virtual environments for design and manufacturing

7/30/2019 VIRTUAL ENVIRONMENTS FOR DESIGN AND MANUFACTURING

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VEDAM: VIRTUAL ENVIRONMENTS FOR

DESIGN AND MANUFACTURING

Scott Angster, Graduate Assistant

School of Mechanical and Materials

Engineering

Washington State University

Pullman, WA 99164-2920

[email protected]

Sankar Jayaram, Assistant Professor

School of Mechanical and Materials

Engineering

Washington State University

Pullman, WA 99164-2920

[email protected]

ABSTRACT

The current demand to reduce the time and cost involved in taking a product from

conceptualization to production has forced companies to turn to new and emerging technologies

in the area of design and manufacturing. One such technology is virtual reality. Current

computer-aided design, computer-aided manufacturing, design for assembly, design for

manufacture and manufacturing simulation tools provide the user with valued information, but

fall short of providing the information that virtual reality techniques could provide. This paper

describes a system called VEDAM, Virtual Environments for Design And Manufacturing, that

has been designed and partially implemented to support virtual design, virtual manufacturing and

virtual assembly. VEDAM is aimed at extending the capabilities of existing parametric

CAD/CAM systems. This paper presents the overall description of VEDAM and a preliminary

implementation.

Keywords: Virtual Manufacturing, Virtual Design, Virtual Assembly, Virtual Reality, Virtual

Prototyping

INTRODUCTION

The current marketplace has demanded that companies reduce the time and cost involved in

taking a product from concept to production. Software for computer-aided design, computer-

aided manufacturing, design for assembly (DFA), design for manufacture (DFM) and

manufacturing simulation have assisted in this reduction of time and cost. Integrated

CAD/CAM, solid modeling, parametric design and feature recognition are all valuable tools that

have been developed for these software products.

The integration of CAD and CAM has allowed engineers to design some of the manufacturing

processes using one unified model representation without having to recreate the model several

times or transfer the model between software systems. Molding and welding plans and

numerical control cutter paths for milling machines and lathes can be generated using solid


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models. If the development of machining operations proves to be difficult for the current design,

modern parametric design abilities of software allow easy and quick modification of the design.

This can be done prior to committing the design to actual manufacturing. Feature recognition

allows software to analyze a design and distinguish between various features that compose the

part. By associating manufacturing operations with these various features, the automatic

generation of manufacturing plans can be accomplished. This results in the elimination of someof the time spent by designers during this phase of the product design. The analysis of these

plans can be done using manufacturing simulation software. Through the creation of three-

dimensional graphical representations of manufacturing plants, designers can now program the

plant to go through a series of motions simulating the manufacturing of parts. Again, if problems

arise at this stage, designs can be modified prior to committing actual manufacturing time.

These software systems have provided significant savings in time and cost, but are still not

able to provide the support needed by engineers to meet the demands of the modern product

development cycle. This has forced companies to look to other emerging technologies to better

equip their engineers in the areas of design and manufacturing. One such technology is virtual

reality. Recent rapid advances of computer hardware have made virtual reality a viabletechnology for engineering applications. Virtual reality is being used in todays design

environment to walk through potential architectural renovations, sit in automobiles to analyze

dashboard layouts and walk through manufacturing simulations to view layout and space

requirements. The next step is the incorporation of virtual reality techniques into the early design

and manufacturing planning of products.

LITERATURE REVIEW

Several groups have recognized the benefits of integrating virtual reality with early design

decisions through virtual design, virtual assembly and manufacturing simulation. Jayaram et al.

laid out the initial requirements for a virtual manufacturing environment (VME) as a part of anapplications development environment [9,10]. Washington State University has developed a

system for the early design evaluation of automobile interiors. This system utilizes Pro/Engineer

models that are brought directly into a virtual design environment. Once immersed in the virtual

environment, a user can evaluate the design, evaluate alternate designs and conduct ergonomic

studies using full human body tracking. [2].

Through joint work at the University of Illinois, Chicago, and Purdue University, a prototype

virtual reality based computer-aided design system has been designed and implemented. The

focus of this work is to allow a simplified method of designing complex mechanical parts

through the use of virtual reality techniques [12]. Work at the Georgia Institute of Technology is

focusing on early design changes based on demanufacturing and servicing criteria. A Virtual

Design Studio is being developed to enable designers to interact with recycling and tooling

experts in a virtual environment. Parts that are being designed will be disassembled within the

virtual environment to identify and correct demanufacturing and servicing problems [11].

