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CNC Programmingscripting~30 mins

First article inspection in CNC Programming - Mini Project: Build & Apply

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First Article Inspection Automation
📖 Scenario: You work in a manufacturing plant where CNC machines produce parts. Before starting full production, you must perform a First Article Inspection (FAI) to check if the parts meet quality standards.To help with this, you want to automate the process of recording measurements from the first batch of parts and flagging any measurements that fall outside acceptable limits.
🎯 Goal: Build a simple script that stores measurement data for parts, sets acceptable tolerance limits, checks which measurements are out of tolerance, and prints the results.
📋 What You'll Learn
Create a dictionary with part names and their measured values
Add a tolerance limit variable for acceptable measurement range
Use a loop to check each part's measurement against the tolerance
Print the parts that fail inspection with their measured values
💡 Why This Matters
🌍 Real World
Automating first article inspection helps manufacturing plants quickly identify parts that do not meet quality standards, saving time and reducing errors.
💼 Career
Quality engineers and CNC programmers use such scripts to ensure parts meet specifications before full production, improving product reliability.
Progress0 / 4 steps
1
Create the measurement data dictionary
Create a dictionary called measurements with these exact entries: 'PartA': 10.05, 'PartB': 9.98, 'PartC': 10.12, 'PartD': 9.95
CNC Programming
Hint

Use curly braces {} to create a dictionary with the exact part names and their measurement values.

2
Set the tolerance limit
Create a variable called tolerance and set it to 0.05 to represent the acceptable deviation from the target measurement.
CNC Programming
Hint

Use a simple assignment to create the tolerance variable with the value 0.05.

3
Check measurements against tolerance
Use a for loop with variables part and value to iterate over measurements.items(). Inside the loop, check if the absolute difference between value and the target 10.0 is greater than tolerance. If so, add the part and value to a new dictionary called failures.
CNC Programming
Hint

Start with an empty dictionary failures. Use a for loop to check each measurement. Use abs(value - 10.0) > tolerance to find out-of-tolerance parts.

4
Print the inspection results
Print the string "Failed parts:". Then print the failures dictionary to show which parts failed the inspection with their measured values.
CNC Programming
Hint

Use two print statements: one for the label and one for the failures dictionary.

Practice

(1/5)
1. What is the main purpose of First article inspection in CNC programming?
easy
A. To program the CNC machine without running it
B. To check the first part made by the CNC program for errors and quality
C. To clean the CNC machine before starting production
D. To speed up the CNC machine for faster production

Solution

  1. Step 1: Understand the term 'First article inspection'

    It means checking the very first part produced by the CNC machine to ensure it meets quality standards.

  2. Step 2: Identify the main goal of this process

    The goal is to catch errors early and confirm the part is made correctly before making many parts.

  3. Final Answer:

    To check the first part made by the CNC program for errors and quality -> Option B

  4. Quick Check:

    First article inspection = check first part quality [OK]
Hint: Remember: First article means first part check [OK]
Common Mistakes:
  • Thinking it speeds up production
  • Confusing it with machine cleaning
  • Assuming it is programming without running
2. Which of the following is the correct sequence for performing a first article inspection?
easy
A. Run program, measure part, adjust program if needed
B. Measure part, run program, adjust program
C. Adjust program, run program, measure part
D. Run program, adjust program, measure part

Solution

  1. Step 1: Identify the logical order of steps

    You first run the CNC program to make the part, then measure it to check accuracy.

  2. Step 2: Adjust the program if measurements show errors

    If the part is not correct, you adjust the program and repeat as needed.

  3. Final Answer:

    Run program, measure part, adjust program if needed -> Option A

  4. Quick Check:

    Run -> Measure -> Adjust = A [OK]
Hint: Think: Make part first, then check and fix [OK]
Common Mistakes:
  • Measuring before making the part
  • Adjusting before measuring
  • Skipping measurement step
3. Given this CNC program snippet for first article inspection:
G01 X10 Y10 F100
M30

What will be the expected output after running this program once?
medium
A. The tool moves in a circular path to X=10, Y=10
B. The tool will not move because feed rate is zero
C. The program will cause a syntax error and stop
D. The tool moves in a straight line to X=10, Y=10 at feed rate 100

Solution

  1. Step 1: Understand G01 command

    G01 means linear move to specified coordinates at given feed rate.

  2. Step 2: Analyze the given coordinates and feed rate

    The tool moves straight to X=10, Y=10 at feed rate 100 units/min.

  3. Final Answer:

    The tool moves in a straight line to X=10, Y=10 at feed rate 100 -> Option D

  4. Quick Check:

    G01 = linear move, feed 100 = speed [OK]
Hint: G01 means straight line move [OK]
Common Mistakes:
  • Confusing G01 with circular move (G02/G03)
  • Assuming feed rate is zero
  • Thinking program has syntax error
4. You run a first article inspection program but the part dimensions are off. The program code is:
G01 X20 Y20 F150
M30

What is the likely error if the part is smaller than expected?
medium
A. Coordinates are incorrect, should be larger values
B. Program missing M03 spindle start command
C. Feed rate is too high causing tool deflection
D. M30 command is placed too early

Solution

  1. Step 1: Check coordinates vs part size

    If the part is smaller, the tool likely did not move far enough, so coordinates are too small.

  2. Step 2: Evaluate other options

    Feed rate affects speed, not size; missing spindle start or M30 early stop won't cause smaller size directly.

  3. Final Answer:

    Coordinates are incorrect, should be larger values -> Option A

  4. Quick Check:

    Wrong coordinates = wrong part size [OK]
Hint: Check coordinates first if part size is wrong [OK]
Common Mistakes:
  • Blaming feed rate for size error
  • Ignoring coordinate values
  • Assuming spindle commands affect size
5. During first article inspection, you notice the part passes all measurements except one hole diameter is slightly too small. What is the best next step?
hard
A. Increase feed rate to cut the hole faster
B. Ignore the small hole difference and start full production
C. Adjust the CNC program tool path or tool size for that hole and rerun inspection
D. Replace the entire CNC program with a new one

Solution

  1. Step 1: Identify the issue with the hole diameter

    The hole is too small, so the tool path or tool size needs adjustment to correct it.

  2. Step 2: Decide the best corrective action

    Adjusting the program and rerunning inspection ensures quality before full production.

  3. Final Answer:

    Adjust the CNC program tool path or tool size for that hole and rerun inspection -> Option C

  4. Quick Check:

    Fix program, then re-inspect = correct approach [OK]
Hint: Fix program for errors before full production [OK]
Common Mistakes:
  • Ignoring defects and producing many parts
  • Changing feed rate without reason
  • Replacing program unnecessarily