G93 machine code represents the Inverse Time Feed Mode in CNC machining. This G-code is crucial for controlling the feed rate on machine tools, particularly in scenarios requiring synchronized multi-axis motion or when the path length varies significantly between blocks.
Understanding G93 Inverse Time Feed Mode
Unlike more common feed modes such as "Feed Per Minute" (G94) or "Feed Per Revolution" (G95), G93 calculates the required feed rate to complete a block of motion within a specified time. When G93 is active, the value programmed with the 'F' word does not represent a linear feed rate (e.g., inches per minute) but rather the inverse of the time, typically expressed in minutes, required to execute the move.
For instance, an F2 in G93 mode would mean the current block should be completed in 1/2 (0.5) minutes. The CNC control then automatically computes the actual axis feed rates based on the distance to be traveled and the specified time.
Here's a quick overview of G93 and related G-codes from the same group:
| Code | Description | Group |
|---|---|---|
| G93 | Inverse Time Feed Mode | 05 |
| G94 | Feed Per Minute Mode | 05 |
| G95 | Feed per Revolution | 05 |
When is G93 Used?
G93 is particularly beneficial in advanced CNC applications where maintaining precise timing for movements is critical:
- Multi-Axis Machining (e.g., 5-axis): In complex simultaneous motion, G93 ensures that all axes arrive at their programmed end points at the same time, preventing jerky movements and maintaining smooth tool paths, which is vital for contouring and surfacing operations.
- CAM System Output: Many Computer-Aided Manufacturing (CAM) software packages generate G-code programs for complex tool paths using G93, as it simplifies the generation of synchronized feed rates. The CAM system calculates the segment lengths and desired times, outputting the appropriate 'F' values.
- Robotics and Automation: For applications where the velocity profile along a path needs to be precisely controlled regardless of segment length, G93 provides a robust method.
- Constant Velocity Machining: While G94 can achieve constant velocity for straight lines, G93 is better suited for maintaining consistent path velocity around curves and complex contours.
Practical Considerations
- Switching Modes: G93 is typically modal, meaning it remains active until another feed mode (like G94 or G95) from the same group is commanded.
- Feed Rate Interpretation: It's crucial for operators and programmers to recognize when G93 is active, as the 'F' word will not correspond to a familiar linear feed rate. Misinterpretation can lead to unexpectedly slow or fast movements.
- Machine Capabilities: Ensure the CNC machine control supports G93 Inverse Time Feed Mode. Most modern controls for multi-axis machines will.
By utilizing G93, machinists and programmers can achieve highly synchronized and precise motion control, especially when dealing with complex geometries and advanced machining strategies.
