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Parting off operation in CNC Programming - Mini Project: Build & Apply

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Parting Off Operation CNC Program
📖 Scenario: You are programming a CNC lathe to perform a parting off operation. This operation cuts off a finished part from the raw material bar. The CNC program must define the cutting parameters and toolpath to safely and accurately complete the cut.
🎯 Goal: Create a simple CNC program that sets up the parting off tool, defines the cutting depth, and executes the parting off cut along the Z-axis.
📋 What You'll Learn
Define the initial tool position
Set the parting off cutting depth
Use a linear move command to perform the cut
Output the final CNC program code
💡 Why This Matters
🌍 Real World
CNC lathe operators and programmers use parting off operations to separate finished parts from raw material bars efficiently and safely.
💼 Career
Understanding how to program parting off operations is essential for CNC machinists and manufacturing engineers to automate production and ensure quality.
Progress0 / 4 steps
1
Set initial tool position
Write a line to set the tool to the starting position at X20.0 and Z5.0 using the command G00.
CNC Programming
Hint

Use rapid positioning command G00 followed by coordinates X20.0 and Z5.0.

2
Set cutting depth variable
Create a variable called cut_depth and set it to -15.0 to represent the Z-axis depth for the parting off cut.
CNC Programming
Hint

Assign -15.0 to cut_depth to specify how far the tool will move along Z.

3
Write parting off move command
Write a linear move command G01 to move the tool from the starting position to the cutting depth along the Z-axis using cut_depth. Use a feed rate of F0.1.
CNC Programming
Hint

Use G01 for linear cutting move to Z-15.0 with feed rate F0.1.

4
Output the final CNC program
Print the complete CNC program lines including the initial position, cutting depth variable, and the parting off move command.
CNC Programming
Hint

Use print statements to output the CNC commands as text lines.

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

  1. 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.

  2. Step 2: Identify the correct operation purpose

    Among the options, only cutting a finished piece from raw stock matches the parting off operation.

  3. Final Answer:

    To cut a finished piece from the raw stock -> Option B

  4. 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

  1. 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.

  2. 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.

  3. Final Answer:

    G01 X20 Z-5 -> Option D

  4. 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

  1. 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.

  2. 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.

  3. Final Answer:

    X15 Z-3 -> Option A

  4. 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

  1. Step 1: Check G71 command syntax

    G71 requires feed rate value after F. Here, F is present but no value is given.

  2. Step 2: Verify other commands

    G00 command is correct for rapid move. Axis letters X and Z are valid. Spindle speed is optional here.

  3. Final Answer:

    Missing feed rate value after F -> Option A

  4. 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

  1. Step 1: Convert diameter to radius for X-axis

    In CNC turning, X value is radius, so diameter 30 mm means X=15 mm.

  2. Step 2: Set Z-axis for length and direction

    Length 5 mm is negative Z direction for parting off, so Z=-5.

  3. Step 3: Confirm feed rate and syntax

    Feed rate F0.08 is valid. So command is G71 X15 Z-5 F0.08.

  4. Final Answer:

    G71 X15 Z-5 F0.08 -> Option C

  5. 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

Ready to prove it?

Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.

10 questions~5 mineasy hard