A System for Automated Fixture Planning with Modular Fixtures

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Depending on objects’ shape, one scheme may be more effiient than the other. If a simple interference
checking sheme recognizes the possibility of interference, a compurationaily intensive algorithm needs to
beusedtoretinetheanswer[Gursoz911.
When the face of one object interferes with the face of another object, two objects are in interference.
Also. if one object is completely within the other object, they are in interference. Intexfemce checking in
fixture planning can be performed between objects or berween the faces of an object depending on the
circumstances in order to minimize the computation time.
?he compuration time for an interference checking algcuithm increases with the number of faces on the
two objects, and it can take a long time if objects are represented by many faces. In order to speed up the
inteaference checking, a few schemes can be used in future planning: 1) simplifiiatioo of object geometry
with a smaller number of faces, 2) consideratiw of only relevant faces, 3) use of a fast scheme to detect
interference possibility, and 4) use of a 2D interference checking scheme.
1) Simplifimtioo of object geometry
When precise interference checking between ob+& is not criiical in tixture planning, it is possible to
speed up the mputariOn by simplifying the object’s gunneuy. Gayneay of fixture componens can be
approximated by simple polyhedra with a small number of faces. For example, a cylinder type object will
have many facers in boundaty npreseotatioa to aumately represent its side surface. By simplifying the
cylinder into a rectangular block, the inmfereoce checking can be done quickly. Details on how each
fixture component is simplified can be found in Chapter 4. When some clearance is needed between
fixture components for easy fixture assembly and defy from me cum paths, the geomeay of fixture
components should be enlarged by adding the necessary clearance.
2) Consideration of relevant faces of objects
Although an object may have many h, only a few faces must be msidered fa interfmnce checking.
For example, when inmfemce checking is required benveen a clrmp and the pars any faces within the
holes in the pan can be ignored ifaciamp is mt placedin a hole. Even ifaclamp IS placed in a hole, faces
within the rest of the holes can be ignored. Other pruning methods are ku.sed in Chapter 5; the
interference checking algorithm is applied between fumre components and the pan.
3) Use of a fast detectioo scheme to detect interference possibility
The possibility of interference between faces can be checked by CMnparing the maximal and minimal
coordinates of both faces in the same way as it is used to check the possibility of interferewe between
objects.
4) Use of 2D interference checking scheme
When a polyhemal object is projmed onto a plane. it can be represented as a polygon. When two objects