virtual manufacturing

COLLOQUIUM

VIRTUAL MANUFACTURING

By

ANURAG CHAUDHARY

(Registration No – 2015PR02)

M.Tech. III Semester (PP RR OO DD UU CC TT II OO NN EE NN GG II NN EE EE RR II NN GG )

Under The Guidance

Of

Dr. Audhesh Narayan

Master of Technology (M.Tech.)

in

PRODUCTION ENGINEERING

Submitted to the

DEPARTMENT OF MECHANICAL ENGINEERING

Motilal Nehru National Institute of Technology Allahabad

Allahabad, UP, India, 211004

September 26, 2016

Virtual Manufacturing

i

ACKNOWLEDGEMENTS

It is a great pleasure to express my sincere gratitude and profound regards to Dr. Audhesh Narayan,

Assistant Professor, Mechanical Engineering Department, MNNIT Allahabad, for his constant

encouragement, valuable guidance and help during the entire course of the work. Words are insufficient to

acknowledge the keen interest taken by him in all aspects of the present work.

I would also like to acknowledge the useful resources of the MNNIT Central Library.

Date:

Anurag Chaudhary

(Reg. No.- 2015PR02)


ii

ABSTRACT

Virtual Manufacturing system is a computer system which can generate the same

information about manufacturing system„s structure, states and behaviours as we

can observe in real manufacturing systems. Virtual reality and virtual

manufacturing often concent rate on an interface between VR technology and

manufacturing and production theory and practice. In terms of manufacturing

education, virtual concept is expected to be more safety, relevant and cost effective

than physical one. It is our belief that the d irection of evolution of manufacturing

theory and practice will become clearer in the future once the role of VR

technology is understood better in developing this interface.

This report describes the Virtual Manufacturing System a virtual world consisting

of a machine shop in which engineering components can be made. The mechanisms

and processes of their manufacture are recorded so that those mechanisms and

processes can be carried out subsequently on real computer -numerically-controlled

machine tools.


iii

CONTENT

I. ACKNOWLEDGEMENTS i

II. ABSTRACT ii

III. LIST OF TABLES iv

IV. LIST OF FIGURES iv

1. INTRODUCTION 1

2. HISTORY OF VIRTUAL MANUFACTURING AND VIRTUAL

REALITY 2-4

3. VIRTUAL REALITY TECHNOLOGIES 5-7

4. VIRTUAL MAUFACTURING 8-16

5. METHODS AND SIMULATION TOOLS USED IN VIRTUAL

MANUFACTURING SYSTEMS 17

6. EDUCATIONAL REQUIREMENTS FOR VIRTUAL

MANUFACTURING SYSTEMS 18-19

7. ECONOMICS AND SOCIO-ECONOMICS 20-23

8. ADEQUACY OF A VIRTUAL MANUFACTURING SYSTEM 24

9. APPLICATIONS OF VM 25-28

10. FUTURE RESEARCH DIRECTION 29

11. CONCLUSION 30

12. REFERENCES 31-32


iv

LIST OF TABLES:

Table I: Overview of Simulation Tools 17 Table II: Factors of Virtual Manufacturing 20

LIST OF FIGURES:

Figure 1: Virtual Manufacturing 10 Figure 2: Virtual Manufacturing Objectives, Scope And Domains 11 Figure 3: Role of Virtual Manufacturing System 18 Figure 4: Academic Research Versus Industrial Tools 22


1

CHAPTER-1

INTRODUCTION

The natural instinct of an engineer who wants to make a new device is to go to a

workshop, find some scrap aluminium or mild steel, and to machine up what is

required. The engineer will do this by eye where dimensions are not critical, and by

measurement where they are. He or she will make mistakes of course - holes may be

drilled in the wrong place initially or, more seriously, material may be cut which is

subsequently needed to support some other part of the component. But eventually a

rough hack at a prototype will emerge[ 1 ]

.

The idea of our Virtual Manufacturing System is to allow de signers to follow that

instinct, but with the added luxury of cost -free second thoughts. The system is a

virtual world representing a machine shop in which engineering components can be

made and, almost as importantly, unmade. This is to say that time can be reversed

to obli terate mistakes, material reappearing to fill erroneous cavities unlike the way

it so inconveniently doesn't in real life. Many people have produced simulation

systems that will replay a pre -determined sequence of machining operations in side

a computer, but we are not aware of any fully-interactive system that is intended to

be a source of such operations, and which is intended to be used by designers as a

design system[ 2 ]

.

The main aim of this report is briefly but completely describe the main features of

the virtual reality technology systems and describe new view to this area - Virtual

Manufacturing. Virtual Manufacturing use of a virtual reality systems for the CAD

of components and processes for manufacturing - for viewing 3D engineering

models to be passed to NC machines for real manufacturing. a lot of tasks in

manufacturing systems have been transferred from workshops into computer

systems and large parts of activities are considered to be carried out as information

processing within computers. For example, draft ing papers and pens had been

replaced with CAD (computer aided design) system. Up -to late 1970s, NC part

programming performed at operating panel of NC controllers had been mainly

substi tuted by CAM (computer aided manufact uring) software nowadays. Virtual

Reality is technology for presentation of complicated information, manipulations

and interactions of person with them by computer. Method of dialogue of person

with computer is named interface and virtual reality is newest of row this

interfaces.


2

CHAPTER-2

HISTORY OF VIRTUAL MANUFACTURING AND VIRTUAL

REALITY

The most advanced current form of the Computer Aided Manufacturing is Virtual

Manufacturing (VM) based on Virtual Reality (VR). The concept of Artificial

Reality appeared already in the 1970s (Miron KRUEGER) and the notion of Virtual

Reality was introduced by Jaron Lanier (1989). In 1990 the concepts of Virtual

World and Virtual Environments appeared. Virtual reality is defined as a computer

generated interactive and immersive 3D environment simulating reality.

Let us have a short glimpse at the last three decades of research in virtual reality

and its highlights[ 3 ]

:

Sensorama - in years 1960-1962 Morton Heilig created a multi -sensory simulator.

A prerecorded film in color and stereo, was augmented by binaural sound, scent,

wind and vibration experiences. This was the first approach to create a virtual

reality system and i t had all the features of such an environment, but it was not

interactive.

