In order to achieve efficient operation over the Internet, each user's interactions
with the remote server while using the tool should not be very frequent, and should
not require a very high bandwidth.
In order for it to be cost-effective to make a VM tool over the Internet rather
than selling copies of the tool to users to run it at their local sites, it should
be a tool that is useful to a large user group, but is relatively difficult or costly
to get copies for direct use at user sites in comparison with how often any single user
might want to use it.
Based on these criteria, we describe four potentially promising areas of application
for VM over the Internet: CAD data translation; distributed manufacturing; production
system design; and manufacturability analysis.
To provide a concrete example of a VM tool operating on the Internet, we have developed
a tool for translating the sat
files used in the ACIS solid modeler into the internationally accepted STEP format,
and have included it in our VM web site. To give the reader a feel for the future
potential of VM on the Internet, we present a scenario describing the possible operation
(over the Internet) of a tool that automatically analyzes designs to formulate suggestions
for how to improve their manufacturability.
1. To maintain and enhance the VM web site.
This included keeping the site publicly available on the Internet, publicizing it
to generate interest in it, and soliciting further information for inclusion in it.
2. To investigate the possibility of including software components in the web site,
including both "canned" demonstrations of VM software, and actual working VM tools
to be run in our server by visitors to the web site.
3. To prepare a prospectus based on the results of the above study, outlining possible
ways of using the Internet to provide access to tools for Virtual Manufacturing.
The next section describes the steps we took to achieve those objectives.
To facilitate maintenance of the web site, we have moved it from its previous temporary
location at the web account of one of the co-authors of this report, to a permanent
location at http://www.isr.umd.edu/Labs/CIM/virtual.html.
We have reformatted and reorganized the pages at the web site, to make them easier
to use and understand.
We have incorporated into the web site the technical reports "Virtual Manufacturing
User Workshop" and "Virtual Manufacturing Technical Workshop," compiled and edited
by Lawrence Associates Inc.
We have incorporated a copy of the article "Automated Manufacturability Analysis:
A Survey," by Gupta, Das, Regli, and Nau. This article provides a detailed survey
of techniques for analyzing the manufacturability of product designs.
We have incorporated "canned" demonstrations of two manufacturing tools developed
at the University of Maryland: the IMACS tool for manufacturability analysis of
machined parts (see Section 3.1), and the OSPAM decision support tool for partnering
in agile manufacturing (see Section 3.2).
We have made arrangements to incorporate information on the virtual manufacturing
work being done by NIST's Manufacturing Systems Engineering group (see Section 3.3).
We have developed a "forms" interface to enable researchers on virtual manufacturing
projects to submit information for inclusion in our web site. A portion of the submission
form is illustrated in Figure 1 on the next page.
We have sent a solicitation to the previous contributors to the web site, inviting
them to use the forms interface to update their contributions.
To publicize the web site, we have announced it on several mailing lists and electronic
newsletters, including the Process Planning mailing list at NIST, the Design Computing
newsletter, and the sci.engr.computing Usenet newsgroup. In our announcement, we invited interested parties to submit information for possible inclusion in the
web site.
We have incorporated a working manufacturing tool that can be run in our server
by remote visitors to the web site. This tool, an ACIS-to-STEP translator, is described
below in Section 3.4.
Some of these steps are discussed further below. Specifically, IMACS and OSPAM are
overviewed in Section 3.1 and 3.2. Section 3.3 outlines an interesting example of
VM research. Finally, Section 3.4 describes the ACIS-to-STEP translator.
Figure 1:
A portion of our web site's interface for submitting information on VM research
projects.
Thus, OSPAM is a design advisor that integrates partnering (including make or buy)
decisions in the design phase, and facilitates design improvements with respect to
partner capabilities. The project is described further in the VM Web site and in
Appendix B.
Example 1: Validation and evaluation of process plans for machined parts
Virtual manufacturing may play a significant role in two areas:
VM may validate the process plan in the computer, thus eliminating the need for
costly prototypes.
Having a valid process plan, VM may estimate the manufacturing times and costs accurately.
