Laser Cladding Based Solid Freeform Fabrication and Direct Metal Deposition

2006 ◽  
Author(s):  
Huan Qi ◽  
Jyotirmoy Mazumder
Keyword(s):  
Laser Beam ◽  
Laser Cladding ◽  
Solid Freeform Fabrication ◽  
Three Dimensional ◽  
High Energy ◽  
Metal Deposition ◽  
Direct Metal Deposition ◽  
Effective Control ◽  
Metal Powders ◽  
Freeform Fabrication

Three-dimensional additive manufacturing or solid freeform fabrication (SFF) techniques, originated in the rapid fabrication of non-functional physical prototypes in polymers (Rapid Prototyping), have matured to the manufacture of functional prototypes, short-run production products, and now even advanced engineering designs. Laser-based material deposition or laser cladding has been used as a SFF technique, in which a laser beam is used as a precise high-energy thermal source to melt preplaced or pneumatically delivered metal powders and make solidified deposits on a substrate. By using laser cladding techniques, three-dimensional fully dense components can be built line-by-line and layer-by-layer directly from a CAD model with tailored material properties. Laser cladding is essentially a fusion and solidification (thermal) process, which involves complicated interactions between the laser beam, metal powders, the base material (substrate), and processing gases. Maintaining a stable and uniform melt pool during laser cladding is critical to produce dimensional accuracy and material integrity. An effective control of energy (laser power) spatial and temporal distributions in either an open-loop or closed-loop laser cladding process is essential to achieve the high quality results. This paper reviews, from a laser-material interaction point of view, various laser cladding based SFF processes, and particularly the direct metal deposition technique.

Improving solid freeform fabrication by laser-based additive manufacturing

2002 ◽  
Vol 216 (9) ◽  
pp. 1253-1264 ◽  
Author(s):  
D Hu ◽  
H Mei ◽  
R Kovacevic
Keyword(s):  
Additive Manufacturing ◽  
Metal Powder ◽  
Laser Cladding ◽  
Closed Loop ◽  
Solid Freeform Fabrication ◽  
Three Dimensional ◽  
Closed Loop Control ◽  
Loop Control ◽  
Freeform Fabrication ◽  
Laser Cladding Process

Solid freeform fabrication (SFF) methods for metal part building, such as three-dimensional laser cladding, are generally less stable and less repeatable than other rapid prototyping methods. A large number of parameters govern the three-dimensional laser cladding process. These parameters are sensitive to the environmental variations, and they also influence each other. This paper introduces the research work in Research Center for Advanced Manufacturing (RCAM) to improve the performance of its developed three-dimensional laser cladding process: laser-based additive manufacturing (LBAM). Metal powder delivery real-time sensing is studied to achieve a further controllable powder delivery that is the key technology to build a composite material or alloy with a functionally gradient distribution. An opto-electronic sensor is designed to sense the powder delivery rate in real time. The experimental results show that the sensor's output voltage has a good linear relationship with the powder delivery rate. A closed-loop control system is also built for heat input control in the LBAM process, based on infrared image sensing. A camera with a high frame rate (up to 800frame/s) is installed coaxially to the top of the laser—nozzle set-up. A full view of the infrared images of the molten pool can be acquired with a short nozzle—substrate distance in different scanning directions, eliminating the image noise from the metal powder. The closed-loop control results show a great improvement in the geometrical accuracy of the built feature.

Solid Freeform Fabrication of Metal Parts by 3D Laser Cladding

2000 ◽  
Author(s):  
Dongming Hu ◽  
Radovan Kovacevic ◽  
Mike Valant
Keyword(s):  
Machine Vision ◽  
Laser Cladding ◽  
High Speed ◽  
Solid Freeform Fabrication ◽  
Effective Means ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Freeform Fabrication ◽  
Metal Parts ◽  
Laser Focusing

Abstract This paper presents the development of a method of three-dimensional laser cladding for Solid Freeform Fabrication (SFF). A SFF system developed at SMU (SMU-SFF) is introduced which can build 3D metal parts by cladding metal powder delivered by a nozzle mounted coaxially to a Nd: YAG laser focusing head. An on-line slicing process that uses machine vision to measure the height of the part being built is also introduced as an effective means of optimizing the cladding process. Further, to explore the effects of the laser cladding parameters on the SFF results, machine vision with a high-speed shutter camera is utilized to observe the laser cladding process. The relationships between processing parameters (laser power, scan velocity) and cladding results are then discussed.