The Ultimate Display – in 1965 Ivan Sutherland proposed the ultimate solution of

virtual reality: an artificial world construction concept that included interactive

graphics, force-feedback, sound, smell and taste.

“The Sword of Damocles” - the first virtual reality system realized in hardware,

not in concept. Ivan Sutherland constructs a device considered as the first Head

Mounted display (HMD), with appropriate head tracking. It supported a stereo view

that was updated correctly according to the user‟s head position and orie ntation.

GROPE - the first prototype of a force -feedback system realized at the University

of North Carolina (UNC) in 1971.

VIDEOPLACE - Artificial Reali ty created in 1975 by Myron Krueger - “a

conceptual environment, with no existence”. In this system the silhouettes of the

users grabbed by the cameras were projected on a large screen. The participants

were able to interact one with the other thanks to the image processing techniques

that determined their positions in 2D screen‟s space.

VCASS - Thomas Furness at the US Air Force‟s Armstrong Medical Research

Laboratories developed in 1982 the Visually Coupled Airborne Systems Simulator –

an advanced flight simulator. The fighter pilot wore a HMD that augmented the out -


3

the window view by the graphics describing targeting or optimal flight path

information.

VIVED - Virtual Visual Environment Display – constructed at the NASA Ames in

1984 with off-the-shelf technology a stereoscopic monochrome HMD.

VPL - the VPL company manufactures the popular Data - Glove (1985) and the Eye

phone HMD (1988) - the first commercially available VR devices.

BOOM - commercialized in 1989 by the Fake Space Labs. BOOM is a small box

containing two CRT monitors that can be viewed through the eye holes. The user

can grab the box, keep it by the eyes and move through the virtual world, as the

mechanical arm measures the position and orientation of the box.

UNC Walkthrough project - in the second half of 1980s at the University of North

Carolina an architectural walkthrough application was developed. Several VR

devices were constructed to improve the quality of this system like: HMDs, optical

trackers and the Pixel -Plane graphics engine.

Virtual Wind Tunnel - developed in early 1990s at the NASA Ames application

that allowed the observation and investigation of flow-fields with the help of

BOOM and Data Glove.

CAVE - presented in 1992 CAVE (CAVE Automatic Virtual Environment) is a

virtual reality and scientific visualization system. Instead of using a HMD it

projects stereoscopic images on the walls of room (user must wear LCD shutter

glasses). This approach assures superior quality and resolution of viewed images,

and wider field of view in comparison to HMD based systems.

Augmented Reality (AR) - a technology that “presents a virtual worl d that enriches,

rather than replaces the real world”. This is achieved by means of see -through HMD

that superimposes virtual three -dimensional objects on real ones. This technology

was previously used to enrich fighter pilot‟s view with addit ional flight information

(VCASS). Thanks to its great potential – the enhancement of human vision –

augmented reali ty became a focus of many research projects in early 1990s.

The term Virtual Manufacturing first came into prominence in the early 1990s, in

part as a result of the U.S. Department of Defense Virtual Manufacturing Initiative.

Both the concept and the term have now gained wide international acceptance and

have somewhat broadened in scope. For the first half of the 1990s, pioneering work

in this field has been done by a handful of major organizations, mainly in the

aerospace, earthmoving equipment, and automobile industries, plus a few


4

specialized academic research groups. Recently accelerating worldwide market

interest has become evident, fueled by price and performance improvements in the

hardware and software technologies required and by increased awareness of the

huge potential of virtual manufacturing. Virtual manufacturing can be considered

one of the enabling technologies for the rapidly developing info rmation technology

infrastructure.

VR representation techniques are widely used which means that they develop

rapidly. In product manufacturing techniques and organization, virtual reality has

become the basis of virtual manufacturing aimed at meeting the expectations of the

users/buyers of products, also as to their low cost and lead time. Virtual

manufacturing includes the fast improvement of manufacturing processes without

drawing on the machines ' operating time fund. It is said that Virtual Manufacturing

is the use of a desktop virtual reality system for the computer -aided design of

components and processes for manufacture[ 4 ]

.


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CHAPTER-3

VIRTUAL REALITY TECHNOLOGIES

Virtual Reality is technology for presentation of complicated information,

manipulations and interactions of person with them by computer. Method of

dialogue of person with computer is named interface and virtual reality is newest of

row this interfaces. After applications of virtual reality in area of computer games

are rise need to exercise these technologies in industry. Main areas of using of

virtual projecting and prototyping are automotive and air industry in this time.

Virtual projecting as very perspective method must by using in area of projecting of

manufacturing systems, too.

Historically, virtual reality has entered into the public awareness as medial toy with

equipment "helmet-glove", which was preferentially determined for wide public and

the price of this system had also to correspond to this fact, so price could not be

very high. As follows, the producers of virtual reality systems have aimed at

developing and providing of the systems for data collecting and analyzing and

systems supporting economic modell ing. It is obvious that , from among areas,

where virtual reali ty systems can be most frequently used are applications based on

3D-space analyzing and physical dimension visualization. Virtual reali ty with

abili ty to show data 3D and attach sounds and touch information increases

extraordinarily data comprehensibility. Along with increasing the number of data

are increased the effects from virtual reality too[ 5 ]

.

After the first applications of Virtual reality (VR) in the field of flight simulators

and computer game creating, arisen the need to implement the virtual technologies

into industry. Product design and virtual prototyping is one of the greatest

successes of VR applications in industry. The main attention in the field of VR

system applications in the technical practice is given to CAD/CAM/CAE systems of

higher level. It is for the cause of realization of export in format VRML (Virtual

Reality Modelling Language). The newest versions of these systems could aid both

existing formats VRML 1.0 and VRML 2.0 (97). The cost of a VR system is very

specific problem. The real cost of an effective system can only be assessed in

relation to the benefits it brings to a company. Such hardware and software is so

expensive that only large corporations could afford to build virtual environments.

One of the possible ways to solve the problem is to implement a VR format to a


6

lower systems with aim actively utilize systems of Computer Integrated

Manufacturing.

VR systems could be divided by ways of communication with user to such groups:

1. Window on World Systems - for displaying the virtual world are used

conventional computer monitors. This system is also called Desktop Virtual

Reality, but usually i t is called as Window on World (WoW).

2. Video Mapping - This system is modification of WoW system, where the siluetes

of human body could be displayed in 2D. User could see themselves on monitors in

interaction with environment.

