AE 224 Metrology and Computer Aided Inspection 1

56
AE 224 Metrology and Computer Aided Inspection [CAI] I

Transcript of AE 224 Metrology and Computer Aided Inspection 1

Page 1: AE 224 Metrology and Computer Aided Inspection 1

AE 224

Metrology and

Computer Aided Inspection [CAI]I

Page 2: AE 224 Metrology and Computer Aided Inspection 1

AE 224 Metrology and Computer Aided Inspection

• Syllabus:• Introduction to Metrology • Fundamentals of dimensional Measurement• Length Standards• Application of light Interference for precision measurements• Fits and tolerances• Concepts and practice of gauging• Comparators and their applications• Linear and angular measurements• Thread and gear inspection• Form, flatness, straightness and alignment measurements• Surface metrology• Co-ordinate metrology• Laser applications in metrology; • Vision inspection• Micro and nano metrology.

Page 3: AE 224 Metrology and Computer Aided Inspection 1

AE 224 Metrology and Computer Aided Inspection

Text Books:• Reference Books

Jain R.K., Engineering Metrology, Khanna Publishers.

• Busch., Fundamentals of Dimensional Metrology, Delmar Publishers (1998)

• Shotbolt, C.S. and Galyer. J., Metrology for Engineers,

5th ed., Cassell Publ. (1990).

Page 4: AE 224 Metrology and Computer Aided Inspection 1

AE 224 Metrology and Computer Aided Inspection

Reference Books:• Graham T. Smith., Industrial Metrology, Surface and

Roundness.• D. J. Whitehouse., Handbook of Surface Metrology.• Bala Muralikrishnan, Jay Raja., Computational Surface

and Roundness Metrology.

Page 5: AE 224 Metrology and Computer Aided Inspection 1

Introduction

• What is Metrology?• Quality in Manufacturing.• Why Precision Length Measurements?• Need for reliable Standards.• Standard of Length.• Shop floor standards.• Traceability.

Page 6: AE 224 Metrology and Computer Aided Inspection 1

What is Metrology ?Metro - logy

from Greek 'metron' [measure], and –logy 

Meaning Measurement Science

In English, the term Metrology is often used for Linear Measurements 

Engineering MetrologyIndustrial MetrologyDimensional Metrology

  Manufacturing Metrology

Page 7: AE 224 Metrology and Computer Aided Inspection 1

Quality in Manufacturing

Changing Concepts on quality and their significanceInspection ProductProcess Control ProcessQuality Assurance DesignTQM People & SystemsStrategic Quality Management Product Life

Quality covers all activities from the concept to thefinal disposal of the product.

Page 8: AE 224 Metrology and Computer Aided Inspection 1

Inspection

• Passive - Inspect - Accept - Reject• Active - Inspect - Infer - Act• Dynamic - Inspect – Act

All three modes of inspection are still practiced in industries

Page 9: AE 224 Metrology and Computer Aided Inspection 1

Tolerance and Inspection

• Wide tolerances - Passive Inspection• Medium Tolerances - Active Inspection• Close Tolerances - Dynamic Inspection

• Passive Inspection – Sampling• Active inspection – SQC• Dynamic Inspection – In-process measurement

Page 10: AE 224 Metrology and Computer Aided Inspection 1

Metrology- Applications

Page 11: AE 224 Metrology and Computer Aided Inspection 1

Why Precision Length Measurements?

Majority of manufacturing measurements deal withdimensions which are in linear units.

Though the dimensions are normally given in mms, thetolerances on these dimensions are given inmicrometers and of late even in nanometers.

All measurements are comparisons.Comparison with reference to a standard

Page 12: AE 224 Metrology and Computer Aided Inspection 1

Measurement Accuracies

Measurement accuracies should be better thanthe accuracy expected in the measured entity.As a thumb rule, the measurement accuracyshould be an order better than the measuredvalue.

