CMM errors

Question 1

What is Abbe error?

Answer 1

Is positional error caused by the combination of the axis of sensing being offset from the axis of motion in combination of angular error in that motion (eg tilt)
The abbe error causes a measurement error if e.g the axis of motion isn’t perfectly straight, which could be caused by the bridge bending down

Question 2

What is pre-travel?

Answer 2

Pre-travel error is the distance the probe keeps moving after initial contact with the workpiece edge before the CMM records the measurement point

Question 3

What is Lobing?

Answer 3

It is the phenomenon of varying pre-travel of a probe.
The amount of pre-travel a probe exhibits is not constant but varies depending on the direction of approach of the probe

Question 4

Machine dynamics create a class of geometry errors. in order to keep them small, what factors have to be adjusted?

Answer 4

Probe approach distance, acceleration settings and probing distance