Welcome to our simple guide on the G331 CNC code. Whether you are new to CNC programming or an experienced machinist, understanding the G331 code is essential.
This guide will explain everything you need to know about this unit mode command—what it is, when to use it, and why it matters.
(Step-by-step.)
Key Takeaways
- G331 is a CNC code for rigid tapping, which synchronizes spindle rotation and feed to match a specific thread pitch.
- The thread pitch and spindle speed must be defined when using G331, and the pitch must match the threaded bore assigned.
- The G331 tapping function remains active until deliberately deactivated by selecting a different modal block type, such as linear motion G01.
- A stationary spindle is crucial when engaging the G331 tapping function, and any rotation can compromise the tapping process.
- The G331 syntax is G331Z.. K.. spindle_name.., where Z.. is the thread depth, K.. is the thread pitch, and spindle_name.. is the spindle speed.
Rigid Tapping Fundamentals
When it concerns tapping operations on CNC machine tools, understanding the fundamentals of rigid tapping is crucial.
You need to know that rigid tapping is a standard feature on most CNC machine tools, allowing for the synchronization of spindle rotation and feed to match a specific thread pitch.
During rigid tapping, the machine’s spindle rotation and feed are coordinated to guarantee precise thread formation. This process involves quickly driving the tap in and out of a hole.
To use G331 for rigid tapping, you must verify the spindle is equipped with a pulse generator and the thread pitch matches the one used for the threaded bore assigned in G331.
G331 and G332 Syntax
You’re ready to plunge into the syntax of G331 and G332, the CNC codes that control rigid tapping operations.
The G331 syntax is G331Z.. K.. spindle_name.., where Z.. is the thread depth, K.. is the thread pitch, and spindle_name.. is the spindle speed.
For G332, the syntax is G332Z.. [ K.. ] [ spindle_name.. ], where Z.. is the retract position, K.. is the thread pitch (optional), and spindle_name.. is the spindle speed (optional).
Note that the thread pitch must match the one used in G331, and the spindle speed defaults to the one in G331 if not programmed.
The thread type is defined by the sign of the thread pitch, with positive for right-hand threads and negative for left-hand threads.
Tapping Function Parameters
Set your CNC machine to tap into the world of precision with the G331 tapping function, which demands a position-controlled spindle tracked by the CNC synchronous to the path motion – no compensatory chuck required.
When using G331, you’ll need to define the thread depth, pitch, and spindle speed. The syntax is G331Z.. K.. spindle_name.., where Z.. is the thread depth, K.. is the thread pitch, and spindle_name.. is the spindle speed. The thread pitch must match the threaded bore assigned in G331, and spindle speed is optional.
| Parameter | Description | Example |
|---|---|---|
| Z.. | Thread depth | 10.5 mm |
| K.. | Thread pitch | 1.5 mm |
| spindle_name.. | Spindle speed | 500 rpm |
Deactivation and Error Messages
Your G331 tapping function remains active until you deliberately deactivate it by selecting a different modal block type, such as linear motion G01, which releases the spindles from coordinated motion.
However, a non-modal block type, such as dwell time with G04, won’t deactivate G331.
Keep in mind the following deactivation and error message rules:
- You’ll get an error message if the pitch or spindle speed with G331 is equal to zero.
- You’ll get an error message if the tapping axis and pitch parameters don’t match.
- G331 can only be used with a position-controlled spindle.
- You must deliberately deactivate G331 to switch to another function.
Precautions and Restrictions
When engaging the G331 tapping function, a stationary spindle is crucial, as any rotation can compromise the tapping process. To guarantee this, use M05 (Stop spindle) or M19 with S.POS (Position spindle) to achieve a standstill.
Precautions and Restrictions Table
| Command | Compatibility with G331/G332 |
|---|---|
| M03, M04, M05, M19 | Not compatible |
| X | Compatible with I |
| Y | Compatible with J |
| Z | Compatible with K |
| Pitch/Spindle Speed = 0 | Invalid, error message output |
CNC Codes Similar to G331
| Code | Mode |
|---|---|
| G32 | Equal pitch thread cutting, inch system |
| G33 | Equal pitch thread cutting, metric system |
| G34 | Increased pitch thread cutting |
| G35 | Reduced pitch thread cutting |
| G76 | Threading compound cycle |
| G84 | Tapping cycle |
| G88 | Side tapping cycle |
| G92 | Thread cutting cycle |
| G332 | Tapping retraction with automatic spindle direction reversal |
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