Design for Manufacturability via Agent Interaction

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Design for Manufacturability via Agent Interaction

• ???
• i-Design Lab.
• Yonsei Univ.

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Abstract

• An approach for making the capability of
  manufacturing process manifest to designers
  starting with the earliest stage of geometry
  specification
• The approach involves a dialogue among design and
  manufacturing agents over Internet.
• The dialog focuses on the specification and
  exchange of process capability models for
  establishing design rules on-demand to ensure
  manufacturability.
• The models include both declarative knowledge
  and, for those aspect of the process that are
  difficult to represent declaratively,
  platform-independent procedural code which is
  automatically loaded onto the designers
  machines.
• The approach is being implemented using agent,
  written in Java language, which exchange
  feature-based capability models.
• The approach is being tested initially on
  machining and shape-deposition processes.

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FIGURE 1. Part of an agent dialog for
transmitting process capabilities into the design
environment. In this case, a KQML message is sent
from the design agent to obtain a list of
standard features that the process can
accommodate. The message content is in Express
and refer to ontologies (formal agreements on
terms and definitions Gruber 1993) of features
and constraints which, in turn, refer to the
PDES/STEP standard STEP 1992 EXPRESS 1992.
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Introduction (1)
A CE Environment, supports DFM
A mechanism to evaluate the manufacturability
according to design rules and evaluating
procedures
The process capability models is provided
on-demand to designers by mfg. services in a
machine-readable, platform-independent format
An Architecture
designers
Mfg. Services
Agents
Agents
Formal comm. Interface (Internet)
Process design inf.
Process design inf.
Designers
Mfg. Services
Agents
Agents

• Motivation
• novel prototyping such as layered shape
  deposition, laser sintering
• Not familiar, not be in the CADs DFM modules
• exploration utilization of these processes
  requires capability models remotely loaded from
  the service provider integrated into the design
  env.

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Introduction (2) More than HTML

• Today, a number of services on the internet
• PC board fabrication, cable harness assembly,
  stereolithography etc.
• Use HTML forms-based interface to acquire
  information from designers and customize
  displayed data to match designer preferences
• To make designers confident about using novel
  manufacturing processes, a more intimate dialogue
  between design manufacturing is required. We
  would like to make all aspect of the mfg. process
  accessible.
• Ex.1) Before submitting designs to mfg. services,
  designers should able to run process simulation
  obtain manufacturability rules and guideline
  load processing constraints have them checked
  and enforced
• gt designers can quickly become familiar with
  mfg. process as there desire.
• Ex.2) When essential to minimize mfg. costs / to
  meet stringent demands / tolerances or materials
  properties,
• gt the designer will want detailed access to
  process characteristics, constraints and costs
  as they apply to his or her design.

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Introduction (3) A mechanism req.

• The MOSIS project for VLSI design and
  prototyping, the ability to submit designs with
  confidence their specifications the adoption of
  conservative design rules to specify features
  with confidence their manufacturability.
• variety of mechanical processes and facilities,
  more over variety of CAD tools, -gt necessary to
  establish a standard mechanism to obtain process
  capability models from disparate processes
  on-demand load them into their preferred CAD
  env.
• The mechanism should designers enable to locate
  candidate services, evaluate the processes and
  acquire capability models to compute the
  manufacturability (include the ease of
  fabrication process planning) with accuracy to
  meet the design requirements.
• The communication mechanism also allow
  unsolicited information (such as updates on
  process capabilities) to be transmitted from mfg.
  facilities to designers.

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Introduction (4) Issues

• Issues to enable such a dialog
• How is process capability represented?
• How are capability models locate and acquired by
  designer?
• How are capability models mapped into the design
  space?
• How is the information contained in these models
  applied during design?
• Particular contributions
• An architecture for information exchange between
  designers and manufacturing services which
  includes
• An object-oriented agent template, with
  specializations for design, service and service
  agents (wrapping CAD process planning software)
• A mechanism for knowledge representation (to
  exchange declarative, procedural and human
  readable inf.)
• A negotiation protocol which outline the sequence
  of communications between designers and
  manufacturing services.
• This approach build upon recent developments in
  the application of agent-based software including
  communication protocols representation language
  to exchange information via the Internet.

