0 W0; Home
T0101 M06 ; Select milling tool
G97 S2000 M03 ; Spindle on (constant RPM)
G00 X0 Z0.1 C0 ; Rapid to a safe position
G13.1 ; Enter polar coordinate interpolation mode (Might be G12.1)
G01 X1.0 C45.0 F5.0 ; Mill the slot (X = radius, C = angle)
G00 Z0.1 ; Rapid retract
G12.1 ; Cancel polar coordinate interpolation mode (Might be G12)
G28 U0 W0; Home
M30 ; Program end

7. Troubleshooting (Work Offset and Coordinate System Issues)

• Unexpected Tool Position:
  • Incorrect Work Offset Selected: Make sure you’re using the correct G54-G59 command.
  • Incorrect Work Offset Values: Double-check the values of your work offsets.
  • G90/G91 Confusion: Understand the difference between absolute and incremental mode.
• Using the incorrect G-Code: Ensure you are using the proper work offset codes, not an undefined command.

8. Frequently Asked Questions (FAQ)

• Q: What is G14 used for on CNC lathes and mills?
  • A: On most modern controls (Fanuc, Siemens, Haas), G14 has no standard, documented function related to coordinate system selection.
• Q: How do I select a different “coordinate system” on my machine?
  • A: You select a different work offset using G54-G59 (or extended work offsets).
• Q: How do I machine features at an angle or on a cylindrical surface?
  • A: Use polar coordinate interpolation (if supported), cylindrical interpolation (if supported), a rotary axis (4th/5th axis machining), or, most commonly, CAM software.
• Q: Where can I find the correct information about G14 for my machine?
  • A: In the programming manual for your specific CNC control system and machine tool.

9. Conclusion

The G14 command is not a standard G-code for selecting coordinate systems, activating secondary coordinate systems, or performing polar coordinate interpolation on modern CNC lathes or machining centers. The correct way to manage different part zero locations is to use work offsets (G54-G59). For complex geometries, and especially for features requiring polar or cylindrical interpolation, CAM software is the recommended approach. Always prioritize using officially supported methods and consult your machine’s documentation for accurate information. Do not rely on potentially misleading or outdated information about non-standard G-codes. Using the proper techniques for the identified control system is vital.