cim - course notes - chapter 2

7/29/2019 CIM - Course Notes - Chapter 2

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Part I Overview of Manufacturing

Chapter 2 Manufacturing Operations

Manufacturingcan be defined as the application of physical

and chemical processes to alter the geometry, properties,

and appearance of a given starting material to make parts

or products; manufacturing also includes the joining ofmultiple parts to make assembled products.

The processes that accomplish manufacturing involve a

combination ofmachinery, tools, power, and manual labor.

Manufacturingis carried out as a sequence of operations.Each successive operation brings the material closer to the

desired final state.


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Chapter 2 Manufacturing OperationsDefinition of manufacturing as a technological process


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Chapter 2 Manufacturing OperationsDefinition of manufacturing as an economic process


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2.1 MANUFACTURING INDUSTRIES AND PRODUCTS

Manufacturing industries

Industry consists of enterprises and organizations that produce and/or

supply goods and/or service (primary, secondary and tertiary industries).

Primary industries:They cultivate and exploit natural resources, such as agriculture and mining.

Agriculture, forestry, fishing, livestock, quarrying, mining, petroleum


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Secondary industries:

They convert the outputs of the primary industries into products.

Manufacturing is the principal activity in this category, but second

industries also include construction and power utilities.

Aerospace, apparel, automotive, basic metals, beverages, building

materials, chemicals, computers, construction, consumer appliances,

electronics, equipment, fabricated metals, food processing, glass,

ceramics, heavy machinery, paper, petroleum refining, pharmaceuticals,

plastics (shaping), power utilities, publishing, textiles, tire and rubber,

wood and furniture


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Tertiary industries:

They constitute the service sector of economy.

Banking, communications, education, entertainment, financialservices, government, health and medical, hotels, information,

insurance, legal services, real estate, repair and maintenance,

restaurants, retail trade, tourism, transportation, wholesale trade


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2.1 MANUFACTURING INDUSTRIES AND PRODUCTSInternational Standard Industrial Classification (ISIC) Codes

ISIC Code

Food, beverages, tobacco 31

Textiles, apparel, leather and fur products 32

Wood and wood products, cork 33 Paper, printing, publishing, bookbinding 34

Chemicals, coal, petroleum, & their products 35

Ceramics, glass, mineral products 36

Basic metals, e.g., steel, aluminum 37

Fabricated products, e.g., cars, machines, etc. 38

Other products, e.g., jewelry, toys 39


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Continuous production

It occurs when the production equipment is used exclusively for the

given product, and the output of the product is uninterrupted.


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Batch production

It occurs when the materials are processed in finite amounts or

quantities. The finite amounts or quantity of material is called a batch.


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Manufactured products

Manufacturing industries with their discrete products

(ISIC codes 38 and 39)


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Final products

Final products can be divided into two major classes:

Consumer goods Purchased directly by consumers such as cars,

computers, TVs, tires, toys, etc.

Capital goods Purchased by other companies to produce goods andsupply services, e.g., commercial aircraft, mainframe

computers, machine tools, railroad equipment and

construction machinery.

There are also companies in industry whose business is primarily toproduce materials, components and supplies for the companies that

make the final products, e.g., sheet steel, bar stocks, metal stampings,

machined parts, plastic moulding, cutting tools, lubricant, etc.


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2.2 MANUFACTURING OPERATIONS

Basic activities

There are certain basic activities that must be carried

out in a factory to convert raw materials into finished

products.

For discrete products:1. Processing and assembly operations

2. Material handling

3. Inspection and testing

4. Coordination and control

The first three activities are considered as physical

activities.


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2.2.1 Processing and Assembly Operations

Manufacturing processes can be divided into two basic types:

(1) Processing operations

A processing operation transforms a work material from

one state of completion to a more advanced state that iscloser to the final desired part or product.

(2) Assembly operations

An assembly operation joins two or more components tocreate a new entity, which is called an assembly or

subassembly.


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Classification of manufacturing processes


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Processing operations

Shaping operations

1. Solidification processes

2. Particulate processing

3. Deformation processes

4. Material removal processes

Property-enhancing operations (heat treatments)

Surface processing operations

Cleaning and surface treatments

Coating and thin-film deposition


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Processing operations Shaping operationsFour categories in terms of the state of the starting

material:

Solidification processes

Casting, moulding Particulate processing

Powder metallurgy, sintering, hot isostatic pressing

Deformation processesForging, extrusion, rolling, drawing, forming, bending

Material removal processesMachining such as turning, drilling, milling, grinding, nontraditional

processes based on lasers, electron beams, chemical erosion, electric

discharge, electrochemical energy


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2.2.1 Processing and Assembly OperationsProcessing operations Property-enhancing operations

These operations are designed to improve mechanical or

physical properties of the work material Heat treatments.

