cycle time calculation-unit_16_product_design_and_cadcam.pdf

7/27/2019 Cycle time calculation-unit_16_product_design_and_cadcam.pdf

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16. Product Design and CAD/CAM

16.1 Unit Introduction16.2 Unit Objectives16.3 Product Design and CAD

16.4 CAD System Hardware16.5 CAM, CAD/CAM, and CIM16.6 Unit Review16.7 Self Assessment Questions16.8 Self Assessment Answers

16.1 Introduction

Product design serves an important function in the production system. It helpsdetermine the eventual commercial success of a product; it determines how theproduction system should be created, and exactly what equipment should be

bought; and it determines how easily, and how cheaply, the product can bemanufactured. The manufacturing support system contains procedures andsystems used to manage production and solve the technical and logisticalproblems associated with designing the products, planning the processes,ordering the materials, controlling work-in-process as it moves through the plant,and delivering products to customers. Product design and its associated use ofcomputer-aided design/computer-aided manufacturing (CAD/CAM) systems,represents one of the most important aspects of the manufacturing supportsystem. In CAD/CAM , both design and manufacturing are tightly integrated intoa continuum of activities. Continuing the integration, we have ComputerIntegrated Manufacturing (CIM), which includes CAD/CAM, but also extends to

embrace the business functions of a manufacturing firm.

In this unit a discussion and definition of product design and CAD are given,where an analysis of the design process and the actual application of computer-aided design principles are highlighted. CAD system hardware is reviewed (seeFigure 16.1), before a general introduction to CAM, together with its relationshipwith CAD, and how it fits into the infrastructure of CIM.


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Figure 16.1: Components of CAD

16.2 Learning Object ives

After completing this unit you will be able to:

BULLET LISTList the six processes of the conventional design process

Define Computer-aided design (CAD)

Specify the benefits of CAD

State the relationship between the Product Data Management system, and the

CAD system

Explain the concept of geometric modelling

Classify types of geometric modelling

Explain Computer-aided engineering (CAE) software, and list typical applications

State how CAD is used to create product prototypes

List the hardware used in a CAD system

State the types of CAD system configurations that may be used

Define Computer-aided manufacturing (CAM)

State and explain the two application areas of CAM

Explain the concept of CAD/CAM


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State why CAD/CAM is used in concurrent engineering environments

Define Computer-integrated manufacturing, and its scopeENDLIST

16.3 Product Design and CAD

Product design is of critical importance to the production system. It contributesmore than any other attribute to the overall design and operation of theproduction system, and its success determines whether the production systemwill be fit for use in making products over the long term.

LEARNING ACTIVIY 16.1Learn more about these concepts at the following web-sites:

Computer-Aided Design (CAD)http://en.wikipedia.org/wiki/Computer-aided_designComputer-Aided Manufacturing (CAM)http://en.wikipedia.org/wiki/Computer_aided_manufacturingComputer Integrated Manufacturing (CIM)http://en.wikipedia.org/wiki/Computer_Integrated_Manufacturing

END LEARNING ACTIVITY 16.1

16.3.1 The Design Process

The general process of design may be seen as an iterative process with six keyphases (see Figure 16.2):

NUMLISTRecognition of needthis involves the realisation that a problem or need existsthat may be solved by design. This may mean identifying some deficiency in acurrent machine design by an engineer, or perceiving some new productopportunity by a salesperson.

Problem definitionthis involves a thorough specification of the item to bedesigned. Specifications include physical characteristics, function, cost, quality,and operating performance.

