Uint 3 advance laser meterology

UNIT 3- ADVANCES IN METROLOGY
S.DHARANI KUMAR
Asst.professor
Department of Mechanical Engineering
SRI ESHWAR COLLEGE OF ENGINEERING
,COIMBATORE ,INDIA

UNIT- III
ADVANCES IN METROLOGY

LASER
 LASER- Light Amplification by Stimulated Emission of Radiation.
 A typical helium-neon laser source a 1mm to 2mm diameter beam
of pure red light having power of 1MW.
 This is used for very accurate measurements of the order of 0.lμm
is 100m.
 The great distance ,the beam has no divergence but then it begins to
expand at a rate of about 1 mm/m

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Electromagnetic radiation is emitted whenever a charged
particle such as an electron gives up energy.
Happens every time when an electron drops from a higher
energy state to a lower energy state, in an atom or ion.
The smallest particle of light energy is described by
quantum mechanics as a photon.
The energy, E, of a photon is determined by its frequency √,
and Planck's constant, h.
E= h √
The difference in energy levels across which an excited
electron drops determines the wavelength of the emitted
light.
LASER THEORY AND OPERATION

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LASING ACTION
• Energy is applied to a medium raising electrons to an
unstable energy level and spontaneously decay to a low
energy metastable state.
• Population inversion is achieved when the majority of
atoms have reached this metastable state.
• Lasing action occurs when an electron spontaneously
returns to its ground state and produces a photon.
• Highly reflective/ partially reflective mirror continue to
direct photons back through the medium.
• The partially reflective mirror allows the transmission of
a coherent radiation that is observed as the “beam”.
• Laser radiation will continue as long as energy is
applied to the lasing medium.

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Argon fluoride (Excimer-UV)
Krypton chloride (Excimer-UV)
Krypton fluoride (Excimer-UV)
Xenon chloride (Excimer-UV)
Xenon fluoride (Excimer-UV)
Helium cadmium (UV)
Nitrogen (UV)
Helium cadmium (violet)
Krypton (blue)
Argon (blue)
Copper vapor (green)
Argon (green)
Krypton (green)
Frequency doubled
Nd YAG (green)
Helium neon (green)
Krypton (yellow)
Copper vapor (yellow)
0.193
0.222
0.248
0.308
0.351
0.325
0.337
0.441
0.476
0.488
0.510
0.514
0.528
0.532
0.543
0.568
0.570
Helium neon (yellow)
Helium neon (orange)
Gold vapor (red)
Helium neon (red)
Krypton (red)
Rohodamine 6G dye (tunable)
Ruby (CrAlO3) (red)
Gallium arsenide (diode-NIR)
Nd:YAG (NIR)
Helium neon (NIR)
Erbium (NIR)
Helium neon (NIR)
Hydrogen fluoride (NIR)
Carbon dioxide (FIR)
Carbon dioxide (FIR)
0.594
0.610
0.627
0.633
0.647
0.570-0.650
0.694
0.840
1.064
1.15
1.504
3.39
2.70
9.6
10.6
UV = ultraviolet (0.200-0.400 µm)
VIS = visible (0.400-0.700 µm)
NIR = near infrared (0.700-1.400 µm)
WAVELENGTHS OF MOST COMMON LASERS
Wavelength (mm)Laser Type Laser Type Wavelength (mm)

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Solid state lasers
Use a crystalline or glass rod which is "doped" with ions
that provide the required energy states.
Ex: Neodymium is a common "dopant" in various solid-
state laser crystals - yttrium orthovanadate (Nd:YVO4),
yttrium lithium fluoride (Nd:YLF) and yttrium aluminium
garnet (Nd:YAG).
Gas lasers
Consist of a gas filled tube placed in the laser cavity .
Voltage (the external pump source) applied to the tube
excite the atoms in the gas to a population inversion.
Ex: He-Ne, Ar, CO2
Types of lasers

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Semiconductor lasers
Works on the principle of recombination radiation.
When electrons in the conduction band combine with
the holes in the valence band, they emit photons.
Ex: GaAs, AlGaAs, InGaAs and InGaAsP alloys
Types of lasers

