Page 132 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

EXERCISE 83 & 84 : Co-ordinate Measuring Machine (CMM)

Objectives
At the end of this exercise you shall be able to
• explain the concepts of CMM
• working principle of CMM
• applications of CMM
• uses of CMM.

Concept of Co-ordinate Measuring Machine (CMM)

Conventionally, measurements were taken visually using Measuring instruments, Gauges or an optical compara-
tor. However, these tools require significant time and have limited accuracy.
On the other hand, a coordinate measuring machine (CMM) measures the height, width, and depth of the part
using coordinate processing technology. In addition, such machines can automatically measure the target, record
the measured data, and obtain GD& T measurements like runout, Total internal run out, cylindricity, symmetricity,
hole position etc ....

A coordinate measuring machine (CMM) is either a contact model that uses touch probes, a spherical object used
to perform measurements, or a non-contact model, which uses other methods such as cameras and lasers. Some
models designed for the automotive industry can even measure targets larger than 1 Om (30 ft) in size.
coordinate Measuring Machine (CMM) accurately measures the geometry of an object along X, Y and Z axes using
a touch-trigger, scanning or vision probe to take a series of precise points on the surface of an object.

Working principle of CMM
CMM(Coordinate Measuring Machine) is an advanced measurement machine works for measure complex and large
component. CMM is a device for measuring the physical characteristics of an object. The machine is controlled by
a computer or an operator.Measurement is done by the probe attached to a third moving axis
Co-ordinate measuring machines of present day are three-axis digital read-out type and these machines work up
with an accuracy of 10 microns. Resolution of present day co-ordinate machine is 1 microns
Applications
• Co-ordinate measuring machines find applications in automobile, machine tool, electronics, space and many
other large companies.
• CMM can be used for determining dimensional accuracy of the components.

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