145 research outputs found
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SLS Materials Development Method for Rapid Manufacturing
As soon as SFF technology development began to make Rapid Prototyping possible the
interest in Rapid Manufacturing (RM) began to grow. The advantages in terms of
functional integration, elimination of tooling and fixtures and mass customization make a
compelling case for RM, leading some in the field to call it the next industrial revolution.
Yet without the materials properties necessary to provide the function and variety
currently available from mass production methods, the application of RM will remain
limited. Developing new materials for the SLS process, one immediate step toward a
larger portfolio of RM materials, is very challenging. The formation of high quality SLS
parts relies on appropriate powder characteristics, thermal cycles and sintering behavior.
Based on a brief examination of the key factors in SLS processing and a research project
to develop a new binder material for Silicon Carbide composites, a systematic materials
development method is proposed in this paper. The method provides guidance for
introducing new SLS materials, support for educating new SLS users and researchers and
direction for several future research projects.Mechanical Engineerin
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Rapid Manufacturing of Silicon Carbide Composites
From the earliest days of SFF technology development, a viable technique for the direct
manufacture of fully-functional parts has been a major technology goal. While direct metal
methods have been demonstrated for a variety of metals including aluminum, steel and titanium,
they have not reached wide commercial application due to processing speed, final material
properties and surface finish. In this paper the development of an SLS-based rapid
manufacturing (RM) platform is reviewed. The core of this platform is a thermosetting binder
system for preform parts in contrast to the thermoplastic materials currently available for SLS.
The preforms may include metal and/or ceramic powders. A variety of fully functional parts
can be prepared from different combinations of materials and post processing steps including
binder pyrolysis, free-standing alloy infiltration, room temperature polymer infiltration and
machining. The main issues of these steps are reviewed followed by a discussion about the
support of RM. This paper is an intermediate report additional materials, applications, process
models and product design strategies will be incorporated into the project in the next year.Mechanical Engineerin
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Indirect Laser Sintering of Corrugated Flow Field Plates for Direct Methanol Fuel Cell Applications
Direct methanol fuel cells (DMFC) hold distinct advantages over traditional hydrogen-based fuel
cells. Their commercialization, however, has been bound by many factors – especially their suboptimal efficiency. This work aims at enhancing the performance of DMFC through the use of
corrugated flow field plates. Our objectives are two-fold – one, to increase the power density of
DMFC by corrugating flow field plates and two, to introduce Laser sintering (LS) as an efficient
and robust method for the manufacture of such plates. Corrugated flow field plates with 10%
more surface area as compared to a planar design were made by LS & tested in a DMFC
environment. Our results show that the particle size of the material used – Graphite – has a
significant effect upon the green strength of LS parts. We also report the performance of
corrugated flow field plates with 10% higher surface area (as compared to planar plates), channel
width and depth of 2mm and an electrode area of 5 cm2. This study is the first experimental
approach to the use of indirect LS for making such fuel cell components.Mechanical Engineerin
Environmental impacts of selective laser melting: do printer, powder, or power dominate?
This life cycle assessment measured environmental impacts of selective laser melting, to determine where most impacts arise: machine and supporting hardware; aluminum powder material used; or electricity used to print. Machine impacts and aluminum powder impacts were calculated by generating life cycle inventories of materials and processing; electricity use was measured by in-line power meter; transport and disposal were also assessed. Impacts were calculated as energy use (megajoules; MJ), ReCiPe Europe Midpoint H, and ReCiPe Europe Endpoint H/A. Previous research has shown that the efficiency of additive manufacturing depends on machine operation patterns; thus, scenarios were demarcated through notation listing different configurations of machine utilization, system idling, and postbuild part removal. Results showed that electricity use during printing was the dominant impact per part for nearly all scenarios, both in MJ and ReCiPe Endpoint H/A. However, some low-utilization scenarios caused printer embodied impacts to dominate these metrics, and some ReCiPe Midpoint H categories were always dominated by other sources. For printer operators, results indicate that maximizing capacity utilization can reduce impacts per part by a factor of 14 to 18, whereas avoiding electron discharge machining part removal can reduce impacts per part by 25% to 28%. For system designers, results indicate that reductions in energy consumption, both in the printer and auxiliary equipment, could significantly reduce the environmental burden of the process
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Instrumented Prototypes
Full scale prototyping can be expensive and time consuming. Virtual prototypes
reduce costs and time but often cannot be relied on for full scale production.
Instrumented SFF prototypes update virtual prototypes, reducing cycle times and costs
for full scale production. Both single and multi-layer access, two different methods for
embedding sensors, are investigated at the University of Texas at Austin. Sensors are
first embedded in a simulated SLS process to determine if embedding off the shelf
sensors is feasible. Foil strain gages are then embedded into cantilever beams using
multi-layer techniques. Both foil strain gages and bead type thermocouples are also
embedded using single layer techniques. The results of the single layer tests will be used
to construct a proof-of-concept prototype for single layer embedding.Mechanical Engineerin
A pragmatic continuum level model for the prediction of the onset of keyholing in laser powder bed fusion
Laser powder bed fusion (L-PBF) is a complex process involving a range of multi-scale and multi-physical phenomena. There has been much research involved in creating numerical models of this process using both high and low fidelity modelling approaches where various approximations are made. Generally, to model single lines within the process to predict melt pool geometry and mode, high fidelity computationally intensive models are used which, for industrial purposes, may not be suitable. The model proposed in this work uses a pragmatic continuum level methodology with an ablation limiting approach at the mesoscale coupled with measured thermophysical properties. This model is compared with single line experiments over a range of input parameters using a modulated yttrium fibre laser with varying power and line speeds for a fixed powder layer thickness. A good trend is found between the predicted and measured width and depth of the tracks for 316L stainless steel where the transition into keyhole mode welds was predicted within 13% of experiments. The work presented highlights that pragmatic reduced physics-based modelling can accurately capture weld geometry which could be applied to more practical based uses in the L-PBF process
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