Machine simulation is an effective way of checking additive manufacturing tool paths for both int... more Machine simulation is an effective way of checking additive manufacturing tool paths for both interferences and errors in part produced. This paper presents an algorithm to visually simulate a multi axis additive manufacturing system as it executes a process plan. Simulation results are intended to be used as a verification step before physically producing the part. Verification is particularly important for large builds of expensive materials. The algorithm uses an octree approach to efficiently model the deposition of part geometry and its changes. This paper discusses development of the simulation algorithm, including both the representation of the additive manufacturing machine and the octree data model of the part being produced.
Laser deposition is an effective process for mold and die repair. In order to improve the part re... more Laser deposition is an effective process for mold and die repair. In order to improve the part repair qualityˈthe process impact on thermal diffusivity and thermal conductivity needs to be understood for laser deposited, welded and virgin H13. In this paper, H13 tool steel samples were made by laser deposition, welding and virgin H13 and then cut into pieces. Experiments were conducted to investigate the thermal diffusivity and conductivity. A laser flash method is used to test these samples. The future work and opportunities are also summarized.
300M steel is used extensively for aircraft landing gears because of its high strength, ductility... more 300M steel is used extensively for aircraft landing gears because of its high strength, ductility and toughness. However, like other high-strength steels, 300M steel is vulnerable to corrosion fatigue and stress corrosion cracking, which can lead to catastrophic consequences in the landing gear. Stainless steels offer a combination of corrosion, wear, and fatigue properties. But for an aircraft landing gear application a higher surface hardness is required. A laser cladding process with fast heating and cooling rates can improve the surface hardness. AISI 4340 steel is used as a lower cost alternative to 300M due to its similar composition. In this study, the influence of laser cladding process parameters, shield gas, and composition of the deposition and dilution zone has been investigated. The microstructures and composition analysis were evaluated by Scanning Electron Microscopy (SEM) and Optical Microscopy. The deposition hardness varies from 330HV to 600HV.
: A predictive model is developed to simulate the evolution of the solidification microstructure ... more : A predictive model is developed to simulate the evolution of the solidification microstructure during the laser deposition process. The microstructure model is coupled with a comprehensive macroscopic thermodynamic model. This model simulates dendritic grain structures and morphological evolution in solidification. Based on the cellular automata approach, this microstructure model takes into account the heterogeneous nucleation both within the melt pool and at the substrate/melt interface, the growth kinetics, and preferential growth directions of dendrites. Both diffusion and convection effects are included. This model enables prediction and visualization of grain structures during and after the deposition process. This model is applied to Ti-6Al-4V.
The Laser Aided Manufacturing Process (LAMP) lab at the University of Missouri Rolla is currently... more The Laser Aided Manufacturing Process (LAMP) lab at the University of Missouri Rolla is currently developing a laser-based part repair system especially for steel dies and molds. The system combines a machining center with a laser deposition center. This hybrid machining-laser deposition repair process reduces the limitations of typical welding repair process such as large heat affected zones, shape deformation etc. In addition, the bonding strength and other mechanical properties of the repaired part using hybrid repair process are better than the process using welding repair process. This process has been used to successfully repair a worn out die core. Due to a faster cooling rate, the hardness of deposited samples is higher than that of welded samples. The fracture surface analysis shows that the deposited samples retain some ductility, indicating that the hardness can be improved via heat treatment.
This paper presents a Laser Additive Manufacturing Process Planning (LAMPP) being developed at th... more This paper presents a Laser Additive Manufacturing Process Planning (LAMPP) being developed at the University of Missouri-Rolla. The off-line planning recognizes difficult-to-build features from an STL file, selects optimal part orientation and building directions based on the skeleton information of the object geometry, and optimizes the sub-process sequences for deposition and machining. During the optimization of the subpart building processes, collaboration between the deposition process planner and the machining process planner is needed to check the deposition availability and machinability. As a result, tool paths for both the laser head and the machining head are automatically generated.
The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-... more The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed. The model is used to predict dilution under varying process parameters for deposits of Ti-6Al-4V. Experimental validation of the predicted dilution is presented. The laser used is a direct diode laser.