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Dye lasers
A dye cell consists of an organic dye mixed with a solvent
pumped by a high energy source of light.
Wide gain spectrum of dyes allows these lasers to be highly
tunable or to produce very short-duration pulses.
Ex: Rhodamine, fluorescein, coumarin, stilbene,
umbelliferone, tetracene and malachite green.
Free electron lasers
Operate by having an electron beam in an optical cavity
pass through a wiggler magnetic field. The change in
direction exerted by the magnetic field on the electrons
causes them to emit photons.
Types of lasers

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Chemical lasers
Powered by a chemical reaction permitting a large
amount of energy to be released quickly.
Ex: Hydrogen fluoride laser, Deuterium.
Excimer lasers
Special sort of gas lasers powered by an electric
discharge in which the lasing medium is an excimer
(an exciplex (excimer complex)).
Laser action in an excimer molecule occurs because it
has a bound (associative) excited state, but a repulsive
(dissociative) ground state.
Types of lasers

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Noble gases such as xenon and krypton are highly
inert and do not usually form chemical compounds.
However, when in an excited state, they can form
temporarily-bound molecules with themselves (dimers)
or with halogens (complexes) such as fluorine and
chlorine.
The excited compound can give up its excess energy
by undergoing spontaneous or stimulated emission.
Commonly used excimer molecules include ArF
(emission at 193 nm), KrCl (222 nm), KrF (248 nm), XeCl
(308 nm), and XeF (351 nm).
Types of lasers

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Fiber lasers
Solid-state lasers where the light is guided through
internal reflection in an optical fiber.
Guiding of light allows extremely long gain regions
providing good cooling conditions.
The fiber's wave guiding properties tend to reduce
thermal distortion of the beam.
Erbium and ytterbium ions are common active species
in such lasers.
Types of lasers

LASER METROLOGY
 A laser beam projected directly onto a position detector is
a method of alignment used in a number of commercially
available system.
 Laser is suitable for more general applications where a
very convenient, collimated and high intensity source is
required (Precision, Accuracy, on contact and hot moving
parts)
 Laser diode and semiconductor lasers have more
advantages at low cost.

LASER TELEMETRIC SYSTEM
Construction:
The Laser telemetric system consist of three
components.
 Transmitter
 Receiver
 Processor electronics

SCHEMATIC DIAGRAM OF LASER TELEMETRIC SYSTEM

Transmitter
 Low power helium ne gas laser
 Synchronous motor
 Collimating lens
 Reflector prism
 Synchronous pulse photo detector
 Replaceable window

ADVANTAGES
 It is possible to detect changes in dimensions
when the product is in continuous processes.
 It can be applied on production machines
and controlled then with closed feedback
loops.

LASER AND LED BASED DISTANCE
MEASURING INSTRUMENTS
It can measure distances from 1m to 2m with
accuracy of the order of 0.1 to 1% of measuring
range.

SCANNING LASER GAUGE
The scanning laser gauge is used for dimensional measurements.

PHOTODIODE ARRAY IMAGE
This method is also used for dimensional measurements.

DIFFRACTION PATTERN TECHNIQUE
 This method is also used for dimensional measurements.
 It is not suitable for large diameter.

LASER TRIANGULATION SENSORS
In this sensor a finely focused laser of light is direct at the
part surface and this light comes from the laser source.
Advantages:
 Quick measurement of deviations is due to change in
surface.
 it can perform automatic calculation on shell metal
stampings.

TWO FREQUENCY LASER
INTERFEROMETER

TWO FREQUENCY LASER
INTERFEROMETER
It consists of six parts namely
 Two way frequency laser head
 Beam directing and splitting optics
 Measurements optics
 Receivers
 Wavelength compensators
 Electronic receivers

Advantages:
 It is ideally suited measuring linear positioning,
straightness in two planes.
 It is highly sensitivity.
 It is free form noise disturbances.