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Introduction (5) contents remain

• Assumptions about mfg design process,
• A model of process capability
• The agent architecture used for information
  exchange.
• agent and technology for sharing objects among
  divers applications.
• focused on the process of layered shape
  deposition and CNC machining services as examples
  of two very different mfg processes.
• Appendix A provides details on capability model
  representation
• Appendix B discusses the agent structure and
  class libraries developed along with pointers to
  down-loadable code for Java Agent Template

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Layers produced by automatic decomposer for
slider crank mechanism
Gray steel, brown copper support material
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Robot Leg compacts
The output of the software is a sequence of 3D
shapes and toolpaths.
Embedded components
Part
Support
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2. Representing Manufacturing capabilities2.1
Design and Manufacturing feature

• Assumption1 doing feature-based design using 3D
  CADs to represent the solid geom.
• To match different design and mfg features,
• Generalized cylinders
• Efforts for mapping from design features to
  manufacturing features and of extracting features
  (holes, custom) from general three dimensional
  geometries, STEP Tools, Inc online service
• geometric primitive that can be specialized to
  include common design and manufacturing features
  including those used by machining and layered
  shape deposition.
• a useful neutral representation for mapping
  manufacturing features lt-gt design space.
• The parameters can be translated into STEP,
  Part42, entities represented according to AP203
  facilitate in multiple CAD systems (see
  Appendix A).

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Fig. 2. Generalized cylinders are a useful
geometric representation that can be sepecialized
to match different design and manufacturing
features and facilitate the mapping between them.
Corresponding STEP entities are labeled.
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2.1 Design and Manufacturing feature (cont.)

• Assumption 2 Manufacturing process can be
  represented in geometric terms as sequences of
  operations (add, modify, remove geometry
  features) from an initial stock part (may be
  null in the material deposition process)
• Process may have additional effects (surface
  finish, material hardness, stress state, ).
• For machining process, mapping between design and
  manufacturing features is fairly close (ex. holes
  pockets produced by drill end-mill)
• For shape-deposition process, rarely any direct
  relation material layer of compacts to the
  design.

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2.2 Process Capability Model

• Represents mfg. services and the processes, using
  Hierarchical taxonomy of manufacturing objects
  (Fig. 3), similar to OO Process.
• Each mfg object lt attributes lt other mfg objects,
• Top mfg service lt mfg process lt materials.
• Process materials lt capability models
  (declarative design rules constraints, process
  simulation procedures, document, )

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Design rules and constraints

• Declarative representation of process-derived
  constraints provide a way of assuring
  manufacturability on separating representation of
  the design and process
• The neutral descriptions of these constraints
  also allow to them be used by constraint
  propagation systems or other reasoning systems
• Multi-level designers process capabilities
• Conservative set of rules ensure easy
  manufacturability.
• Increasingly sophisticated analysis and
  simulation used for designs can not confirm to
  the easy rule.
• Few exception flagging to save time.

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Design rules and constraints (cont.)

• Constraints associated with manufacturing
  features are often easier to express.
• Machining layered shape deposition design rules
  can be express in terms of the specializations of
  generalized cylinders
• Machining, feature constraints for easy
  machining
• maximum length/diameter ratios for holes or
  depth/corner-radius ratios for efficient
  machining with standard drilled and end-mills.
• Maximum envelope of a part and general
  specifications on tolerances and surface finish,
  refined in terms of part size and overall
  geometry.
• -gt Appendix A table 1.

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Design rules and constraints (cont.)

• Layered shape deposition constraints for easy
  shape deposition -gt Appendix A table 2.
• Whether the geometry of the design can
  efficiently be decomposed into layers.
  Decomposition function of surface profiles,
  desired surface finish
• If both undercut non-undercut features are
  contained within the same horizontal band, the
  band must be split into a set of compacts.
• This complication can be avoided by building the
  design from primives that taper monotonically in
  the direction of layering.