Modeling of Spatially Controlled Biomolecules in Three-Dimensional Porous Alginate Structures

2010 ◽  
Vol 4 (4) ◽  
Author(s):  
Ibrahim T. Ozbolat ◽  
Bahattin Koc
Keyword(s):  
Computer Aided Design ◽  
Solid Freeform Fabrication ◽  
Imaging Techniques ◽  
Release Kinetics ◽  
Three Dimensional ◽  
Control Release ◽  
Stochastic Approach ◽  
Distribution Characteristics ◽  
Porous Structures ◽  
Freeform Fabrication

This paper presents a computer-aided design (CAD) of 3D porous tissue scaffolds with spatial control of encapsulated biomolecule distributions. A localized control of encapsulated biomolecule distribution over 3D structures is proposed to control release kinetics spatially for tissue engineering and drug release. Imaging techniques are applied to explore distribution of microspheres over porous structures. Using microspheres in this study represents a framework for modeling the distribution characteristics of encapsulated proteins, growth factors, cells, and drugs. A quantification study is then performed to assure microsphere variation over various structures under imaging analysis. The obtained distribution characteristics are mimicked by the developed stochastic modeling study of microsphere distribution over 3D engineered freeform structures. Based on the stochastic approach, 3D porous structures are modeled and designed in CAD. Modeling of microsphere and encapsulating biomaterial distribution in this work helps develop comprehensive modeling of biomolecule release kinetics for further research. A novel multichamber single nozzle solid freeform fabrication technique is utilized to fabricate sample structures. The presented methods are implemented and illustrative examples are presented in this paper.

A Computational Design Framework for a Rapid Solid Freeform Fabrication Process

2000 ◽  
Author(s):  
Deepesh Khandelwal ◽  
T. Kesavadas
Keyword(s):  
Solid Freeform Fabrication ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Computational Design ◽  
Freeform Fabrication ◽  
3D Cad ◽  
Build Time ◽  
Cad Models ◽  
Efficient Machine ◽  
Novel Concept

Abstract Solid Freeform Fabrication (SFF) techniques in recent years have shown tremendous promise in reducing the design time of products. This technique enables designers to get three-dimensional physical prototypes from 3D CAD models. Although SFF has gained popularity, the manufacturing time and cost have limited its use to small and medium sized parts. In this paper we have proposed a novel concept for rapidly building SFF parts by inserting prefabricated inserts into the fabricated part. A computational algorithm was developed for determining ideal placement of inserts/cores in the CAD model of the part being prototyped using a heuristic optimization technique called Simulated Annealing. This approach will also allow the designers to build multi-material prototypes using the Rapid Prototyping (RP) technique. By using cheaper pre-fabricates instead of costly photopolymers, the production cost of the SFFs can be reduced. Additionally it will also reduce build time, resulting in efficient machine utilization.

Three-Dimensional Finite Element Analysis of Melting in an Alloy Irradiated With a High Energy Laser Beam

2003 ◽  
Author(s):  
Bhavani Kasula ◽  
Pradip Majumdar
Keyword(s):  
Mathematical Model ◽  
Material Processing ◽  
Finite Element ◽  
Laser Beam ◽  
Molten Pool ◽  
Three Dimensional ◽  
High Energy ◽  
Convective Boundary ◽  
Energy Laser ◽  
High Energy Laser

Lasers are being widely used in the material processing industry lately. In this work, study is performed on the resluting temperature and stress distribution, the width and depth of the melt pool in the heat-affected zone during material processing with a high energy Gussian laser beam. A three-dimensional enthalphy-based mathematical model is developed to study the effect of high energy laser beam on the formation of molten pool. The mathematical model is based on a three-dimensional transient heat equation taking into consideration the power intensity of the Gussian laser beam and phase diagram of the material. A computational algorithm is implemented to evaluate the temperature distributions as well as shape and size of molten pool. The numerical solution with the applied heat flux and convective boundary conditions is obtained usign a 3-D finite element code.

