metrology & quality control (mqc) and notes/third year... · metrology and quality control...
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Metrology & Quality Control
(MQC)
TE - Mechanical
Asst. Prof. Rohan R. Ozarkar
RCPIT, Shirpur
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
Metrology and Quality Control (MQC)
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)
Metrology and Quality Control (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
Classification of Method of Measurements
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
Classification of Method of Measurements
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)
Classification of Method of Measurements
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
Classification of Method of Measurements
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
Classification of Method of Measurements
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
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
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.
WringingCare of Slip gauges
Types of Slip gauges
Types Accuracy Flatness
AA (Master Slip gauges)
A (Reference Slip Gauges)
B (Working Sip Gauges)
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.
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
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
Non Precision Linear Measurement
Caliper
Types of Caliper
Firm (fix) Joint Spring TypeInternal External External Internal
Non Precision Linear Measurement
Wire Gauges Screw pitch Gauges
Precision Linear Measurement
CharacteristicsHigh degree of accuracy SensitivityPrecision
Proper calibrationLess wearingMinimum inertia
Fillet Gauges Feeler Gauges
Precision Linear Measurement
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
Precision Linear Measurement
Micrometer The screw is attached to a concentric cylinder or thimble the circumference ofwhich is divided into a number of equal parts.