Metrology 4 Flashcards
What is coordinate measuring?
Coordinate measurement allows an engineer to compare one component to another using the dimensions of the two components. i.e. comparing a component to a master copy.
What are CMMs?
Coordinate Measuring Machines. It describes metrology machines or instruments which measure coordinates.
Name the variations of CMMs
Bridge - LK Ultra
Cantilever Arm - greater accessibility but rigidity issues which means lower accuracy.
What are Optical CMMs?
Non contact CMM. Usually have a bridge structure.
What are Multi-axis Measurement Arms?
Flexible robotic measuring arms.
FARO-ARM
ROMER 3000i
Describe the 8 point measurement strategy
Selection of features on the workpiece to be measured.
- Definition of the workpiece datum(s) used within the coordinate system.
- Selection of the workpiece orientation.
- Selection of the workpiece holding method.
- Qualification of the CMM probe.
- Definition of the probing strategy.
- Programming of the CMM.
- Analysis and recording of the results.
What are some limitations of CMMs?
Cannot measure interior features.
Measurement of some features are impractical
Measurement of some features are not cost effective
What coordinate system is used with cylinders?
Cylindrical Polar - One rotary and two linear
What coordinate system is used with spheres?
Spherical Polar - Two rotary and one linear
Name some types of probes
One touch trigger probes
Scanning Probes
Non-contact probes
Why are non-contact probes not really used commercially?
- Limited to line of sight
- Limited resolution and accuracy
- Engineering mistrust
- Reliability
- Compatibility
What rules are used when designing a stylus?
Keep the styli short and stiff
Keep the ball as large as possible