3. Immersive Systems - basic VR systems, which enables user to be in virtual

environment. The feeling to be in is created by Head Mounted Displays (HMD).

This HMD could be with or without limitation of moving.

4. Telepresence - Attached to a high - speed network, VR takes telepresence to next

level. Participants can be thousands of kilometers apart and yet feel as if they are

all standing in the same virtual office or laboratory, with their product, design, or

experiment right in front of them not only talking about it , but interacting with it ,

change it etc.

Distribution of VR systems by hardware equipment is in these levels. Some levels

are not strictly kept, mainly in VR systems of higher levels[ 6 ]

.

For a long time people have been gathering a great amount of various data. The

management of megabytes or even gigabytes of information is no easy task. In

order to make the full use of it , special visualization techniques were developed.

Their goal is to make the data perceptible and easily accessible for humans.

Desktop computers equipped with visualization packages and simple interface

devices are far from being an optimal solution for data presentation and

manipulation. Virtual reality promises a more intuitive way of interaction.

The first attempts to apply VR as a visualization tool were architectural

walkthrough systems. The pioneering works in this field were done at the

University of North Carolina beginning after year 1986, with the new system

generations developed constantly. Many other research groups created impressive

applications as well - just to mention the visualization of St. Peter Basilica at the

Vatican presented at the Virtual Reality World‟95 congress in Stuttgart or

commercial Virtual Kitchen design tool. What is so fantastic about VR to make it

superior to a standard computer graphics? The feeling of presence and the sense of


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space in a virtual building, which cannot be reached even by the most realistic sti ll

pictures or animations. One can watch i t and perceive i t under different l ighting

conditions just like real facilit ies. One can even walk through non -existent houses -

the destroyed ones .

Another discipline where VR is also very usefu l is scientific visualization. The

navigation through the huge amount of data visualized in three-dimensional space is

almost as easy as walking. An impressive example of such an application is the

Virtual Wind Tunnel, developed at the NASA Ames Research Center. Using this

program the scientists have the possibility to use a data glove to input and

manipulate the streams of virtual smoke in the airflow around a digital model of an

airplane or space-shuttle. Moving around (using a BOOM display technology) t hey

can watch and analyze the dynamic behavior of airflow and easily find the areas of

instability. The advantages of such a visualization system are convincing - it is

clear that using this technology, the design process of complicated shapes of e.g.,

an aircraft , does not require the building of expensive wooden models any more. It

makes the design phase much shorter and cheaper. The success of NASA Ames

encouraged the other companies to build similar installations - at Eurographics‟95

Volkswagen in cooperation with the German Fraunhofer Institute presented a

prototype of a virtual wind tunnel for exploration of airflow around car bodies.

Other disciplines of scientific visualization that have also profited of virtual reali ty

include visualization of chemical molecules , the digital terrain data of Mars

surface etc.

Virtual engineering is currently approached in various ways. Because virtual

engineering is an emerging technology, its terminology and definit ion are not

completely established. In manufacturing, the major component of virtual

engineering is virtual manufacturing.


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CHAPTER-4

VIRTUAL MAUFACTURING

Virtual manufacturing is defined as an integrated, synthetic manufacturing

environment exercised to enhance all levels of decision and control. It can be

categorized into three groups according to the

A. TYPE OF PRODUCT AND PROCESS DESIGN[8]

a) Design-centered VM: provides manufacturing information to the designer during

the design phase. In this case VM is the use of manufacturing -based simulations to

optimize the design of product and processes for a specific manufacturing goal

(DFA, quality, flexibility, …) or the use of simulations of processes to evaluate

many production scenario at many levels of fidelity and scope to inform design and

production decisions.

b) Production-centered VM: uses the simulation capabili ty to modelize

manufacturing processes with the purpose of allowing inexpensive, fast evaluation

of many processing alternatives. From this point of view VM is the production

based converse of Integrated Product Process Development (IPPD) which optimizes

manufacturing processes and adds analytical produc tion simulation to other

integration and analysis technologies to allow high confidence validation of new

processes and paradigms.

c) Control-centered VM: is the addition of simulations to control models and actual

processes allowing for seamless simulation for optimization during the actual

production cycle.

B. TYPE OF SYSTEM INTEGRATION According to the definitions proposed by

Onosato and Iwata[ 9 ]

, every manufacturing system can be decomposed into two

different sub-systems:

a) Real Physical System (RPS): An RPS is composed of substantial enti ties such

as materials, parts and machines that exist in the real world.

b) Real Informational System (RIS): An RIS involves the activities of information

processing and decision making.

c) Virtual Physical System (VPS): A computer system that simulates the responses

of a real physical system is a virtual physical system, which can be represented by

a factory model, product model, and a production process model. The production

process models are used to determine the interactions between the factory model

and each of the product models.


9

d) Virtual Information System (VIS): A computer system that simulates a RIS and

generates control commands for the RPS is called a „virtual informational system

(VIS).

C. TYPE OF FUNCTIONAL USAGE VM is used in the interactive simulation of

various manufacturing processes such as virtual prototyping, virtual machining,

virtual inspection, virtual assembly and virtual operational system.

Virtual Prototyping (VP) mainly deals with the pro cesses, tooling, and equipment

such as injection molding processes[ 1 0 ]

. VM is allied to the Virtual Prototyping, the

Virtual CAD and Virtual CAM made most of the t ime by simulation. Roger W Pryor

discussed in his paper on the potential real benefits that can be realized through

cost saving, minimization of number of prototype models .

Virtual machining mainly deals with cutting processes such as turning, milling,

drilling and grinding, etc. The VM technology is used to study the factors affecting

the quality, machining time and costs based on modeling and simulation of the

material removal process as well as the relative motion between the tool and the

work piece.

Virtual inspection makes use of the VM technology to model and simulate the

inspection process, and the physical and mechanical properties of the inspection

equipment.

In Virtual Assembly, VM is mainly used to investigate the assembly processes, the

mechanical and physical characterist ics of the equipment and tooling, the

interrelationship among dif ferent parts and the factors affecting the quality based

on modeling and simulation .

A virtual assembly environment would enable a user to evaluate parts that are

designed to fit together with other parts. Issues such as handling ease of assembly

and order of assembly can be studied with virtual assembly.