Synthesisclosely related with the following step, analysis, synthesis refers tothe bundling of information that occurs after problem definition, and concurrentlyduring analysis, and after re-analysis.
http://en.wikipedia.org/wiki/Computer-aided_designhttp://en.wikipedia.org/wiki/Computer-aided_designhttp://en.wikipedia.org/wiki/Computer_aided_manufacturinghttp://en.wikipedia.org/wiki/Computer_aided_manufacturinghttp://en.wikipedia.org/wiki/Computer_Integrated_Manufacturinghttp://en.wikipedia.org/wiki/Computer_Integrated_Manufacturinghttp://en.wikipedia.org/wiki/Computer_Integrated_Manufacturinghttp://en.wikipedia.org/wiki/Computer_aided_manufacturinghttp://en.wikipedia.org/wiki/Computer-aided_design


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Analysis and optimizationclosely related to the previous step, analysis isconcerned with the investigation of design specification information, and theoptimization of this information, as well as a synthesis of new information, asrequired.

Evaluationinvolves measuring the design against the specifications establishedin the problem definition phase. This evaluation may require the building andtesting of prototype models to assess operative performance metrics for theproposed design. This may lead to the re-design of certain or all elements.

Presentationthis is the final phase, where the design is documented by meansof drawings, material specifications, assembly lists, and so on. Documentationmeans that the design database is created.ENDLIST

Figure 16.1: Design Process and Computer aided design

KEYPOINT


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The use of a CAD system creates huge amounts of additional data that is oftenstored and managed in a product data management (PDM) system. A PDMsystem consists of computer software that provides links between users and acentral database, where engineering design data and related documentation isstored. The PDM system manages the database by tracking the identities of

users, facilitating and documenting engineering changes, recording a history ofthe engineering changes on each part and product, and providing documentationmanagement functions.

KEYPOINTThe output of the CAD system is stored in a product data management (PDM)system. A PDM system consists of computer software that provides linksbetween users and a central database, where engineering design data andrelated documentation is stored.END KEYPOINT

The CAD system can facilitate four of the design phases depicted in Figure 16.2.

Geometric modelling is a special use of CAD data to create a mathematicaldescription of the geometry of an object. The geometric model, which containsthe mathematical description, is contained in the computer memory; and the CADsystemupon accessing the computer memorycan display the resultant modelas an image on its graphics terminal, allowing the operator to manipulate certainaspects of the geometric model displayed. The operator can create newgeometric models from basic building blocks available in the system, can zoom-in on certain features of the image on-screen, can move two or more geometricmodels into close relation to each other, and so on. These capabilities allow the

operator to interrogate existing product models, and create new variations onexisting products to cater for a wide variety of needs.

KEYPOINTGeometric modelling creates a mathematical description of the geometry of anobject, so that the subsequent description can be displayed as an image on CADsystems, which may be manipulated by the operator.END KEYPOINT

There are two types of geometric models used in CAD; these are:

NUMLISTTwo-dimensional modellingdating from the late 1960s and early 1970s, whenthe first CAD systems began to appear, this is primarily used for designproblems, such as flat objects and layouts of buildings. To enable some degreeof three-dimensionality, these models were often drawn from various viewpoints,so as to capture the multitude of dimensions on an individual product.


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Three-dimensional modellingemerging after two-dimensional modelling, thesesystems are capable of modelling an object in three dimensions according touser instructions, which has been found useful for conceptualising the object, asthe three-dimensional model can be displayed in various views and from differentangles.

ENDLIST

KEYPOINTGeometric modelling can appear in the form of two-dimensional modelling, andthree-dimensional modelling.END KEYPOINT

Geometric models in CAD can also be classified as wire-frame models, or solidmodels (see Figure 16.3). Wire-frame models use inter-connecting lines to depictthe object drawn; these inter-connecting lines can sometimes be confusing whenused on complex part geometries, as multiple overlapping lines may occur. Solid

models are objects that have been modelled in solid three dimensions, providingthe user with a vision of the object that is similar to its appearance in reality.

(a) (b)Figure 16.3: Wire-frame model (a), and Solid model (b)

KEYPOINTGeometric models in CAD can also be classified as wire-frame models, or solidmodels.END KEYPOINT

16.3.2.1 Engineering Analys is

Once a design has been developed, it must then be subjected to engineeringanalysis. This engineering analysis may include various tests, depending on the

product, but may include: stress-strain calculations, heat transfer analysis, ordynamic simulation. These analyses tend to be quite complex, which has led tothe development of computer-aided engineering (CAE) software packages, sothat complicated engineering analysis may be performed by computer.

