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MM 323 MANUFACTURING SYSTEMS

INTRODUCTION

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What is Manufacturing?

The word manufacture is derived from two Latin wordsmanus (hand) and factus (make); the combination

means made by hand

Made by hand accurately described the fabrication

methods that were used when the English wordmanufacture was first coined around 1567 A.D.

Most modern manufacturing operations are

accomplished by mechanized and automated

equipment that is supervised by human workers

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Manufacturing System Defined

A collection of integrated equipment and human resources,

whose function is to perform one or more processing

and/or assembly operations on a starting raw material,

part, or set of parts

Equipment includes

Production machines and tools

Material handling and work positioning devices

Computer systems

Human resources are required either full-time or periodically

to keep the system running

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Manufacturing Systems in the Production

System

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Components of a Manufacturing System

1. Production machines

2. Material handling system

3. Computer system to coordinate and/or control the

preceding components4. Human workers to operate and manage the system

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Examples of Manufacturing Systems

Single-station cells

Machine clusters

Manual assembly lines

Automated transfer linesAutomated assembly systems

Machine cells (cellular manufacturing)

Flexible manufacturing systems

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Example for Single-station cells

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Manufacturing - Technologically

Manufacturing

as a technical

process

Application of physical and chemical processes toalter the geometry, properties, and/or appearance

of a starting material to make parts or products

Manufacturing also includes assembly

Almost always carried out as a sequence ofoperations

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Manufacturing - Economically

Manufacturing

as an economic

process

Transformation of materials into items of greatervalue by means of one or more processing and/or

assembly operations

Manufacturing adds value to the material by

changing its shape or properties, or by combiningit with other materials

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Manufacturing Capability

A manufacturing plant consists ofprocesses andsystems (and people, of course) designed to

transform a certain limited range of materials

into products of increased value

The three building blocks - materials,processes, and systems - are the subject of

modern manufacturing

Manufacturing capability includes:

1. Technological processing capability2. Physical product limitations

3. Production capacity

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Limitations and Capabilities of a

Manufacturing Plant

Manufacturing capability- the technical and physical

limitations of a manufacturing firm and each of its plants

Three dimensions of manufacturing capability:

1. Technological processing capability - the available set ofmanufacturing processes

2. Physical size and weight of product

3. Production capacity (plant capacity) max production

quantity that can be made in a given time under assumed

operating conditions

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1. Technological Processing Capability

The available set of manufacturing processes inthe plant (or company)

Certain manufacturing processes are suited to

certain materials

By specializing in certain processes, theplant is also specializing in certain materials

Includes not only the physical processes, but

also the expertise of the plant personnel

Examples: A machine shop cannot roll steel

A steel mill cannot build cars

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3. Production Capacity

Defined as the maximum quantity that a plantcan produce in a given time period (e.g.,

month or year) under assumed operating

conditions

Operating conditions refer to number ofshifts per week, hours per shift, direct labor

manning levels in the plant, and so on

Usually measured in terms of output units,

such as tons of steel or number of cars

produced by the plant

Also calledplant capacity

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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

A processing operation transforms a work material from one state of

completion to a more advanced state using energy to alter its shape,

properties or appearance to add value to the material.

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Manufacturing Processes

Manufacturing processes Converts unfinished materials to finished products

Often is a set of steps

Machine tool is an assembly that produces a desired result

Two basic types:

1. Processing operations - transform a work material from one

state of completion to a more advanced state

Operations that change the geometry, properties, orappearance of the starting material

2. Assembly operations - join two or more components to

create a new entity

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Classification of manufacturing processes

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Processing Operations

Alters a materials shape, physical properties, orappearance in order to add value

Three categories of processing operations:

1. Shaping operations - alter the geometry of the

starting work material2. Property-enhancing operations - improve

physical properties without changing shape

3. Surface processing operations - to clean,

treat, coat, or deposit material on exteriorsurface of the work

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Shaping Processes Four Categories

1. Solidification processes - starting materialis a heated liquid or semifluid

2. Particulate processing - starting material

consists of powders

3. Deformation processes - starting materialis a ductile solid (commonly metal)

4. Material removal processes - starting

material is a ductile or brittle solid

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Solidification Processes

Starting material is heated sufficiently totransform it into a liquid or highly plastic state

Examples: metal casting, plastic molding

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Particulate Processing

Starting materials are powders of metals orceramics

Usually involves pressing and sintering, in

which powders are first compressed and then

heated to bond the individual particles

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Deformation Processes

Starting workpart is shaped by application offorces that exceed the yield strength of the

material

Examples: (a) forging, (b) extrusion

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Material Removal Processes

Excess material removed from the starting pieceso what remains is the desired geometry