Virtual operational control makes use of VM technology to investigate the material

flow and information flow as well as the factors affecting the operation of a

manufacturing system.

We can also classify virtual engineering in terms of production life cycle as virtual

design, digital simulation, virtual prototyping, and virtual factory. Virtual design is

done on virtual reality equipment. Digital simulation permits the verification and

validation of the product 's operation without using physical prototypes. Virtual

prototyping builds a simulated prototype that possesses the same geometry and


10

physical behavior as the real product. Virtual factory is a simulation of factory

production line.

There are many definition of Virtual Manufacturing (VM). Iwata (1993) defines

VM as follows: "A virtual manufacturing system is a computer system which can

generate the same information about a manufacturing system's structure, states and

behaviours as we can observe in real manufacturing systems".

The report from the 1994 Virtual Manufacturing User Workshop includes an in-

depth analysis of VM and its definition: "Virtual Manufacturing is an integrated

synthetic manufacturing environment exercised to enhance all levels of decision

and control" was annotated extensively to cover all the current functional and

business aspects of manufacturing. Also the practical side of manufacturing

virtuality is highlighted in this useful analysis. A comprehensive and thorough

survey of li terature on VM problems relating to production design and control can

be found in a study done at the University of Maryland[ 1 1 ,1 2 ]

.

Figure 1: Virtual Manufacturing

Environment: supports the construction, provides tools, models, equipment,

methodologies and organizational principles,

Exercising: constructing and executing specific manufacturing simulations using

the environment which can be composed of real and simulated objects, activities

and processes,

Enhance: increase the value, accuracy, validity,

Levels: from product concept to disposal, from factory equipment to the enterprise

and beyond, from material transformation to knowledge transformation,


11

Decision: understand the impact of change (visualize, organize, identify

alternatives)

The definition of VM given by a Bath University project team deserves attention.

According to this definition: "Virtual Manufacturing is the use of a desk -top virtual

reality system for the computer aided design of components and processes for

manufacturing - for creating viewing three dimensional engineering models to be

passed to numerically controlled machines for real manufacturing". This definition

emphasizes the functions aiding the machining process.

We choose to define the objectives, scope and the domains concer ned by the Virtual

Manufacturing thanks to the 3D matrix represented in Fig. 2 which has been

proposed by IWB, Munich[ 1 2 ]

.

Figure 2: Virtual Manufacturing Objectives, Scope And Domains

The vertical plans represent the three main aspects of manufacturing today:

Logistics, Productions and Assembly, which cover all aspects directly related to the

manufacturing of industrial goods. The horizontal planes represent the different

levels within the factory. At the lowest level (microscopic level), VM has to deal

with unit operations, which include the behavior and properties of material, the

models of machine tool – cutting tool – work piece-fixture system. These models

are then encapsulated to become VM cells inheriting the characterist ics of the lower

level plus some extra characteristics from new objects such as a virtual robot.

Finally, the macroscopic level (factory level) is derived from all relevant sub -

systems. The last axis deals with the methods we can use to achieve VM systems.


12

It is unquestionable that virtual manufacturing aids real manufacturing processes

and systems and it is perfected as the information technologies, the manufacturing

systems and the business demands develop. In this context, Virtual Manufacturing

should be recognized as an advanced information structure of Real Manufacturing

Systems, which integrates the available information tools and the virtual

environment immersiveness to achieve business -manufacturing goals.

Virtual manufacturing is used loosely in a number of contexts. It refers broadly to

the modelling of manufacturing systems and components with effective use of

audiovisual and/or other sensory features to simulate or design alternatives for an

actual manufacturing environment, mainly through effective use of computers. The

motivation is to enhance our abil ity to predict potential problems and inefficiencies

in product functionality and manufacturabili ty before real manufacturing occurs.

Another term that is sometimes mentioned in the context of virtual manufacturing is

agile manufacturing - sometimes defined as a structure within which agili ty is

achieved through the integration of three primary resources: organization, people,

and technologies. A way to achieve this is through innovative management

structures and organization, a skil l base of knowledgeable and empowered people,

and flexible and intelligent technologies. Whereas agility focuses on the ability to

make rapid changes in products and processes based on the voice of the customer,

virtual manufacturing provides a means for doing so. One area in which virtual

manufacturing has made an impact is that of rapid prototyping machines, building

prototypes by precise deposition of layer upon layer of powdered metal, a process

known as stereo lithography. Virtual reality (VR) has been used by companies such

as General Motors and Caterpillar to build electronic prototypes of vehicles,

instead of physical prototypes. This process reduces product development time

significantly.

The combination of information technology (IT) and production technology has

greatly changed traditional manufacturing industries. Many manufacturing tasks

have been carried out as information processing within computers. For example,

mechanical engineers can design and evaluate a new part in a 3D CAD syste m

without constructing a real prototype. As many activities in manufacturing systems

can be carried out using computer systems, the concept of virtual manufacturing

(VM) has now evolved.


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VM is defined as an integrated synthetic manufacturing environment for enhancing

all levels of decision and control in a manufacturing system. VM is the integration

of VR and manufacturing technologies. The scope of VM can range from an

integration of the design sub -functions (such as drafting, finite element analysis

and prototyping) to the complete functions within a manufacturing enterprise, such

as planning, operations and control .

However, a practical VM system is highly multidisciplinary in nature. Many of

these research projects and commercial software for VM systems have restrictions

in their implementation. Firstly, many machining theories and heuristics need to be

modeled in a VM system. However, most VM applications are designed only for

specific problems in pre-defined conditions. There is no one VM application having

all the technologies necessary to model a real machining process. Secondly, each

constructing process of a new VM system is akin to the reinvention of "wheels".

Besides geometrical modelling of machines, analytical modelling of machining

parameters, such as the cutting force, also has to be developed for every specific

task. Lastly, various VM systems are developed with different programming and

modelling languages, making them less flexible and scalable due to incompatibili ty

problems. Any change m one part would require the whole system to be modified.

During a VM simulation process, 3D graphics or VR will be an enabling tool to

improve human-to-human or human-to-machine communications. VM addresses the

collaboration and integration among distributed entities involved in the entire

production process. However, VM is regarded as evolutionary rather than

revolutionary. It employs computer simulation, which is not a new field, to model

products and their fabrication processes, and aims to improve the decision-making

processes along the entire production cycle. Networked VR plays an essential role

in VM development.