GAUGE WIDE DIAMETER FORM THE
DIFFRACTION PATTERN FORMED IN A LASER
Measuring the diameter of thin wire using the
interference fringes thereby resulting the diffraction of light
by the wire in the laser beam.

GAUGE WIDE DIAMETER FORM THE
DIFFRACTION PATTERN FORMED IN A LASER

ADVANTAGES:
 Accurate measurement are possible relatively for short
distances.
 Wire diameters from 0.005 to 0.2mm can be measured.

PRINCIPLE OF LASER
 The photon emitted during stimulated emission has the
same energy, phase and frequency as the incident photon.
 This principle states that the photon comes in contact
with another atom or molecule in the higher energy level
E2 then it will cause the atom to return to ground state
energy level E1 by releasing another photon.

LASER INTERFEROMETRY
Component:
 Two frequency Laser source
 Optical elements
 Laser head’ s measurement receiver
 Measurement display

TWO FREQUENCY LASER SOURCE
 It is generally He-Ne type that generates stable coherent
light beam of two frequencies.one polarized vertically
and another horizontally relative to the plane of the
mounting feet.

OPTICAL ELEMENTS
Various Optical Elements
 Beam splitter
 Beam benders
 Retro reflectors

TYPES OF LASER INTERFEROMETER
1. Standard Interferometer

2. Signal Beams Interferometer
 Beam traveling between the interferometer and the retro
reflector.
 Its operation same as standard interferometer.
 The interferometer and retro reflector for this system are
smaller than the standard system.

LASER INTERFEROMETER
Components Of Laser Interferometer.
 Two frequency zeeman laser
 Beam splitter
 Fixed internal cube corner
 External cube corner
 Photo detector
 Amplifier
 Pulse converter

LASER INTERFEROMETER AC OR ACLI

2.TWYMAN-GREEN
INTERFEROMETER
 The Twyman-Green interferometer is used as a polarizing
interferometer with variable amplitude balancing between
sample and reference waves.
 For an exact measurement of the test surface, the instrument
error can be determined by an absolute measurement. This error
is compensated by storing the same in microprocessor system
and subtracting from the measurement of the test surface.

2. TWYMAN-GREEN
INTERFEROMETER

3.DUAL FREQUENCY LASER
INTERFEORMETER
 This instrument is used to measure displacement,
high-precision measurements of length, angle, speeds and
refractive indices as well as derived static and dynamic
quantities.
 This system can be used for both incremental
displacement and angle measurements. Due to large
counting range it is possible to attain a resolution of 2mm
in 10m measuring range.

4.LASER INTERFEROMETER DC OR DCLI

INTERFEROMETRIC
MEASUREMENT OFANGLE

 With the help of two retro reflectors placed at a fixed
distance and a length measuring laser interferometer the
change in angle can be measured to an accuracy of 0.1
second. The device uses sine Principle.
 The line joining the poles the retro-reflectors makes the
hypotenuse of the right triangle. The change in the path
difference of the reflected beam represents the side of the
triangle opposite to the angle being measured.

MACHINE TOOLTESTING
 The accuracy of manufactured parts depends on the
accuracy of machine tools.
 The quality of work piece depends on Rigidity and
stiffness of machine tool and its components.
 Alignment of various components in relation to one
another Quality and accuracy of
 driving mechanism and control devices.
 It can be classified into
1. Static tests
2. Dynamic tests.

Static tests:
If the alignment of the components of the machine tool are
checked under static conditions then the test are called static test.
Dynamic tests:
If the alignment tests are carried out under dynamic loading
condition. The accuracy of machine tools which cut metal by
removing chips is tested by two types of test namely.
1. Geometrical tests
2. Practical tests.

Geometrical tests:
In this test, dimensions of components, position of
components and displacement of component relative to one
another is checked.
Practical tests:
In these test, test pieces are machined in the machines. The
test pieces must be appropriate to the fundamental purpose for
which the machine has been designed.

TYPE OF GEOMETRICAL CHECKS
ON MACHINE TOOLS.
Different types of geometrical tests conducted on
machine tools are as follows:
1. Straightness.
2. Flatness.
3. Parallelism, equidistance and coincidence.
4. Rectilinear movements or squareness of straight line
and plane.
5. Rotations.