Furthermore VM may estimate other important measures, such as part quality.
VM-based process plan validation includes two levels of sophistication: First the
tool path specified in the process plan may be verified through simulation. In this
case a solid model of the work piece and a model of the machine tool are used to
simulate the machining process. The cutting tool follows the prescribed path removing material
from the work piece. Thus, infeasible tool trajectories (such as those interfering
with portions of the machine tool, fixtures or the work piece) are easily detected
and corrected. The second level of sophistication determines whether the cutting
parameters specified in the plan are appropriate or even feasible. For example,
high depth of cuts may lead to machine tool chatter and thus damage the work piece,
the cutting tool or even the machine tool itself. In addition, high feed rates may lead to
unacceptable surface roughness with respect to the designers specifications.
Research has already focused on tool path verification using VM. For example, investigators
at the National Institute of Standards and Technology have used the PART generative
process planner and Denebs simulation software to develop a tool verification program for three-axes milling [6] (see also Section 3.1). To the best of our knowledge,
however, no VM work to-date has examined the appropriateness of machining parameters
in a process plan of a certain design; this despite the proliferation of analytical models describing the physics of most machining processes. Such models may be used
in conjunction with the solid models of the work piece and the machine tool to construct
a virtual machining process. In virtual machining the analytical models will represent the physics of the cutting process, while the solid models will represent the
process geometry. Thus, given a part design, the machine tool to be used and the
parts process plan, the virtual machining process can be run to not only verify the
tool path, but also to predict whether the selected machining parameters will lead to undesirable
results (chatter, poor surface roughness, excessive dimensional variability, and
excessive tool wear).
Beyond plan verification, virtual machining may be used to estimate accurately the
merit of a process plan, and, based on this evaluation, determine appropriate process
conditions to improve (and even optimize) the plan. With virtual machining, the
fidelity of the machining time and cost estimates is expected to improve. In addition,
modeling the process physics will allow to predict the quality
of the machined part, which cannot be determined easily and reliably without producing
several physical prototypes. This information is invaluable to both the designer
and the process planner. The former may use it to modify the design in order to
improve its manufacturability. The latter may use it to tune the machining parameters
and improve, or even optimize, the plan. All this can be done early at the design/planning
cycle without resorting to costly prototypes.
Example 2: Process design
As already mentioned in Example 1 above, models that describe the process physics
are critical for the construction of dependable virtual processes. However, although
process modeling is a mature subject, it has yet to play a significant role in concurrent engineering. One of the major reasons for this is the lack of unified ways to deal
with process models. This appears to be a major roadblock for virtual manufacturing;
especially in assessing the feasibility of producing a design with a certain set
of manufacturing processes and evaluating the ease of manufacture with these processes.
Thus, novel representations are necessary to capture the physical models of various
processes (i.e. analytical, statistical and simulation-based models) and to provide
unified interaction mechanisms with the virtual manufacturing environment. Having developed
such representations, it is possible to construct virtual processes and use them
to:
Determine the feasibility of a process and a given process plan to yield the desired
product characteristics.
Evaluate process performance with respect to processing time, cost and quality of
the manufactured product.
Support process design, i.e. the tuning of critical process parameters to optimize
process performance.
Example 3: Optimization of production plans and schedules
Simulation is suitable for production lines, in which all products follow similar
sequences of operations. It does not deal effectively with job shops, which produce
small batches of numerous product types with diverse production routings. In these
cases the effort to build a simulation model is almost prohibitive due to the large volume
of the necessary production data.
Simulation is suitable for push-type systems, in which the shop orders are launched
upon the receipt of the customer orders. Most simulation packages are ineffective
for just-in-time production, which is increasingly popular in current practice.