Current VR and Web technologies have provided the feasibil ity to implement VM

systems. However, this is not an easy task due to the following factors :

The conflicting requirements of real -time machining and rendering. Generally, a

high level of detail for a scene description would result in a high complexity of the

virtual scene.

The conflict ing requirements of static data structure and dynamic modelling. In the

virtual machining environment, a dynamically modeled work piece is essential.


14

The requirements for a consistent environment to avoid confusion and provide

navigational cues to prevent a user from getting lost in the VR environment.

The importance of an adequate sense of immersion in the VR environment, without

which even a highly detailed rendering will not help a user interact effectively in

the virtual 3D environment using conventional 2D interfaces such as a keyboard.

Representative applications of virtual reality technology are presented in a number

of areas. Applications in manufacturing or pointers to i t have been emphasized

particularly. Immersive display technology can be used for creating virtual

prototypes of products and processes. The user can then be exposed to an

environment that is next best only to an actual product or process. Examples from

the product standpoint include virtual prototyping of a product, such as

earthmoving equipment, instead of expensive physical prototyping. From the

process standpoint, such examples include detailed layout design involving hard -to

quantify factors such as adequate illumination, sources of distractions for operators

caused by heavy goods, and personnel movement .

The issues here are concerned with CAD model portability among systems, trade-

offs between highly-detailed models and real -time interaction and display, rapid

prototyping, collaborative design using VR over distance, use of the World Wide

Web for virtual manufacturing in small and medium-sized business, using

qualitative information (illumination, sound levels, ease of supervision, handicap

accessibility) to design manufacturing systems, use of intell igent and autonomous

agents in virtual environments, and determining the validity of VR versus reality

(quantitative testing of virtual versus real assemblies/equipment).

A number of initiatives in this area have been undertaken at the National Institute

of Standards and Technology (MIST). Engineering tool kit environments are needed

that integrate clusters of functions that manufacturing engineers need in order to

perform related sets of tasks. Integrated production system engineering

environments would provide functions to specify, design, engineer, simulate,

analyze, and evaluate a production system. Some examples of the functions that

might be included in an integrated production system engineering environment

are[ 7 ]

:

Identification of product specifications and production system requirements,

Productibility analysis for individual products,

Modelling and specification of manufacturing processes,


15

Measurement and analysis of process capabili ties,

Modification of product designs to address manufacturability issues,

Plant layout and facilities planning,

Simulat ion and analysis of system performance,

Consideration of various economic/cost trade -offs of different manufacturing

processes, systems, tools, and materials,

Analysis supporting selection of systems/vendors,

Procurement of manufacturing equipment and supp ort systems,

Specification of interfaces and the integration of information systems,

Task and workplace design,

Management, scheduling, and tracking of projects.

The interoperability of the commercial engineering tools that are available today is

extremely l imited, so as users move back and forth between different software

applications carrying out the engineering process, (hey must reenter data. Examples

of production systems that may eventually be engineered using this type of

integrated environment include transfer l ines, group technology cells, automated or

manually operated workstation's, customized multipurpose equipment, and entire

plants.

Manufacturers and their worldwide subcontractors and main suppliers can establish

agile manufacturing teams that will work together on the design, virtual

prototyping, and simulated assembly of a particular product while establishing

confidence in the virtual supply chain. Using the most advanced VR systems,

geographically remote members of the team can meet together in the same virtual

design environment to discuss and implement changes to virtual prototypes.

Examples of recent developments in virtual collaborative environments include

projection of gestures and movements of multiple remote designers as voice-

activated avatars to help explain the intention of the designer to others in real time

using high-speed ATM networks.

For monitoring and control of complex manufacturing systems, four dimensions can

be conceived to express complexity[ 6 ]

:

1. Space permits us to examine the physical location, layout, and flow issues

cri tical in all manufacturing operations.

2. Time permits us to address facil ity l ife -cycle and operational dynamic issues,

beginning with concurrent engineering of the production process and testing


16

facili ties during product design, extending through production and decline of the

initial generation product(s), cycling through the same process for future-

generation products.

3. Process allows us to study the coherent integration of engineering, management,

and manufacturing processes, it permits examination of the important, yet intricate

interplay of relationships between classically isolated functions. As examples,

consider relationships between production planning and purchasing, production

control and marketing, quality and maintenance, and design and manufacturing.

Processes involve decisions ranging from long-range operational planning to

machine/device-level short-term planning and control . The integration bet ween

various levels of aggregation is essential.

4. Network deals with organization and infrastructure integration. Whereas the third

dimension focuses on the actions, this dimension concentrates on the actors and

their needs and responsibilities. Clearly including personnel, the set of actors also

includes ail devices, equipment, and workstations; al l organizational units, be they

cells, teams, departments, or factories; and all external interactors, such as

customers, vendors, subcontractors, and partners. Issues such as contrasting

hierarchically controlled networks with hierarchical , autonomous agent networks

must be addressed.

Virtual manufacturing techniques enhance our ability to understand the four

dimensions described above by addressing issues such as designing products that

can be evaluated and tested for structural properties, ergonomic Functionality, and

reliability, without having to build actual scale models; designing products for

aesthetic value, meeting individual customer preferences; ens uring Facil ity and

equipment compliance with various Federally mandated standards, Facilitating

remote operation and control of equipment (telemanufacturing and telerobotics);

developing processes to ensure manufacturabil ity without having to manufacture

the product (e.g. avoiding destructive testing); developing production plans and

schedules and simulating their correctness; and educating employees on advanced

manufacturing techniques, worldwide, with emphasis on safety[ 5 ]

.


17

CHAPTER-5

METHODS AND SIMULATION TOOLS USED IN VIRTUAL

MANUFACTURING SYSTEMS VM has two main core activities. The first one is the “Modeling Activity” which

determines what to model and degree of thought that is needed. The second on is

the “Simulation Activity” which represent s model in a computer based environment

and compare to the response of the real system with degree of accuracy and

precision[ 1 1 ]

.

