Metrology & Quality Control (MQC) and Notes/Third Year... · Metrology and Quality Control (MQC) Syllabus details Metrology 1 Metrology Theory (Y) Numerical (N) 2 Design of gauges

Metrology & Quality Control

(MQC)

TE - Mechanical

Asst. Prof. Rohan R. Ozarkar

RCPIT, Shirpur

[email protected]

mailto:[email protected]

Metrology and Quality Control (MQC)

Examination scheme:

MQC

Theory Lab

3 - Credits 1 - Credit

100 - marks 50 - marks

ESE

80

ISE

20

Theory

100

ICA

25

ESE

25

Lab

50

Practical + Oral


Syllabus details

Metrology

1 Metrology Theory (Y)

Numerical(N)

2 Design of gauges & Metrology Theory (Y)

Numerical(Y)

3 Metrology of Screw thread, Gear & recent trend in metrology Theory (Y)

Numerical(Y)

Quality Control

4 Quality control Theory (Y)

Numerical(N)

5 Statistical Quality Control Theory (Y)

Numerical(Y)

Unit - 1

Metrology

Asst. Prof. Rohan Ozarkar

RCPIT, Shirpur

MQC


Unit 1 – Metrology

1 Definition: - ( 1. Measurement, 2. Precision, 3. Accuracy, 4. Sensitivity)Classification of method of measurement

Theory (Y)

Numerical(N)

2 Linear Measurement- Standards ( 1. Line standards, 2. End standards)- Classification of standards- Precision measurement (Precision measuring instruments and their characteristics)- Slip gauge

Theory (Y)

Numerical(N)

3

4.

Straightness, Flatness and Squareness- Surface plates, measurement of straightness- Flatness testing, - Squareness testing, - Roundness testingMachine tool metrology Measurement by light wave interference- (Basic principle, sources of light, optical flats, fringe patterns and their interpretation, testing of flat, convex and concave and irregular surface, checking of slip gauges)

Theory (Y)

Theory (Y)

Numerical(N)

Numerical(N)

Metrology

Metrology is science concerned with establishment, reproduction, conversion and transfer of units

of measurement and their standard.

Definition

Metrology is science concerned with measurement and includes both theoretical and practical

problems with reference to measurement, whatever their level of accuracy and what ever field of

science and technology they occur.

Definition [BS 5233:1975]

Metrology

(Greek word)

Metro - Measurement

Logy – study of

Metrology

Types of metrology

Scientific Metrology

Industrial Metrology

Legal Metrology

Fundamental Metrology

Develop & Maintain standardseg- Lab ,preservation

Function / Testingeg – workshop, production line

Transparencyeg – weight, petrol

11 basic quantitiesMass, electricity, length, time, frequency,

thermometry, ionizing radiation & radioactivity, amount of substance, etc.

Need of inspection

1. Establishment of standards

2. Meet interchangeability

3. Reduced scrap and wastage

4. Improve quality (raw material, product, etc.)

5. Reduced rejection percentage

6. Find out shortcoming

Measurements

Terminology of Measurement

Measurand Reference Comparator

Quantity to measuredeg- length

To which comparison is madeeg – scale

Device for comparingeg – eye

Measurement is defined as process of numerical evaluation of dimension or the process ofcomparison with standard measuring instrument.

Definition

Classification of Method of Measurements

1. Direct method

2. Indirect method

3. Absolute (Fundamental) method

4. Comparison method

5. Substitution method

6. Coincidence (differential) method

7. Transportation method

8. Deflection method

9. Complementary method

10.Null measurement method


Direct Method

• Simple method

• Value is directly measured (without calculation)

• Contact & non-contact type

• eg- Scale, protector.

Indirect Method

• Obtain by measuring other quantities

• eg- angle by sine bar, density (with mass & volume)

• eg- Weight = Length x Width x Height x Density


Comparison method

• Quantity compared with known value

• Deviation from master gauge is measured

• eg- Comparators (dial gauge)

Absolute (Fundamental) method

• Measure particular quantity with base (defined)

quantity

• It directly in related with the definition

• eg- length w.r.t. length (m, yd)


Coincidence (differential) method

• Very small difference between measuring &

reference value

• Measurement coincides with certain lines

• eg- Micrometer (LC & circular scale reading)

Deflection method

• Quantity measured is directly indicated by deflection

of pointer on scale

• eg- Dial indicator for pressure measurement


Complementary method

• The value of quantity to be measured is combined

with known value of the same quantity

• eg- Volume determination by liquid displacement

Transportation method

• Value of the quantity to be measured is first

balanced by an initial known value A of the same

quantity ; next the value of the quantity to be

measured is put in the place of that known value

and is balanced again by a second known value B.

• eg- determination of a mass by means of a

balance and known weights


Contact method

• Sensor/Measuring tip touch the surface area

• eg- length w.r.t. length (m, yd)

• eg- sensors

Null measurement method

• Type of differential measurement

• Difference between measured and known value is

zero.

• eg- Potentiometer

Measuring Instruments

Classification of Measuring Instrument

On basis of function

Length

Angle

Surface roughness

Geometrical form checking

On basis of accuracy

Most accurate

Moderate accurate

Below moderate

On basis of precision

Precision

Non-precision

Factors affecting accuracy of measuring Instrument

• Standard of calibration• Work piece control• Inherent characteristics of measuring instruments (Range)• Inspector (Human factor)• Environmental factor

Accuracy

Accuracy is closeness of agreement between independent test results and accepted referencevalue.

