Feedforward Laser Power Specification for Uniform Cooling of Thin-Walled Parts

2004 ◽  
Author(s):  
Umesh A. Korde ◽  
Michael A. Langerman ◽  
Gregory A. Buck ◽  
Vojislav D. Kalanovic
Keyword(s):  
Laser Power ◽  
Thermal Model ◽  
Deposition Process ◽  
Ongoing Research ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
The Matrix ◽  
Thin Walled ◽  
The Time Domain ◽  
Power Sequence

This paper presents results from ongoing research on thermal-model based feedforward specification of laser power in a laser powder deposition process. The goal of this algorithm is to compute, before deposition of a layer, the laser power sequence and distribution that would produce a desired temperature distribution over that layer. This in turn will enable uniform cooling of the layer and avoid build up of residual stresses. In this paper, results based on a simplified thermal model and second-order spatial discretization are presented. Two types of discretization in the time domain are examined. The matrix-exponential-based discretization is expected to be more accurate at lower laser speeds. The desired laser power sequence and the resulting temperature histories for a prescribed laser speed are discussed within the context of a thin-walled part.

Simulation of Geometry and Heat Transfer in a Thin Wall Produced by Direct Laser Powder Deposition

2011 ◽  
Vol 227 ◽  
pp. 134-137
Author(s):  
Karim Kheloufi ◽  
El Hachemi Amara
Keyword(s):  
Three Dimensional ◽  
Deposition Process ◽  
Thin Wall ◽  
Three Dimensional Model ◽  
Laser Powder Deposition ◽  
Commercial Code ◽  
Geometrical Features ◽  
Direct Laser ◽  
Powder Deposition ◽  
Single Bead

A three dimensional model for direct laser powder deposition process is developed to simulate the geometry and the thermal field in building a single-bead wall (thin-wall). This model was employed using the Fluent commercial code to which several modules were appended (User Defined Functions UDF). The temperature distribution, the geometrical features of the generated structure, and thermal cycles have been carried out. We show that the results analysis can provide guidance for the process parameter selection in LPD. , and develop a base for further residual stress analysis.

Control of the Clad Height in Laser Powder Deposition Process Using a PID Controller

2006 ◽  
Author(s):  
Alireza Fathi ◽  
Mohammad Durali ◽  
Ehsan Toyserkani ◽  
Amir Khajepour
Keyword(s):  
Control Variable ◽  
Deposition Process ◽  
Processing Technique ◽  
Hammerstein Model ◽  
Model Parameters ◽  
Nonlinear Dynamic Model ◽  
Scanning Velocity ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
Metallic Parts

Laser Powder Deposition (LPD) process is an advanced material processing technique which has many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for the process. In this paper, the problem of controlling the clad height in the LPD process is studied. Due to a faster response of the process to change in scanning velocity over the laser power, the scanning velocity is selected as the input control variable. Since the governing equations of the LPD process are complex for designing a controller, an identified nonlinear dynamic model is used. The model is a Hammerstein model with a linear dynamic and a nonlinear memoryless block. The model parameters are identified offline using experimental data. The controller has a proportional-integral-derivation (PID) architecture. The controller was implemented on the real plant to asses its performance in the fabrication of several metallic parts composed of stainless steel.

Preliminary Design of a Calorimeter for Experimental Determination of Effective Absorptivity of Metal Substrates During Laser Powder Deposition

2005 ◽  
Author(s):  
Jacob J. Koester ◽  
Michael A. Langerman ◽  
Umesh A. Korde ◽  
James W. Sears ◽  
Gregory A. Buck
Keyword(s):  
Experimental Data ◽  
Thermal Model ◽  
Laser Energy ◽  
Metal Substrate ◽  
Published Data ◽  
Preliminary Design ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
Laser Energy Absorption

A thermal model of the laser powder deposition (LPD) process has been developed and tested. Results obtained from the model, however, are dependent upon the magnitude of the laser energy absorbed during the process. Although spectral absorptivities of metal surfaces are described in literature, during the LPD process, the powder increases the energy delivered to the substrate. There are no published data regarding this affect. Therefore, the SDSM&T Additive Manufacturing Laboratory (AML) is developing a calorimeter to experimentally investigate the affect of the powder on laser energy absorption at the metal substrate. The preliminary design is described in this paper with discussion on measures being taken to increase the accuracy of experimental data.

Application of vibration in the laser powder deposition process

2009 ◽  
Vol 11 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Ehsan Foroozmehr ◽  
Dechao Lin ◽  
Radovan Kovacevic
Keyword(s):  
Deposition Process ◽  
Laser Powder Deposition ◽  
Powder Deposition

Adaptive Modeling of Laser Powder Deposition Process for Control and Monitoring Application

2005 ◽  
Author(s):  
Mohammad Durali ◽  
Alireza Fathi ◽  
Amir Khajepour ◽  
Ehsan Toyserkani
Keyword(s):  
Kalman Filter ◽  
System Identification ◽  
Least Square Method ◽  
Deposition Process ◽  
Least Square ◽  
Filter Method ◽  
Recursive Least Square ◽  
Noise Elimination ◽  
Laser Powder Deposition ◽  
Powder Deposition

Laser Powder Deposition technique is an advanced production method with many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for this method. This article presents method for in time identification of the process for modeling and adaptation of proper control strategy. ARMAX structure is chosen for system model. Recursive least square method and Kalman Filter methods are adopted for system identification, and their performance are compared. Experimental data was used for system identification, and proper filtering schemes are devised here for noise elimination and increased estimation results. It was concluded that although both methods yield efficient performance and accurate results, Kalman Filter method gives better results in parameter estimations. The comparison of the results shows that this method can be used very efficiently in control and monitoring of Laser Powder Deposition process.

Thermal Control of Laser Powder Deposition: Heat Transfer Considerations

2004 ◽  
Author(s):  
Michael A. Langerman ◽  
Gregory A. Buck ◽  
Umesh A. Korde ◽  
Vojislav D. Kalanovic
Keyword(s):  
Computer Aided Design ◽  
Thermal Model ◽  
Thermal Control ◽  
Free Form ◽  
Component Part ◽  
System Control ◽  
Forming Process ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
Melt Pool Size

Laser based solid free-form fabrication is an emerging metallurgical forming process aimed at rapid production of high quality, near net shape products directly from starting powders. Laser powder deposition shares, with other free-form technologies, the common characteristic that part fabrication occurs directly from a 3-D computer aided design (CAD) model. The microstructure evolution and resulting material properties of the component part (strength, ductility, etc.) fabricated using laser deposition are dependent upon process operating parameters such as melt pool size, laser power, head (manipulator) speed, and powder flow rate. Presently, set points for these parameters are often determined through manual manipulation of the system control and trial and error. This paper discusses the development of a path-planning, feed-forward, process-driven control system algorithm that generates a component part thermal history within given constraints, thereby assuring optimal part quality and minimizing final residual stresses. A thermal model of the deposition process drives the control algorithm. The development of the thermal model is the subject of this paper. The model accounts for temperature-dependent properties and phase change processes. Model validation studies are presented including comparisons with known analytic solutions as well as comparisons with data from experiments conducted in the laser laboratory at SDSM&T.

Sign in / Sign up

Export Citation Format

Share Document