The parting off operation starts by positioning the tool, activating the spindle, cutting through the workpiece, then retracting and stopping the spindle before ending.
This CNC code performs a parting off by moving the tool from X0 to X-10 at a slow feed rate, then stops the spindle and ends.
Execution Table
Step
Line Number
Command
Action
Tool Position
Spindle Status
Feed Rate
Output
1
N10
G54
Set work coordinate system
At machine zero
Off
N/A
Work offset set
2
N20
M03 S1200
Start spindle clockwise at 1200 RPM
At machine zero
On (1200 RPM)
N/A
Spindle running
3
N30
G01 X0 Z0 F0.1
Move tool to start position
X0 Z0
On (1200 RPM)
0.1
Tool at start of cut
4
N40
G01 X-10 F0.05
Cut parting off by moving tool to X-10
X-10 Z0
On (1200 RPM)
0.05
Cut complete
5
N50
M05
Stop spindle
X-10 Z0
Off
N/A
Spindle stopped
6
N60
M30
End program
X-10 Z0
Off
N/A
Program ended
💡 Program ends after spindle stops and M30 command executes
Variable Tracker
Variable
Start
After Step 1
After Step 2
After Step 3
After Step 4
After Step 5
Final
Tool Position
Machine zero
Machine zero
Machine zero
X0 Z0
X-10 Z0
X-10 Z0
X-10 Z0
Spindle Status
Off
Off
On (1200 RPM)
On (1200 RPM)
On (1200 RPM)
Off
Off
Feed Rate
N/A
N/A
N/A
0.1
0.05
N/A
N/A
Key Moments - 3 Insights
Why does the feed rate change between steps 3 and 4?
At step 3, the tool moves to the start position with a faster feed rate (0.1). At step 4, the feed rate slows to 0.05 to carefully cut through the material during parting off, as shown in the execution_table rows 3 and 4.
What happens if the spindle is not turned on before cutting?
If the spindle is off, the tool cannot cut properly. The execution_table shows spindle status turning on at step 2 before cutting starts at step 4, ensuring the tool spins to cut the workpiece.
Why is the tool retracted after the cut?
After cutting (step 4), the tool stays at X-10. The spindle stops at step 5, and the program ends at step 6. Retracting prevents damage and prepares for the next operation, as indicated by tool position and spindle status in the variable_tracker.
Visual Quiz - 3 Questions
Test your understanding
Look at the execution table, what is the tool position after step 4?
AMachine zero
BX0 Z0
CX-10 Z0
DX10 Z0
💡 Hint
Check the 'Tool Position' column in row 4 of the execution_table.
At which step does the spindle stop spinning?
AStep 3
BStep 5
CStep 4
DStep 6
💡 Hint
Look at the 'Spindle Status' column and find when it changes to 'Off'.
If the feed rate at step 4 was increased to 0.1, what would change in the execution?
ACutting would be faster but risk tool damage
BSpindle speed would increase
CTool position would not change
DProgram would end earlier
💡 Hint
Refer to the 'Feed Rate' column in variable_tracker and consider cutting speed effects.
Concept Snapshot
Parting off operation in CNC:
- Position tool at start (G01 X0 Z0)
- Start spindle (M03 S1200)
- Cut by moving tool across workpiece (G01 X-10 F0.05)
- Stop spindle (M05)
- End program (M30)
Feed rate slows during cut for safety.
Full Transcript
This visual execution trace shows a CNC parting off operation. The program starts by setting the work coordinate system. The spindle is turned on at 1200 RPM. The tool moves quickly to the start position at X0 Z0. Then it moves slowly to X-10 to cut through the workpiece, performing the parting off. After the cut, the spindle stops and the program ends. Variables like tool position, spindle status, and feed rate change step by step, helping beginners see how the operation progresses safely and effectively.
Practice
(1/5)
1. What is the main purpose of a parting off operation in CNC turning?
easy
A. To drill holes in the workpiece
B. To cut a finished piece from the raw stock
C. To polish the surface of the workpiece
D. To measure the length of the stock
Solution
Step 1: Understand the definition of parting off
Parting off is a CNC turning process used to separate a finished part from the raw material.
