Robert G. Landers (landersr@mst.edu, 573-341-4586), Frank Liou, Mallik Boddu, and Vishnu Thaylan

The Laser Metal Deposition (LMD) process is a novel manufacturing process capable of creating functional prototypes and parts with very thin sections, functional gradient materials, and embedded sensors. Currently, extensive experimentation is required to determine suitable process parameters (i.e., laser power, table velocity, and powder flow rate) for LMD processes and only near-net shape parts may be produced. Subsequent processing is required if dimensional accuracy is critical. Further, due to the variability of the LMD process, constant process parameters will often not guarantee the part will meet quality specifications in terms of mechanical properties (e.g., hardness, porosity), even if the parameter settings are derived from empirical process models. The project objectives are to 1) seek a fundamental understanding of the LMD process by creating dynamic models that relate the part morphology and melt pool temperature to the process parameters and 2) create on-line process control strategies that adjust the process parameters to regulate part quality. The dynamic models and control strategies will be validated via comprehensive experimental studies in the Laser Aided Manufacturing Processes Laboratory at the Missouri University of Science and Technology.

1. "Modeling for the Control of the Laser Aided Manufacturing Process (LAMP),� M. R. Boddu, V. Thayalan, and R. G. Landers, 2003 Fourteenth Annual Solid Freeform Fabrication Symposium, Austin, Texas, August 4-6.

Abstract: Many state-of-the-art Rapid Prototyping (RP) technologies adopt lasers to fabricate 3-D solid parts by material deposition in layers. The ability of these RP technologies to control the process requires a thorough understanding of the process mechanics. This paper presents the analysis of an analytical, dynamic model explaining the complex phenomenon of Laser Aided Manufacturing Process (LAMP). The equilibrium of the dynamic model is analyzed and dynamic simulations are performed to determine its stability characteristics. This model forms the basis for the real-time control of the LAMP.

2. "Process Control of Laser Metal Deposition Manufacturing - A Simulation Study,� R. G. Landers, 2003, Fourteenth Annual Solid Freeform Fabrication Symposium, Austin, Texas, August 4-6.

Abstract: The laser metal deposition process is a rapid manufacturing operation capable of producing functional prototypes with complex geometries and thin sections. This process inherently contains significant uncertainties and, therefore, extensive experimentation must be performed to determine suitable process parameters. An alternative is to directly control the process on-line using feedback control methodologies. In this paper, a nonlinear control strategy based on feedback linearization is created to automatically regulate the bead morphology and melt pool temperature. Extensive simulation studies are conducted to validate the control strategy.

3. "System Integration and Real-Time Control Architecture of a Laser Aided Manufacturing Process,� M. R. Boddu, R. G. Landers, S. Musti, S. Agarwal, J.-Z. Ruan, and F. W. Liou, 2002, Thirteenth Annual Solid Freeform Fabrication Symposium, Austin, Texas, August 5-7, pp. 522-529.

Abstract: This paper discusses a hybrid deposition-removal manufacturing system being developed at the University of Missouri-Rolla. The system consists of a laser system, five-axis CNC machining center, and powder feeder system. A description of the control software, real-time control architecture, and integration of various subsystems to build the hybrid system is given. The interaction of the real-time controller with various sensors and subsystems to monitor and regulate the process is presented. The communication between integrated process planning for the system and real-time control is also discussed in this paper.

4. "Empirical Modeling and Vision Based Control for the Laser Metal Deposition Process,� M. R. Boddu, S. Musti, R. G. Landers, S. Agarwal, and F. W. Liou, 2001, Twelfth Annual Solid Freeform Fabrication Symposium, Austin, Texas, August 6-8, pp. 452-459.

Abstract: This paper gives a brief description of the laser aided manufacturing process. Empirical models describing the process dynamics of the laser aided metal deposition process is developed based on some of the models found in the literature. These models provide the basis for process planning and real time control. An embedded vision system, a two color temperature sensor, and a laser displacement sensor are incorporated for real time monitoring and control of the deposition process. The temperature profile of the surface and geometric characteristics of the melt pool are studied to ensure consistent operation of the process.

5. "Control of Laser Cladding Processes for Rapid Prototyping - A Review,� M. R. Boddu, R. G. Landers, and F. W. Liou, 2001 Twelfth Annual Solid Freeform Fabrication Symposium, Austin, Texas, August 6-8, pp. 460-467.

Abstract: Lasers have wide-ranging applications in the manufacturing field (e.g., cladding, welding, cutting, machining, drilling). Extensive work is being conducted to apply laser cladding as a Rapid Prototyping (RP) process. In this paper the authors illustrate various principles of laser cladding in rapid prototyping. Important process parameters for the control of the laser cladding process are discussed as well as the experimental methods adopted, and results obtained by, various authors.