However, if these problems are addressed effectively, simulation (and virtual manufacturing
in general) has the potential to yield major contributions to both operations management,
and product and process design. In operations management, simulation may support production planning and scheduling, especially when combined with powerful
optimization tools. For example, simulation combined with perturbation analysis
may be used to optimize batch sizes for minimizing inventory and set-up costs. In
this case, perturbation analysis will be used to evaluate the necessary cost gradients efficiently
from a small number of simulation runs. Similar approaches may be used to determine
optimal threshold values for the Work -in-Process at bottleneck workstations, beyond which no work orders are released to these bottlenecks. As another example, simulation
may be combined with simulated annealing or genetic algorithms to optimize the schedule
of bottleneck workstations.
In product/process design simulation may play a significant role in integrating product
design and process planning with production planning and scheduling. Given a design
and a process plan (or a set of alternative plans), various production scenaria may
be simulated to determine the impact of the new product on the operations of the shop.
By doing so, the designer will be able to determine early in the design stage the
effect of certain design decisions in production planning and scheduling. Furthermore, the process planner will be able to determine alternative plans that are appropriate
for certain states of the shop. It should be emphasized, however, that product design
and process planning are time-independent (static) activities, while production planning and scheduling are dynamic activities. This complicates their integration
and presents a challenging topic for further research.
In order for virtual manufacturing to have major impact in these areas, discrete event
simulation should be integrated to the existing information systems of a manufacturing
company. For example, production simulations should be built with minimal user input using typical MRP II data, such as Bills-of-Materials, Workcenters, Production
Routings, Customer Demand and Shop Floor Control data. In addition, both the CAD
and the process planning systems should be integrated in this practical VM environment
in order to enable the use of simulation for trade-offs in design and planning.
The Internet has recently become a major information resource provider for industry, and its demand keeps growing. The World Wide Web (WWW) plays an especially important role in providing information service on the Internet. Most current WWW applications are processed in batch mode and thus do not require intensive user interactions. Application areas include:
Product and service suppliers information:
examples are Thomas Register of American Manufactures for manufactured products [7]
and Internet Shopping Network for computer goods, home and office supplies [8];
Quotation and bidding:
Examples include a product information and on-line quotation system from Power Computing
[9], and a real-time auction tool from Onsale [10];
Tracking System,
for example, UPS's package tracking system/service information [11];
Software Product Demos,
for example, TAE Plus demonstration Program (a GUI development tool) [12] and the
NIST Tool Kit (Data Probe and STEP class library release) [13];
Education (training and tutorial,
e.g., computer-based learning systems which aid students with their understanding
of the complex phenomena underlying engineering domains from the INTERACT project
[14].
Not all of the services provided on the Internet are free. Several billing mechanisms
are being deployed: membership, pay by charge card, and pay by e-cash. In the first
case, each member of the service will be given an account number (users name) and
a password in order to use the service. In the second case, users may supply their charge
card number in an electronic order form on the Web to order product or services.
Finally, E-cash is an electronic currency which is being developed by the Amsterdam-based company Digicash and will be offered by Mark Twain Bancshares [15]. In order to
use pay-by-e-cash method, both buyers and sellers must have accounts in Mark Twain
Bancshares. A buyer electronically withdraws the so-called coins, specially encoded
symbol strings, from his/her account and transmits them to the seller to buy products or
services.
4.2.2. Transmitting VM Information over the Internet
HTML documents may be useful for sending certain kinds of Virtual Manufacturing information
over the Internet, by transmitting design and manufacturing data to a web browser
from a program running at a remote location. Examples include STEP files, CAD models, and text data such as the results of a design or manufacturing analysis or the
information found in a manufacturer's catalog. However, the utility of this approach
may be limited by the available bandwidth. For example, if one is trying to view
a CAD image in a web browser, it may take several minutes to transmit and interpret the
image. This makes it impossible to do interactive operations (such as rotating the
CAD model) in real time.
For certain kinds of VM data, it may be possible to alleviate the bandwidth problem
by transmitting the data not as bitmapped images, but instead using the Virtual Reality
Modeling Language (VRML). VRML is a language for describing multi-participant interactive 3D simulations. Its initial intended application is the creation of virtual
worlds network via the Internet and hyperlinked over the World Wide Web. All aspects
of virtual world display and interaction can be defined using VRML. It is the intention of SGI and the other designers of VRML that it become the standard language for
interactive 3D simulation within the World Wide Web.