Page 13: AE 224 Metrology and Computer Aided Inspection 1

Systematic and Random Errors

• Systematic errors are caused by assignable factors such as setting errors, temperature, humidity, …

• Random errors are caused by unknown sources, including human errors.

Page 14: AE 224 Metrology and Computer Aided Inspection 1

Accuracy and Precision

Page 15: AE 224 Metrology and Computer Aided Inspection 1

Measurement Accuracies

1

)(1

2

1

n

xx

n

xx

n

ii

n

ii

Average ------Mean Variation ----- Standard deviation

Page 16: AE 224 Metrology and Computer Aided Inspection 1

Precision of a Measurement device

Page 17: AE 224 Metrology and Computer Aided Inspection 1

Measurement Accuracies

Take an example of a dimension:10mm + 5 mm (tolerance 10 mm)

For checking this we need an accuracy of 1 mm.That instrument is to be calibrated to 0. 1 mmThat in turn has to be calibrated to 0.01mmThat in turn has to be calibrated to 0.001mmAnd so on …………………. …..Where to stop?

Page 18: AE 224 Metrology and Computer Aided Inspection 1

Tolerance Trend

Page 19: AE 224 Metrology and Computer Aided Inspection 1

Length Standards

• Basic Standards of Length – Meter ; Yard• Auxiliary Standards• Shop floor reference• Slip Gauges and accessories

Page 20: AE 224 Metrology and Computer Aided Inspection 1

• 1889 Physical

Meter Standard

Page 21: AE 224 Metrology and Computer Aided Inspection 1

• 1960 Wavelength Wavelength of Krypton- 86

was accepted to define the meter.

1 650 763.73 wavelengths in a vacuum of the radiation of krypton-86 is one Meter

(m)

Meter Standard

Page 22: AE 224 Metrology and Computer Aided Inspection 1

• 1983 In terms of time. New definition of Meter in Seconds!

Meter is the length travelled by light in

1 / 299 792 458 s.

Meter Standard

Page 23: AE 224 Metrology and Computer Aided Inspection 1

Laser Standard

It was also in 1960 that the first laser was constructed and by the mid 1970s lasers were being used as length standards. This is now realized by iodine-stabilized helium-neon lasers.

Page 24: AE 224 Metrology and Computer Aided Inspection 1

Line and End Standards

• In line standard, the distance between two lines marked on it, is the specified length.Original meter was a line standard.

• In End standard, the distance between the ends of a bar or a block is the specified distance.

• Line standards need auxiliary set ups to measure.• End stands need only simple accessories for their

applications.

Page 25: AE 224 Metrology and Computer Aided Inspection 1

Shop floor measurements

Auxiliary Standards:-Length BarsBlock or Slip Gauges

A box of Slip gauges

Reference (‘00’)Calibration (' 0 ')Inspection (‘ I’ )Workshop (‘II’)

Page 26: AE 224 Metrology and Computer Aided Inspection 1

Shop floor measurements

Slip gauge accessories

Page 27: AE 224 Metrology and Computer Aided Inspection 1

Shop floor measurements

Auxiliary Standards:-Length Bars

A box of Length Bars

Page 28: AE 224 Metrology and Computer Aided Inspection 1

Airy Points

• Definition: The best points for supporting a bar horizontally so that the end slopes become zero. If the bar is of length L and there are n supports, the supports should be separated by distance L/sqrt(n2-1). For two support this is 0.5773 L .

Page 29: AE 224 Metrology and Computer Aided Inspection 1

Support points

Page 30: AE 224 Metrology and Computer Aided Inspection 1

Traceability

For international trade there is the need toadhere to the standard scrupulously – especiallywith diminishing tolerances.

This means that all linear measurements doneare to be traceable to the standard of length –the meter.

Page 31: AE 224 Metrology and Computer Aided Inspection 1

Traceability

It is practically impossible to directly refer to the meterfor all measurements. So it is done by reference tosecondary or auxiliary standards which are calibratedwith reference to the standard meter.

