657 research outputs found
Modeling of the Metal Powder Flow with Carrier Gas in Coaxial Nozzle for Direct Laser Deposition Process
In direct laser deposition process, metal powder is directly fed with carrier gas
through the coaxial nozzle into the melt pool created by the laser to form the solid parts.
Many operational parameters of the process depend on the characteristic of the powder
stream structure below the exit of the coaxial nozzle. In this paper, a computational
approach is developed for the simulation of the gas-particle flow in the coaxial nozzle.
By taking into account the nozzle geometry and operating parameters, such as width and
inclination angle of powder passage and carrier gas velocity, the developed
computational code allows the simulation, optimization and control of the delivery of the
metal powders.Mechanical Engineerin
Product Focused Freeform Fabrication Education
Presented in this paper is our experience of teaching freeform fabrication to students at
the Missouri University of Science and Technology, and to high school students and
teachers. The emphasis of the curriculum is exposing students to rapid product
development technologies with the goal of creating awareness to emerging career
opportunities in CAD/CAM. Starting from solid modeling, principles of freeform
fabrication, to applications of rapid prototyping and manufacturing in industry sponsored
product development projects, students can learn in-depth freeform fabrication
technologies. Interactive course content with hands-on experience for product
development is the key towards the success of the program.Mechanical Engineerin
Sensitivity Analysis of Process Parameters in Laser Deposition
In laser cladding with powder injection process, process output parameters, including
melt pool temperature and melt pool dimensions, are critical for part quality. This paper uses
simulation and experiments to investigate the effect of the process input parameters: laser power,
powder mass flow rate, and scanning speed on the output parameters. Numerical simulations and
experiments are conducted using a factorial design. The results are statistically analyzed to
determine the significant factors and their interactions. The simulation results are compared to
experimental results. The quantitative agreement/disagreement is discussed and further research is
outlined.Mechanical Engineerin
Experimental Investigation of Laser Metal Deposition of Functionally Graded Copper and Steel
Laser metal deposition is an emerging technology for producing fully dense
metallic parts. This process shows a promising future for the deposition of functionally
graded steel - copper alloys. Good thermal conductivity of copper and a high wear
resistance of steel can be achieved in dies and cores. However, to accomplish this, there
are many issues to be resolved, such as the formation of an undesirable phase,
solidification cracking, porosity at the interface and difference in thermal coefficient of
expansion between steel and copper. The influences of process variables, such as laser
power, laser scan speed, composition, powder flow rate, on the success of the process,
should be studied.Mechanical Engineerin
Numerical and Experimental Analysis of the Powder Flow Streams in the Laser Aided Material Deposition Process
Axial powder stream concentration between the nozzle end and the deposition point is an
important process parameter in the laser aided material deposition process. The powder
concentration is greatly influenced by the nozzle geometry in use. This paper describes the
numerical and experimental analysis of this important parameter in relation to the coaxial nozzle.
The experiments are performed with the different nozzle geometries to generate various flow
patterns of the gravity fed powder in a cold stream. The results of the experimental analysis are
compared with the numerical simulation and found justified. These results are used in concluding
the significance of important nozzle parameters for various powder concentration modes.Mechanical Engineerin
Thermocouple Embedding for the Production of a Substrate for Rapid Manufacturing
Mechanical Engineerin
Design of Embedded Resistance Heating Element Using Rapid Manufacturing Process
Mechanical Engineerin
Workpiece Alignment for Hybrid Laser Aided Part Repair Process
Work piece alignment is a key issue for hybrid laser aided part repair, a process utilizing
both machining and laser deposition. Proper alignment can greatly improve the accuracy of the
repair process. This paper introduces a method for aligning a physical work piece and a CAD
model using a Renishaw touch probe and software tools. Also discussed is a model for
computing 5-axis CNC positions based on a desired work piece orientation.Mechanical Engineerin
Variable Powder Flow Rate Control in Laser Metal Deposition Processes
This paper proposes a novel technique, called Variable Powder Flow Rate Control (VPFRC), for
the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to
adjust the powder flow rate to maintain a uniform powder deposition per unit length even when
disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the
powder delivery system motor and the powder transport system (i.e., five–meter pipe, powder
dispenser, and cladding head) are first constructed. A general tracking controller is then designed
to track variable powder flow rate references. Since the powder flow rate at the nozzle exit
cannot be directly measured, it is estimated using the powder transport system model. The input
to this model is the DC motor rotation speed, which is estimated on–line using a Kalman filter.
Experiments are conducted to examine the performance of the proposed control methodology.
The experimental results demonstrate that VPFRC is successful in maintaining a uniform track
morphology, even when the motion control system accelerates and decelerates.Mechanical Engineerin
Laser Deposition Cladding On-Line Inspection Using 3-D Scanner
Laser deposition directly deposits metal cladding to fabricate and repair components. In
order to finish the fabrication or repair, 3-D shape of the deposition needs to be inspected, and
thus it can be determined if it has sufficient cladding to fabricate a part after deposition process.
In the present hybrid system in the Laser Aided Manufacturing Lab (LAMP) at the University of
Missouri - Rolla, a CMM system is used to do the inspection. A CMM requires point-by-point
contact, which is time consuming and difficult to plan for an irregular deposition geometry. Also,
the CMM is a separate device, which requires removal of the part from the hybrid system, which
can induce fixture errors. The 3-D scanner is a non-contact tool to measure the 3-D shape of laser
deposition cladding which is fast and accurate. In this paper, A prototype non-contact 3-D
scanner approach has been implemented to inspect the free-form and complex parts built by laser
deposition. Registration of the measured model and 3-D CAD model allows
the comparison between the two models. It enables us to determine if the deposition is sufficient
before machining.Mechanical Engineerin
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