PURPOSE OF MACHINE TOOL
TESTING
 The dimensions of any work piece, its surface finishes and
geometry depends on the accuracy of machine tool for its
manufacture.
 In mass production the various components produced should be
of high accuracy to be assembled on a non-sensitive basis.
 The increasing demand for accurately machined components
has led to improvement of geometric accuracy of machine tools.
For this purpose various checks on different components of the
machine tool are carried out.

VARIOUS TESTS CONDUCTED ON
ANY MACHINE TOOLS
1. Test for level of installation of machine tool in horizontal and
vertical planes.
2. Test for flatness of machine bed and for straightness and
parallelism of bed ways on bearing surface.
3. Test for perpendicularity of guide ways to other guide ways.
4. Test for true running of the main spindle and its axial
movements.
5. Test for parallelism of spindle axis to guide ways or bearing
surfaces.
6. Test for line of movement of various members like spindle
and table cross slides etc.

USE OF LASER FOR ALIGNMENT
TESTING
 The alignment tests can be carried out over greater distances and to
a greater degree of accuracy using laser equipment.
 Laser equipment produces real straight line, whereas an alignment
telescope provides an imaginary line that cannot be seen in space.
 This is important when it is necessary to check number of
components to a predetermined straight ‘ line. Particularly if they
are spaced relatively long distances apart, as in aircraft production
and in shipbuilding.
 Laser equipment can also be used for checking flatness of
machined surface by direct displacement. By using are optical
square in conjunction with laser equipment squareness can be
checked with reference to the laser base line.

ALIGNMENT TESTS ON MILLING
MACHINE
1. Cutter spindle axial slip or float
2. Eccentricity of external diameter
3. True running of internal taper
4. Surface parallel with longitudinal movement
5. Traverse movement parallel with spindle axis
6. Center T-slot square with the arbor
7. Test on column
8. Over arm parallel with the spindle.

1.Eccentricity of external diameter

2.Surface parallel with longitudinal movement

3.True running of internal taper

4.Work table surface parallel with arbor rising
towards overarm

5.Center T-slot square with the arbor

7.overram parallel with spindle

8.Central T-slot parallel with longitudinal movement

ALIGNMENT TESTS ON PILLAR TYPE
DRILLING MACHINE
1. Flatness of clamping surface of base
2. Flatness of clamping surface of table
3. Perpendicularity of drill head guide to the base plate
4. Perpendicularity of drill head guide with table
5. Perpendicularity of spindle sleeve with its vertical movement
6. True running of spindle taper
7. Parallelism of the spindle axis with its vertical movement
8. Squareness of clamping surface of table to its axis
9. Total deflection.

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Alignment tests on pillar type drilling machine
* Properly Installed – In both horizontal (longitudinal and transverse
directions) and vertical directions.
1. Flatness of clamping surface
of base:
* Straight edge on two gauge blocks
* Feeler gauges gives error
* Error should not exceed 0.1/1000 mm
clamping surface
* Surface should be concave only
2. Flatness of clamping surface
of table:

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3. Perpendicularity of drill head
guide to the base plate :
* Tested in both vertical plane(a) and in
a plane at 900 to the above plane (b)
* Frame level with graduations from
0.03 to 0.05 mm/m
* Error should not exceed 0.25/1000
mm for (a) and 0.15/1000 mm for (b)
4. Perpendicularity of drill head
guide with table :
5. Perpendicularity of spindle
sleeve with base plate :
* Tested in both the planes using frame
level
mm for plane (a) and 0.15/1000 mm for
plane (b)

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6. True running of spindle taper
:
* Test mandrel is palced in the
tapered hole of spindle
* Dial indicator
* Spindle rotated slowly
mm for machines with taper upto
Morse No. 2 and 0.04/300 mm for
machines with taper larger than Morse
No. 2

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7. Parallelism of the spindle
axis with its vertical
movement :
* Test is performed into twp
planes A & B
* Test mandrel and dial indicator
* Spindle is adjusted in the middle
position of its travel
* Permissible errors are : For
machines with taper upto Morse
No. 2 0.03/100 mm for plane A
and 0.03/100 mm for plane B.
* For machines with taper larger
than Morse No. 2 0.05/300 mm for
plane A and 0.05/300 mm for plane
B.