KEYPOINTComputer-aided engineering (CAE) software packages are used to performcomplex engineering calculations by computer.


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END KEYPOINT

CAE packages in common use with CAD systems include:

BULLETLIST

Mass properties analysisinvolving the computation of features on the solidmodel, such as volume, surface area, weight, and centre of gravity;

Interference checkingthis checks to see if multiple components in a productdesign would actually interfere with each other in reality;

Tolerance analysisthis determines how product tolerances would affect productfunction and performance, how easy it would be to assemble the product, andhow variations in component dimensions may affect the overall size of theassembly;

Finite element analysisthis aids in stress-strain, heat transfer, fluid flow, andother engineering calculations;

Kinematic and dynamic analysisthis studies the operation of mechanicallinkages and analyzes their motions; and

Discrete-event simulationthis models complex operational systems whereevents occur at discrete moments in time and affect the status and performanceof the system.ENDLIST

KEYPOINTCommon CAE packages include: mass properties analysis; interferencechecking; tolerance analysis; finite element analysis; kinematic and dynamicanalysis; and discrete-event simulation.END KEYPOINT

16.3.2.2 Design Evaluation and Review

Following comprehensive engineering analysis, the proposed design must beevaluated and reviewed for consistency. Some CAD features that are helpful inevaluating and reviewing a proposed design include:

BULLETLISTAutomatic dimensioningupon model completion, the CAD software canautomatically generate the dimensions of the drawn model;


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Error checkingthis checks the accuracy and consistency of dimensions andtolerances, to assess whether the proper design documentation format has beenfollowed;

Animation of discrete-event simulation solutionsthis displays the result as a

discrete-event simulation, where input parameters, probability distributions, andother factors can be changed to assess their effect on the performance of thesystem being modelled; and

Plant layout design scoresthis provides numerical scores for plant layoutdesigns, based upon such factors as material flow, and closeness ratings.ENDLIST

KEYPOINTCAD features helpful in evaluating and reviewing a proposed design include:automatic dimensioning; error checking; animation of discrete-event simulation

solutions; and plant layout design scores.END KEYPOINT

In many cases, the geometric model is now used to replace the physicalprototype that would traditionally be built at this stage. Physical prototypes areusually time-consuming to create, and analyse; and so replacements in the formof rapid prototyping, and virtual prototypingboth based upon the geometricmodel, may be used instead.

KEYPOINTEvaluating and reviewing a proposed design can use the CAD geometric model

to create a prototype, either by rapid prototyping or virtual prototyping.END KEYPOINT

Rapid prototyping is a term applied to a family of fabrication technologies thatallow engineering prototypes of solid parts to be made in a minimum lead time,based upon the CAD geometric model. This is done by dividing the solid objectinto layers, and then defining the area of each layer. The rapid prototypingprocess then fabricates the object by starting at the base layer, and buildingtowards the top layer. The fidelity of the approximation that is produced by thismethod is dependent on the layer thickness used at the start (with greateraccuracy achieved with thinner layers used).

Virtual prototyping is based upon virtual reality technology, and uses the CADgeometric model to construct a digital mock-up of the product. This mock-upallows the designer to obtain the sensation of the real physical product, withoutactually building the physical prototype.

KEYPOINT


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Rapid prototyping creates a physical prototype by means of segmenting the CADgeometric model into a series of layers, and building to that specification; whilevirtual prototyping uses the CAD geometric model to construct a digital mock-upof the product.END KEYPOINT

16.3.2.3 Automated Drafting

CAD may also be used as a presentation application, in that the CAD system canproduce highly accurate engineering drawings quickly and conveniently, and alsoprovide associated documentation as necessary. It is estimated that a CADsystem increases productivity in the drafting function by about fivefold overmanual preparation of drawings.