The following methods are necessary to achieve VM system:

Manufacturing characterization confines measure and analyze the variables that

influence material transformation during manufacturing. Modeling and

representation technologies provide different kinds of models for representation,

standardization the processes in such a way that the information can be shared

between all software applications (Knowledge based systems, Object oriented,

feature based models). Visualization, environment construction technologies

includes Virtual reality techniques, augmented reality technology, graphical user

interfaces for representation of information to the user in a meaningful manner and

easily comprehensible. Verification, validation and measurement the tools and

methodologies needed to support the verification and validation of a virtual

manufacturing system. Multidiscipline optimization: VM and simulation are usually

no self-standing research disciplines, they often are used in combination with

“traditional” manufacturing research. Nowadays numerous tools are available for

simulating manufacturing levels. Table[ 1 2 ]

shows the overview of simulation tools

applicable in manufacturing process.

Table I: Overview of Simulation Tools


18

CHAPTER-6

EDUCATIONAL REQUIREMENTS FOR VIRTUAL

MANUFACTURING SYSTEMS

Figure 3: Role of Virtual Manufacturing System

Old-fashioned manufacturing systems without virtual concept have processed

material and data by user operation and physical facilities. Nowadays, however,

manufacturing systems consist of two parts: one is a physical system, the other is a

virtual one. Since virtual systems are const ructed and operated in the computer

systems, the virtual can be more safety and more cost -effectively. And after the

verification of the data in the virtual environment, the error-free data transmitted

into the physical environment. There for the relationship between the physical and

virtual manufacturing systems can be collaborative.

To obtain the maximized effectiveness of the virtual manufacturing system, there

are some essential requirements.

3 D visualization

Since almost al l manufacturing facil ities such as an NC machine, a robot

manipulator and a work table, have 3 dimensional shape, showing the 3 D geometric

information can achieve the insight reasoning of the object‟s status. For interactive

and dynamic visualization, the recommended features are:


19

zoom in/out, zoom certain region,

rotating, panning

perspective and orthogonal projection

Identical Man-Machine Interface

To train the facility operation, user interfaces of virtual simulator are required

identical with the real physical facilities. The enumerated virtual facility interfaces

are:

control panels and teach pendant with push button, rotate switch, jogging tool

screens showing status

Simulation

Based-on 3 D geometric model, the systems are required to support the following

items:

discrete-event simulation handling with user -inputs as well as system-generated

events

detection of coll ision

estimation of cycle t ime

Interface and monitoring

CAD interface for input model construction

generation of next-step data such as an NC code or a robot program file

transmission of information into the real manufacturing system

teacher‟s monitoring of student‟s practice status


20

CHAPTER-7

ECONOMICS AND SOCIO-ECONOMICS

Table II: Factors of Virtual Manufacturing

EXPECTED BENEFITS

As small modifications in manufacturing can have important effects in ter ms of cost

and quality, Virtual Manufacturing will provide manufacturers with the confidence

of knowing that they can deliver quali ty products to market on time and within the

initial budget. The expected benefits of VM are:

From the product point of view it will reduce time -to-market, reduce the number of

physical prototype models, improve quality, …: in the design phase, VM adds

manufacturing information in order to allow simulation of many manufacturing

alternatives: one can optimize the design of product and processes for a specific

goal (assembly, lean operations, …) or evaluate many production scenarios at

different levels of fidelity,

From the production point of view it will reduce material waste, reduce cost of

tooling, improve the confidence in the process, lower manufacturing cost,…: in the

production phase, VM optimizes manufacturing processes including the physics

level and can add analytical production simulation to other integration and analysis

technologies to allow high confidence validation of new processes or paradig ms. In

terms of control, VM can simulate the behavior of themachine tool including the


21

tool and part interaction (geometric and physical analysis), the NC controller

(motion analysis , look-ahead)…

If we consider flow simulation, object -oriented discrete events simulations allow t o

efficiently model, experiment and analyze facility layout and process flow. They

are an aid for the determination of optimal layout and the optimization of

production lines in order to accommodate different order sizes and product mixes.

The existence of graphical -3D kinematics simulation are used for the design,

evaluation and off-l ine programming of work-cells with the simulation of true

controller of robot and allows mixed environment composed of virtual and real

machines.

The finite element analysis tool is widespread and as a powerful engineering desig n

tool it enables companies to simulate all kind of fabrication and to test them in a

realistic manner. In combination with optimization tool, it can be used for decision-

making. It allows reducing the number of prototypes as virtual prototype as cheaper

than building physical models. It reduces the cost of tooling and improves the

quality, …

VM and simulation change the procedure of product and process development.

Prototyping will change to virtual prototyping so that the first real prototype will

be nearly ready for production. This is intended to reduce t ime and cost for any

industrial product. Virtual manufacturing will contribu te to the following

benefits[ 1 1 ]

:

1. Quality: Design For Manufacturing and higher quality of the tools and work

instructions available to support production;

2. Shorter cycle time: increase the abil i ty to go directly into production without

false starts;

3. Producibility: Optimize the design of the manufacturing system in coordination

with the product design ; first article production that is trouble -free, high quality,

involves no reworks and meets requirements.

4. Flexibil ity: Execute product changeovers rapidly, mix production of different

products, return to producing previously shelved products;

5. Responsiveness: respond to customer “what -ifs” about the impact of various

funding profiles and delivery schedule with impro ved accuracy and timeless,

6. Customer relations: improved relations through the increased participation of

the customer in the Integrated Product Process Development process.


22

ECONOMIC ASPECTS

It is important to understand the difference between academic research and

industrial tools in term of economic aspects.

Figure 4: Academic Research Versus Industrial Tools

The shape of the face in the diagram presented in Figure[ 1 2 ]

, is defined by two

curves:

– “effort against level of detail” where “level of detail” refers to the accuracy of

the model of simulation (the number of elements in the mesh of a FEM model or the

fact if only static forces are taken into account for a simulation , …

– “effort against development in time” is a type of time axis and refers to future

progress and technological developments ( e.g. more powerful computers or

improved VR equipment).

Universities develop new technologies focusing on technology itself. Researchers

do not care how long the simulation will need to calculate the results and they not

only develop the simulation but they need to develop the tools and methods to

evaluate wether the simulation is working fine and wether the results are exact. On

the other hand, industrial users focus on reliability of the technology, maturity

economic aspects (referring to the effort axis) and on the integration of these

techniques within exist ing information technology systems of the companies ( e.g.

existing CAD-CAM systems, …). To our mind, Virtual Manufacturing is, for a part

of its scope, still an academic topic. But in the future, i t will become easier to use

these technologies and it will move in the area of industrial application and then


23

investments will pay off. For example in the automotive and aerospace companies

in the late 60‟s, CAD was struggling for acceptance. Now 3 -D geometry is the basis

of the design process. It took 35 years for CAD-CAM to evolve from a novel

approach used by pioneers to an established way of doing things. During this

period, hardware, software, operating systems have evolved as well as education

and organizations within the enterprise in order to support these new tools. Today,

some techniques are daily used in industry, some are mature but their uses are not

widespread and some are still under development.