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8. Squareness of clamping surface
of table to its axis :
* Dial indicator
* Table is slowly rotated
mm diameter

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9. Squareness of spindle
axis with table :
* Straight edge placed
in position AA’ and BB’
* Work table in
middle position of its vertical
travel
* Dial indicator
* A – 1800 – A’
* The permissible
errors are 0.08/300 mm for
AA’ and 0.05/300 mm for
BB’.

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10. Total deflection :
* Drill head and table are arranged
in their middle position.
* Dial indicator
* Dynamometer

ALIGNMENT TESTS ON LATHE
1. Leveling the machine.
2. True running of locating cylinder of main spindle.
3. Axial slip of the main spindle and true running of shoulder face of
spindle nose.
4. True running of headstock center.
5. Parallelism of main spindle to saddle movement.
6. True running of taper socket in the main spindle.
7. Movement of upper slide parallel with main spindle in vertical
plane.
8. Parallelism of tailstock guide way with the movement of carriage.
9. Parallelism of tailstock sleeve taper socket to saddle movement.

2.Parallelism of spindle axis and bed

3.True running of headstock center

4.True running of taper socket in main spindle

5.Alignment of both the center's in vertical plane

6.Cross slide perpendicular to
spindle axis

Coordinate Measuring
Machine (CMM)

TYPES OF MEASURING MACHINES
1. Length bar measuring machine.
2. Newall measuring machine.
3. Universal measuring machine.
4. Co-ordinate measuring machine.
5. Computer controlled co-ordinate measuring machine.

Coordinate Measuring Machines
• Coordinate metrology is concerned with the
measurement of the actual shape and dimensions of an
object and comparing these with the desired shape and
dimensions.
• In this connection, coordinate metrology consists of the
evaluation of the location, orientation, dimensions, and
geometry of the part or object.
• A Coordinate Measuring Machine (CMM) is an
electromechanical system designed to perform
coordinate metrology.

COORDINATE MEASURING MACHINE (CMM)
Measuring machine consisting of a contact probe and a mechanism to
position the probe in three-dimensions relative to surfaces and features of a
work part
The probe is fastened to a structure that allows movement relative to the
part
Part is fixture on worktable connected to structure
The location coordinates of the probe can be accurately recorded as it
contacts the part surface to obtain part geometry data

• A CMM consists of a constant probe that can be positioned in 3D space
relative to the surface of a work part, and the x, y, and z coordinates of
the probe can be accurately and precisely recorded to obtain dimensional
data concerning the part geometry

accomplish measurements in 3D, a basic CMM is composed of the following
components:
 Probe head and probe to contact the work part surface.
 Mechanical structure that provides motion of the probe in three Cartesian axes
and displacement transducers to measure the coordinate values of each axis.
• In addition, many CMM have the following components:
 Drive system and control unit to move each of the three axes
 Digital computer system with application software.

CMM
CMM – Coordinate Measuring Machine
Flatness
Roundnes
s
Cylindricity

CMM Mechanical Structure
(a) Cantilever (b) Moving bridge (c) Fixed
bridge

CMM Mechanical Structure
(d) Horizontal Arm (e) Gantry
(f) Column

CANTILEVER TYPE
A vertical probe moves in the z-axis
Carried by a cantilevered arm that moves in the y-axis
This arm also moves laterally through the x-axis
Advantage- a fixed table allows good accessibility to the
work piece
Disadvantage- the bending caused by the cantilever design
The cantilever design offers a long table with relatively small
measuring ranges in the other two axis.
Suitable for measuring long, thin part

MOVING BRIDGE TYPE
Most widely used
Has stationary table to support work piece to be
measured and a moving bridge
Disadvantage- with this design, the phenomenon of
yawing (sometimes called walking) can occur- affect
the accuracy
Advantage- reduce bending effect