Sintering of powered metals and ceramics is also a heat

treatment.These operations do not alter part shape except

unintentionally in some cases, e.g., warping of a metal part

during heat treatment or shrinkage of a ceramic part during

sintering.


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2.2.1 Processing and Assembly OperationsProcessing operations Surface processing operations

Cleaning

Chemical and mechanical processes to remove dirt, oil and

other contaminants

Surface treatmentMechanical working such as shot peening and sand blasting,

and physical process such as diffusion and ion implantation

Coating and thin film deposition

Electroplating, anodizing, thermal spray, slurry/sintering,physical vapor deposition, chemical vapor deposition


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Assembly operations

Joining processes

Welding

Brazing and soldering

Adhesive bonding

Mechanical assembly

Threaded fasteners (e.g., bolts and nuts, screws)

Rivets

Interference fits (e.g., press fitting, shrink fits)

Other


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2.2.2 Other Factory Operations

Material handling and storage

Moving and storing materials between processing and/or

assembly operations

Inspection and testingQuality control activities, e.g., dimension tolerance

Coordination and control

Regulation of individual processing and assembly operations

and management of plant level activities


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Time spent in material handling


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Inspection and testing

Inspection Examination of the product and its

components to determine whether they

conform to design specifications

Inspection for variables Measuring

Inspection of attributes Gaging

Testing Observing the product (or part, material,

subassembly) during actual operation orunder conditions that might occur during

operation


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Coordination and control

Regulation of individual processing and assembly

operations

Process control

Quality control Management of plant level activities

Production planning and control

Overall quality control


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2.3 PRODUCTION FACILITIES

A manufacturing company attempts to organize its

facilities in the most efficient way to serve the particular

mission of the plant.

Certain types of plants are recognized as the most

appropriate way to organize for a given type of

manufacturing.

The most appropriate type depends on:

Types of products made

Production quantity

Product variety


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2.3 PRODUCTION FACILITIES

Product variety

Number of different product or part designs or types

produced in the plant

Inverse relationship between production quantity and

product variety in factory operations

The higher the product variety, the lower the production quantity.

Product variety classification:

Hard product variety

Products differ greatly, few common components in an

assembly Soft product variety

Small differences between products, many common

components in an assembly


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2.3.1 Low Production Quantity

Job shop Make low quantities of specialized and

customized products (1 to 100 unit/year)

Also include production of components for these products

Products are typically complex (e.g., specialized machinery,

prototypes, space capsules)

Equipment is general purpose.

Plant layouts:

Fixed position

Process layout


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Fixed-position layout


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Process layout


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2.3.2 Medium Production Quantities

1. Batch production A batch of a given product is

produced, and then the facility is changed over to

produce another product

Changeover takes time Setup time Typical layout Process layout

Hard product variety

2. Cellular manufacturing A mixture of products is made

without significant changeover time between products Typical layout Cellular layout

Soft product variety


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2.3.2 Medium Production Quantities

Cellular layout


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2.3.3 High Production

Quantity production Equipment is dedicated to the

manufacture of one product.

Standard machines tooled for high production (e.g.,

stamping presses, molding machines) Typical layout Process layout

Flow line production Multiple workstations arranged in

sequence

Product requires multiple processing or assembly steps.

Product layout is most common.


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2.3.3 High Production

Product layout


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Relationships between plant layout and type of

production facility


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2.4.1 Production Quantity and Product Variety

Q = Production quantity, the number of units of a given part

or product that are produced annually by a plant

P= Product variety

j= Identifier of each part or product styleQj= Annual quantity of stylej

Total number of product units =

Product variety

Hard product variety = Differences between products

Soft product variety = Differences between models of

products

P

j

jf QQ1


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P1 = Number of distinct product lines produced by the plant

Represents hard product variety

P2 = Number of models in a product line

Represents soft product variety

The total number of product models is given by

where the subscriptjidentifies the product line,j= 1, 2, , P1.