KEYPOINT

CAD may also be used for automated draftingthat is, the creation andpresentation of highly accurate engineering drawings.END KEYPOINT

16.4 CAD System Hardware

Hardware is used in CAD systems is described in Table 16.1. The relationshipbetween the components discussed is depicted in Figure 16.4.

Table 16.1: Hardware used in CAD systemsHardware DescriptionDesign workstations This has the following functions: (1) communication with the computers

central processing unit; (2) continuously generate a graphic image; (3)provide digital descriptions of the image; (4) translate user commandsinto operating functions; and (5) facilitate interaction between the userand the system.CAD workstation design has an important influence on the convenience,productivity, and quality of users output. The workstation consists of adisplay terminal and a set of user input devices, with which the userinteracts with geometric model via: entering alphanumeric data; enteringsystem commands to perform various graphics operations; and bycontrolling cursor position on the display screen.

Digital computer This uses a high-speed central processing unit to process CADoperations. There are several CAD system configurations, such as hostand terminal; engineering workstation; and a CAD system based upon apersonal computer. These are discussed in the paragraphs below.

Output devices These include plotters and printers, which generate the output from theCAD system. Plotters include: pen plotters, which are x-y plotters ofvarious type, used to produce high accuracy line drawings;andelectrostatic plotters, which are based upon the same principal asphotocopying, and produce lower quality drawings. Printers usedinclude inkjet printers, where drawings are produced by high-speed jets


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of ink impacting the paper.Secondary Storage This includes various storage devices attached to the CAD system to

store programmes and data files. The storage mediums used caninclude: magnetic discs, magnetic tape, floppy discs, external hard-drives etc.

Figure 16.4: Configuration of a typical CAD system

KEYPOINTThe hardware used in a CAD system includes: design workstations; digitalcomputers; output devices, such as plotters and printers; and various secondarystorage devices.END KEYPOINT

16.5 CAM, CAD/CAM, and CIM

We can now give more precise explanations of the terms CAM and CIM and theirrelationships to CAD.

16.5.1 Computer-Aided Manufacturing

Computer-Aided Manufacturing (CAM) is the effective use of computertechnology in manufacturing planning and control. It is closely associated withcertain functions in manufacturing engineering, such as process planning andnumerical control (NC) part programming. It is applied in two broad categories:manufacturing planning, and manufacturing control.

KEYPOINTComputer-Aided Manufacturing (CAM) is the application of computer technologyto the areas of manufacturing planning and control.END KEYPOINT

Manufacturing planning concerns the use of CAM to support the productionfunction, without a direct connection between the computer and the process.


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Effective planning is achieved off-line; that is, the computer is used to provideinformation for planning and managing production activities, without directlyaccessing the process in real-time.

Important applications of CAM in manufacturing planning are outlined in Table

16.2.

Table 16.2: Applications of CAM for manufacturing planningAppl icat ion Descript ion

Computer-aidedprocess planning(CAPP)

This is concerned with creation and dissemination of route sheets thatlist the sequence of operations and work centres required to producethe product and its components.

Computer-aided NCpart programming

We discussed numerical control in unit 5. This application supports thecreation of computer-assisted part programmes for numerical control,which represents a more efficient solution for their creation overtraditional manual methods.

Computerizedmachinability data

systems

This is concerned with creation and dissemination of part programmesthat can determine optimal cutting conditions for machine tools in the

factory.Computerized workstandards

These are computer packages that can be deployed to determine timestandards for direct labour jobs in the factory. They supersede tediousmanual time-and-motion studies used to perform the same task.

Cost estimating This is a programme that can estimate the cost of a new product, bycomputerizing several of the key steps required to prepare theestimate (such as the application of labour and overhead rates to thesequence of planned operations).

Production andinventory planning

Functions here include maintenance of inventory records, automaticre-ordering of stock items when inventory is depleted, productionscheduling, maintaining current priorities for the different productionorders, material requirements planning, and capacity planning.

