Fall Quarter 1998

ME/IE 8773-8774

Improving Automated Process Planning: Addressing the
"Chicken-and-the-Egg Set-Up/Fixture" Dilemma

by

Caroline C. Hayes, Ph.D.
Associate Professor, I.E.
Department of Mechanical Engineering
University of Minnesota
Minneapolis, MN 55455

Wednesday, November 18, 1998
1:25 p.m. UNITE Channel A
Room 108 Mechanical Engineering
Coffee available in 152 ME following the seminar

Coordinator is an automated set-up planner that addresses the "chicken-and-the-egg" fixture/set-up problem in 3 and 5 axis CNC machining. This is a circular difficulty in which one needs fixturing information in order to sequence set-ups. However, one must already know the set-up sequence, and hence the shape of the part in each set-up, in order to plan for fixtures. Where is one to begin? Most automated process planners take a cyclic approach. First they make an educated guess at a good set-up sequence and then determine the fixturing implications. If feasible fixturing cannot be found then the planner will go back and modify the set-up sequence possibly several times. The result is a feasible plan, but not necessarily one that makes particularly good global choices. Coordinator addresses the fixture/set-up problem using a least-commitment approach in which fixturing and set-up options are simultaneously explored in increasing levels of detail. It does so using a representation called "Medusa" of multiple possible part shapes and faces that might arise during processing are represented. This allows some of the higher level fixturing analysis to be moved up-stream, prior to set-up sequencing, so that it can be used to determine a better sequence on the first try. This greatly reduces the need for iterative adjustment and allows better overall setup/fixture decisions to be made, resulting in higher quality plans.

Dr. Caroline Hayes received her B.S. in 1983 in Math, her M.S. in 1985 in Knowledge-Based Systems and her Ph.D. in Robotics, all at Carnegie Mellon University in Pittsburgh Pa. From 1991 to 1998 she was an assistant professor in the department of Computer Science at the University of Illinois in Urbana, Illinois. She joined the department of Mechanical and Industrial Engineering at the University of Minnesota in February of this year. She is an associate editor for IEEE Transactions of Data and Knowledge Engineering. Her areas of research include decision support for areas such as manufacturing planning, design, and military decision making.

Informal Faculty Luncheon: Wednesday, November 18, 1998, 11:45 a.m., Room 405, Campus Club. Professor Hayes will be able to attend.