1. introduction

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

Ref.: OECD(2004), ( ) 는 국가별 수위도시 인구비중

Various Concepts of National Income Gross National Product (GNP)

Gross Domestic Product (GDP)

Net National Product (NNP)/National Income

Personal Income

Definition

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

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

Main thrusts in manufacturing engineering Automation CAD/CAM/CAE/…

Manufacture with higher precision precision engineering

Sustainable Manufacture green growth, green economy, …

Definition

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

Accuracy the degree of closeness of a measured OR calculated quantity to its actual (true) value

Precision the degree of reproducibility

Precision, Accuracy, & Smoothness

High precision, but low accuracy High accuracy, but low precision

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

Bias the difference between the mean value & specified dimension Mathematical expression

dm = L –

where, L = specified (or nominal) dimension, = sample mean

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.

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.

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-

1iii )y(Py

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.

2,(t nafd

,(t af

2i )xx(

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.

1in1 m

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).

,(t af

2,(t nafd

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

Why high precision?

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

Hard disk drive Aluminum alloy disk + magnetic head Rotational speed = 5,200 ~ 7,200 RPM

Hard disk drive RPM is getting higher.

ball bearing air bearing aluminum alloy disk ceramic disk

Boeing B747-200

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.

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.

1. introduction

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