mm 323 man sys 2012 fall 1 introduction
TRANSCRIPT
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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