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Subject: Master's project: Computer-aided Process Planning for Prismatic Parts

Date: 10/06/00 at 8:47 PM
Posted by: Georg Thimm
E-mail: mgeorg@ntu.edu.sg
Message Posted:

I am looking for a Master student for a project on computer-aided
process planning for prismatic parts; see the project outline
below. During the project, some theoretical work on geometric and
dimensional tolerancing, as well as implementation of a system in Java
is required. The project is suitable for a mechanical engineer with
some object oriented programming skills or a computer scientist
willing to learn something on mechanical engineering.

The project is part of a large, long term research program on virtual
manufacturing and a collaboration project headed by Assoc. Prof.
Graeme Britton, Assoc. Prof. Fok Sai Cheong, and Assoc. Prof. Tor Shu Beng.

Details on terms, conditions (including scholarships) are available
at: http://www.ntu.edu.sg/registrar/postgraduate/research/.

Information on the design research center are available at
http://www.drc.ntu.edu.sg/. Also, I'm happy to answer more detailed
questions via email (mgeorg@ntu.edu.sg).

BTW., if you are interested in experiencing Asian cultures and food
(ranging form Indian, over Malay to Chinese), there is probably no
better place to do so.

Looking forward to see you at Singapore,

Dr. Georg Thimm Tel ++65 790 5010
School of MPE, Nanyang Technological University, Fax ++65 791 1859
50 Nanyang Avenue, Singapore 639798 Email: mgeorg@ntu.edu.sg
WWW: http://www.drc.ntu.edu.sg/users/mgeorg

Project outline

Tolerance analysis and control are important during manufacturing to
ensure that parts meet design specifications. Traditionally, tolerance
analysis is performed manually using tolerance charts. Manual charting
is tedious and error prone, hence recent research has focused on
automating tolerance analysis and control during process planning.

Britton and Whybrew [1] overcame this problem by developing a rooted
tree technique that generates acyclic (rooted) tree representations of
process plans. The technique has been incorporated in a research
software program CAPPFD for process planning of prismatic parts
[2][3]. Recently, Thimm and Britton further analysed the rooted tree
technique and deleloped a system that is able to support all process
planning steps, starting from a design and ending with a
shop-floor-ready process plan. The disadvantage of this techniques is
it ignores geometric dimensions and tolerances.

Graph theoretic techniques are being developed that explicitly
incorporate geometric dimensions and tolerances. Rong [4] discusses
machining errors for linear dimensions and angular dimensions and has
developed a datum-machining surface relationship graph (DMG) to
automatically determine relationship models of the dimension and
tolerance chains. This includes the representation of the 3-2-1 datum
system and the related position of each surface, and an analysis of
location errors. Rong's approach is not suitable for macro-planning,
but it is suitable for micro-planning.

Huang and Zhang [5] have developed a graph-based approach for setup
planning of manufacturing processes for rotational and prismatic
parts. Their work is focused on fixturing and fixture design rather
than process sequencing, but they are able to sequence setups. However
their graphs become very complicated and are not practical in our

The aim of the project is to develop a 3D, graph technique for process
planning that can facilitate the planning and control of geometric
dimensions and tolerances, as well as dimensional tolerances, and
incorporate other types of process planning information, e.g., jig and
fixture information, tool information, and mathematical descriptions
of machining processes. Further research and an implementation of a
computer-aided process planning system will use a generic
representation technique based on surfaces in order to facilitate
direct integration of CAPP with CAD modelers.


A draft paper on the graph theoretical approach and the process
planning system for rotational parts can be obtained on request from
Georg Thimm (mgeorg@ntu.edu.sg).

[1] K. Whybrew, G. A. Britton, D.F. Robinson, and Y. Sermsuti-Anuwat, ``A
Graph Theoretic Approach to Tolerance Charting'', International Journal
of Advanced Manufacturing Technology, 5, pp. 175-183, 1990.

[2] Y. Sermsuti-Anuwat, Computer-Aided Process Planning and Fixture Design
(CAPPFD), Ph.D. Thesis, University of Canterbury, New Zealand, 1992.

[3] Y. Sermsuti-Anuwat, K. Whybrew, and H. McCallion, ``CAPPFD - A Tolerance
based Feature Sequencing CAPP System'', Journal of Systems Engineering,
5(1), pp. 2-15, 1995.

[4] Y. Rong, ``Tolerance and Accuracy Analysis in Computer-Aided Fixture
Design'', Advanced Tolerancing Techniques, ed. Hong-Chao Zhang, John
Wiley & Sons Inc., pp. 381-425, 1997.

[5] H. S. Huang, and H. C. Zhang, ``Tolerance Analysis for Setup Planning in
CAPP'', Advanced Tolerancing Techniques, ed. Hong-Chao Zhang, John Wiley
& Sons Inc., pp. 427-460, 1997.

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