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Simulation functions

• Declarative representations of process-related
  constraints or characteristics are impractical,
  Provide functions
• to simulate the effects of processing on the
  design
• to analyze elements of the design from the
  standpoint of manufacturability
• Ex. When machining a part with thin wall section,
  simulate the actions of milling the part using a
  dynamic milling model.
• can help the designer to understand of the
  process and encourage DFM.
• Portability problem with procedural code against
  declarative expressions -gt in neutral format (ex.
  STEP)
• what if questions in batch mode -gt use machine
  independent Java language

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3. Information Architecture

• Agent architecture
• A mechanism for encapsulating and exchanging
  distributed knowledge and functionality.
• Scalable, modular system with well-defined
  interfaces. engineering agents interface
  agents
• Autonomous
• Encapsulate functionality
• Use an agent communication language
• Templates
• Communicates asynchronously with other agents
  distributed over internet using KQML as comm.
  Language
• Java Agent Template http//cdr.stanford.edu/ABR

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3. Information Architecture (cont.)

• functional Community level 3 classes
• Service agent
• engineering service on the internet.
• Standalone app. Integrated with legacy s/w
  local database
• Broker agent
• Standalone process, A consortium of service
  agents and function
• a central directory for agent names, addresses
  and descriptions.
• Simple type ANS (Agent Name Server)
• Client agent
• Potentially transient processes, Java Applet
  loaded via WWW
• Use brokers to discover specific service
  functionality directly communicate to access.

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3. Information Architecture (cont.)

• Because of the diversity of Mfg process design
  env., needs specialized graphical interfaces
  communication infrastructures.
• functional Individual level 4 classes
• Agent-context
• separate the both agent and communication code
  from the execution environment user interface.
• Same agent to be implemented as a stand-alone
  app., applet, daemon process, not directly depend
  on the presence of GUI.
• communication interface
• message output
• Interface between an agent its contexts
• the agent it self
• Synchronously Accepts outputs messages (in
  KQML) via communication interface
• Resources knowledge and functionality
  (addresses, classes, languages, ontologies)

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3.1 Agents, distributed objects, CORBA and Java

• design paradigm (Agents and distributed object)
  an agent-based system built on a distributed
  object substrate.
• Agent
• use formal message structure protocol (KQML)
• maintain state infomation.
• A level of abstraction above distributed objects
• implementation (Java and CORBA)
• Java provide a robust mechanism, minimal
  overhead, object-oriented, platform-independent,
  can dynamically import new code.
• There are no barrier to integrating Java Template
  with CORBA objects

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3.1 Agents, distributed objects, CORBA and Java
(cont.)

• Example scenario
• Pro/Engineer CAD platform
• Shape deposition, CNC machining mfg process
• -gt http//cdr.standford.edu/RVPP/
• Cax tools ? design agents,Mfg service ? service
  agent
• Comm. Is facilitated by service broker.

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Sequence of designers actions

• 1. Locate potential service/process combination.
• 2. Evaluate a specific manufacturing service.
• 3. Evaluate a process.
• Acquire process capability model
• 4. Use the process capability model to constrain
  the design process.
• Feature constraint -gtprocess simulation
• 5. Submit the design for fabrication.

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4. Implementation status and future work

• An approach enabling s/w agent to
• Locate each other
• exchange messages
• automatically load resources
• declarative(constaints) procedural(process
  simulations)
• Implemented with Java Agent Template
• Next step
• Experiment with agent dialogues among design and
  manufacturing services to evaluate the
  effectiveness and limitations of this approach.
• An object class hierarchy for process
  descriptions and capabilities has been
  established.
• The generalized cylinder has been adopted as
  initial generic feature type.
• Initial experiments will be conducted in
  collaboration with prototyping services.

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Appendix A Generalized cylinder representation
and constraints

• Generalized cylinder feature
• Nominal geometry is defined by the following sets
  of constraints
• Axis Constraints parameterized axis function
  x(s), y(s), z(s) and their derivatives (the
  curvature and torsion of the axis)
• Cross-sectional surface constraints closed curve
  defining the edge of the surface.
• Sweeping transformation constraints properties
  of the transformation (dependency on axis arc
  length)
• The CGS operation to combine into more complex
  solids
• Operator constraints subset of union,
  difference
• Operand constraints coordinate transformation
  matrix

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Appendix A. Table 1, 2
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Appendix B details on the Java Agent Template

• Agent Life Cycle
• Execute of the Agent Context create itself,
  associated communication interface, message
  output and GUI components.
• Initialization file is retrieved and
  processed(contains a set of KQML messages, one
  of which has been the address of ANS)
• Connect to the internet and registration with the
  ANS
• Transformation address invalidation message is
  sent to the ANS
• Addressing every agent possesses a unique name
  and address. Address consist of a host name and a
  port. An ANS maintain an archive of all agent
  names and address (and enforces unique naming)

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Appendix B details on the Java Agent Template
(cont.)