Examples: machining such as turning, drilling,

and milling; also grinding and nontraditional

processes

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Waste in Shaping Processes

Desirable to minimize waste in part shaping Material removal processes are wasteful in

unit operations, simply by the way they work

Most casting, molding, and particulate

processing operations waste little material Terminology for minimum waste processes:

Net shape processes - when most of the

starting material is used and no

subsequent machining is required Near net shape processes - when

minimum amount of machining is required

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Property-Enhancing Processes

Performed to improve mechanical or physicalproperties of work material

Part shape is not altered, except

unintentionally

Example: unintentional warping of a heattreated part

Examples:

Heat treatment of metals and glasses

Sintering of powdered metals and ceramics

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Surface Processing Operations

Cleaning - chemical and mechanicalprocesses to remove dirt, oil, and other

contaminants from the surface

Surface treatments - mechanical working

such as sand blasting, and physicalprocesses like diffusion

Coating and thin film deposition - coating

exterior surface of the workpart

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Other Factory Operations that require new sytems

Material Handling and

Storage Systems

Inspection and testing Systems

Coordination and control Systems

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Inspection and Testing

Inspection and testing are generally considered part ofquality control. The purpose of inspection is to determine

whether the manufactured product meets the established

design standards and specifications. For example,

inspection examines whether the actual dimensions of a

mechanical part are within the tolerances indicated on theengineering drawing for the part.

Testing is generally concerned with the functional

specifications of the final product rather than the individualparts that go into the product. For example, final testing of

the product ensures that it functions and operates in the

manner specified by the product designer.

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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 or under

conditions that might occur during operation

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Hardness testing equipments

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Measurement by a gage

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A tensile testing machine

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An ultrasonic testing device

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Computer Control System

The control function in manufacturing includes both theregulation of individual processing and assembly

operations, and the management of plant-level activities.

Control at the process level involves the achievement ofcertain performance objectives by proper manipulation of

the inputs to the process.

Control at the plant level includes effective use of labor,

maintenance of the equipment, moving materials in thefactory, shipping products of good quality on schedule,

and keeping plant operating costs at the minimum level

possible.

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Manufacturing control

Manufacturing control is concerned with managingand controlling the physical operations in the factory to

implement the manufacturing plans. The flow of

information is from planning to control. Information also

flows back and forth between manufacturing control andthe factory operations.

Included with the control function are shop floor control,

inventory control, quality control, and various othercontrol activities. Process control is also included if the

plant uses automatic process control in its operations.

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Shop Floor Control

Shop floor control is concerned with the problem of monitoring the

progress of the product as it is being processed, assembled, moved, andinspected in the factory. The sections of a traditional production planning

and control department that are involved in shop floor control include

scheduling, dispatching, and expediting. Production scheduling isconcerned with assigning start dates and due dates to the various parts

(and products) that are to be made in the factory. This requires that theparts be scheduled one by one through the various production machines

listed on the route sheet for each part. Based on the production schedule,

dispatching involves issuing the individual work orders to the machineoperators to accomplish the processing of the parts. The dispatching

function is performed in some plants by the shop foremen, in other plantsby a person called the dispatcher. Even with the best plans and

schedules, things sometimes go wrong (e.g., machine breakdowns,

improper tooling, parts delayed at the vendor). The expeditercomparesthe actual progress of a production order against the schedule. For orders

that fall behind, the expediter attempts to take the necessary correctiveaction to complete the order on time.

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Inventory control

Inventory control attempts to strike a properbalance between the danger of too little inventory (with

possible stock-outs of materials) and the expense of

having too much inventory. Shop floor control is also

concerned with inventory in the sense that the materialsbeing processed in the factory represent inventory

(called work-in-process).

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Quality control

Quality control assures that the quality of theproduct and its components meet the standards

specified by the product designer. To accomplish

its mission, quality control depends on the

inspection activities performed in the factory at

various times throughout the manufacture of the

product. Also, raw materials and components from

outside sources must be inspected when they arereceived. Final inspection and testing of the

finished product is performed to ensure functional

quality and appearance.

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Computer Control System

Typical computer functions in a manufacturingsystem:

Communicate instructions to workers

Download part programs to computer-controlled

machines Control material handling system

Schedule production

Failure diagnosis when malfunctions occur

Safety monitoring Quality control

Operations management