Metrology-5-Coordinate Measurement Machines Flashcards
What does a Coordinate measurement allow an engineer to do?
1.Compare one component to another using the dimensions of the two components.
What two kinds of axes can Coordinates of dimensions be measured in?
Cartesian or Polar
What does the term Coordinate Measuring Machine CMM describe?
Metrology machines or instruments which measure coordinates.
What do CMM machines range from?
Simple manually operated systems to highly sophisticated computer controlled fully automatic systems.
What similarities to automatic and manual CMMs have?
Rigidity, thermal stability and dimensional stability etc.
What are the majority of CMMs now supplied with?
Powerful user-friendly software packages that CMM record and process data.
CMMs have different configurations
What are the steps involved in the general measurement strategy of CMMs?
- 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 determines which workpiece features require measurements?
Manufacturing and functionality requirements.
* Some features may not be measurable using a CMM.
* Some features may be impracticable to measure with a CMM.
* Some features may not be cost effective to measure with a CMM.
* Ideally the strategy should only require one set-up to measure all features,
and in reality a minimum number of set-ups should be used.
What may be different between the workpiece and CMM?
Coordinate systems may be rectilinear with familiar notation (X, Y, Z).
Define the cylindrically polar coordinate system
One rotary and two linear axes
Define the spherically polar coordinate system
One linear and two rotary axes
What are the advantages of a Touch Trigger probe?
Reduced interaction with the workpiece
Why haven’t TTPs seen much commercial success?
TTP problems:
1. Limited to line of isgt
2. Limited resolution and accuracy
3. Engineering mistrust
4. Reliability
5. Compatibility
What are the basic rules for TTP stylus selection?
Keep the stylus short and stiff
Keep the stylus ball as large as possible
What probes are prone to stylus deformation unless they are thick, short and rigid?
Manual probes