• Message Interpretation
• The message is parsed, at the top level,
  according the KQML syntax.
• The ontology field for the message is checked
  against the agents local ontologies resource. If
  the specified ontology subclass is not present,
  the agent retrieves it before continuing with
  the message processing.
• If the specified Ontology is successfully
  obtained, the interpretMessage() method of this
  ontology object is called to process the present
  message. This method first checks the Language
  field, fi the language is not locally known, it
  is retrieved before further processing if the
  language is supported and can be obtained, the
  content field of the message is parsed according
  to that language.
• The action to be taken on the message content is
  encoded with the ontology class.

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3.1 Agents, distributed objects, CORBA and Java
(cont.)

• Service broker represent a group of service agent
  and can provide high level filtering for
  designers.
• Information concerning process capabilities and
  design characteristics will be exchange between
  agents

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Sequence of actions taken by the designer

• 3.2 Locate potential service/process
  combinations.
• The designer execute design agent (via WWW applet
  from service broker site / by execute a
  stand-alone agent
• The agent is initialized with location of one or
  more service broker agents (representing groups
  of manufacturing services)
• The designer will submit to the selected service
  broker (via design agent) information about the
  design requirements which can be used for
  high-level filtering of potential service/process
  combinations.
• This filter has not implemented but important in
  overall process and should be based on the
  following general categories of design
  constraints
• Purchasing/scheduling constraints ( maximum
  /hour for machining time, minimum lot size,
  maximum lead time)
• Physical constraints material properties,
  geometry (required stock size / general volume,
  symmetries, solid features, surface types,
  tolerances)

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Sequence of actions taken by the designer (cont.)

• 3.3 Evaluate a specific manufacturing service.
• Once a list of potential mfg services has been
  obtained, the designer will undertake a detailed
  evaluation of the characteristics and
  capabilities of each.
• Each services is modeled by a hierarchy of
  manufacturing objects. Communication between the
  design agent and service agent will enable the
  designer to search this processes/material
  combinations. As the designer browses through the
  human-readable documentation provided by the
  service, the design agent builds an object model
  of the manufacturing service and its process.

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Sequence of actions taken by the designer (cont.)

• 3.4 Evaluate a process.
• The next step is to acquire process capability
  models.
• Declarative components of the capability model
  will be exchanged using KQML messages,Procedural
  elements will be loaded as Java classes.
• In the present implementation, the capability
  model provides information for evaluating the
  manufacturability of a designs nominal geometry.
  Design rules consist of constraints on the
  geometry of generalized cylinder features and on
  the CGS operations used to combine those features
  into more complex solid.
• Constrains (Appendix A) are represented
  declaratively using the Express languages.
• Each capabiliry model will also include process
  simulation procedures which take design meeting
  the constraints and return, if the simulation is
  successful, trees of processing feature used to
  realize the design.

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Sequence of actions taken by the designer (cont.)

• 3.5 Use the process capability model to constrain
  the design process.
• Acquired capability models will be mapped into a
  format suitable for integration with the
  designers preferred CAD system(STEP AP 203).
• Feature constraints will be applied against all
  feature instantiations and CGS operations
  attempted by the designer.
• Process simulations will be configured to accept
  input from the CAD system and return output which
  can be mapped from the CAD system can use.
• These simulation procedures may be entirely
  represented by local java code or can be
  implemented as a Java interface (locally
  executed) which communicates to analysis code
  running on a remote machine.

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Sequence of actions taken by the designer (cont.)

• 3.6 Submit the design for fablication.
• Completed designs will be submitted to the
  service agent which provided the process
  capability model. The manufacturing service
  represented by this agent can be then conduct
  process planning and quote generation in light of
  the applied costraints.