Computer-aided line

balancing

This programme helps to find the best allocation of work elements

among stations on an assembly line. Can be used in situations wherethe line balancing problem is particularly complex and difficult, owingto the number of workstations, and complicating factors.

KEYPOINTApplications of CAM for manufacturing planning include: Computer-aidedprocess planning (CAPP); Computer-aided NC part programming; Computerizedmachinability data systems; Computerized work standards; Cost estimating;Production and inventory planning; and Computer-aided line balancing.END KEYPOINT

Manufacturing control uses CAM applications to manage and control the physicaloperations of the factory. Here computer systems are developed that can beused to implement the manufacturing control function. Important applications ofCAM in manufacturing control are outlined in Table 16.3.

Table 16.3: Applications of CAM for manufacturing controlAppl icat ion Descript ion

Process monitoring and control This is concerned with observing and regulating the productionequipment and manufacturing processes in the plant. They


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include the control of transfer lines, assembly lines, numericalcontrol, robotics, material handling, and flexible manufacturingsystems.

Quality control This includes a variety of approaches to maintain the highestpossible quality levels in the manufactured product. Theyinclude the use of quality functional deployment techniques.

Shop floor control This refers to the use of production management techniquesto collect data from factory operations, and the deployment ofthis data to aid the control of production and inventory in thefactory.

Inventory control This is concerned with maintaining the most appropriate levelsof inventory in the face of two opposing objectives: minimizingthe investment and storage costs of holding inventory; andmaximizing service to customers.

J ust-in-time production systems J ust-in-time (J IT) production systems deliver the right numberof components to downstream workstations, at the right time.

J IT refers to both production operations and supplier deliveryoperations.

KEYPOINTApplications of CAM for manufacturing control include: process monitoring andcontrol; quality control; shop floor control; inventory control; and just-in-timeproduction systems.END KEYPOINT

16.5.2 CAD/CAM

The integration of CAD functions with CAM applications gives us the acronymCAD/CAM. CAD/CAM is concerned with engineering functions in both design

and manufacturing; it denotes an integration of design and manufacturingactivities by means of computer systems. Since the way a product ismanufactured depends upon the specific design that is supplied, the combiningof CAD with CAM in CAD/CAM, creates a direct link between product design andproduct manufacture that can be exploited in the production system.Conventional practices, practiced for many years in industry, saw design andmanufacturing as essentially separate functions: engineering drawings werecreated by the design department, and these were later used by manufacturingengineers to develop the process plan. This two-step procedure was time-consuming and duplicated the efforts of design and manufacturing personnel.The application of CAD/CAM removed this problem. In an ideal CAD/CAM

system, it is possible to take the design specification of the product as it residesin the CAD database, and convert it automatically into a process plan for makingthe product. As such, therefore, CAD/CAM operates as a system that facilitatesconcurrent engineering practices.

KEYPOINT


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CAD/CAM is concerned with engineering functions in both design andmanufacturing; it denotes an integration of design and manufacturing activities bymeans of computer systems.END KEYPOINT

The term concurrent engineering defines a system whereby the whole life cycleof a product is considered concurrently. The pressure to decrease design anddevelopment time-scales is leading companies to conduct the design,development, analysis and the production of manufacturing information intandem. Within this setting, advances such as CAD/CAM help to avoid certainproblems occurring, such as a lack of quality design or a lack of communicationbetween design and manufacturing personnel, as everybody understands andappreciates what everyone else is doing. The organisation of the company in thecase of a concurrent engineering approach is usually dictated by product grouprather than by individual function, with applications such as CAD/CAM beingcross-functional, rather than being department-specific.