1

1

2

P

j

jPP


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Example 2.1

Product Lines and Product Models

A company specializes in home entertainment products. It

produces only TVs and audio systems. In its TV line it offers

15 different models, and in its audio line it offers 5 models.

What is the totality of product models?

Solution


20515

1

1

2

P

j

jPP


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2.4.2 Product and Part Complexity

Qualitative and quantitative aspects

Product and part complexity

For assembled products, the more parts, the more

complex the product is.

For manufactured components, a possible measure

of part complexity is the number of processing steps

required to produce the component.

Product complexity np = Number of parts in product

Part complexity no = Number of operations per part


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Typical number of processing operations required to fabricate various parts


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Production plants distinguished by np

and no

values


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The total number of products made annually in a plant is the

sum of the quantities of individual products. The total number

of parts manufactured by the plant per year is

where Pis the total number of different part or product styles;

Qj is the annual quantity of product stylej; npj is the number

of parts in productj.

pj

P

j

jpf nQn

1


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The total number of processing operations performed by the

plant is

where nojk is the number of processing operations for each

part k, assumed over the number of parts in productj, npj.

The parameternofprovides a numerical value for the total

activity level in the plant.

p jn

kojkpj

P

jjof nnQn 11


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pjn

k

ojkpj

P

j

jof nnQn11

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2

3

3

3

4352

5

2

2210

Product 1 (Quantity = 10) and Product 2 (Quantity = 5)

Product 1 2 parts (Part 1 2 operations, Part 2 5 operations)

Product 2 3 parts (Part 1 4 operations, Part 2 3 operations,

Part 3 2 operations)

operations


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Simplified for purposes of conceptualization:

Assume that the number of products Pare in equal quantities Q ,

all products have the same number of components np, and all

components require an equal number of processing steps no.

Total number of product units Qf= PQ

Total number of parts produced npf= PQnp

Total number of operations nof= PQnpno


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Example 2.2

A Production System Problem

Suppose a company has designed a new product line and is planning to build a

new plant to manufacture this product line. The new line consists of 100 differentproduct styles, and for each product type the company wants to produce 10000

units annually. The products average 1000 components each, and the average

number of processing steps required for each component is 10. All parts will be

made in the plant. Each processing step takes an average of I min. Determine

(a) how many products, (b) how many parts, and (c) how many productionoperations will be required each year, and (d) how many workers will be needed

for the plant, if it operates one eight-hour shift for 250 day/yr and one worker

works on one machine?


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Solution(a) The total number of units to be produced by the plant is

Q = PQ = 100 10000 = 106 products annually

(b) The total number of parts produced is

npf= PQnp = 106

1000 = 109

parts annually(c) The number of distinct production operations is

nof= PQnpno = 109 10 = 1010 operations

(d) The total time to be used to perform these operations is

H= 1010 1/60 = 1.67 108 hr

If each worker works 2000 hr/yr (250 day/yr 8 hr/yr), then the total

number of workers required is

workers833332000

1067.18

w


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2.4.3 Limitations and Capabilities of a Manufacturing Plant

Manufacturing capability - Technical and physical

limitations of a manufacturing firm and each of its plants

Three dimensions of manufacturing capability:

1. Technological processing capability - Available set ofmanufacturing processes

2. Physical size and weight of product

3. Production capacity (plant capacity) - Production quantity

that can be made in a given time. Plant capacity is often

measured in terms of output units such as annual tons of

steel produced by a steel mill, or number of cars produced

by a final assembly plant.


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2.5 LEAN PRODUCTION

Definition: Operating the factory with the minimum possible

resources and yet maximizing the amount of work

accomplished

Resources include workers, equipment, time, space,materials

Complete products in the minimum possible time and

achieve a very high quality level to completely satisfy the

customer In short, lean production means doing more with less, and

doing it better.


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2.5 LEAN PRODUCTION

Manufacturing activities can be divided into three

categories:

Value-adding activities

Contribute value to the work unit, including processing and assembly

operations that alter the part or product in a way towards the need of the

customer

Auxiliary activities

Support the value-adding activities but do not themselves contribute value

to the part or product Wasteful activities

Do not add value nor do they support the value adding activities. If not

performed, there would be no adverse effects on the product.


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2.5 LEAN PRODUCTION

The programs associated with lean production are

the following:

Just-in-time delivery of parts

Worker involvement Continuous improvement

Reduced setup times

Stop the process when something is wrong

Error prevention

Total productive maintenance

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