This paper presents the usage of vibration in laser direct deposition of Ti64. The vibration is u... more This paper presents the usage of vibration in laser direct deposition of Ti64. The vibration is used to refine the crystalline structure of the deposition. The vibration device vibrates in the laser deposition system along the Z axis. A design of experiments approach is applied in studying the effect of vibration on the deposited material. Vibration during deposition led to grain refinement and an increase in microhardness over that of samples from no-vibration. Also, vibration frequency is a significant factor. From the experiment results, it is found that a vibration frequency greater than 20Hz is desirable.
Volume 5: 37th Design Automation Conference, Parts A and B, 2011
Simulation of a machine is very important before laser metal deposition is performed, as a tool t... more Simulation of a machine is very important before laser metal deposition is performed, as a tool to check collision detection and validate deposition result. There are several kinds of machines that are used for laser deposition and hence there is a need for a generalized concept for visual simulation of various kinds of machines. This paper presents the research conducted on describing each machine configuration in a generic format. A parent–child list and a dependency list obtained from the machine configuration are utilized to form the generic format. Such a format can be used to describe linear and rotational motion of the machines parts. This method has been tested on various examples to demonstrate its robustness and efficiency.
Journal of Manufacturing Science and Engineering, 2011
A laser metal deposition height control methodology is presented in this paper. The height contro... more A laser metal deposition height control methodology is presented in this paper. The height controller utilizes a particle swarm optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. Using the estimated model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using iterative learning control (ILC). The model parameter estimation performance using PSO is evaluated using a four-layer single track deposition, and the powder flow rate reference generation performance using ILC is tested using simulation. The results show that PSO and ILC perform well in estimating model parameters and generating powder flow rate references, respectively. The proposed height control methodology is then tested experimentally for tracking a constant height reference with constant traverse speed and constant laser power. The experimental results indicate that the controller ...
The metal layered manufacturing processes have provided industries with a fast method to build fu... more The metal layered manufacturing processes have provided industries with a fast method to build functional parts directly from CAD models. This paper compares current metal layered manufacturing technologies from including powder based metal deposition, selective laser sinstering (SLS), wire feed deposition etc. The characteristics of each process, including its industrial applications, advantages/disadvantages, costs etc are discussed. In addition, the comparison between each process in terms of build rate, suitable metal etc. is presented in this paper.
Machine simulation is an effective way of checking additive manufacturing tool paths for both int... more Machine simulation is an effective way of checking additive manufacturing tool paths for both interferences and errors in part produced. This paper presents an algorithm to visually simulate a multi axis additive manufacturing system as it executes a process plan. Simulation results are intended to be used as a verification step before physically producing the part. Verification is particularly important for large builds of expensive materials. The algorithm uses an octree approach to efficiently model the deposition of part geometry and its changes. This paper discusses development of the simulation algorithm, including both the representation of the additive manufacturing machine and the octree data model of the part being produced.
Laser deposition is an effective process for mold and die repair. In order to improve the part re... more Laser deposition is an effective process for mold and die repair. In order to improve the part repair qualityˈthe process impact on thermal diffusivity and thermal conductivity needs to be understood for laser deposited, welded and virgin H13. In this paper, H13 tool steel samples were made by laser deposition, welding and virgin H13 and then cut into pieces. Experiments were conducted to investigate the thermal diffusivity and conductivity. A laser flash method is used to test these samples. The future work and opportunities are also summarized.
300M steel is used extensively for aircraft landing gears because of its high strength, ductility... more 300M steel is used extensively for aircraft landing gears because of its high strength, ductility and toughness. However, like other high-strength steels, 300M steel is vulnerable to corrosion fatigue and stress corrosion cracking, which can lead to catastrophic consequences in the landing gear. Stainless steels offer a combination of corrosion, wear, and fatigue properties. But for an aircraft landing gear application a higher surface hardness is required. A laser cladding process with fast heating and cooling rates can improve the surface hardness. AISI 4340 steel is used as a lower cost alternative to 300M due to its similar composition. In this study, the influence of laser cladding process parameters, shield gas, and composition of the deposition and dilution zone has been investigated. The microstructures and composition analysis were evaluated by Scanning Electron Microscopy (SEM) and Optical Microscopy. The deposition hardness varies from 330HV to 600HV.
