Page 135 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

c Analog scanning probes
which maintain contact with the work piece surface during data collection.
2 Non contact probes.

a Laser probes
b Vision probes Hard probes
Hard probes
To use a hard probe, the CMM operator manually brings the probe into contact with the work piece, allows the
machine to settle and manually signals the CMM to record the probe’s position. The CMM’s software automatically
adjusts the readings to compensate for the diameter of the probe tip. For instance, when reading a bore diameter,
the software compensates for the diameter of the CMM probe tip so that the actual diameter of the bore is shown.
They are most frequently used to measure curved surfaces, distances between work piece features, angles and
the diameter and centreline location of bores in applications that require low to medium accuracy.

Touch trigger probes
Touch trigger probes are precision-built, touch-sensitive devices that generate an electronic signal each time the
probe contacts a point on the work piece. Contact with the part is usually indicated by an LED and an audible
“beep.” The probe head itself is mounted at the end of one of the CMM’s moving axes. It can be rotated manually
or automatically, and can accommodate many different stylus tips and attachments. These features make the trig-
ger probe a versatile and flexible data-gathering device.This design improves the accuracy of touch trigger probe
measurement results because it eliminates the effect of stylus bending and inaccuracies caused by the probe’s
internal electromechanical parts.

Analog scanning probes

Analeg scanning probes are a type of contact probe used to measure contoured surfaces such as sheet metal
assemblies. The analog scanning probe remains in contact with the work piece surface as it moves and produces
analog readings rather than digital measurements.

Continuous analog scanning is a relatively new technology. It adds versatility to CMMs by offering dramatically
increased levels of data acquisition, which speeds and improves the accuracy of measurement and inspection
operations.

120

CITS : C G & M - Fitter - Exercise 83 & 84