Definition (ISO-5725)

Accuracy is agreement of measured value with true value of measured quantity.

Definition

Precision

Precision is closeness of agreement between independent test results obtained understipulated condition.

Definition (ISO-5725)

Precision is repeatability of measuring process. It includes to what extent the identicallyperformed measurements agree with each other.

Definition

Accuracy and Precision

Accuracy

• Closeness with true value

• One reading

Precision

• Closeness of measured values with each other

• More than one ding compared with each other

Figure Precision Accuracy

a Low Low

b Low High

c High Low

d High High

Sensitivity

Sensitivity of instrument denotes the smallest change in value of measured variable to whichinstrument respond.

Definition

Sensitivity is the ratio of scale spacing to scale division value.

Definition

Amplification factor or gear ratio

Load Cell

Force, F

Output, Vo

Output, Vo (V)

Input, Fi (kN)

Slope = Vo/F

V/kN

Error

Sensitivity of instrument denotes the smallest change in value of measured variable to whichinstrument respond.

Definition

Types of errors

Absolute Error

True Absolute ErrorApparent Absolute

Error

Relative Error Percentage Error

ErrorTypes of errors

Static Error

Reading Error

Parallax error

Interpolation Error

Alignment (Cosine) Error Characteristic Error

Environmental Error

Loading Error Dynamic Error

Controllable

(Systematic) Error

Calibration Error

Stylus pressure

Error

Avoidable Error

Random (Non-

consistent) Error

Standard

System of measurement

FPS System Metric SystemInternational

System of Units (SI)

Quantity to measuredeg- length

To which comparison is madeeg – scale

Device for comparingeg – eye

A standard is define as a something that is set up and established by authority as a rule for themeasurement of a quantity, weight, value or quality

Definition

History of Measurement

3000 BC – Cubit – in Egypt (CUBIT = to the length of forearm (from the elbow to the tip of the middle figure)Rapid development made in engineering during the 19th century ere due to improvedmaterials available and more accurate measuring techniques developed.

It was not until 1855 that first accurate standard was made in England. It was knownas Imperial standard Yard.

Other one is International Prototype Meter. These two are material standard.In contrast to these two wavelength standards adopted as length standard later on

Type of Standard

Types of Standard

Line Standard End Standard Wavelength Standard

Distance between inscribed lines on bar

eg- meter, yard

Distance between two flat parallel faces

eg- End bar, micrometer

Wavelength of monochromatic light is used

eg- Krypton-86

Slip Gauges / Gauge block

Precision Linear Measurement

Slip Gauges Slip gauges are rectangular blocks of high grade steel with exceptionally closetolerance.Also called as Gauge blocks or Johanson Gauges.They are hardened (800 HV) for maximum wear resistance.They made of tungsten carbide and finished by high grade lapping.

Terminology

d X W = cross-section area= 9 mm x 30-35 mm



WringingCare of Slip gauges

Types of Slip gauges

Types Accuracy Flatness

AA (Master Slip gauges)

A (Reference Slip Gauges)

B (Working Sip Gauges)



DismantlingCare of Slip gauges

Grades of Slip gauges (Accuracy)

Grades Purpose

Grade 00 Reference ( Standard room)

Grade 0 Inspection (Setting Comparator)

Grade k Calibration

Grade 1 Inspection (Setting Sine bar)

Grade 2 Workshop ( setting machine tool)

Slip Gauges

Slip Gauges


Set of Slip Gauges

Linear Measurement

Types of Linear Measurement Instrument

According to contact

Direct Measuring

Graduated Non-Graduated

Indirect Measuring

According to precision

Non-Precision Precision

Length, diameter, thickness, Height

Scale, Vernier calipers

Calipers, Straight edges

Scale, Calipers Vernier, Micrometer instruments

Non Precision Linear Measurement

Scale

Types of Scale

Narrow tempered steel rule

Short rule with holder

Angular Rule

Steel measuring tape


Caliper

Types of Caliper

Firm (fix) Joint Spring TypeInternal External External Internal


Combination Set


Wire Gauges Screw pitch Gauges


CharacteristicsHigh degree of accuracy SensitivityPrecision

Proper calibrationLess wearingMinimum inertia

Fillet Gauges Feeler Gauges


Vernier Caliper When two scales (main and auxiliary scales) or division slightly different in size areused, the difference between them can be utilized to enhance the accuracy ofmeasurement


Vernier Caliper


Vernier Caliper


Types Vernier Caliper






Micrometer The screw is attached to a concentric cylinder or thimble the circumference ofwhich is divided into a number of equal parts.


Micrometer


Types Micrometer

Inside MicrometerDepth Micrometer

Venire Micrometer


Types Micrometer

Screw thread Micrometer

Digital Micrometer

Dial Micrometer

Documents

Metrology & Quality Control (MQC) and Notes/Third Year... · Metrology and Quality Control (MQC) Syllabus details Metrology 1 Metrology Theory (Y) Numerical (N) 2 Design of gauges