Another way to address the bandwidth problem is by transmitting computer code specifying
programs to be executed at the local site. In principle, this could be any code
that could run on the local machinebut in practice, it is more likely to be code
written in a language specifically developed for that purpose, such as HotJava or Telescript.
Programming languages and environments have been developed specifically designed
for the exchange of executable software components (often in an interpreted language) over a network. On the receiving end of these exchanges, a viewer or interpreter
executes the program and enables it to interact with the user. In spite of the enormous
security issues at stake, languages such as Sun Microsystems' Java (see http://java.sun.com) and General Magic's Telescript (see http://www.genmagic.com/Telescript/index.html) provide generic tools to extend the reach of software over a computer network.
With these tools, one can compose interactive transmittable programs that contain
documents in a variety of media, or control for physical devices (e.g. machine tools).
HotJava is a World-Wide Web browser built using Sun's Java, an object-oriented programming
language. The essential difference between the HotJava and other browsers is that
it allows users to dynamically interact with the browser without overloading the
network traffic. In order to do this, HotJava adds a new type of HTML tag: APP, for
"applet." An applet is a program written in the Java language to be run within HotJava.
Developers use Java to write applets, compile them, and install them on the server.
HotJava can dynamically link the Java code from the host and execute it on the local
machine. Currently, the HotJava browser is still in the alpha release. It is available
on Solaris (2.3 or higher) and Windows NT/95. More information on Java and HotJava can be found at http://www.sun.com and in the Usenet newsgroups comp.lang.java and alt.www.hotjava.
Intriguingly related to these tools are many current application development environments
in commercial software systems. These tools are already being used by applications
builders to construct modular ``add on'' software packages to be coupled with other tools (by analogy, one might thing of these tools as application-specific forms
of Java). In the computer-aided design market examples include Pro/Engineer's Pro/Develop,
EDS/Unigraphics' GRIP and the MicroStation Development Language (MDL) from Bentley Systems. Programming environments such as these can be used to create network-savvy
software modules to be shared, executed, or purchased over the network from within
a single CAD environment.
4.2.3. Example Application Areas for VM Development on the Internet
In order to achieve efficient operation over the Internet, each user's interactions
with the remote server while using the tool should not be very frequent, and should
not require a very high bandwidth.
In order for it to be cost-effective to make a VM tool over the Internet rather than
selling copies of the tool to users to run it at their local sites, it should be
a tool that is useful to a large user group, but is relatively difficult or costly
to get copies for direct use at user sites in comparison with how often any single user
might want to use it.
With these criteria in mind, we now provide three brief examples of potentially promising
areas of application for VM over the Internet: CAD data translation, distributed
manufacturing, and production system design. Following these examples, Section 4.3
provides a detailed scenario for the use of VM techniques over the Internet in a specific
application area.
Example 1: CAD data translation
The ACIS to STEP translator developed as a part of this project (see section 3.4)
is a clear example of the simplest type of VM applications that can be used over
the Internet. This application meets several of the criteria mentioned above:
it requires simple file transfers between the client and server sites;
it is computationally intensive at the server site only;
it is very useful to a large user group.
We envision that such services may be provided by Internet brokers. The service described
in Section 3.4 is highly applicable to users who occasionally exchange product files
in the STEP format. However, users that frequently use STEP files for data exchange will tend to purchase one or more of the commercial STEP translators and use
them at their site. It is noted that the development of such translators is a straightforward
task of limited research interest.
Example 2: Manufacturing resource models for distributed manufacturing
A highly distributed VM application is the evaluation of a product design with respect
to the production capabilities of potential manufacturers, and the subsequent selection
of the most appropriate partners for a virtual enterprise to manufacture the candidate product. We have been working on this problem for over two years and we are
currently completing the OSPAM software system which provides decision support for
this application (see Section 3.2 and Appendix B).
