CNC Quality Control and Inspection Flashcards

In GD&T, what does the 'flatness' callout control?

Answer: The variation of all points on a surface lying within two parallel planes

Flatness controls how much a surface can deviate from a theoretically perfect flat plane, defined by a tolerance zone between two parallel planes.

What does 'true position' (⊕) tolerance in GD&T define?

Answer: The allowed zone within which the center axis or point of a feature must lie

True position defines a cylindrical (or 2D) tolerance zone centered on the theoretically exact position within which the feature's center must fall.

What is Statistical Process Control (SPC) primarily used for in CNC machining?

Answer: Monitoring production processes to detect trends before defects occur

SPC uses control charts and statistical methods to monitor process output over time, identifying when a process is trending out of control before it produces scrap.

In precision measurement, what does 'gauge R&R' study evaluate?

Answer: The repeatability and reproducibility of a measurement system

Gauge R&R (Repeatability and Reproducibility) studies determine how much of the measurement variation comes from the gauge itself versus the parts being measured.

What does 'MMC' (Maximum Material Condition) mean in GD&T?

Answer: The condition where the feature contains the maximum amount of material (smallest hole, largest shaft)

MMC is the condition where a feature contains the most material: for a hole, this is its smallest allowable diameter; for a shaft, it is its largest allowable diameter.

What is the primary purpose of a control chart's Upper Control Limit (UCL) and Lower Control Limit (LCL)?

Answer: They define the bounds of normal process variation (typically ±3 sigma) to detect out-of-control conditions

UCL and LCL are set at ±3 standard deviations from the process mean, and any point outside these limits signals that a special cause of variation is present.