3,527 research outputs found
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Software Testbed for Selective Laser Sintering
Computer software plays an important role in the implementation of Solid Freeform
Fabrication (SFF) technologies. This paper describes a software testbed for processing
part geometry for a particular SFF technology, selective laser sintering (SLS), that is built
around the separation of the slicing and rasterization operations to accommodate geometric
information from a variety of sources. The paper also discusses the process control
software being developed for a new high-temperat rkstation for SLS of metal
powders. This program features a high-resolution data rmat, the ability to interpolate
to achieve a desired resolution, and a menu-driven user interface with graphical feedback
and process simulation capabilities.Mechanical Engineerin
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Systems Issues in Solid Freeform Fabrication
This paper is concerned with the systems aspects of the Solid Freeform Fabrication (SFF) technology, i.e., the issues that deal with getting an external geometric CAD model to automatically control the physical layering fabrication process as directly as possible, regardless ofthe source of the model. The general systems issues are described, the state of systems research is given, and open research questions are posed.Mechanical Engineerin
Freeform Fabrication of Ionomeric Polymer-Metal Composite Actuators
Ionomeric polymer-metal composite (IPMC) actuators are a type of soft electromechanically active material which offers
large displacement, rapid motion with only ~1V stimulus. IPMC’s are entering commercial applications in toys (Ashley
2003) and biomedical devices (Soltanpour 2001; Shahinpoor 2002; Shahinpoor, Shahinpoor et al. 2003; Soltanpour and
Shahinpoor 2003; Soltanpour and Shahinpoor 2004), but unfortunately they can only actuate by bending, limiting their
utility. Freeform fabrication offers a possible means of producing IPMC with novel geometry and/or tightly integrated with
mechanisms which can yield linear or more complex motion. We have developed materials and processes which allow us to
freeform fabricate complete IPMC actuators and their fabrication substrate which will allow integration within other
freeform fabricated devices. We have produced simple IPMC’s using our multiple material freeform fabrication system, and
have demonstrated operation in air for more than 40 minutes and 256 bidirectional actuation cycles. The output stress scaled
to input power is two orders of magnitude inferior to that of the best reported performance for devices produced in the
traditional manner, but only slightly inferior to devices produced in a more similar manner. Possible explanations and paths
to improvement are presented. Freeform fabrication of complete electroactive polymer actuators in unusual geometries,
with tailored actuation behavior, and integrated with other freeform fabricated active components, will enable advances in
biomedical device engineering, biologically inspired robotics, and other fields. This work constitutes the first
demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.Mechanical Engineerin
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Computer Aspects of Solid Freeform Fabrication: Geometry, Process Control, and Design
Solid Freefonn Fabrication (SFF) is a class of manufacturing technologies aimed at the
production of mechanical components without part-specific tooling or process planning. Originally
used for creating modelsfor visualization, many industrial users of SFF technologies are realizing
the greater potentialofSFF as legitimate manufacturing processes for producing patterns and, in
some cases, functional.parts. Thus, SFF is becoming an important aspect of the product
realization process in these industries.
Solid Freefonn Fabrication arose from the dream of "push-button" prototyping, in which
solid reproductions of three-dimensional geometric models are created automatically under
computer control. Perhaps more than any other class of manufacturing technologies, computer
software development has been an integral part of the emergence of SFF. As SFF technologies
evolve toward the ability to create functional parts, computer issues gain more importance.
This paper discusses three aspects of software design for SFF: processing of geometric
data, global and local control of SFF processes, and computer-based analysis and design for SFF
manufacturing. The discussion of geometric processing issues focuses on accuracy and
completeness of input models, and the algorithms required to process such models. The interplay
between the physics of SFF processing and the desired output geometry is discussed in terms of
the development of model-based control algorithms for SFF. These two areas, geometric
processing and control, are necessary for the practical implementation of any SFF technology.
However, for SFF to realize its potential as an alternative for manufacturing functional parts,
engineers must be provided with analysis and design tools for predicting mechanical properties,
ensuring dimensional accuracy, choosing appropriate materials, selecting process parameter
values, etc. For each of these three different but related areas of software design, the state-of-theart
is assessed, contemporary research is summarized, and future needs are outlined.Mechanical Engineerin
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Direct Extrusion Freeforming of Ceramic Pastes
Microextrusion freeforming of ceramic lattices from high solids ceramic pastes provides
multi-scale hierarchical void structures with the advantages of low shrinkage stress and high
sintered density. Alumina lattices were directly fabricated using 80-500 Pm diameter filaments.