Although most of the design critiquing and partner selection tasks may be performed
at a single site, it is clear that the data describing the capabilities and historical
performance of a firm should be owned and maintained by that firm in a manufacturing
resource model that is accessible over the Internet. Tools such as OSPAM should
be able to access and query these information models in order to compare the design
requirements against the firms capabilities. This suggests that the manufacturing
resource data are not included in simple HTML documents, but rather they are stored in databases
that can be queried by remote applications. Mediator or agent technology may be
appropriate to enable the integration of these heterogeneous databases and the applications that use them.
Figure 3:
Manufacturing facility design process and information.
Example 3: Design of production systems
The design of production systems is a mature subject, certain aspects of which have
been thoroughly researched [16]. Figure 3 (taken from [17])
shows the major steps of the manufacturing facility design process and the data needed
by this process. Numerous methods have been developed for certain steps of Figure
3, such as cell formation and resource layout. Other design steps have not been
adequately addressed, including the design of the material handling network, and the integration
of the entire shop design process. Virtual manufacturing tools may be used to evaluate
and validate the systems designed by these methods. Beyond discrete event simulation (which can determine important operational system measures such cumulative
material handling time and distance), animation and virtual reality may be used to
illustrate the entire shop in operation as experienced by the shop staff.
Several software packages have been developed for production system design, including
PDS of the University of Maryland [18,19]
which addresses many of the steps of Figure 3. Although such packages have a wide
applicability, manufacturing shop design or redesign is not a frequent activity and,
thus, the software are not used on a regular basis by most manufacturers. Thus,
this application is an appropriate candidate for use over the Internet. It is also noted
that most of the information exchange between the client and server sites is limited
to file exchanges as Figure
3
implies. For example, the inputs of the design software include typical MRP II data,
such as work centers, production routings and forecasted product demand, all of which
can be represented as text. Much of the output may also be described in a textual
form. It is noted, however, that the exchange of evaluation and validation data will
be probably limited to the values of performance indicators rather than animation
or virtual reality images.
Redesign and re-planning of machined components may be needed if the production conditions are different from those that were anticipated during the component design phase. This can occur, for example, in the production of spare parts for aging equipment. In this case, the production quantities are much lower than when the original equipment was built, and the manufacturer of the spare parts may have different capabilities (e.g., due to new technology) than the manufacturer of the original equipment.
4.3.2. Previous Approaches
Redesigning a product usually consists of two steps: (1) identifying ``redesign clues''
(information about what attributes of the design need improvement and why), and modifying
these design attributes in order to synthesize an improved design. Existing approaches to this task can be classified as direct and indirect approaches, as described
below.
In direct systems [20,21,22] rules are used to identify infeasible design attributes
from direct inspection of the design description. These infeasible design attributes
are then modified using predefined rules to create improved designs. Due to interactions among machining operations, it can be very difficult to determine the manufacturability
of a design directly from the design description---and thus the applicability of
direct systems is rather limited.
Indirect systems [23,24,25] proceed by generating a detailed manufacturing plan, and modifying various portions
of the plan in order to reduce its cost. Once this has been done designs that correspond
to these modified plans are presented to the user as possible redesigns. Although these systems have wider applicability than direct systems, they have several limitations:
There may be many possible alternative plans for manufacturing the product, and
it is not clear which of these plans to use as a basis for generating redesign suggestions.
Selecting the most promising plan for the initial design may not necessarily produce the best redesign suggestions.
If the initial design is not manufacturable, then there will be no plan for the
design, and thus no clear way to generate redesign suggestions.
Since most existing indirect systems do not take into account the design's functionality,
this makes it difficult to ensure that the proposed changes will not violate functionality
requirements.
4.3.3. Our Suggested Approach
(a) an example part P1;
(b) design constraints for P1;
(c) a modified version of P1.
Figure 4: A machined part P1 , some of its design constraints in an assembly, and a modified version of P1 that can be machined in fewer setups.