The University of Bath in Bath, UK has developed an interactive virtual manufacturing

environment. This system models a machine shop floor containing a three-axis numerical


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control milling machine and a five-axis robot for painting. The user can mount a workpiece on

the milling machine, choose a tool and perform direct machining operations, such as axial

movements or predefined sequences, or load a part-program from memory [4]. This software

does not provide the users with the ability to create their own machines or interact with them in a

natural manner.

A virtual workshop for mechanical design was developed at Massachusetts Institute of

Technology[3]. The goal of the project was to develop a simulated workshop for designers to do

conceptual design work while having to take into account manufacturing processes. The

simulated workshop consists of a band saw, a drill press, a milling machine, a radial arm saw and

a table saw. This software provides only a two-dimensional interface to the user. There is no

link to an integrated, parametric CAD/CAM system.

Deneb Robotics has commercially available software for manufacturing simulation, virtual

milling, virtual spray painting, virtual arc welding and telerobotics. Most of the these systems

are precompiled software tools where all work is done using Denebs graphical user interface on

the screen for setting up the manufacturing plant, etc. and all subsequent interaction is also doneon the screen via the mouse and keyboard.

The research discussed in this paper differs from the existing work being done in this area in

several ways. The most important difference is in the manner in which the user interacts with the

environment. Other than the graphical user interface that will be used to start one of the virtual

environments or switch between them, and the parametric CAD/CAM-based machine

development environment, the user interacts with the system in an immersive three-dimensional

environment using advanced input and output devices. The other key distinction between this

research and other related work is the integration of the proposed system with a parametric

CAD/CAM system.

PROBLEM DEFINITION

Software for computer-aided design, computer-aided manufacturing, design for assembly,

design for manufacture, and manufacturing simulation have reduced design time, redesign costs

and manufacturing costs. However, there is still often a need to produce physical mock-ups to

test assembly requirements, manufacturing plans or ergonomic functionality. The next step in

reducing design time and cost is the integration of virtual reality technology into the conceptual

design and process planning stages [5].

Current CAD/CAM, DFA, DFM and manufacturing simulation tools provide the designer

with valued information but may fall short of providing the information that new techniquesusing virtual reality technology could provide. Current CAD/CAM software such as

Pro/Engineer and I-DEAS Master Series, provide powerful design environments using

parametric design methods and solid modeling. One drawback is that the designer is limited to

the size of the viewing area of the monitor being used. A large part or assembly must be viewed

in either a scaled down view to analyze the entire design or in true scale with limited view.

Current DFA software attempt to reduce the number of parts by merging several parts into one to


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reduce the number of assembly procedures required. This may, in fact, cause handling

difficulties, either machine-related or human-related, later on in the manufacturing process.

Current DFM software may indicate that the part can be produced using a series of

manufacturing processes without the knowledge of the actual manufacturing plants capabilities.

Current manufacturing simulation software are often limited to predefined functionality for both

machines and human models. If the projected plans for manufacturing a part involves a humanoperator or handler, a predefined human model can not give back true human feedback

concerning ease of fit, ease of handling, etc.

Many of the above issues can be addressed with the use of virtual reality technology. By

using new and emerging three-dimensional input and output devices, a designer can be

immersed in any one of several virtual environments. True-scale, three-dimensional models can

be viewed and modified by the designer in a virtual design environment. Parts can be picked up

and assembled in a virtual assembly environment [6,7]. Manufacturing plants can be replicated

to allow engineers to test numerical code, fixtures or entire assembly lines in a virtual

manufacturing environment [3, 4, 5, 8]. It was the objective of this research to design and

implement a system called VEDAM, Virtual Environments for Design and Manufacturing, thatallows designers to incorporate these virtual reality techniques into the design and process

planning stages of the product.