: A predictive model is developed to simulate the evolution of the solidification microstructure ... more : A predictive model is developed to simulate the evolution of the solidification microstructure during the laser deposition process. The microstructure model is coupled with a comprehensive macroscopic thermodynamic model. This model simulates dendritic grain structures and morphological evolution in solidification. Based on the cellular automata approach, this microstructure model takes into account the heterogeneous nucleation both within the melt pool and at the substrate/melt interface, the growth kinetics, and preferential growth directions of dendrites. Both diffusion and convection effects are included. This model enables prediction and visualization of grain structures during and after the deposition process. This model is applied to Ti-6Al-4V.
The Laser Aided Manufacturing Process (LAMP) lab at the University of Missouri Rolla is currently... more The Laser Aided Manufacturing Process (LAMP) lab at the University of Missouri Rolla is currently developing a laser-based part repair system especially for steel dies and molds. The system combines a machining center with a laser deposition center. This hybrid machining-laser deposition repair process reduces the limitations of typical welding repair process such as large heat affected zones, shape deformation etc. In addition, the bonding strength and other mechanical properties of the repaired part using hybrid repair process are better than the process using welding repair process. This process has been used to successfully repair a worn out die core. Due to a faster cooling rate, the hardness of deposited samples is higher than that of welded samples. The fracture surface analysis shows that the deposited samples retain some ductility, indicating that the hardness can be improved via heat treatment.
This paper presents a Laser Additive Manufacturing Process Planning (LAMPP) being developed at th... more This paper presents a Laser Additive Manufacturing Process Planning (LAMPP) being developed at the University of Missouri-Rolla. The off-line planning recognizes difficult-to-build features from an STL file, selects optimal part orientation and building directions based on the skeleton information of the object geometry, and optimizes the sub-process sequences for deposition and machining. During the optimization of the subpart building processes, collaboration between the deposition process planner and the machining process planner is needed to check the deposition availability and machinability. As a result, tool paths for both the laser head and the machining head are automatically generated.
The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-... more The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed. The model is used to predict dilution under varying process parameters for deposits of Ti-6Al-4V. Experimental validation of the predicted dilution is presented. The laser used is a direct diode laser.
This paper presents the usage of vibration in laser direct deposition of Ti64. The vibration is u... more This paper presents the usage of vibration in laser direct deposition of Ti64. The vibration is used to refine the crystalline structure of the deposition. The vibration device vibrates in the laser deposition system along the Z axis. A design of experiments approach is applied in studying the effect of vibration on the deposited material. Vibration during deposition led to grain refinement and an increase in microhardness over that of samples from no-vibration. Also, vibration frequency is a significant factor. From the experiment results, it is found that a vibration frequency greater than 20Hz is desirable.
Volume 5: 37th Design Automation Conference, Parts A and B, 2011
Simulation of a machine is very important before laser metal deposition is performed, as a tool t... more Simulation of a machine is very important before laser metal deposition is performed, as a tool to check collision detection and validate deposition result. There are several kinds of machines that are used for laser deposition and hence there is a need for a generalized concept for visual simulation of various kinds of machines. This paper presents the research conducted on describing each machine configuration in a generic format. A parent–child list and a dependency list obtained from the machine configuration are utilized to form the generic format. Such a format can be used to describe linear and rotational motion of the machines parts. This method has been tested on various examples to demonstrate its robustness and efficiency.
Journal of Manufacturing Science and Engineering, 2011
A laser metal deposition height control methodology is presented in this paper. The height contro... more A laser metal deposition height control methodology is presented in this paper. The height controller utilizes a particle swarm optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. Using the estimated model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using iterative learning control (ILC). The model parameter estimation performance using PSO is evaluated using a four-layer single track deposition, and the powder flow rate reference generation performance using ILC is tested using simulation. The results show that PSO and ILC perform well in estimating model parameters and generating powder flow rate references, respectively. The proposed height control methodology is then tested experimentally for tracking a constant height reference with constant traverse speed and constant laser power. The experimental results indicate that the controller ...
The metal layered manufacturing processes have provided industries with a fast method to build fu... more The metal layered manufacturing processes have provided industries with a fast method to build functional parts directly from CAD models. This paper compares current metal layered manufacturing technologies from including powder based metal deposition, selective laser sinstering (SLS), wire feed deposition etc. The characteristics of each process, including its industrial applications, advantages/disadvantages, costs etc are discussed. In addition, the comparison between each process in terms of build rate, suitable metal etc. is presented in this paper.
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