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© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
In an industrialized nation, manufacturing is the main wealth creating activity.
About 1/3 of the value of all goods & services produced in a nation
Manufacturing
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Definition
Ref.: OECD(2004), ( ) 는 국가별 수위도시 인구비중
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Various Concepts of National Income Gross National Product (GNP)
Gross Domestic Product (GDP)
Net National Product (NNP)/National Income
Personal Income
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
GNP ( 국민 총 생산 ) The total money value of all final goods & services produced by the residents of a country in one year period
GNP = C + I + G + (X – M) C = Consumption Expenditure
I = Investment
G = Government Expenditures
X – M = Net Exports
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
GDP ( 국내 총 생산 ) The total market value at current prices of all final goods & services produced within a year by the factors of production located within a country
Distinction between GDP and GNP GDP = GNP – Net Foreign Income from Abroad
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Main thrusts in manufacturing engineering Automation CAD/CAM/CAE/…
Manufacture with higher precision precision engineering
Sustainable Manufacture green growth, green economy, …
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Various Definitions Precision engineering may be broadly defined as work
at the forefont of current technology, implicitly in the field of metrology and manufacturing technology [McKeown].
The achievement of dimensions & tolerances in the order of 0.01 mm and surface roughness of 0.001 mm (1 nm)
Any technology related to features of nanometer scale: thin film, fine particles, chemical synthesis, advanced microlithography, and so forth [Drexler].
The technology of manufacture to dimensions or tolerances in the range of 0.1 – 100 nm (from the size of the atom to the wavelength of light) [Franks].
Definition
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Accuracy the degree of closeness of a measured OR calculated quantity to its actual (true) value
Precision the degree of reproducibility
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
High precision, but low accuracy High accuracy, but low precision
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Suppose you machine a certain dimension of a part to length L.
machine with a machine tool
measure the machined parts with a sufficiently accurate instrument
plot the results as the frequency distribution
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
_
y_
y
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Bias the difference between the mean value & specified dimension Mathematical expression
dm = L –
where, L = specified (or nominal) dimension, = sample mean
_
x_
x
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Probability Distribution The probability distribution of a discrete random variable (r.v.)
a list of probabilities associated with each of its possible values
The probability density function of a continuous r.v.
a function which can be integrated to obtain the probability that
the r.v. takes a value in a given interval.
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Probability Distribution A random variable is a function that associates a unique
numerical value with every outcome of an experiment. A coin is tossed ten times. The r.v. X is the number of tails that are
noted. X can only take the values 0,1,....,10, so X is a discrete r.v. A light bulb is burned until it burns out. The r.v. Y is its lifetime in
hours. Y can take any positive real value, so Y is a continuous r.v.
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Population mean, m the mean of a probability distribution (=population) Mathematically y continuous
y discrete
m = E(y), where, E = expected value operator.
Sample mean, A point estimator of a population mean (=the mean of a sam-
ple)
nx
x i_
m
n
1iii )y(Py
)y(yf
Precision, Accuracy, & Smoothness
_
x
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Accuracy,
= t-distribution value when the degree of freedom is
f = n-1 and the probability is (1-a).
n = the sample size (i.e. number of data points used)
a = the significance level
n = the unbiased variance a non-negative number which gives an idea of how widely spread the values of the random variable are likely to be.
nx)
2,(t nafd
d
)2
,(t af
n
1i
2i )xx(
1n1n
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Unbiased The long-run average or expected value of the point estimator should be the parameter that is being estimated.
E( ) = = = = = m
∴ is an unbiased estimator of m.
y
n
yE
n
1ii
n
1iiyE
n1
n
1iiyE
n1
n
1in1 m
y
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Example If we take n = 21 and n = 4 mm2 with a = 0.05 = 95% reliability,
= ?
∴ = 0.192 mm.
The accuracy of the machining process is evaluated as 0.192 mm with a probability of 0.95 (or 95% reliability).
)2
,(t af
nx)
2,(t nafd
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Precision, e
measured by how small the dispersion e is from the mean value Mathematically
Example
= 4.18 mm.
this machining process has a precision of 4.18 mm with a probability of 0.95.
nafe x)2
,(t
nafe x)2
,(t
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
_
y_
y
Why high precision?
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
State of Current Technology PE is the science underlying the manufacture of high precision
machinery. Traditional precision machines: watches and cameras Computers and their peripheral equipments Video equipments Aerospace equipments, measuring equipments (including astro-
nomical telescopes, etc.) High precision machine tools Telecommunication devices
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Hard disk drive Aluminum alloy disk + magnetic head Rotational speed = 5,200 ~ 7,200 RPM
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Hard disk drive RPM is getting higher.
ball bearing air bearing aluminum alloy disk ceramic disk
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Boeing B747-200
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
a = 0.3~1.0 mm ± 0.02 mm
q = 5°
Plane-reflection type diffraction grating The critical component of spectroscope A spectroscope is a device that lets us find out what things
are made of. It works by taking light and splitting it up into its component colors.
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Shaper-type ruling engine engraves grooves spaced at 600 to 1200 lines per mm.
= 83 grooves onto the width of a hair, about 100 mm. accumulated pitch error must not exceed 0.2 mm for 1200
grooves.
Precision, Accuracy, & Smoothness
© 2008-2015 Young-Woo Park
Pre
cisi
on E
ngin
eerin
gDepartment of Mechatronics Engineering CHUNGNAM NATIONAL UNIVERSITY
Precision, Accuracy, & Smoothness