FIXED BRIDGE TYPE
In the fixed bridge configuration, the bridge is
rigidly attached to the machine bed
This design eliminates the phenomenon of walking
and provides high rigidity

COLUMN TYPE
Often referred to as universal measuring machine
instead of CMM
The column type CMM construction provides
exceptional rigidity and accuracy
These machines are usually reserved for gauge
rooms rather than inspection

HORIZONTALARM TYPE
Unlike the previous machines, the basic horizontal arm-
type CMM
Also referred to as layout machine
Has a moving arm, and the probe is carried along the y-
axis
Advantage- provides a large area, unobstructed work
area
Ideal configuration for measurement of automobile parts

GANTRY TYPE
The support of work piece is independent of the x and y axes,
both are overhead, supported by four vertical columns rising
from the floor
This setup allows you to walk along the work piece with the
probe, which is helpful for extremely large pieces

CMM Operation and Programming
• Positioning the probe relative to the part can be accomplished in several ways, ranging from
manual operation to direct computer control.
• Computer-controlled CMMs operate much like CNC machine tools, and these machines
must be programmed.
CMM Controls
• The methods of operating and controlling a CMM can be classified into four
main categories:
1. Manual drive,
2. Manual drive with computer-assisted data processing,
3. Motor drive with computer-assisted data processing, and
4. Direct Computer Control with computer-assisted data processing.

CMM Controls
• In manual drive CMM, the human operator physically move the probe along the
machine’s axes to make contact with the part and record the measurements.
• The measurements are provided by a digital readout, which the operator can
record either manually or with paper print out.
• Any calculations on the data must be made by the operator.
• A CMM with manual drive and computer-assisted data processing provides some data
processing and computational capability for performing the calculations required to
evaluate a give part feature.
• The types of data processing and computations range from simple conversioons between
units to more complicated geometry calculations, such as determining the angle between
two planes.

CMM Controls
• A motor-driven CMM with computer-assisted data processing uses electric
motors to drive the probe along the machine axes under operator control.
• A joystick or similar device is used as the means of controlling the motion.
• Motor-driven CMMs are generally equipped with data processing to accomplish
the geometric computations required in feature assessment.
• A CMM with direct computer control (DCC) operates like a CNC machine tool.
It is motorized and the movements of the coordinate axes are controlled by a
dedicated computer under program control.
• The computer also performs the various data processing and calculation
functions.
• As with a CNC machine tool, the DCC CMM requires part programming.

DCC CMM Programming
• There are twp principle methods of programming a DCC measuring machine:
1. Manual leadthrough method.
2. Off-line programming.
• In the Manual Lead through method, the operator leads the CMM probe through the various
motions required in the inspection sequence, indicating the points and surfaces that are to be
measured and recording these into the control memory.
• During regular operation, the CMM controller plays back the program to execute the
inspection procedure.
• Off-line Programming is accomplished in the manner of computer-assisted NC part
programming, The program is prepared off-line based on the part drawing and then
downloaded to the CMM controller for execution.

TYPES OF PROBES
Two general categories
1. Contact (see figure)
• Touch-trigger probe
• Analog scanning probe
2. Noncontact
For inspection of printed circuit board, measuring a clay of
wax model, when the object being measured would be
deformed by the for of stylus
• laser probes
• video probes

CONTACT PROBES
1. Touch trigger probe
• As the sensor makes contact with the part, the difference in contact resistance indicates that
the probe has been deflected
• The computer records this contact point coordinate space
• An LED light and an audible signal usually indicate contact
• Touch probe assemblies consist of three components; probe head, probe and stylus
2. Analog scanning probe
• Use to measure contour surfaces, complex, irregular
• Remains in contact with the surface of the part as it moves
• Improve the speed and accuracy

NON-CONTACT PROBE
1. Laser scanning probe
• Laser probes project a light beam onto the surface of a part
• When the light beam is triggered, the position of beam is read by triangulation through
a lens in the probe receptor
• Laser tool have a high degree of speed and accuracy
2. Video probe
• The feature are measured by computer ‘count’ of the pixels of the electronic image
• The camera is capable of generating multitude of measurements points within a single
video frame