Direct Freeform Fabrication Technique for Bio-Manufacturing of Pre-Seeded, Spatially Heterogeneous, Anatomically-Shaped Alginate Hydrogel Implants

2005 ◽  
Author(s):  
Daniel L. Cohen ◽  
Evan Malone ◽  
Hod Lipson ◽  
Lawrence J. Bonassar
Keyword(s):  
Tissue Engineering ◽  
Solid Freeform Fabrication ◽  
Crosslinking Agent ◽  
Three Dimensional ◽  
Patient Specific ◽  
Efficient Production ◽  
Alginate Hydrogel ◽  
Freeform Fabrication ◽  
Patient Specific Implants ◽  
Multiple Material

A major challenge in orthopaedic tissue engineering is the generation of cell-seeded implants with structures that mimic native tissue, both in terms of anatomic geometries and intratissue cell distributions. By combining the strengths of injection molding tissue engineering with those of Solid Freeform Fabrication (SFF), three-dimensional pre-seeded implants were fabricated without custom-tooling, enabling efficient production of patient-specific implants. The incorporation of SFF technology also enables the fabrication of geometrically complex, multiple-material implants with spatially heterogeneous cell distributions that could not otherwise be produced. Using a custom-built robotic SFF platform and gel deposition tools, alginate hydrogel was used with calcium sulfate as a crosslinking agent to produce pre-seeded living implants of arbitrary geometries. The process was determined to be sterile and viable at 94±5%. The GAG production was found to be about half that of a similarly molded samples. The compressive elastic modulus was determined to be 1.462±0.113 kPa.

Development of HA-PLGA Scaffold Encapsulating Intact BMP-2 Using Solid Freeform Fabrication Technology

2011 ◽  
Author(s):  
Jin-Hyung Shim ◽  
Jong Young Kim ◽  
Kyung Shin Kang ◽  
Jung Kyu Park ◽  
Sei Kwang Hahn ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Bone Regeneration ◽  
Porous Scaffold ◽  
Solid Freeform Fabrication ◽  
Three Dimensional ◽  
Porous Scaffolds ◽  
Prolonged Release ◽  
Cellular Activity ◽  
Freeform Fabrication

Tissue engineering is an interdisciplinary field that focuses on restoring and repairing tissues or organs. Cells, scaffolds, and biomolecules are recognized as three main components of tissue engineering. Solid freeform fabrication (SFF) technology is required to fabricate three-dimensional (3D) porous scaffolds to provide a 3D environment for cellular activity. SFF technology is especially advantageous for achieving a fully interconnected, porous scaffold. Bone morphogenic protein-2 (BMP-2), an important biomolecule, is widely used in bone tissue engineering to enhance bone regeneration activity. However, methods for the direct incorporation of intact BMP-2 within 3D scaffolds are rare. In this work, 3D porous scaffolds with poly(lactic-co-glycolic acid) chemically grafted hyaluronic acid (HA-PLGA), in which intact BMP-2 was directly encapsulated, were successfully fabricated using SFF technology. BMP-2 was previously protected by poly(ethylene glycol) (PEG), and the BMP-2/PEG complex was incorporated in HA-PLGA using an organic solvent. The HAPLGA/PEG/BMP-2 mixture was dissolved in chloroform and deposited via a multi-head deposition system (MHDS), one type of SFF technology, to fabricate a scaffold for tissue engineering. An additional air blower system and suction were installed in the MHDS for the solvent-based fabrication method. An in vitro evaluation of BMP-2 release was conducted, and prolonged release of intact BMP-2, for up to 28 days, was confirmed. After confirmation of advanced proliferation of pre osteoblasts, a superior differentiation effect of the HA-PLGA/PEG/BMP-2 scaffold was validated by measuring high expression levels of bone-specific markers, such as alkaline phosphatase (ALP) and osteocalcin (OC). We show that our solvent-based fabrication is a non-toxic method for restoring cellular activity. Moreover, the HAPLGA/PEG/BMP-2 scaffold was effective for bone regeneration.

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