Page 130 - Mechatronics for Safety, Security and Dependability in a New Era

Ch24-I044963.fm Page 114 Monday, August 7, 2006 11:27 AM
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designers' intentions and finished parts' specifications into technologically feasible plans describing how to
manufacture a functional part efficiently and precisely. The task of automatically generating a process plan from a
solid model representation of a part is normally subdivided into several activities such as: selection of the
machining operations and so on. A process plan should primarily consist of a Manufacturing feature (MF) set
which describes the most suitable removal volume set and a machining sequence which are considered optimum
for the design intentions and the current manufacturing conditions. Most of current manufacturing systems
perform fixed process planning which often leads to provide "fixed plans" for production. Those plans are only
applicable in the situation where no errors and disturbances are found during the manufacturing process and no
alterations are made to facilities in workshop [1]. Moreover, in some cases, because manufacturing features
interpretations are predefined in a fixed way, only small number of plans can be generated as candidates. In
addition, those outputted process plans are usually proven not the most efficient and precise for manufacturing.
Because a great deal of useful embedded information in the part model is ignored, the determined sequences often
fail to satisfy the desirable functions. As a result, the flexibility of process planning becomes an essential and
effective way to create more candidates for resolving this problem. To realize the flexibility, our proposed system
generates more functionally and technically satisfactory candidates. Finally, the most optimum process plan will
be chosen from the candidates by comparing machining time of each plan.

Raw stock Finished part
Raw
stock
Finished part
" 1 r
Extraction of TRV
Extraction of TRV
Decomposition of TRV to MCPs
Decomposition of TRV to MCPs
Constraint
Constraint
Conditions
Conditions
nditions
Generation of desirable MFs
Generation of desirable MFs
Recomposition of remained MCPs
Recomposition of remained MCPs
Constraint
Constraint
Conditions
Conditions
nditions
Determination of Machining
Determination of Machining
Evaluation of the Machining time
Evaluation of the Machining time
Figure 1: Core parts of the system
2. SYSTEM ARCHITECTURE

This system provides functions of generating one or more candidates of MF set to suit variable machining
circumstances, sequencing the MFs and determining the best process plan which can realize the designed part,
respecting the desired quality at high efficiency. The overall goal of this flexible process planning system is
obtained through the following main steps shown in Fig.l.. The manufacturing feature recognition is executed
based on judging the number of the open faces of the feature, by retrieving and modifying the familiar cases from
database, case-based reasoning decides machining conditions including tools, cutting conditions, tool path and so