2,798 research outputs found
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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
Multi-function based modeling of 3D heterogeneous wound scaffolds for improved wound healing
This paper presents a new multi-function based modeling of 3D heterogeneous porous wound scaffolds to improve wound healing process for complex deep acute or chronic wounds. An imaging-based approach is developed to extract 3D wound geometry and recognize wound features. Linear healing fashion of the wound margin towards the wound center is mimicked. Blending process is thus applied to the extracted geometry to partition the scaffold into a number of uniformly gradient healing regions. Computer models of 3D engineered porous wound scaffolds are then developed for solid freeform modeling and fabrication. Spatial variation over biomaterial and loaded bio-molecule concentration is developed based on wound healing requirements. Release of bio-molecules over the uniform healing regions is controlled by varying their amount and entrapping biomaterial concentration. Thus, localized controlled release is developed to improve wound healing. A prototype multi-syringe single nozzle deposition system is used to fabricate a sample scaffold. Proposed methodology is implemented and illustrative examples are presented in this paper
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
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Hybrid Prototypes to Assist Modeling Automotive Seats
The development of new modular seats is an important issue in the automotive industry.
However, is very time consuming and costly. Virtual models and hybrid prototypes could
accelerate the car seats development process. The hybrid prototypes are mainly manufactured by
rapid prototyping with multi materials. The objective of this paper is to establish a methodology
to develop innovative lightweight multi-functional, modular car seats to be used in Multi-Purpose
Vehicles (MPV), by means of FEA simulation and rapid prototyping additive/subtractive
technologies utilizing multi materials. A case study is presented to validate the developed
methodology. The manufactured hybrid prototype’s reproduces the main functionalities of the
MPV modular seat, namely its three key positions: normal, stored and table.Mechanical Engineerin
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Direct Laser Fabrication of a Gas Turbine Engine Component - Microstructure and Properties - Part I
This paper presents the development of a new technique for the production of abrasive
turbine blade tips by direct laser processing. This superalloy cermet component is an integral part
of the low pressure turbine sealing system in a demonstrator engine. Direct laser fabrication of
this component fiom a bed a loose powder results in significant cost savings and improved
performance over the currently employed production technique. The technology has been
demonstrated by fabricating a prototype lot of 100 blade tips, which will be subjected to an engine
test. This is the first instance of a direct fabrication method applied to the production of functional
engine hardware. This research was funded by the United States Air Force contract F33615-94-
C-2424 titled "Affordable Turbine Blade Tips".Mechanical Engineerin
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Prototyping Large-Sized Objects Using Freeform Thick Layers of Plastic Foam
Current Rapid Prototyping systems are primarily aimed at small-sized objects containing many
shape details. In this paper a Rapid Prototyping technology is presented that is aimed at largesized objects having a complex, freeform outer shape. This new technology builds the model out
ofthick layers, each having freeform outside faces. The paper will present: an overview of current
methods to produce large prototypes, the basics of the new method, the technology used to
produce the layers, the toolpath planning and finally the overall system design.Mechanical Engineerin
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A Combinatorial Parametric Engineering Model for Solid Freeform Fabrication
Fabricated parts are often represented as compact connected smooth 3-manifolds with
boundary, where the boundaries consist of compact smooth 2-manifolds. This class of mathematical
structures includes topological spaces with enclosed voids and tunnels. Useful information about these
structures are coded into level functions (Morse functions) which map points in the 3-manifold onto their
height above a fixed plane. By definition, Morse functions are smooth functions, all of whose critical
points are nondegenerate. This information is presented by the Reeb graph construction that develops a
topologically informative skeleton of the manifold whose nodes are the critical points of the Morse function
and whose edges are associated with the connected components between critical slices. This approach
accurately captures the SFF process: using a solid geometric model of the part, defining surface
boundaries; selecting a part orientation; forming planar slices, decomposing the solid into a sequence of
thin cross-sectional polyhedral layers; and then fabricating the part by producing the polyhedra by additive
manufacturing. This note will define a qualitative and combinatorial parametric engineering model of the
SFF part design process. The objects under study will be abstract simplicial complexes K with boundary
∂K. Systems of labeled 2-surfaces in K, called slices, will be associated with the cross-sectional polyhedral
layers. The labeled slices are mapped into a family of digraph automata, which, unlike cellular automata,
are defined not on regular lattices with simple connectivities (cells usually have either 4 or 8 cell
neighborhoods) but on unrestricted digraphs whose connectivities are irregular and more complicated.Mechanical Engineerin
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Thermal Modeling and Experimental Validation in the LENSâ„¢ Process
Several aspects of the thermal behavior of deposited stainless steel 410 (SS410) during the
Laser Engineered Net Shaping (LENSTM) process were investigated experimentally and
numerically. Thermal images in the molten pool and surrounding area were recorded using a
two-wavelength imaging pyrometer system, and analyzed using ThermaVizTM software to obtain
the temperature distribution. The molten pool size, temperature gradient, and cooling rate were
obtained from the recorded history of temperature profiles. The dynamic shape of the molten
pool, including the pool size in both travel direction and depth direction, was investigated and
the effect of different process parameters was illustrated. The thermal experiments were
performed in a LENSTM 850 machine with a 3kW IPG laser for different process parameters. A
three-dimensional finite element model was developed to calculate the temperature distribution
in the LENS process as a function of time and process parameters. The modeling results showed
good agreement with the experimental data.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
From 3D Models to 3D Prints: an Overview of the Processing Pipeline
Due to the wide diffusion of 3D printing technologies, geometric algorithms
for Additive Manufacturing are being invented at an impressive speed. Each
single step, in particular along the Process Planning pipeline, can now count
on dozens of methods that prepare the 3D model for fabrication, while analysing
and optimizing geometry and machine instructions for various objectives. This
report provides a classification of this huge state of the art, and elicits the
relation between each single algorithm and a list of desirable objectives
during Process Planning. The objectives themselves are listed and discussed,
along with possible needs for tradeoffs. Additive Manufacturing technologies
are broadly categorized to explicitly relate classes of devices and supported
features. Finally, this report offers an analysis of the state of the art while
discussing open and challenging problems from both an academic and an
industrial perspective.Comment: European Union (EU); Horizon 2020; H2020-FoF-2015; RIA - Research and
Innovation action; Grant agreement N. 68044
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