PROPOSED SOLUTION

As stated earlier, there are several areas in which virtual reality can assist in the design and

manufacturing planning of a product. These include parametric design changes within a virtual

design environment, virtual assembly, virtual manufacturing, and human-integrated design. A

system to support these concepts would be linked to an existing parametric design software

system, such as Pro/Engineer, as seen in Figure 1. This figure shows the proposed system,

VEDAM, and its components, the Machine Modeling Environment (MME), the Virtual DesignEnvironment (VDE), the Virtual Assembly Environment (VAE), and the Virtual Manufacturing

Environment (VME) [1]. During a design session, the user would enter into the virtual

environments via the main interface to test designs or manufacturing ideas. All required data

from the CAD/CAM system would then be passed into the virtual environments. Upon exiting

the virtual environments the user would have the option of passing data back into the CAD/CAM

system. VEDAM, combined with a parametric CAD/CAM system, would provide a complete

system for engineers to evaluate potential designs and process plans.

The most general requirement of any virtual reality software system is the existence of a

virtual environment for the user, such that the user feels as if he/she is part of the environment

and can easily interact with this environment. To develop this type of natural interaction, several

issues including the graphical backbone, the input devices and the output devices need to be

addressed.


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Data

Integrator

VDE

VAE

VME

User

VEDAM

Data Flow

Interaction

Parametric

CAD/CAM

System

MME

MainInterfaceLegend

Figure 1. VEDAM System

Machine Modeling Environment

The machine modeling environment (MME) is the only environment which is not a virtual

environment. This environment is part of the parametric CAD/CAM system. The goal of the

MME would be to provide an environment to the user that would allow the creation of any

machine found on a factory floor. This would include mills, lathes, conveyors, robots, etc. This

capability would be provided by customizing an existing parametric CAD/CAM system. This

environment would provide the user with the ability to duplicate the functionality of the real

machine with the virtual machine. Once a machine is created, it can then be positioned on a

factory floor with other machines that have previously been created. The functional requirementsof this environment would include the following:

Axial movement association - Provide the functionality for specifying which assemblies of

the virtual machine correspond to the various axial movements of the real machine.

Button/switch/toggle library - Library of parametrically defined buttons and switches.

Cutter descriptions - Geometry, material, etc. of available cutters.

Machine parameter set up - A predefined list of machine parameters and the capability of

adding user-defined parameters.

Functional association of assemblies - During the operation of a machine, many actions of

the machine are dependent on other actions. This type of functional dependence of machineactions would be supported.

NC code support - Support for various levels of NC codes.

Machine layout- Laying out the factory floor using machines created using the MME.


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Virtual Design Environment

The virtual environment that would aid in the design of new parts is the virtual design

environment. After completing an initial design using an existing, commercial, parametric

CAD/CAM system, the model would be imported into the virtual design environment. The

design would be evaluated in a true three-dimensional environment, not limited by screen size.Parametric design changes would be made and evaluated within the virtual environment. Once

the user is satisfied with the design, the data would then be sent back to the CAD system

database. The process of modifying the parametric model would require the following:

Three-dimensional user interface - In the immersive VEDAM system, the user must have a

method for communicating with the system other than through the use of keyboard/mouse.

Parameter selection modes - A method for selecting a parameter for modification.

Data transfer mechanism - A mechanism would have to be created that takes the values

entered in the design environment and sends them to the parametric CAD/CAM system.

Virtual Assembly Environment

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. This environment would allow the user to focus on the assembly

process. First, the users will get immediate feedback when they attempt to handle the parts to be

assembled. Next are the issues of ease of assembly and order of assembly. These ideas would be

addressed with the concept of a soft volume combined with human feedback. The volume of the

path swept out by a part moving through space is often called a soft volume. Also, after the

assembly process has been studied, a partial process plan will have been developed which

dictates the order of assembly. The virtual assembly environment presents some new tasks to the

functionality of the VEDAM system. These include:

Grasping objects - Grasping of parts using an instrumented glove.

Tracking objects - Tracking the movement of the part through space during assembly.

Assembly constraints - When a part is assembled with another part, there are assembly

constraints that must be met such as axial alignment, surface mating or surface alignment.

Interference checking - Interferences between parts, assemblies, and soft volumes.

Virtual Manufacturing Environment

A virtual manufacturing environment (VME) would enable a designer to test NC code,fixtures, assembly lines, etc. in a virtual factory to ensure that the proposed process plans can be

achieved in the real factory [3, 4, 5, 8]. This process would speed up the generation of full

process plans by taking into account the actual factory capabilities during the design stage.