The concurrent engineering practice involves work through multi-disciplinaryteams comprising expertise from every area of the organisation, from materialsright through to marketing and sales. There may also be input from outsidespecialists. This is opposed to the conventional engineering approach, wherebythe responsibility for the product moves from department to department. Forexample, the materials personnel may purchase the raw materials, which theysee as suited to the finished product, but this may not comply with theexpectations of the maintenance people or the production engineers. In theconcurrent engineering approach the materials, production and maintenancestaff would all be working together, enhancing communication on a project team.

Leadership of such teams will vary according to the stage in the product lifecycle.

KEYPOINTConcurrent engineering defines a system whereby the whole life cycle of aproduct is considered concurrently. CAD/CAM is an example of an applicationwidely used in concurrent engineering.END KEYPOINT

16.5.3 Computer-Integrated Manufacturing

Computer-integrated manufacturing (CIM) includes all of the engineeringfunctions of CAD/CAM, but it also includes the firms business functions that arerelated to manufacturing. The component geometry developed through the use ofCAD systems may be reused in the generation of manufacturing instructions fornumerically controlled production processes, and in the planning ofmanufacturing operations through computer aided process planning (CAPP).This is in line with our discussion above.


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Further, they suggest that these activities in turn feed information, together withbill of materials information, from CAD, into an activity called computer aidedproduction management (CAPM). All of these manufacturing activities areintegrated through the use of computer aids and a shared database. They are

collectively known in industry as CIM, and they can be summarised in a graphicalformat as shown in Figure 16.8. The computer aids the interface between designand manufacture through the interaction between CAD and CAM, by developingcomputer aided process plans. There are problems with this approach: computerplans are trying to generate and automate process plans for manufacturing, whilethe ideal scenario would be to automate the techniques of design formanufacture and design for assembly in the CAPP system. Examples aretechniques for product/process analysis that gives the manufacturer an influenceor input into the design. CAPP systems constitute both process planning andproduct/process analysis with influences from CAD and CAM.

CIM Environment

CAD

CAPP

CAM

CAPM

Geometry

Routes

Geometry

Billofmaterials

Priority

Marketneeds

Manufacturingstrategy

Manufacturingcell capability

profile

Cell capacityprofile

Manufacturing

Figure 16.8: Data Exchange in a CIM Environment

KEYPOINTComputer-integrated manufacturing (CIM) includes all of the engineeringfunctions of CAD/CAM, but it also includes the firms business functions that arerelated to manufacturing.

END KEYPOINT

Comparing the scope of CIM to the more limited scope of CAD/CAM, isinstructive (see Figure 16.9). The ideal CIM system applies computer andcommunications technology to all the operational functions and informationprocessing functions in manufacturing, from order receipt through design andproduction, to product shipment. CAD/CAM, on the other hand, is not so all-embracing, and does not cover what may loosely be termed the business


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functions of the factory. Thus, at higher levels, CIM subsumes CAD/CAM, andadds functions of its own.

Figure 16.9: The scope of CAD/CAM and CIM

KEYPOINTCIM has a wider scope than CAD/CAM, so that at higher levels CIM subsumesCAD/CAM and adds functions of its own.END KEYPOINT

A specific examination of the computerized elements of a CIM system may alsobe analysed (see Figure 16.10). Here we can see the elements of CAD and CAM

being captured within the CIM remit, at different stages of design andmanufacturing. CIM adds a series of computerized business systems thataccount for peripheral elements entering and exiting the manufacturing system,proper. Customer orders are initially logged by an order entry system, withproduct specifications being derived from this, and acting as initial input to thedesign function, where CAD functions may occur. The output of the designdepartment, in its turn, serves as input to manufacturing engineering at bothcontrol and planning levels, and both product and process planning is performedin detail. Full implementation of CIM results in the automation of the informationflow through every aspect of the companys organization. During the process,accounting and payroll activities ensure that personnel, product and production

considerations are fully in line with planned expenditure; while at process end,customer billing completes the operation of the CIM architecture.


