This is in response to your inquiry about research in the area of virtual manufacturing. My work on Scanned Thermal Rapid Prototyping is currently supported by a NSF Young Investigator Award and a grant from the SME Education Foundation, and is closest to the topic areas of Simulation (area 7) and Manufacturing Characterization (Area 10) of your survey. Scanned Thermal Rapid Prototyping addresses the challenge of simultaneous simulation and control of the part geometry and thermal state, in rapiud prototyping methods with combined mass and heat transfer. Conventional Rapid Prototyping techniques with off-line scheduling of the source path can not cope with disturbances of the material and process conditions, resulting in poor dimensional tolerances, unacceptable material structure and properties and residual stresses or distortions of the prototype. In Scanned Thermal Rapid Prototyping, involving material removal (e.g. laminated object manufacturing, Laser milling) or addition (fused material deposition, thermal spray techniques) in successive layers, the heat source (Laser or plasma arc) and material supply (wire feed or spray nozzle) scan the top surface of the part in a real-time controlled trajectory, to deposit a new material layer. The layered profile shape is measured in-process by a 3-D scanning (Laser stripe) optical system, while the temperature field is monitored by an infrared pyrometry camera. The geometric and thermal data are integrated by the computer-controller that modulates the source power and material feed, and drives the source in a n optimized scanned motion trajectory. This thermogeometrical feedback control drastically improves the quality and productivity of rapid prototyping methods, especially when a small number of functional prototypes is desired to be produced directly on the RP device. This offres a competitive alternative to conventional part production by dedicated dies. References on the simulation mdeling and virtual manufacturing techniques are: C. Doumanidis, "Thermal Manufacturing Process Control by Lumped MIMO and Distributed-Parameter Methods", ASME J. of Dynamic Suystems, Measurement and Control (accepted April 1994). C. Doumanidis, "Robust Multivariable Control and Simulation of Time-Varying Thermal Manufacturing Processes", IASTED Intl. Colnf. on Modelling and Simulation, Pittsburgh, PA, April 1995. C. Doumanidis, "Heat Treatment Control by Polytope Methods", American Control Conference 1995, Seattle, WA, June 1995. C. Doumanidis, "Real-Time Optimization of Thermal Eigenstructure in Manufa- cturing Process Modeling and Control", 10th Intl. Conf. on Math. and Comp. Modelling and Scientific Computing, Boston, MA, July 1995. C. Doumanidis, B. Marquis, "Thermally Optimal Design by Simulation of Scanned Material Processing Methods", IASTED Intl. Conf. on Applied Modelling, Simulation and Optimization, Cancun, Mexico, June 1995. C. Doumanidis, "Automated Guidance of the Heat Source Motion in Robotic Thermal Materials Processing", IASTED Intl. Conf. on Robotics and Manufactu- ring, Cancun, Mexico, June 1995.
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