Redesigning parts such that they can be handled easier or machined easier can be costly when

done at a late stage of the design process.


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The VME would allow the user to use the virtual factory created in the MME. The user

would be able to pick up and place parts on any one of the factory machines. To operate a

machine the user would be able to turn dials, flip switches, move levers or whatever the

particular machine requires. Movement around the factory floor could be achieved in a number

of ways such as using hand gestures, voice commands or just simply walking. When operating a

machine, fixtures and jigs will be used to hold workpieces in each machine. Bits, blades, andother cutting tools would be changeable and only fit those machines they are intended for. The

actual machining operation would be physically modeled. This means the forces causing tool

wear, surface quality, etc. would be calculated and made available to the user.

After each machining process is completed, the user would have the option of saving the part

being produced. The storage of each step of the process would create a drawing for each step in

the process plan. These could be referenced for quality control issues during production.

Functional requirements of the virtual manufacturing environment include the following:

User/Environment interaction - The interaction between the user and machines and the

interaction between the user and the parts.Environment interaction - Interaction between various components of the environment itself

such as the interaction between the machine and the cutter as well as the cutter and the part.

Physical modeling - Physically modeling the machining process such as cutting forces, cutter

wear, surface quality and power requirements.

Human-Integrated Design

One of the virtues of using virtual environments for analyzing designs and manufacturing

plans is the concept of human-integrated design. Once the user is immersed into the virtual

environment, he/she will get a better sense of the assembly processes, manufacturing processes

or handling processes involved with a part that is being evaluated. This is because it is the user

who will be performing these tasks, not a simulated human. The analysis of repetitive motion

injuries, space or movement requirements and manufacturing time requirements would all be

possible since there will be actual human feedback. This will provide a new direct feedback of

human factors into the design and process planning stages. The incorporation of a full human

model into the VEDAM system involves the following:

User/human model position correlation - Full three-dimensional tracking of the user to

accurately match the position of the human model with that of the user.

User/human model size correlation - A scaleable human model for the software system to be

compatible with all different size users.

ARCHITECTURE

Based on the functional requirements specified above, an object-oriented analysis of the

VEDAM system architecture was conducted. The decision to use an object-oriented approach

was based on ease of future modification, extension and flexibility of the system. This analysis

provided a list of classes that would enable the VEDAM system to be created in steps, where


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each step produces more features that can be added to the system. The object-oriented analysis

can be seen in Figure 2.

Input

Manager

FOBGloveOutput

Manager

Interaction

Manager

Human

Model

Machine

Fixture

Cutting

Tool

Stock

Workpiece

Assembly

Geometry

Model

Manager

Legend

A B A uses B

Figure 2. VEDAM Architecture

This figure shows most of the classes that were designed to be part of the VEDAM system.

The interaction of the classes is also shown by the arrow indicating which classes are using other

classes. At the heart of the system is the interact manager. This class is responsible for all

interaction between the user and the system as well as the interaction between the various parts of

the system. A model manager is provided to handle all data transfer between the CAD/CAMsystem and VEDAM. The human model provides all of the functions necessary for incorporating

a full human model into the system. The input managerand output managerprovide the utilities

for communicating with all of the various virtual reality hardware. The various classes that

compose the machine, parts, stock, workpieces, etc., provide all of the methods necessary for the

actual machining inside the virtual manufacturing environment as well as the assembly

procedures for the virtual assembly environment.

INITIAL IMPLEMENTATION

After completing the object-oriented analysis of the VEDAM system, an initial

implementation of the system was completed. The system was created on a Silicon GraphicsCrimson workstation with Reality Engine graphics. All classes were developed using C++ and

the graphics were created using Performer 2.0. The virtual reality hardware used in this

implementation include a Virtual Research VR4 helmet, a Virtual Technologies 22-sensor

Cyberglove, and an Ascension Flock of Birds tracking system with an ERT and six birds.

This system uses most of the classes that were identified during the analysis phase. A

prototype of both the virtual manufacturing environment and the virtual design environment have


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been implemented. The machine class was created during the process of modeling a table-top

milling machine, shown in Figure 3. The modeling of the milling machine was done in

Pro/Engineer and, through the use of the model manager, brought in to the VEDAM system.

