Advanced CNC Motion Control: G93, G94, G95 Explained with Real-World Examples

Meta Description: Understand how to use G93, G94, and G95 motion control codes in CNC machining. Learn feedrate modes, use-cases, and real-world G-code examples for maximum precision.

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🔍 What Are G93, G94, and G95?

These G-codes define how feedrates are interpreted by the CNC controller:

• G93: Inverse time feedrate (used in multi-axis / 5-axis machining)
• G94: Feed per minute (standard for milling)
• G95: Feed per revolution (commonly used in turning)

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📘 G93 – Inverse Time Feedrate

G93 sets feedrate in inverse time mode. That means the programmed F value defines the time it should take to make the move.

G93
G1 X50. Y50. F2.0

This line tells the machine to move from the current position to X50 Y50 in 0.5 seconds (1 / F).

✅ Use Case:

G93 is often used in 5-axis simultaneous motion to maintain constant tool engagement on complex surfaces.

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📘 G94 – Feed Per Minute (Default for Milling)

G94 is the default mode in most CNC mills. The F value represents the feedrate in mm/min or inch/min.

G94
G1 X100. F200.

This moves the machine at 200 mm/min.

✅ Use Case:

Used in all standard linear and contouring operations on 3-axis mills, routers, and vertical machining centers.

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📘 G95 – Feed Per Revolution (Default for Lathes)

G95 sets feedrate in mm/rev or inch/rev, synchronizing feed with spindle rotation.

G95
G1 X-20. F0.2

This moves at 0.2 mm per spindle revolution.

✅ Use Case:

Crucial in CNC turning where surface finish and cutting force are dependent on feed per revolution.

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⚙️ Switching Between Feed Modes

These modes are modal. You only need to define them once per program unless changed later.

G94 (Start with feed per minute)
...
G95 (Switch to feed per revolution in turning operation)
...
G94 (Back to milling)

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📊 Feed Mode Comparison Table

G-Code	Mode	Typical Use	Feedrate Unit
G93	Inverse Time	5-axis motion, probing cycles	Seconds per move (1/F)
G94	Feed per Minute	Milling, Drilling	mm/min or inch/min
G95	Feed per Revolution	Turning, Boring	mm/rev or inch/rev

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🧠 Advanced Applications of G93

In simultaneous multi-axis machining, G93 is used to keep tool load constant. Example:

G93
G1 A15. B30. C45. F1.0

This ensures the move is completed in 1 second, distributing motion across all rotary axes.

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🔧 Practical Tips for Feedrate Modes

• Use G94 for general contouring and drilling
• Use G95 when spindle speed matters for chip control
• Use G93 with caution – inverse time requires tight simulation

⚠️ Note:

When using G93, F values less than 1.0 indicate longer movements. Always simulate before running on real parts.

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🔄 Macro Integration Example

Macro-based mode switching logic can ensure proper feed control:

IF [#4120 EQ 1] THEN G95 (Auto-set for turning)
IF [#4120 EQ 2] THEN G94 (Set back for milling)

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📈 Summary

• G93 – Best for 5-axis high-end applications
• G94 – Ideal for 3-axis milling and drilling
• G95 – Perfect for turning with consistent chip load

Mastering feedrate modes lets you optimize speed, finish, and part accuracy. Always test feed logic in simulation first before production runs.