of 42
8/13/2019 Unit IV Johnson
1/42
LASER AND ADVANCES INMETROLOGY
Unit 4
8/13/2019 Unit IV Johnson
2/42
Syllabus
Precision instruments based on laserPrinciplelaser interferometerapplication in linear, angular measurements and machine toolmetrology
Coordinate measuring machine (CMM)Constructional features types
Applicationsdigital devices
Computer aided inspection
8/13/2019 Unit IV Johnson
3/42
PRINCIPLE OF LASER
The sequence of triggered identical photon from stimulated atom is
known as stimulated emission
This multiplication of photon through stimulated emission leads to
coherent, powerful, monochromatic, collimated beam of light emission
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
8/13/2019 Unit IV Johnson
4/42
LASER INTERFEROMETRY
Two frequency Laser source
Optical elements
Beam splitter
Beam benders
Retro reflectors
Laser head s measurement receiver
Measurement display
8/13/2019 Unit IV Johnson
5/42
USE OF LASER
Laser Telemetric systemLaser and LED based distance measuringinstruments
Scanning Laser gaugeDiffraction pattern techniqueGauging wide diameter from the diffraction patternformed in a laser
8/13/2019 Unit IV Johnson
6/42
Laser Telemetric system
8/13/2019 Unit IV Johnson
7/42
LASER AND LED BASED DISTANCE MEASURINGINSTRUMENTS
8/13/2019 Unit IV Johnson
8/42
Scanning Laser gauge
8/13/2019 Unit IV Johnson
9/42
Diffraction pattern technique
These are used to measure small gaps and smalldiameter parts A parallel coherent laser beam is diffracted by a
small part and a lens on a linear diode array focusesthe resultant pattern.The measurement accuracy is more for smaller parts
8/13/2019 Unit IV Johnson
10/42
Gauging wide diameter from the diffractionpattern formed in a laser
8/13/2019 Unit IV Johnson
11/42
LASER INTERFEROMETER
8/13/2019 Unit IV Johnson
12/42
Beam splitter
8/13/2019 Unit IV Johnson
13/42
Various version of ACLI
Standard Interferometer Signal beamsInterferometer
8/13/2019 Unit IV Johnson
14/42
MICHELSON INTERFEROMETER
8/13/2019 Unit IV Johnson
15/42
TWYMAN-GREEN INTERFEROMETER
8/13/2019 Unit IV Johnson
16/42
MACHINE TOOL TESTING
The accuracy of manufactured parts depends on theaccuracy of machine toolsIt can be classified into
Static testsDynamic tests
8/13/2019 Unit IV Johnson
17/42
Static tests - If the alignment of the components ofthe machine tool are checked under static conditionsthen the test are called static test
Dynamic tests - If the alignment tests are carriedout under dynamic loading condition. The accuracyof machine tools which cut metal by removing chipsis tested by two types of test namely.
Geometrical testsPractical tests
8/13/2019 Unit IV Johnson
18/42
Geometrical tests : In this test, dimensions ofcomponents, position of components anddisplacement of component relative to one another ischecked.Practical tests : In these test, test pieces aremachined in the machines. The test pieces must beappropriate to the fundamental purpose for which
the machine has been designed
8/13/2019 Unit IV Johnson
19/42
PURPOSE OF MACHINE TOOL TESTING
The dimensions of any work piece
Surface finishes and geometry depends on the
accuracy of machine tool for its manufacture
High accuracy
8/13/2019 Unit IV Johnson
20/42
TYPE OF GEOMETRICAL CHECKS ON MACHINE TOOL
Straightness.
Flatness.
Parallelism, equi-distance and coincidence.
Rectilinear movements or squareness of straight line
and plane.
Rotations
8/13/2019 Unit IV Johnson
21/42
MAIN SPINDLE IS TO BE TESTED FOR
Out of round.EccentricityRadial throw of an axis.
Run outPeriodical axial slipCamming
8/13/2019 Unit IV Johnson
22/42
VARIOUS TESTS CONDUCTED ON ANY MACHINE TOOLS
Test for level of installation of machine tool in horizontaland vertical planes.Test for flatness of machine bed and for straightness andparallelism of bed ways on bearing surface.Test for perpendicularity of guide ways to other guide ways.Test for true running of the main spindle and its axialmovements.Test for parallelism of spindle axis to guide ways or bearingsurfaces.Test for line of movement of various members like spindleand table cross slides etc
8/13/2019 Unit IV Johnson
23/42
CMM
8/13/2019 Unit IV Johnson
24/42
Measuring machines are used for measurement oflength over the outer surfaces of a length bar or anyother long member
It is more useful and advantageous than verniercalipers, micrometer, screw gaugesThe co-ordinate measuring machine is used forcontact inspection of parts
Savings in inspection 5 to 10 percent of the time isrequired on a CMM compared to manual inspectionmethods
8/13/2019 Unit IV Johnson
25/42
TYPES OF MEASURING MACHINES
Length bar measuring machine
Newall measuring machine
Universal measuring machine
Co-ordinate measuring machine
Computer controlled co-ordinate measuring machine
8/13/2019 Unit IV Johnson
26/42
Types of CMM
8/13/2019 Unit IV Johnson
27/42
Working
8/13/2019 Unit IV Johnson
28/42
CAUSES OF ERRORS IN CMM
The table and probes are in imperfect alignment.The probes may have a degree of run out and move upand down in the Z-axis may occur perpendicularityerrorsDimensional 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 andreversal error.Error due to digitization.Environment
8/13/2019 Unit IV Johnson
29/42
The length of the probe should be minimum toreduce deflectionThe weight of the work piece may change the
geometry of the guide ways Variation in temperature of CMM
8/13/2019 Unit IV Johnson
30/42
CALIBRATION OF THREE CO-ORDINATE MEASURINGMACHINE
8/13/2019 Unit IV Johnson
31/42
APPLICATION
Automobile, machine tool, electronics, space etc.,Machines are best suited for the test and inspectionof test equipment, gauges and tools
Aircraft and space vehiclesdetermination of shape
8/13/2019 Unit IV Johnson
32/42
ADVANTAGES
The inspection rate is increased. Accuracy is more.Operators error can be minimized.
Skill requirements of the operator is reduced.Reduced inspection fixturing 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
8/13/2019 Unit IV Johnson
33/42
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 besquare to each other.There may be errors in digital system
8/13/2019 Unit IV Johnson
34/42
COMPUTER CONTROLLED CMM
8/13/2019 Unit IV Johnson
35/42
Types
8/13/2019 Unit IV Johnson
36/42
8/13/2019 Unit IV Johnson
37/42
CNC-CMM
8/13/2019 Unit IV Johnson
38/42
8/13/2019 Unit IV Johnson
39/42
FLEXIBLE INSPECTION SYSTEM
8/13/2019 Unit IV Johnson
40/42
MACHINE VISION
A Vision system can be defined as a system forautomatic acquisition and analysis of images toobtain desired data for interpreting or controlling anactivity
Machine vision can be defined as a means ofsimulating the image recognition and analysis
capabilities of the human system with electronic andelectro mechanical techniques
8/13/2019 Unit IV Johnson
41/42
Four types of machine vision system
Image formation
Processing of image in a form suitable for analysis by
computerDefining and analyzing the characteristic of image
Interpretation of image and decision-making
8/13/2019 Unit IV Johnson
42/42
Compiled by:
A.JOHNSON SANTHOSH
Assistant Professor,Department of Mechanical Engineering,PPG Institute of Technology,Coimbatore.