Assembly Sequencing and Fixturing
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The purpose of this project is to develop techniques for
performing automatic assembly sequencing and fixturing concurrently. That
is, given only a geometric description of a product, we wish to produce:
Unlike in previous assembly-planning research in the literature, the
sequence and fixture are generated concurrently (rather than first
one and then the other). This approach, called "sequence/fixture
co-design", raises a host of new issues.
- a sequence of part insertions which will assemble the product from its
- a fixture to hold the product in place during assembly, such that each
intermediate subassembly is stable under gravity and all
part-against-part "insertion forces".
The long-term vision for this work is a CAD tool which can provide
immediate feedback to a team of product designers about the ease of
assembling the proposed product.
Recently-developed techniques for sequence/fixture co-design have been
implemented for the case of planar assemblies, in a prototype system called
Given a geometric description of an assembly, Atlas will generate an
assembly sequence and a fixture for that assembly. The fixture is represented
as a continuum of possible fixturing locations, rather than as a
finite set of discrete elements.
An example of Atlas' output appears below. The yellow line shows the final
(non-minimized) fixture; the corresponding assembly sequence inserts the
rightmost part downward, then all other parts from left to right. This
assembly and every intermediate subassembly are guaranteed to be stable
under gravity and all insertion forces.
Atlas (the Greek mythological one) fixturing the heavens
Starting with the empty fixture,
Insert part 6 in direction (0, -1).
Insert part 3 in direction (1, 0).
Insert part 2 in direction (1, 0).
Insert part 1 in direction (1, 0).
Insert part 0 in direction (1, 0).
Insert part 4 in direction (1, 0).
Insert part 5 in direction (1, 0).
Although the current implementation of Atlas is restricted to planar
assemblies, all of its techniques extend to the three-dimensional case as
B. Romney, "Atlas:
An Automatic Assembly Sequencing and Fixturing System".
Proc. Intl. Conf. on the Theory and Practice of Geometric
Modelling, Tübingen, Germany, October 1996. (To appear.)
B. Romney, "Issues in
the Co-Design of Assembly Sequences and Fixtures".Manuscript.
Related Web Sites
Assembly-Planning Group at Stanford, and its
papers and publications.
STAAT project in assembly sequencing.
This project was in many ways the forerunner of Atlas, and was the
subject of an award-winning paper.
Romney's home page