CALIBRATION OF THREE CO-ORDINATE MEASURING MACHINE

APPLICATIONS
1) Co-ordinate measuring machines find applications in automobile, machine tool,
electronics, space and many other large companies.
2) These machines are best suited for the test and inspection of test equipment,
gauges and tools.
3) For aircraft and space vehicles, hundred percent inspections is carried out by
using
CMM.
4) CMM can be used for determining dimensional accuracy of the components.
5) These are ideal for determination of shape and position, maximum metal
condition,

6) CMM can also be used for sorting tasks to achieve optimum pairing of components
within tolerance limits.
7) CMMs are also best for ensuring economic viability of NC machines by reducing
their
downtime for inspection results. They also help in reducing cost, rework cost at the
appropriate time with a suitable CMM.

ADVANTAGES
The inspection rate is increased.
Accuracy is more.
Operators error can be minimized.
Skill requirements of the operator is reduced.
Reduced inspection fix Turing and maintenance cost.
Reduction in calculating and recording time.
Reduction in set up time.
No need of separate go / no go gauges for each feature.
Reduction of scrap and good part rejection.
Reduction in off line analysis time.

DISADVANTAGES
The table and probe may not be in perfect alignment.
The probe may have run out.
The probe moving in Z-axis may have some perpendicular errors.
Probe while moving in X and Y direction may not be square to each
other.
There may be errors in digital system.

CAUSES OF ERRORS IN CMM
The table and probes are in imperfect alignment. The probes may have a degree of
run out and move up and down in the Z-axis may occur perpendicularity errors. So
CMM should be calibrated with master plates before using the machine.
Dimensional errors of a CMM is influenced by
Straightness and perpendicularity of the guide ways.
Scale division and adjustment.
Probe length.
Probe system calibration, repeatability, zero point setting and reversal error.
Error due to digitization.
Environment

Other errors can be controlled by the manufacture and minimized by the
measuring software. The length of the probe should be minimum to reduce
deflection.
The weight of the work piece may change the geometry of the guide ways and
therefore, the work piece must not exceed maximum weight.
Variation in temperature of CMM, specimen and measuring lab influence the
uncertainly of measurements.
Translation errors occur from error in the scale division and error in straightness
perpendicular to the corresponding axis direction.
Perpendicularity error occurs if three axes are not orthogonal.

COMPARISON BETWEEN CONVENTIONALAND
COORDINATE MEASURING TECHNOLOGY
CONVENTIONAL METROLOGY COORDINATE METROLOGY
Manual, time consuming alignment of the test piece Alignment of the test piece not necessary
Single purpose and multi-point measuring instruments
making it hard to adapt to changing measuring
task
Simple adaptation to the measuring test by software
Comparison of measurement with material measures,
i.e., gauge block
Comparison of measurement with mathematical or
numerical value
Separate determination of size, form, location and
orientation with different machines
Determination of size, form, location and orientation
in one setup using one reference system

FEATURES OF CMM SOFTWARE
Measurement of diameter, center distance, length.
Measurement of plane and spatial carvers.
Minimum CNC programmed.
Data communications.
Digital input and output command.
Program me for the measurement of spur, helical, bevel’ and hypoid
gears.
Interface to CAD software

Generally software packages contains some or all of the following capabilities:
1. Resolution selection
2. Conversion between SI and English (mm and inch)
3. Conversion of rectangular coordinates to polar coordinates
4. Axis scaling
5. Datum selection and reset
6. Circle center and diameter solution
7. Bolt-circle center and diameter
8. Save and recall previous datum
9. Nominal and tolerance entry
10. Out-of tolerance computation

