CNC CNC Quality Control and Inspection 1 — Questions and Answers
Question 1: What instrument is used to measure the inside diameter of a precision bore in CNC quality inspection?
- Outside micrometer
- Telescoping gauge with outside micrometer (Correct answer)
- Vernier caliper
- Depth micrometer
Correct answer: Telescoping gauge with outside micrometer
A telescoping gauge expands to fit the bore diameter, then the set distance is measured with an outside micrometer to get an accurate inside diameter reading.
Question 2: In GD&T, what does the symbol for 'perpendicularity' look like?
- A circle with crosshairs
- An upside-down T (⊥) (Correct answer)
- Two parallel lines (//)
- A circle with a target
Correct answer: An upside-down T (⊥)
Perpendicularity in GD&T is represented by an upside-down T symbol (⊥), indicating that a surface or axis must be 90° to the referenced datum.
Question 3: What does 'Cpk' measure in CNC manufacturing process capability?
- The cutting speed in meters per minute
- How well a process is centered within specification limits (Correct answer)
- The number of defects per million opportunities
- The surface roughness average value
Correct answer: How well a process is centered within specification limits
Cpk measures process capability while accounting for how well the process mean is centered between the upper and lower specification limits.
Question 4: When using a CMM (Coordinate Measuring Machine), what is a 'datum reference frame'?
- The software version used to program the measurement routine
- The three mutually perpendicular planes that establish the coordinate system for measurement (Correct answer)
- The stylus tip diameter used for the measurement
- The ambient temperature at which measurements are taken
Correct answer: The three mutually perpendicular planes that establish the coordinate system for measurement
A datum reference frame consists of three mutually perpendicular datum planes (A, B, C) that establish the origin and orientation for all CMM measurements.
Question 5: What does Ra measure in surface finish inspection?
- The maximum peak-to-valley height
- The arithmetic average roughness of the surface profile (Correct answer)
- The root mean square of roughness values
- The spacing between adjacent surface peaks
Correct answer: The arithmetic average roughness of the surface profile
Ra is the arithmetic mean of the absolute values of the profile deviations from the mean line, providing an average roughness value for the surface.
Question 6: What is the purpose of a go/no-go gauge in CNC production inspection?
- To measure the exact diameter of a finished feature
- To quickly verify that a feature is within its tolerance limits without measuring the actual dimension (Correct answer)
- To check surface finish on critical bores
- To confirm a thread's pitch and lead angle
Correct answer: To quickly verify that a feature is within its tolerance limits without measuring the actual dimension
A go/no-go gauge has two ends: the 'go' end must fit, confirming the feature is not undersize; the 'no-go' end must not fit, confirming it is not oversize.
CNC CNC Quality Control and Inspection 1
What instrument is used to measure the inside diameter of a precision bore in CNC quality inspection?