Like wise all other measuring instruments are to becalibrated with secondary standards, ensuringtraceability to the meter.

ISO 9000 recommends this.

Page 32: AE 224 Metrology and Computer Aided Inspection 1

Light Interference for Precision Measurements

• Interference of light.• Optical flat.• Simple set-up for interference.• Measurement of length by comparison.• Slip gauge comparison.• Distance measurement using interference.• “Absolute” Measurement of Length. • Laser Interferometer.

Page 33: AE 224 Metrology and Computer Aided Inspection 1

Whitworth’s flat surface generation

Production of Master Surfaces and Squares

Page 34: AE 224 Metrology and Computer Aided Inspection 1

Light Interference

Page 35: AE 224 Metrology and Computer Aided Inspection 1

Principle of Distance Measurement

Page 36: AE 224 Metrology and Computer Aided Inspection 1

Surface and Form Measurements

Page 37: AE 224 Metrology and Computer Aided Inspection 1

Slip Gauge Interferometer

Page 38: AE 224 Metrology and Computer Aided Inspection 1

Laser Interferometer

Page 39: AE 224 Metrology and Computer Aided Inspection 1

Tolerancing

Page 40: AE 224 Metrology and Computer Aided Inspection 1

Fundamental Deviations

Page 41: AE 224 Metrology and Computer Aided Inspection 1

Specifying Fits

Page 42: AE 224 Metrology and Computer Aided Inspection 1

Quality of fits

Page 43: AE 224 Metrology and Computer Aided Inspection 1

Types of Fits

Page 44: AE 224 Metrology and Computer Aided Inspection 1

Hole and Shaft Basis System

Page 45: AE 224 Metrology and Computer Aided Inspection 1

Preferred Fit Families

• For hole tolerances, tolerance zones H7, H8, H9 and H11 are used preferably.

• For shaft tolerances, tolerance zones h6, h7, h9 and h11 are used preferably.

• Preferred Fits • Clearance fits: H11/c11, H9/d9, H8/f7, H7/g6, H7/h6,

C11/h11, D9/h9, F8/h7, G7/h6Transition fits: H7/k6, H7/n6, K7/h6, N7/h6Interference fits: H7/p6, H7/s6, H7/u6, P7/h6, S7/h6, U7/h6

Page 46: AE 224 Metrology and Computer Aided Inspection 1

Standard Fits• Loose Running H11/ c11• Free Running H9/ d9• Loose Running H11/ c11• Easy Running - Good quality easy to do-H8/ f8• Sliding H7/ g6• Close Clearance - Spigots and locations H8 f7• Location/Clearance H7/ h6• Location- slight interference H7/ k6• Location/Transition H7/ n6• Location/Interference- Press fit which can be separated H7/ p6• Medium Drive H7/s6• Force H7/u6

Page 47: AE 224 Metrology and Computer Aided Inspection 1
Page 48: AE 224 Metrology and Computer Aided Inspection 1

Gauges

Plug Gauge

Page 49: AE 224 Metrology and Computer Aided Inspection 1

Gauges

Page 50: AE 224 Metrology and Computer Aided Inspection 1

Gauges

Page 51: AE 224 Metrology and Computer Aided Inspection 1

Adjustable Gap Gauge

Page 52: AE 224 Metrology and Computer Aided Inspection 1

Ring Gauge

Page 53: AE 224 Metrology and Computer Aided Inspection 1

Taylor’s Rules on Gauge Design

Page 54: AE 224 Metrology and Computer Aided Inspection 1

Fundamentals of Linear Measurements

• Abbe Principle• Measuring force and Measurement• Environment• Contact and Non-contact measurement• Measurement and Sensing

Page 55: AE 224 Metrology and Computer Aided Inspection 1

Abbe Principle

• The scale of a linear measuring system should be co-linear with the spatial dimension or displacement to be measured or else the measurement must be corrected for the associated Abbé error.

Page 56: AE 224 Metrology and Computer Aided Inspection 1

Abbe Error