1. Obtain the initial design,
as a file submitted via the Internet. This design will consist of a CAD model in
a standard format(e.g., a STEP file or an ACIS sat file), plus a set of design constraints
arising from the intended functionality of the design. To attempt a complete approach for representing and reasoning about design functionality is a very complex taskbut
we do not believe it will be necessary to represent the functional requirements in
a detailed manner. Instead, we note that the functional requirements give rise to
various constraints on what kinds of modifications to the product design might be permissible---and
the designer can be asked to attach such constraints as annotations to the CAD model,
in a simple constraint language. For example, Figure 4 shows some of the constraints that a designer might specify on a part that is intended to mate with
other parts in an assembly.
Figure 5:
Some of the machining operations for the part P1.
Often there is more than one machining operation capable of creating the same portion
of the design.
2. Preprocess the initial design
. Generate a set of manufacturing features F
for the design (see Figure 5). Our work on the automated extraction of machining
features from CAD designs [26,27] suggests one possible approach for doing this.
Along with this feature set, identify relationships among the features that will
dictate precedence constraints among the operations. Each feature represents some portion of
the design that may be created using a single manufacturing operation. Since the
features may overlap, the feature set F
may include a number of alternative ways to manufacture various portions of the design;
and thus an operation plan for the design will correspond to a subset of the features
in F
.
3. Analyze manufacturability of the initial design
. Generate alternative operation plans [28,29] for manufacturing the design, as alternative
subsets of the feature set F
. Evaluate them by considering tradeoffs among criteria such as cost, time, and quality,
to find the plan that best satisfies whatever combination of criteria the user specifies.
This plan will establish a baseline for evaluating possible design modifications below---and if this plan is satisfactory to the user, then the user may elect
to stop here without requesting redesign suggestions at all.
Figure 6:
Generating a side-milling feature as an alternative to an end-milling feature.
4. Generate local modifications
. Use both direct and indirect techniques to generate alternatives to various features
in the feature set F
. One possible way to do this is by means of feature modification operators [30].
For example, Figure 6 shows a modification that produces a slot-milling feature
as an alternative to an end-milling feature. Identify and discard any alternatives
that violate the constraints specified by the designer in Step 1. For example, if there were
a constraint saying that the rounded ends of the end-milling feature in Figure 6
were important, then the slot-milling feature would be discarded. Augment the feature
set to include the new features.
5. Synthesize manufacturing descriptions
. From the augmented feature set F
, generate combinations of the features that are sufficient to constitute complete
designs. Each such combination of features represents a possible alternative modified
version of the original design. Identify and discard any alternative designs that
violate the constraints specified by the designer in Step 1. For the others, generate
and evaluate manufacturing plans using the approach described in Step 3. Use the
results of this analysis to rank the alternatives using the same optimization criteria
as before.
6. Provide feedback.
The best designs found represent possible ways to modify the design to improve its
manufacturability. Send CAD models of these designs over the Internet to the designer,
as alternative suggestions for redesign.
4.3.4. Anticipated Impact
Table 1:
Discrete manufacturing operations for various types of products.
Assembly Cutting Joining Forming
Sheet-metal parts
Machined parts
Electro-mechanical assemblies
Such a system, if implemented, would directly support the goals of agile manufacturing,
i.e. the ability to respond rapidly to the market demand for cost-effective, customized
products of high quality. Specifically we envision the following benefits:
The system will provide the means to speed up the redesign process. This is especially
important in the current defense and commercial business environment, in which the
designer is forced to design a large number of custom variations of a product, each
of which is produced in low quantity.
The system would ensure DFM. It will provide such suggestions automatically, and
will synthesize design variations with improved cost, lead time, and quality. This
will help designers determine what changes to a design will best improve its manufacturability.
The functionality of the system is directly applicable to the redesign of highly manufacturable
spare parts for out-of-production equipment. For such parts the design changes will
take advantage of new manufacturing technology introduced since the original equipment was built; in addition, the changes will adapt the design of a spare part
for low quantity, batch production.
The design support provided by the system will reduce the need for costly changes
after the product has been launched to production. Preventing such changes will
also eliminate the associated production delays.
The suggestions provided by the system during redesign will illustrate to the designer
configurations that are favorable for manufacturability. Thus, the automated redesign
system will also act as a DFM education tool for the designer.
