A System for Automated Fixture Planning with Modular Fixtures

2.2. Generative FWe Planning Systems
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A generative fixture planning approach does not rely on accumulated knowledge or rules but rather
automatically generates piaos by identifyii fixture component types and their Locations based m various
analytical mehods and fixluring principles.
Early research on the automated fixture planning with a generative approach used kinematic restraint of
the pan as the primary condition to generate locarions of the fixture components. Tbat is, if a set of pint
contacts on the part geomeny can completely restrain the part’s motion and satisfy the fixnrring principles
on. locating, supporting, and. clampmg,. the.cmtact pints.can be used for locations for actual fixture
components.
Mani[Mani 881 has propsed a system based on Reuleaux’s study on planar kinematic
restraints @euleam 761 hat generates 2D future plans that reshain the part’s motion in the plane with a
number of point mtacts. Once a set of point contacts are. genaated, lacating points and clamping points
are determined based on fixturing mpks and heuristics. These points rcprcsent & location of modular
components. The actual seltction of the componentn and the neceswy damping forces are to be
duermined by a tool designer. Mani’s appmach is Limited to generating fixtu~~ plans with side clamps
because clamping forces are. allowed only in the plane. Figure 2-1 sbows an exemplary pian gene& by
his system.
Figure 2-1: A fixnue plan generated by Mani Mani 881
Chou [Chou 881 has developed a system that generam 3D fixture plans by resWining the part’s motion
in space. The problem of d n i n g the pt is decomposed into two sub problem% reswiOiog 1) the x-y
nanslarion and thez rotarim olthe -and 2) the ztranslation and the x-ymcuion. Accurding to his
method, it seems that 2 M 3 points for clamping are used to restrain the part along with 3 point contacts for
the locators and 4 points fQ the mpports. Both overhead clamps and side damp are. required in each
fume plan. Figure 2-2 shows two sample fim plans gemzated by his system. Four small dislcs placed
under the part repremt contact points for supports such as rest bums. The hee small cylinders on the
part sides represent contact pohts for the locato~. The three small con= repnsent contact poinu for either
overhead 01 side clamps.