Once the machine class was created, several other machines were created and brought in to the

VEDAM system. These include a table-top lathe and a water jet. The lathe can be seen in Figure

4. The user interacts with the machines in the same fashion as with the real machines. A genericcontroller was created to provide the functions of XYZ axis control, floating zero support, and

load and run NC codes. The motion of the machines are tied into the current graphics display

frame rate as to accurately portray the proper feed rates.

The virtual design environment is built around the use of a three-dimensional graphical user

interface. This interface provides the user with a menu system that the user interacts with by

selecting menu items with a touch of the finger. When the user selects a model to be analyzed,

the model manager extracts the needed parametric data from the CAD/CAM database. The

model is then displayed to the user. The user can then modify the parameters through the use of

the graphical user interface. After modifications, the model managersends the information back

to the CAD/CAM system where the model is regenerated. The model is then redisplayed to theuser reflecting the modified parameters. Figure 5 shows the parameters of the model being

displayed to the user as well as a keypad that is used for entering in new values for a parameter.

CONCLUSIONS

This paper has described the system requirements of a virtual reality system that would aid

engineers in the conceptual design and manufacturing process planning stages of a product. By

linking such a system to an existing parametric CAD/CAM system, engineers can immediately

obtain the benefits of using a VR system. The analysis of designs in a true, three-dimensional

environment, manufacturing the part in a replication of the actual factory and the assembly of

mating parts are all valuable tasks in the early stages of a products design cycle. The initialimplementation of this system has formed the basis for a full implementation of the VEDAM

system.

REFERENCES

[1] Angster, S.R., VEDAM: Virtual Environments for Design and Manufacturing,

Ph.D. Dissertation, Washington State University, December 1996.

[2] Angster, S.R., Gowda, S., Jayaram, S., Feasibility Study on Virtual Reality for

Ergonomic Design, IFIP 5.0 Workshop on Virtual Prototyping, September, 1994.

[3] Barrus, J.W., The Virtual Workshop: A Simulated Environment for Mechanical Design,

Ph.D. Dissertation, Massachusetts Institute of Technology, September, 1993.

[4] Bayliss, G.M., Bower, A., Taylor, R.I., and Willis, P.J., Virtual Manufacturing, Presented

at CSG 94 - Set Theoretic Modelling Techniques and Applications, Winchester, UK,

April 13-14, 1994.


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[5] Bennet, G.R., Virtual Reality Simulation Bridges the Gap Between Manufacturing and

Design, Mechanical Incorporated Engineer, April/May, 1995.

[6] Connacher, H., Jayaram, S., and Lyons, K., Virtual Assembly Design Environment,

Proceedings of the 15th

ASME International Computers in EngineeringConference, Boston, MA, September 17-21, 1995.

[7] Connacher, H., Jayaram, S., and Lyons, K., Virtual Assembly Using Virtual Reality

Techniques, accepted for publication in CAD, 1996.

[8] Jaques, M., Strickland, P., Oliver, T.J.,Design by Manufacturing Simulation:

Concurrent Engineering Meets Virtual Reality, Mechatronics, 1995.

[9] Jayaram, S., CADMADE - An Approach Towards a Device-Independent Standard for

CAD/CAM Software Development, Ph.D. Dissertation, VPI & SU, April 1989.

[10] Jayaram, S., and Myklebust, A., Device Independent Programming Environments for

CAD/CAM Software Creation, CAD, Volume 25, No. 2, February 1993.

[11] Rosen, D.W., Bras, B., Mistree, F., and Goel, A., Virtual Prototyping for Product

Demanufacture and Service Using a Virtual Design Studio Approach, ASME

Computers in Engineering Conference, 1995.

[12] Trika, S.N., Banerjee, P., and Kashyap, R.L., Virtual Reality Interfaces for Feature-

Based Computer-Aided Design Systems, accepted for publication in CAD, 1996.


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Figure 3. Table-Top Milling Machine - Virtual and Actual

Figure 4. Table-Top Lathe - Virtual and Actual

Figure 5. VDE Images - Model Parameters and Keypad

virtual environments for design and manufacturing

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