6) Touch Trigger Probes Flashcards
What is a touch trigger probe?
A mechanical Switch measuring when contact between part and machine is made.
What type of measurement is a touch trigger probe?
contact measurement.
What ability does a scanning probe have?
To scan continuously along surface
What is the purpose of the probe head?
The movement of probe to match part geometry.
3 axis and 5 axis heads
5 axis much faster.
How many contact points are needed to constrain a part?
To constrain part, 6 contact points needed.
What is kelvin coupling? 6 point contact for complete constraint.
Touch trigger probe must operate at higher accuracy than tolerance of part manufactured
How do touch trigger probes work? What are the internals?
Electrical switch. Once the electrical circuit is broken, contact is measured.
How can the touch trigger probe signal be described?
Trigger signal:
Desired - Binary signal , on or off.
Reality - brief moment in time, signal is not on or off (arcing). This produces uncertainty.
What is Pre Travel?
When the stylus moves vs the circuit being broken.
What is Lobing, in terms of CMM measurement
Because of triangular orientation, different ways the contact can be broken - Depending on force direction.
What is Probe Hysteresis?
The difference in measuring internal and external 20mm of gauge blocks
Stylus selection, what is the ideal stylus?
Firstly based on part geometry, then the ideal is:
The stylus should be short and stiff.
The ball should be as large as possible.
What is the purpose of a non contact probe?
Reduce interaction with the workpiece.
What are the limitations of non contact probes?
Limited to line of sight
Limited resolution and accuracy
Engineering mistrust
Reliability
Compatibility