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Figure 16.10: Computerized elements of a CIM system

KEYPOINTCIM adds a series of computerized business systems that account for peripheralelements entering and exiting the manufacturing system, alongside those thatemerge from CAD/CAM.END KEYPOINT

16.6 Unit Review

BULLETLISTProduct design, and associated CAD/CAM systems, are important parts of themanufacturing support system.

The conventional design process consists of six processes: recognition of need;problem definition; synthesis; analysis and optimization; evaluation; andpresentation.

Computer-aided design (CAD) is any design activity that involves the effectiveuse of a computer to create, modify, analyze, or document an engineeringdesign.

Benefits of CAD include: increased design productivity; increased availablegeometric forms in the design; improved quality of the design; improved design


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documentation; creation of a manufacturing database; and designstandardization.

The output of the CAD system is stored in a product data management (PDM)system. A PDM system consists of computer software that provides links

between users and a central database, where engineering design data andrelated documentation is stored.

Geometric modelling creates a mathematical description of the geometry of anobject, so that the subsequent description can be displayed as an image on CADsystems, which may be manipulated by the operator.

Geometric modelling can appear in the form of two-dimensional modelling, andthree-dimensional modelling.

Geometric models in CAD can also be classified as wire-frame models, or solid

models.

Computer-aided engineering (CAE) software packages are used to performcomplex engineering calculations by computer.

Common CAE packages include: mass properties analysis; interferencechecking; tolerance analysis; finite element analysis; kinematic and dynamicanalysis; and discrete-event simulation.

CAD features helpful in evaluating and reviewing a proposed design include:automatic dimensioning; error checking; animation of discrete-event simulation

solutions; and plant layout design scores.

Evaluating and reviewing a proposed design can use the CAD geometric modelto create a prototype, either by rapid prototyping or virtual prototyping.

Rapid prototyping creates a physical prototype by means of segmenting the CADgeometric model into a series of layers, and building to that specification; whilevirtual prototyping uses the CAD geometric model to construct a digital mock-upof the product.

CAD may also be used for automated draftingthat is, the creation andpresentation of highly accurate engineering drawings.

The hardware used in a CAD system includes: design workstations; digitalcomputers; output devices, such as plotters and printers; and various secondarystorage devices.


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Different types of CAD system configurations may be used, including: host andterminal configurations; engineering workstation configurations; and CADsystems based on the use of personal computers.

Computer-Aided Manufacturing (CAM) is the application of computer technology

to the areas of manufacturing planning and control.

CAM can be considered to have principal application areas: manufacturingplanning, and manufacturing control.

Manufacturing planning uses CAM in an off-line setting; that is, computers areused to support planning and management activities, without a direct connectionbeing maintained between the computer and the process.

Applications of CAM for manufacturing planning include: Computer-aidedprocess planning (CAPP); Computer-aided NC part programming; Computerized

machinability data systems; Computerized work standards; Cost estimating;Production and inventory planning; and Computer-aided line balancing.

Manufacturing control uses CAM applications to manage and control the physicaloperations of the factory.

Applications of CAM for manufacturing control include: process monitoring andcontrol; quality control; shop floor control; inventory control; and just-in-timeproduction systems.

CAD/CAM is concerned with engineering functions in both design and

manufacturing; it denotes an integration of design and manufacturing activities bymeans of computer systems.

Concurrent engineering defines a system whereby the whole life cycle of aproduct is considered concurrently. CAD/CAM is an example of an applicationwidely used in concurrent engineering.

Computer-integrated manufacturing (CIM) includes all of the engineeringfunctions of CAD/CAM, but it also includes the firms business functions that arerelated to manufacturing.

CIM has a wider scope than CAD/CAM, so that at higher levels CIM subsumesCAD/CAM and adds functions of its own.

CIM adds a series of computerized business systems that account for peripheralelements entering and exiting the manufacturing system, alongside those thatemerge from CAD/CAM.ENDLIST


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16.7 Self-Assessment Questions

NUMLISTWhat are the six processes of the conventional design process?

What is Computer-aided design (CAD)?

What are the benefits of CAD?