We report here on the implementation of design and fabrication of these scaffolds for band gap
materials and micro fluidic devices.Mechanical Engineerin
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Multi-Nozzle Biopolymer Deposition for Freeform Fabrication of Tissue Constructs
Advanced freeform fabrication techniques have been recently used for the construction of tissue
scaffolds because of the process repeatability and capability of high accuracy in fabrication
resolution at the macro and micro scales. Among many applicable tissue scaffolding materials,
polymeric materials have unique properties in terms of the biocompatibility and degradation, and
have thus been widely utilized in tissue engineering applications. Hydrogels, such as alginate,
has been one of the most important polymer scaffolding materials because of its biocompatibility
and internal structure similarity to that of the extracellular matrix of many tissues, and its
relatively moderate processing. Three-dimensional deposition has been an entreating freeform
fabrication method of biopolymer and particularly hydrogel scaffolds because of its readiness to
deposit fluids at ambient temperatures. This paper presents a recent development of biopolymer
deposition based freeform fabrication for 3-diemnsinal tissue scaffolds. The system
configuration of multi-nozzles used in the deposition of sodium alginate solutions and Poly-?-
Caprolactone (PCL) are described. Studies on polymer deposition feasibility and structural
formability are conducted, and the preliminary results are presented.Mechanical Engineerin
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Geometry and Procedure for Benchmarking SFF and Hybrid Fabrication Process Resolution
Since the advent of SFF and RP a number of SFF benchmarking geometries and methodologies
have been developed and employed with some similarities but limited standardization. Minimal
information has been published in regard to a standard method of measuring the resolution limits or
capabilities of SFF and SFF-based hybrid processes. In an effort to benchmark resolution limits of SFF
and Hybrid Fabrication processes, several benchmarking geometries were developed to capture the
resolution capabilities, specifically hole size and rod size range, of multiple hybrid fabrication path steps
and a hybrid path as a whole. These useful geometries are shared with the SFF community and
procedures for their use are described in this paper.Mechanical Engineerin
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Mobile Paving System (MPS): A New Large Scale Freeform Fabrication Method
In the last decade, significant opportunities for automation have been identified in the area of
construction. Soaring labor and material costs have driven multiple research efforts in
construction automation. In this paper, we present a novel means for construction automation
that involves the fusion of the rapid prototyping, controls and mechatronics technologies. The
resultant autonomous construction mechanism has been designed for commercial applications.
Mobile Paving System (MPS) is a new freeform fabrication process which is capable of rapidly
producing variable profiles such as curbs and sidewalks out of materials like cement and asphalt.
Path generation and guidance of the construction operation is controlled by a mobile robot. This
article presents an overview of research and development efforts that are aimed at establishing
the feasibility and the potential of the process.Mechanical Engineerin
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The Characteristics and Applications of Ceramic Laser Fusion and Ceramic Laser Sintering
The aim of present study is to investigate the possible application of the ceramic parts
which are fabricated with the process of Ceramic Laser Fusion or Ceramic Laser Sintering.
The experimental results reveal: (1) CLF can lead to a reduction in the porosity of the
ceramic part but also can induce micro-cracks. Therefore, this process cannot produce a part
with the required strength by a post-process of infiltration; (2) CLS is capable of fabricating a
ceramic part with high porosity. By adjusting the slurry formulation and varying the scanning
energy, the open porosity can be over 90vol% of the total porosity. After a post-process of
infiltration, the density can be increased to 95%; therefore, CLS can apply to produce a part
with high strength. Because the high open porosity leads to a good permeability, the process
of CLS is suitable for the fabrication of ceramic shell mold.Mechanical Engineerin
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Freeform Bioprinting of Liver Encapsulated in Alginate Hydrogels Tissue Constructs for Pharmacokinetic Study
An in vitro model that can be realistically and inexpensively used to predict human response to
various drug administration and toxic chemical exposure is needed. By fabricating a microscale
3D physiological tissue construct consisting of an array of channels and tissue-embedded
chambers, one can selectively develop various biomimicking mammalian tissues for a number of
pharmaceutical applications, for example, experimental pharmaceutical screening for drug
efficacy and toxicity along with apprehending the disposition and metabolic profile of a
candidate drug. This paper addresses issues relating to the development and implementation of a
bioprinting process for freeform fabrication of a 3D cell-encapsulated hydrogel-based tissue
construct, the direct integration onto a microfluidic device for pharmacokinetic study, and the
underlying engineering science for the fabrication of a 3D microscale tissue chamber as well as
its application in pharmacokinetic study. To this end, a prototype 3D microfluidic tissue chamber
embedded with liver cells encapsulated within a hydrogel matrix construct is bioprinted as a
physiological in vitro model for pharmacokinetic study. The developed fabrication processes are
further validated and parameters optimized by assessing cell viability and liver cell phenotype, in
which metabolic and synthetic liver functions are quantitated.Mechanical Engineerin
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