| Summary: | 碩士 === 元智大學 === 機械工程研究所 === 82 === With the increasing product geometry complexity, product
functional requirements， and the arise of reverse engineering
technology，the integration of CMM(Coordinate Measuring
Machine) and CAD/CAM in mold/die design and manufacturing has
taken its role. The successful implementation of reverse
engineering technology starts from the digization of the procut'
s geometry. First, the problem is how to perform path planning
so that the surface geometry can best be preserved. Then, the
next question is how to interface these digitized point data
into the commercial CAD/CAM systems most efficiently and
accurately.When the point data were translated into the CAD/CAM
systems, the choose of proper surface building procedure is
very important. The machining scheduling and cutting process
parameters may contribute to the accuracy of the final reverse-
manufactured die. In the thesis, the rapid prototyping of die
by reverse engineering technology was investigated. The part
was digitized by CMM in section line format. The point data set
was reformatted and translated into the SmartCAM package. The
part surface geometry was rebuilt from section lines into
lofted surface.In order to speed up tool path generation, data
reduction capability inside SmartCAM was utilized to build the
model. An experiment was designed to evaluate various error
sources such as digitization, model building and surface model
selection.A CAD model of complex free-form surface was built.
From the CAD model, one hundred thousand projection points was
created and were used as error checking points. After the part
was machined, coordinates of fifteen hundred points of these
check points was measured by CMM.It was found that the
inconsistancy in coordinate orientation of machining and
measurement systems was the major error sources. Sharp edges or
boundaries may be lost in the digization process. Surface model
built by the data reduction set with cubic spline curve fitting
will only contribute minor error.
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