CMM Probing

Question 1

What happens when the Kinematic resistive touch probe approaches an edge?

Answer 1

1) When the stylus approaches the workpiece face, the circuit is still closed and resistance is at its minimum
2) Stylus makes contact, circuit still closed, resistance still at minimum
3) Contact force resisted by spring force resulting in bending of stylus; resistance increases as 1 or 2 contact patches lose intimacy
4) Contact force overcomes spring force causing stylus to pivot resulting in 1 or 2 contact moving apart; resistance increases strongly triggering CMM to record location of probe as a measuring point
5) Probe withdraws and stylus reseats

Question 1

Explain the design of a KINEMATIC RESISTIVE TOUCH PROBE

Answer 1

1) Ring with 3 sets of steel spheres providing 6 points of contact in a kinematic location. Spheres of each set don’t touch each other but sets are connected via a wire to create a circuit

2) Spring-loaded core element with 3 steel rods. each one resting between a set of spheres, bridging the gap and closing the circuit

Question 2

List the step-by-step measuring procedure of a CMM.

Answer 2

1st step (Datuming) - Part coordinate system is determined using points obtained on the part’s surface. 3 points to create plane, 2 to create line, 1 to finalise the datum

2nd step : Acquire points on components surface. 3 points min for circle; 4 points min for sphere; 5 points min for cylinder; 3 points min for plane; 3 points min on each face for angle/line of intersection of two planes

3rd step: Define the components geometric features using the points; does by operator

4th: Extract information
5th: Inspection report, report is handed to customer