What is the relationship between the Product Data Management system, and theCAD system?

What is meant by the concept of geometric modelling?

Classify types of geometric modelling.

What is Computer-aided engineering (CAE) software? List typical applications ofCAE software.

How is CAD used to create product prototypes?

What hardware is used in a CAD system?

What are the different types of CAD system configurations that may be used?

What is Computer-aided manufacturing (CAM)?

What are the two application areas of CAM?

What is meant by the concept of CAD/CAM?

Why is CAD/CAM used in concurrent engineering environments?

What is Computer-integrated manufacturing (CIM)? What is its scope?ENDLIST

16.8 Answers to Self-Assessment Questions

NUMLISTThe conventional design process consists of six processes: recognition of need;problem definition; synthesis; analysis and optimization; evaluation; andpresentation.


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Computer-aided design (CAD) is any design activity that involves the effectiveuse of a computer to create, modify, analyze, or document an engineeringdesign.

The benefits of CAD include: increased design productivity; increased available

geometric forms in the design; improved quality of the design; improved designdocumentation; creation of a manufacturing database; and designstandardization.

The output of the CAD system is stored in a product data management (PDM)system. A PDM system consists of computer software that provides linksbetween users and a central database, where engineering design data andrelated documentation is stored.

Geometric modelling creates a mathematical description of the geometry of anobject, so that the subsequent description can be displayed as an image on CAD

systems, which may be manipulated by the operator.

Geometric modelling can appear in the form of two-dimensional modelling, andthree-dimensional modelling. Geometric models in CAD can also be classified aswire-frame models, or solid models.

Computer-aided engineering (CAE) software packages are used to performcomplex engineering calculations by computer. Common CAE packages include:mass properties analysis; interference checking; tolerance analysis; finiteelement analysis; kinematic and dynamic analysis; and discrete-event simulation.

Evaluating and reviewing a proposed design can use the CAD geometric modelto create a prototype, either by rapid prototyping or virtual prototyping. Rapidprototyping creates a physical prototype by means of segmenting the CADgeometric model into a series of layers, and building to that specification; whilevirtual prototyping uses the CAD geometric model to construct a digital mock-upof the product.

The hardware used in a CAD system includes: design workstations; digitalcomputers; output devices, such as plotters and printers; and various secondarystorage devices.

Different types of CAD system configurations may be used, including: host andterminal configurations; engineering workstation configurations; and CADsystems based on the use of personal computers.

Computer-Aided Manufacturing (CAM) is the application of computer technologyto the areas of manufacturing planning and control.


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CAM can be considered to have principal application areas: manufacturingplanning, and manufacturing control. Manufacturing planning uses CAM in anoff-line setting; that is, computers are used to support planning andmanagement activities, without a direct connection being maintained between thecomputer and the process. Manufacturing control uses CAM applications to

manage and control the physical operations of the factory.

CAD/CAM is concerned with engineering functions in both design andmanufacturing; it denotes an integration of design and manufacturing activities bymeans of computer systems.

The term concurrent engineering defines a system whereby the whole life cycleof a product is considered concurrently. The pressure to decrease design anddevelopment time-scales is leading companies to conduct the design,development, analysis and the production of manufacturing information intandem. Within this setting, advances such as CAD/CAM help to avoid certain

problems occurring, such as a lack of quality design or a lack of communicationbetween design and manufacturing personnel, as everybody understands andappreciates what everyone else is doing. The organisation of the company in thecase of a concurrent engineering approach is usually dictated by product grouprather than by individual function, with applications such as CAD/CAM beingcross-functional, rather than being department-specific.

Computer-integrated manufacturing (CIM) includes all of the engineeringfunctions of CAD/CAM, but it also includes the firms business functions that arerelated to manufacturing. CIM has a wider scope than CAD/CAM, so that athigher levels CIM subsumes CAD/CAM and adds functions of its own.

ENDLIST

cycle time calculation-unit_16_product_design_and_cadcam.pdf

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