Advancing Design-for-Assembly: The Next Generation in Assembly Planning Page: 4 of 8
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engineering is also considered. In Section 4 the output
capabilities of the system are discussed while Section 5
presents some experimental results of system applications.
Finally, the paper concludes with a discussion of limitations
specific to Archimedes 4 as well as providing future areas
2 Archimedes 2 Review
The Archimedes 2 system was seen as a sequence of
modules, each viewing the product at a greater level of
Design Module User _-
Geometry 4 0 State-Space
Figure 2. The architecture of Archimedes 2.
detail and supplying more detailed assembly plans and
designer feedback than the previous one. At the top is the
design module, which captures and represents the
geometric, mechanical, and other information about the
product required for analysis. The design module only
required design consistency; it did not apply any
manufacturing constraints. At the bottom is the robotic
workcell; all details must by definition be present in the
assembly plans executed there. The architecture of the
system is shown in Figure 2. Using industry-standard
languages for portability, maintainability, and compatibility
with industrial users was a primary focus in writing
Archimedes 2. Due to space limitations, the reader is
referred to  for more detailed descriptions of the
There were several specific areas of limitations to the
Archimedes 2 system, most of them were and still are
difficult issues not addressed adequately by any assembly
planners to date. The Archimedes 4.0 system has made
substantial progress in addressing those limitations. Some
of the limitations included: lack of constraint representation
(e.g., gripper design and grasp planning, fixture design,
and motion planning), efficient search algorithms,
inadequate facility for users to interact with the software,
and a lack of non-geometric data representation.
3 Archimedes 4.0
The Archimedes 4.0 system is a constraint-based
interactive assembly planning software tool used to plan,
optimize, simulate, visualize, and document sequences of
assembly . Given a CAD model of the product, the
program automatically finds part-to-part contacts, generates
collision-free insertion motions, and chooses assembly
order. The engineer specifies a quality metric in terms of
application-specific costs for standard assembly process
steps, such as part insertion, fastening, and subassembly
inversion. Combined with an engineer's knowledge of
application-specific assembly process requirements,
Archimedes allows systematic exploration of the space of
possible assembly sequences. The engineer uses a simple
graphical interface to place constraints on the valid
assembly sequences, such as defining subassemblies,
requiring that certain parts be placed consecutively with or
before other parts, declaring preferred directions, etc. The
user interface is critical to effectiveness and user acceptance
of an interactive planning system.
Archimedes 4.0 is implemented in C++ using ACIS*
solid modeling kernel and Tcl/Tk for the graphical
interface. The planner allows users to add product-specific
assembly process constraints through the graphical user
interface [13, 14]. Disassembly operations are generated
using the NDBG approach discussed in . Animation
and user interface routines use OpenGLTM and X
The system considers thousands of combinations of
ordering and operation choices in its search for the best
assembly sequences and ranks the valid sequences by the
quality metric. Graphical visualization enables the
engineer to easily identify process requirements to add as
sequence constraints. Planning is fast, enabling an iterative
constrain-plan-view-constrain cycle. For some restricted
classes of products, it determines plans that optimize a
given cost function, graphically illustrates those plans with
simulated robots, and facilitates the generation of robotic
programs to carry out those plans in a robotic workcell.
Figure 3 represents the overall structure of the system.
At the top-middle and on the left-hand side are the design
and constraint modules, which capture and represent the
geometric, mechanical, and other information about the
product required for analysis. These constraints come from
a wide variety of sources: design requirements, part and
tool accessibility, assembly line and workcell layout,
requirements of special operations, and even supplier
relationships can drive the choice of a feasible or preferred
The modules listed on the right-hand side are the output
modules. They include options to capture the sequences in
the form of 3D-animations and videos, textual scripts and
snap-shots that can be used for maintenance instructions
and technical publications. The system also generates
skeleton scripts to run robots, cost analysis information,
and ergonomic analysis information.
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Calton, T.L. Advancing Design-for-Assembly: The Next Generation in Assembly Planning, article, December 9, 1998; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc672724/m1/4/: accessed October 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.