24

CHAPTER-8

ADEQUACY OF A VIRTUAL MANUFACTURING SYSTEM

It will depend on the adequacy of the model that how much the virtual system is

close to the real system. The adequacy of a virtual manufacturing system is defined

as the agreed degree of accuracy and precision between the responds of the VMS

and the real system under the same conditions in all points of the modeling space.

Two problems arise here, how accurate and how precise the virtual model is.

Accuracy determines the deviation of the results produced by VMS from the

results, produced by the real system.

Precision defines the spread of modeling results. There is a curious detail here: the

problem is how to increase the spread of simulation results rather than to reduce i t.

VMS often exhibits a "perfectly precise" behavior, yielding repeti tive constant

responses at a point of the modeling space, something which is quite far from the

real si tuation. To implant a stochastic character to the VMS, methods of the

imitation modeling are employed in which the principal factors are modeled as

stochastic to emulate a stochastic system behavior.

The process of proving the adequacy of a VMS is called validation . If the VMS

does not represent adequately the real system, i t should be improved iteratively

until the desired degree of accuracy and precision is achieved. Th is process is

referred to as a calibration .


25

CHAPTER-9

APPLICATIONS OF VM The virtual manufacturing has been successfully applied to many fields such as,

automobile manufacturing, aeronautics and astronautics, railway locomotives,

communication, education and so on, which has an overpowering influence on

industrial circles.

A. Automotive domain[ 1 3 ]

The Integrated-Computer Aided Research on Virtual

Engineering Design and Prototyping Lab of Wisconsin University developed a set

of virtual foundry platform which make use of solid glasses to observe three-

dimensional image, establish multifarious geometric model by language and ma ke

sure geometry size and place with data glove. American Daimler Chrysler

Automotive Company adopted virtual prototype technology in their research of

automobile part and thus shortened the developing period. American Caterpillar

Co., the world‟s leading manufacturer of engineering machinery and construction

equipment, applied virtual prototype techno logy in the design optimization and the

internal visibility evaluation of loaders. The shape design using the virtual

technology can be modified and evaluated at any time. The modeling data after

scheme confirming can be directly used for the stamping tool design, simulation

and processing, even for the marketing and propaganda. Application of V M is used

in automobile factory shop floor and also in car driving simulation . Song Cheng

describes a case research of D auto -company‟s virtual paint shop established with

the technology of three dimensional simulations.

B. Aerospace domain Virtual Manufacturing in aerospace industry is used in FEA

to design and optimize parts, e.g. reduce the weight of frames by integral

construction, in 3D-kinematics simulation to program automatic riveting machines,

and few works dealing with augmented reality and virtual reality to support

complex assembly and service tasks in aircraft design[ 1 2 ]

. The aero engine model

created in virtual environment describes where tools are developed and used to help

manufacturing and design engineers to take action and decisions on problems

normally solved only by experience. Henrik R[ 1 4 ]

explained application of VM in

aircraft domain by considering Turbine Exhaust Casing (TEC). TEC is

manufactured by fabrication and about 200 welds are needed to manufacture the

product. Issues have been identified with the robustness of the geometrical

tolerances created during production. Several welding sequence concepts were


26

investigated to find a more robust manufacturing sequence. From the welding

simulations it was shown that the residual stresses could be lowered using a

different welding sequence. Moreover, to further avoid the issue with geometrical

tolerances a pre-deformation was given to the product before we lding, the amount

of needed pre deformation was calculated by the virtual welding simulation tool.

C. Healthcare domain Healthcare is one of the biggest adopters of virtual re ality

which encompasses surgery simulation, phobia treatment, robotic surgery and skil ls

training[ 1 5 ]

. One of the advantages of this technology is that it allows healthcare

professionals to learn new skills as well as refreshing existing ones in a safe

environment. Plus it allows this without causing any danger to the patients. Virtual

manufacturing applications in the healthcare industry are associated with many

leading areas of medical technology innovation including robot -assisted surgery,

augmented reality (AR) surgery, computer -assisted surgery (CAS), image-guided

surgery (IGS), surgical navigation, multi -modality image fusion, medical imaging

3D reconstruction, pre-operative surgical planning, virtual colonoscopy, virtual

surgical simulation, virtual reality exposure therapy (VRET), and VR physical

rehabilitation and motor skills training. Stent design influences the post -procedural

hemodynamic and solid mechanical envir onment of the stented artery by

introducing non-physiologic flow patterns and elevated vessel strain. This

alteration in the mechanical environment is known to be an important factor in the

long-term performance of stented vessels. Because of their cri tical function, stent

design is validated by methods such as FEA.

D. Home Appliance domain The virtual kitchen equipment system developed by a

Japanese company Matsushita allows customers to experience functions of a variety

of equipment in virtual kitchen environment before the purchase of actual

equipment. These choosing results can be stored and send to the production

department through computer network and be manufactured.

E Other applications of VM explicated[ 1 6 ]

Product shape style designs of

conventional automobiles adopt the plastic to manufacture the shape model. The

shape design using the virtual technology can be modified and evaluated at any

time. In the shape design of other products such as building and decoration,

cosmetic packing, communication, etc. has great advantages. In piping system

design , through the implementation of v irtual technology, the designer can enter

into virtual assembly by conducting piping layout and check the potential


27

interference and other problems. Product movement and dynamics simulation

displays the product behavior and dynamically perform the product performance.