In order to achieve efficient operation over the Internet, each user's interactions
with the remote server should not be very frequent, and should not require a very
high bandwidth.
In order for it to be cost-effective to make a VM tool over the Internet rather than
selling copies of the tool to users to run it at their local sites, it should be
a tool that is useful to a large user group, but is relatively difficult or costly
to get copies for direct use at user sites in comparison with how often any single user
might want to use it.
To provide a concrete example of such a VM tool, we have developed a tool for translating
the sat
files used in the ACIS solid modeler into the internationally accepted STEP format,
and have included it in the VM web site. Furthermore, in our report we have described
four other potentially promising areas of application for VM over the Internet:
CAD data translation;
distributed manufacturing;
production system design;
manufacturability analysis.
For the fourth area, we have presented a detailed scenario, describing the possible
operation (over the Internet) of a tool that automatically analyzes designs to formulate
suggestions for how to improve their manufacturability.
Determine whether or not the design attributes (e.g., shape, dimensions, tolerances,
surface finishes) can be achieved.
If the design is found to be manufacturable, determine a manufacturability rating,
to reflect the ease (or difficulty) with which the design can be manufactured.
If the design is not manufacturable, then identify the design attributes that pose
manufacturability problems.
In general, a design's manufacturability is a measure of the effort required to manufacture
the part according to the design specifications. Our approach to measuring manufacturability
is to estimate the manufacturing time and cost. Since all manufacturing operations have measurable time and cost, these can be used as an underlying basis
to form a suitable manufacturability rating. Ratings based on time and cost can
easily be combined into a overall rating. Moreover, they present a realistic view
of the difficulty in manufacturing a proposed design and can be used to aid management in
making make-or-buy decisions.
side-milling feature:
face-milling feature:
end-milling feature:
drilling feature:
Setup 1:Setup 2:
Setup 3:
3.29 minutes:
2.54 minutes:
Acknowledgements.
The work on IMACS has been supported in part by National Science Foundation Grants
NSFD EEC 94-02384, IRI-9306580, DDM-9201779, and by the University of Maryland General
Research Board. Software grants were provided by Spatial Technologies, Ithaca Software, EDS/Unigraphics, and Bentley Systems, Inc. General Electric Corporation, through
their Forgivable Loan program, has provided additional support to William Regli.
Personnel.
Faculty and students involved in various aspects of the IMACS project have included
Diganta Das, Alex Elinson, Satyandra K. Gupta, Ioannis Minis, Dana S. Nau, William
C. Regli, and Guangming Zhang. The project leader is Dana Nau.
1. International Standards Organization, "Integrated Resources: Geometric and Topological
Representation," ISO 10303-42.
2. Ioannis Minis and Jeffrey W. Herrmann, "Design Evaluation and Partner Selection
for Agile Manufacturing," submitted to IIE transactions.
3. Vijay Ramachandran, 1995, "Information Models for Agile Manufacturing," Master's
Thesis, University of Maryland at College Park.
4. International Standards Organization, "Product Data Representation and Exchange:
Implementation Methods - Clear text encoding," ISO 10303-21.
5. Edward Lin, Ioannis Minis, Dana S. Nau, and William C. Regli, "Contribution to Virtual
Manufacturing Background Research," Technical Report, The University of Maryland,
1995. Also available at http://www.isr.umd.edu/Labs/CIM/virtual.html.
6. NIST Virtual Manufacturing Web Site, http://elib.cme.nist.gov/msid/trojs/metk/homepage.html.
7. Thomas Register of American Manufactures, http://www.thomasregister.com.
8. Internet Shopping Network, http://www4.internet.net.
9. Power Computing, http://www.powercc.com.
10. Auction on the Web, http://www.onsale.com.
11. UPS package tracking system/service information, http://www.ups.com.
12. TAE Plus Demonstration Programs, http://www.cen.com.
13. NIST Tool Kit, http://www.hike.te.chiba-u.ac.jp/ikeda/documentation/STEP/nist-tk.html.
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