CMM
CMM – Coordinate Measuring Machine

$$* IIT Delhi- DMIS File For Verifying Cylindricity:
Generated by Bhaskar
$$-> DMIS File Number - 1
$$-> Manifold Part / MFG001
DMISMN / DMIS Program
UNITS / MM, ANGDEC
$$-> FEATNO / 128
$$ Verify Gtol g01
T(CYLINDRICITY)= TOL / CYLCTY, 0.005000
OUTPUT / FA(M_CY1), TA(CYLINDRICITY)
$$-> END /
ENDFIL
$$* IIT Delhi- DMIS File For Verifying Conicity:
Generated by Bhaskar
UNITS / MM, ANGDEC
$$-> FEATNO / 88
$$ Verify Gtol g02
T(CONICITY)= TOL / CNCTY, 0.005000
OUTPUT / FA(M_CN02), TA(CONICITY)
$$-> END /
ENDFIL
DMIS

$$* IIT Delhi- DMIS File For Measuring A Cylinder: Generated by
Bhaskar
UNITS / MM, ANGDEC
S(1)= SNSDEF / PROBE, INDEX, POL, 0.000000, 0.000000, $
0.000000, 0.000000, 1.000000, 100.000000, 4.000000
$$-> FEATNO / 128
MODE / PROG, AUTO
SNSLCT / S(1)
FEDRAT / MESVEL, MPM, 15.000000
FEDRAT / POSVEL, MPM, 20.000000
ACLRAT / MESACL, MPMM, 5.000000
ACLRAT / POSACL, MPMM, 10.000000
PRCOMP / OFF
SNSET / APPRCH, 5.500000
SNSET / RETRCT, 5.500000
SNSET / CLRSRF, 0.000000
F(M_CY01)= FEAT / CYLNDR, INNER, CART, $
0.000000, 0.000000, 0.000000, $
0.000000, 0.000000, -1.000000, 30.000000
F(BND_20)= FEAT / PLANE, CART, $
0.000000, 0.000000, 0.000000, $
0.000000, 0.000000, 1.000000,
F(BND_21)= FEAT / PLANE, CART, $
0.000000, 0.000000, -10.000000, $
0.000000, 0.000000, -1.000000,
BOUND / F(M_CY1), F(BND_20), F(BND_21)
MEAS / CYLNDR, F(M_CY1), 32
..........................
GOTO / 0.000000, 0.000000, -2.000000
PTMEAS / CART, 13.000000, 0.000000, -2.000000, $
1.000000, 0.000000, 0.000000
PTMEAS / CART, 9.192388, 9.192388, -2.000000, $
0.707107, 0.707107, 0.000000
$$* IIT Delhi- DMIS File For Measuring A Cone: Generated by Bhaskar
UNITS / MM, ANGDEC
0.000000, 0.000000, 1.000000, 100.000000, 2.000000
$$-> FEATNO / 88
MODE / PROG, AUTO
SNSLCT / S(2)
FEDRAT / MESVEL, MPM, 15.000000
FEDRAT / POSVEL, MPM, 20.000000
ACLRAT / MESACL, MPMM, 5.000000
ACLRAT / POSACL, MPMM, 10.000000
PRCOMP / OFF
SNSET / APPRCH, 0.249996
SNSET / RETRCT, 0.249996
SNSET / CLRSRF, 0.000000
F(M_CN02)= FEAT / CONE, INNER, CART, $
0.000000, 0.000000, -44.999981, $
0.000000, 0.000000, 1.000000, 36.870000
MEAS / CONE, F(M_CN02), 6.000000
RAPID / 1.000000
GOTO / 0.0000000000, 0.0000000000, 2.000000
RAPID / 1.000000
GOTO / 0.000000, 0.000000, 2.000000
RAPID / 1.000000
GOTO / 0.000000, 0.000000, -37.000000
PTMEAS / CART, 6.000008, 0.000000, -37.000000, $
-0.799999, 0.000000, 0.600001
PTMEAS / CART, 0.000000, 6.000008, -37.000000, $
0.000000, -0.799999, 0.600001
PTMEAS / CART, -0.000000, -6.000008, -37.000000, $
0.000000, 0.799999, 0.600001
DMIS

INTEGRATION OF CAD/CAM WITH INSPECTION SYSTEM

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