The product design must solve the movement coordination and cooperation of each

link on the production line. The usage of simulation technology can intuitively

conduct the configuration and design, and guarantee the working coordination. In

Product assembly simulation the coordination and assembly property of mechanical

product is the place where most errors of the designers emerge. In the past , the

error at final stage leads to the scrapping of parts and delay manufacture product

which causes more economic losses and damage. The implementation of virtual

assembly technology can conduct the verification in the stage of design, and ensure

the correctness of design to avoid the loss. The adoption of virtual reality

technology in virtual prototype suitably helps in 3D modeling of products, and then

set the model into VE to control, simulate and analyze. Simulation and optimization

of the productive process of enterprise are used in the productive technology by

formulating the products, man power of the factory, reasonable allocation of

manufacturing resources, material storage and transportation system. LIU Qing-ling

addressed the VM system provides the working environment of collaboration for the

virtual enterprise partners, that affords collaboration support for each link of the

whole course of orders of users, originali ty in product, design, production of parts,

set assembling, sales and after sale services. Virtual Simulation is an important

technologic method accounting for complex design and testing of designing

proposal. Yongkang Ma explains in his research that the elem ents such as welding

robots and fixtures of workstation for body-in-white welding are analysed and

optimized using digital modelling method of work station.

F. Virtual Teaching Platform of Digital Design and Ma nufacturing To promote

students‟ learning interest and improve teaching effects Jianping Liu and Qing

Yang adopts a virtual teaching platform of digital design and manufacturing in

innovation teaching methodology. Yu Zhang explains virtual reali ty technology in

program -based learning helps students to establish their spatial concepts and

enhance their understanding on engineering drawings . Huang Xin represents motion

simulation of entire product mechanisms could be achie ved by means of the

function of intelligent simulation . Liu Jianping suggests that with the help of the

CAD software, students can easily understand how to read technical drawing and

replicate same in software, and the cost of design can also be saved.


28

G. Virtual Training Hazim El-Mounayri concluded that the architecture of a virtual

training environment (VTE) was used to develop the corresponding system for the

case of CNC milling. A recent application of VE based training includes training

for operation of engineering facilities, CNC manu facturing. The Learning

Environments Agent (LEA) engine includes a hierarchical process knowledge base

engine, an unstructured knowledge base engine for lecture delivery; a rule based

expert system for natural -language understanding, and an interface for driving

human-like virtual characters. Integrated Virtual Reality Environment for Synthesis

and Simulation engine was used to drive the virtual environment, display the

engineering facility and manage a multimodal input from a variety of sources. A

general geometric modeling approach is based on modeling precisely the geometries

involved in the machining operation, including work-piece geometry and tool

geometry.

H. The Development Of Virtual Manufacturing Mold On Automobile Panels The

development process of mould virtual manufacturing. At first, the desired

production is analysized, and then concept design is performed. After that, the

optimized design and system integration can be performed. In a virtual

environment, the virtual product model can be constru cted by using relevant

software[ 1 7 ]

. This is a gradual process. According to the product development

requirement, virtual model function, the behavior of simulation model and

performance of the virtual simulation analysis are compelled by adopting

corresponding simulation analysis tools. Th en modeling and simulation analysis are

repeated which bases on the results of the simulation analysis. When the

improvement and model of virtual manufacturing mold meet the original design

objective, then the real manufacturing is expected to start before the automobile

panels being put on production, al l the production has gone through the inspection

of virtual practice. Thus the potential difficulties of production and unreasonable

design can be removed through the virtual analysis. Then all the design c an be

modified or redesigned until the entire manufacturing process can be reasonably

and smoothly finished. Therefore it can not only shorten the period of development

cycle and reduce the cost of development, but also can improve the quali ty of

products.


29

CHAPTER-10

FUTURE RESEARCH DIRECTION

The research on virtual manufacturing technology is still at the stage of system

framework and general technology, while the application oriented research on the

key technology needs to be developed. The future research directions are as

follows:

VP technology and system of assembly simulation, production process,

scheduling simulation and NC machining process simulation should be based

on photorealistic animation.

Man-machine cooperation solution in virtual environment and virtual

manufacturing with the virtual reali ty technology.

The distributed/collaborative simulation technology of the hybrid model

based on complex system.

Requirements of a large amount of CPU power for real-t ime simulation.

Open system architecture for virtual manufacturing research based on the

distributed processing environments.

Selective addition to animation

Shop floor based generic models

VM methodology for process characterization

Technologies to simulate assembly operations

Declarative representation of product and processes

Natural language for VM meta -model

Cost database and integration

VM user interface (communication between VM knowledge base and user)

VM verification & validation methods, algorithms & tools

Process model and simulation validation

Methodology for using a VM system

VM framework (guidelines, integration standards, etc.)

Methodology for design abstraction

Tools to relate conceptual design with possible manufacturing methods and

processes and cost estimates based on manufacturing features

Manufacturing engineering automation (knowledge -based computer

applications to perform manufacturing engineering decision making)

Simulation architecture


30

CHAPTER-11

CONCLUSION

The term global virtual manufacturing (GVM) extends the definition of VM to

include, and emphasize, the use of Internet/intranet global communications

networks for virtual component sourcing, and multisite multiorganization vir tual

collaborative design and testing environments. Companies that commit to GVM may

be able to dramatically shorten the time to market for new products, cut the cost of

prototyping and preproduction engineering, enable many more variations to be tried

out before committing to manufacture, and Increase the range and effectiveness of

quality assurance testing. Virtual prototypes can be virtually assembled, tested, and

inspected as part of production planning and operative graining procedures; They

can be demonstrated, market tested, used to brief and rain sales and customer staff,

transmitted instantly from site to site via communications links, and modified and

recycled rapidly in response to feedback.

Designers do not design in real time but manufacturing does occur in real time. It is

therefore necessary for a design by manufacture system to be able to relax and

tighten the applied constraints as required by the designer. Additionally, multiple

levels of constraints may be applied in different circumstances; for example there

are several possible ways of dealing with feed rates:

no constraint (pure design, don't care about feed rates);

feedback constraint (design with manufacturing in mind) use colour, sound, and

labels to indicate physical quantities such as rate of metal removal;

full constraint (manufacturing conditions) don't allow constraints to be broken.

For the flexibil ity and performance we require, be believe that a constraint system

based on rules, rather than physical modelling, will best meet our needs.

Virtual reality and virtual manufacturing often concentrate on an interface between

VR technology and manufacturing and production theory and practice. In this report

we concentrate on the role of VR technology in developing this interface. It is our

belief that the direction of evolution of manufacturing theory and practice will

become clearer in the future once the role of VR technology is understood better in

developing this interface.


31

CHAPTER-12

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