Step 2: Identify the correct operation purpose
Among the options, only cutting a finished piece from raw stock matches the parting off operation.
Final Answer:
To cut a finished piece from the raw stock -> Option B
Quick Check:
Parting off = Cutting finished piece [OK]
Hint: Parting off always means cutting off the finished part [OK]
Common Mistakes:
Confusing parting off with drilling or polishing
Thinking parting off measures stock length
Assuming parting off smooths surfaces
2. Which of the following is the correct G-code command to start a parting off operation with feed rate control?
easy
A. G71 X20 Z-5 F0.1
B. G00 X20 Z-5 F0.1
C. G71 X20 Z-5 S1000
D. G01 X20 Z-5
Solution
Step 1: Identify G-code for parting off with feed rate
G01 is the linear interpolation command used for controlled feed moves, including parting off, with feed rate control.
Step 2: Check options for correct syntax
G01 X20 Z-5 moves the tool linearly to X20 Z-5 at the current feed rate. G71 is for rough turning cycles, not typically used for simple parting off moves with feed rate control.
Final Answer:
G01 X20 Z-5 -> Option D
Quick Check:
G01 = linear feed move for parting off [OK]
Hint: G01 is used for feed controlled linear moves like parting off [OK]
Common Mistakes:
Using G00 which is rapid move, not cutting
Omitting feed rate (F) in parting off
Confusing spindle speed (S) with feed rate (F)
3. Given the following CNC code snippet for parting off:
G71 X15 Z-3 F0.05
G00 X20 Z0
G71 X15 Z-3 F0.05
What will be the final position of the tool after execution?
medium
A. X15 Z-3
B. X15 Z0
C. X20 Z0
D. X20 Z-3
Solution
Step 1: Analyze the G-code sequence
The first G71 command moves tool to X15 Z-3 with feed. Then G00 moves tool rapidly to X20 Z0.
Step 2: Identify final tool position
The last command G71 X15 Z-3 F0.05 moves the tool to X15 Z-3 with feed. Thus, final position is X15 Z-3.
Final Answer:
X15 Z-3 -> Option A
Quick Check:
Last G71 to X15 Z-3 [OK]
Hint: Final position from last command execution [OK]
Common Mistakes:
Stopping analysis after the G00 rapid move
Ignoring the final G71 command
Confusing rapid positioning with final cut position
4. Identify the error in this parting off CNC code snippet:
G71 X10 Z-2 F
G00 X15 Z0
medium
A. Missing feed rate value after F
B. Incorrect use of G00 command
C. Wrong axis letter used
D. Spindle speed not set
Solution
Step 1: Check G71 command syntax
G71 requires feed rate value after F. Here, F is present but no value is given.
Step 2: Verify other commands
G00 command is correct for rapid move. Axis letters X and Z are valid. Spindle speed is optional here.
Final Answer:
Missing feed rate value after F -> Option A
Quick Check:
F must have a value [OK]
Hint: Always provide a value after F for feed rate [OK]
Common Mistakes:
Leaving F without a number
Confusing G00 with cutting move
Thinking spindle speed is mandatory here
5. You want to part off a piece with a diameter of 30 mm and length 5 mm using G71. Which command correctly sets the tool path for this operation?
hard
A. G71 X30 Z-5 F0.08
B. G71 X15 Z5 F0.08
C. G71 X15 Z-5 F0.08
D. G71 X30 Z5 F0.08
Solution
Step 1: Convert diameter to radius for X-axis
In CNC turning, X value is radius, so diameter 30 mm means X=15 mm.
Step 2: Set Z-axis for length and direction
Length 5 mm is negative Z direction for parting off, so Z=-5.
Step 3: Confirm feed rate and syntax
Feed rate F0.08 is valid. So command is G71 X15 Z-5 F0.08.
Final Answer:
G71 X15 Z-5 F0.08 -> Option C
Quick Check:
X=radius=15, Z=-5 length, feed set [OK]
Hint: X is radius (half diameter), Z negative for parting off length [OK]
Common Mistakes:
Using diameter instead of radius for X
Setting Z positive instead of negative
Omitting feed rate or using wrong sign
Recommended
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