Optical/Laser/Vision Measurement

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

PowerPoint to accompany

Krar • Gill • Smid

Technology of Machine Tools6th Edition

Optical/Laser/Vision

Measurement Unit 94

94-2

Objectives

• Define both contact measurement and non-contact measurement

• Describe laser measurement and identify the equipment used for measurement

• Explain scanning probe technology• List the advantages of video-

measuring systems

94-3

Measurement: Contact or Noncontact

• Contact measurement – Occurs when measuring probe:

• Touches workpiece at specified points • Remains in constant contact while recording data

points

– Uses touch-trigger probe (TTP) method– Used on CMMs for many years

• Noncontact measurement means no contact or probing of workpiece

94-4

Touch-Trigger Probe Method

• Two dimensional (2D) head systems– Axial mode used for profiling– Radial mode used with contour surfaces

• Three dimensional (3D) probing head– Used for measuring and inspecting convoluted

part surfaces– Where measurements must be made with 3D

movements not in machine axes movements

94-5

Axial-ScanningMode

Z axis is free tomove while theX and Y axes arelocked

94-6

Radial-Scanning

Mode

Z-axis is locked, and the X and Yaxes are free tomove

94-7

3D Probe Head

Capable of simultaneouslymeasuring inthree axes –X, Y, Z

94-8

Optical Comparators

• Light passes through condenser lens and projected against workpiece– Shadow transmitted through projecting-lens

system which magnifies image and projects it onto a mirror

– Image further magnified and reflected to view screen

– Image compared with master form– Vernier protractor screen also available

94-9

Optical Comparators

• Workpiece surface also checked by surface illuminator– Lights up face of workpiece, allowing image to

be projected onto screen

• Magnification depends on lens used– Interchangeable lenses– 5X, 10X, 31.25X, 50X, 62.5X, 90X, 100X, 125X

• Used on small, odd-shaped workpieces

94-10

Laser Measurement

• Gives ability and flexibility of noncontact measuring

• Proving valuable asset

• Used in the following:– Manufacturing for welding, machining, heat

treatment, measuring, inspection, laser marking, and bar coding

94-11

Laser-Tool Measurement

• Allows verification of tool integrity, tool wear compensation, and all other aspects of cutting tools

• Uses high-precision laser beam and photodiode for measuring operations

• CNC machines uses signals generated by system following interruption of laser beam

94-12

Laser Scan Micrometer

• Highly accurate– Accuracy 62 mm and repeatability of 60.15 mm

• Workpiece located in center of laser beam– Creates shadow in path of scanning beam

– Enables unit to determine edges of part

• Uses uniform high-intensity LED (Light-Emitting Diode) light source and HL-CCD (High-speed Linear Charged-Coupled Device)– Signal digitally processed so high speed sampling at rate

of 2400 samples per second

94-13

Laser Scan Microscope

• Two magnifying lenses– Located specific distance apart– Set distance from eye of observer

• Light source used to illuminate sample part

• Have accuracy of ½ millionth of an inch

94-14

Laser Surface-Finish Measurement

• Permits precise, high quality measurement and verification of contours from profile

• Hardware based on laser interferometric probe system– Resolution of 5 nm– Up to 150,000 measuring points captured at

speeds between 0.02 mm/s and 2 mm/s

• Technologies eliminate environmental influences

94-15

Scanning Probes

• Collect large amounts of data in very short time– Analyze and virtually display data

• Noncontact measurement so unaffected by vibration and industrial lighting conditions– Can be used on shop floor where measurements

and corrections made while workpiece still in machine

94-16

Reverse Engineering

• Ability to reproduce parts direction from samples

• Parts scanned using scanning CMMs to probe surface or contour of part to be copied– Can provide hundreds of data points allowing

for better quality part

94-17

Advantages of Video Measuring• Locate randomly oriented parts• Adapt to varying orientations, take

measurements and compare them• Used for measuring, inspection, R&D,

teaching and documentation• Comfortable for use over long periods since

user looking at monitor• Graphical part display provided for

measuring sequences

94-18

Video Microscope

• Starting to replace traditional optical microscopes

• Allow image to be magnified onto large monitors or projected

• Equipped with video output device which can record and permanently store digital images

• Limited by magnification of current video systems

94-19

Video Magnifiers

• Provides means of electronically enhanced optical-image magnification– Small parts with three-dimensional

characteristics

• Magnification range between 4X and 50X (or higher)– Black and white or in color

94-20

Applications Using Video Magnifiers

• In-process inspection

• Quality control

• Examination of engineering prototypes

• ISO training programs

94-21

Advantages of Video Magnifiers

• Monitor screens provide ergonomic benefits

• More than one person can view component

• Reduce inspection time

94-22

Scanning CMMs

• Simple way of automatically collecting large number of data location points– Measure or define shape of object or workpiece

• Coordinate measure machine vital to inspection and measurement

• Equipped with scanning heads– Digitize and create graphical part representation

94-23

Inspection for the Future

• Trend toward nano-technology products– Smaller, lighter, and too fragile to measure

with conventional mechanical contact

• Noncontact scanning will provide ability to perform these operations quickly and accurately with no damage to parts