16 research outputs found
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Effect of Polymer Coatings as Intermediate Binders on Sintering of Ceramic Parts
It has been proposed that a thin polymer layer applied to the
surfaces of finely divided ceramic powders would serve as a suitable
intermediate binder for Selective Layer Sintering of ceramic pans. In this
study, the effects of completeness and fraction of coa nd particle size
distribution on sintering rates and strengths of coated ridized glass are
examined. The effect of the coating as a binder during Selective Layer
Sintering as well as the binder's burnout capability during post processing
steps are also investigated.Mechanical Engineerin
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Post-Processing of Selective Laser Sintered Polycarbonate Parts
St\ldies were conducted·to det~rmine the effect of
press\lre onpost-prpeessingofpolycarbonate coupons. No
significant differences betweencou.pons processed at
atmospheric •cQndidons.. andcouponsprpeessedin.vacuum
were •observed. However, anisotropic shrinkage .was
observedin.thez-directionnormal to thesintering plane.
Thisphenomenawasfurtl1erinvestigated usingsYIllmetrical
polycarbonatecubespr9(iuced by Selective LaserSintering
using yariedlas~rpoweryariedpowderlayer thickness, and
varied powder bed temperaturesMechanical Engineerin
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Microencapsulation of Finely Divided Ceramic Powders
Polymer coated alumina particles have been prepared by spray
drying alumina powder with a polymer emulsion. Powders containing a
maximum of 50% wt. were obtained. The coated particles were compared
to mixtures of alumina and polymer. Oven sintering tests show the coated
material to compact more than the mixed and pure polymer materials.
Strong, well defined parts with layer thicknesses of 0.002" were produced
from both coated and mixed materials by the Selective Layer Sintering
process.Mechanical Engineerin
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Drying of Colloidal Binder Infiltrated Ceramic Green Parts Produced by Selective Laser Sintering™
Colloidal ceramic binders have been used to strengthen ceramic
green shapes produced by Selective Laser Sintering. This paper
focuses on the effectiveness of the colloid infiltration with
respect to the physical properties of the colloidal binder. Mass
gains, strength gains, and dimensional changes resulting from
infiltration were monitored. Controlled drying experiments were
conducted to predict the factors influencing drying times for
complex shapes.Mechanical Engineerin
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Laser Sintering Model for Composite Materials
A computer model for the sintering of ceramic/polymer composite
materials has been established based on empirical sintering rate data. The
model calculates sintering depths which result from variations in the
operating parameters which include laser power, beam speed, scan
spacing, scan vector length, and initial temperatures of the powder and
surroundings. Sintering depths measured in multiple layer parts made of
polymer coated ceramic powders are compared to sintering depths
calculated by the sintering model.Mechanical Engineerin
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Ceramic Structures by Selective Laser Sintering of Microencapsulated, Finely Divided Ceramic Materials
The feasibility of producing ceramic green parts by Selective Laser Sintering
from microencapsulated, finely divide ceramic powders has been reported in
an earlier paper. Post-processing of a silica/zirconium orthosilicate system
and an alumina system, both utilizing a polymer binder in the form of a
coating, are discussed in this paper. Ceramic green parts require postprocessing
to remove the intermediate polymer binder and to impart strength
properties to the ceramic bodies. In this paper, the use of ceramic cements
and high temperature firing to realize strengths will be discussed. The effects
of cement concentration and controlled drying rates on the strengths and
dimensional accuracy of the ceramic bodies are also discussed.Mechanical Engineerin
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Materials for Biomedical Applications
This paper discusses two ceramic material systems for selective laser sintering (SLS) that are
being developed for biomedical applications for use in repair of bone defects. SLS is the
preferred method of fabricating ceramic implants that exhibit well defined porous
microstructures. Implants fabricated in this. manner have proven effective in-vivo showing
excellent biocompatibility as well as considerable osseous integration and remodeling of the
imp'ant materialMechanical Engineerin
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Modeling of Polymer Degradation in SLS
A simple computer model has been developed to predict the thermal
degradation of polymer binders used in the fabrication of composite
green shapes from high temperature ceramic materials.
Decomposition rate kinetics of the polymer materials were
determined and incorporated into the model. The polymer
degradation occurring in three separate powder systems was
determined as a function of applied laser energy. Agreement
between model results and experimental data is quite good.
(Key Words: Polymer, Degradation, Selective Laser Sintering,
Composites).Mechanical Engineerin
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Silicon Carbide Preforms for Metal Infiltration by Selective Laser Sintering™ of Polymer Encapsulated Powders
A polymer encapsulated silicon carbide system has been developed for
use with Selective Laser Sintering. Extensive studies with this material
have provided information pertaining to processing and material
parameters which most affect the strengths and densities of resulting
green parts. The important parameters considered were particle size
distribution of the powders, laser scanning conditions, and laser beam
diameter. Simple and complex shapes were easily produced with this
material using optimized parameters. Green objects were infused with
metal by Lanxide using their pressureless infiltration process to produce
both metal matrix and ceramic matrix composites.
(Key Words: Silicon Carbide, Encapsulation, Polymer, Selective Laser
Sintering, Composites).Mechanical Engineerin
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Interfacing Reverse Engineering Data to Rapid Prototyping
Rapid prototyping has become an increasing part of product development process chains resulting in
reduced time to market and reduced development costs. As manufacturers strive to further reduce
development cycles to maintain market competitiveness, the use ofreverse engineering technologies have
started to play key roles in the product development cycles. Integration of these technologies into existing
development cycles provides tools to maintain design integrity during development stages as well as
between successive product lines. One aspect ofreverse engineering is the intert'acing of data obtained
from these technologies to manufacturing processes such as rapid prototyping. This paper discusses work
at Daimler-Benz to develop a set ofinterlacing tools as part of a larger reverse engineering process loop.
These tools include facilities to generate contiguous surt'ace meshes from a collection ofmeasured views
as well as automatic feature detection and hole closure.Mechanical Engineerin