1,838 research outputs found
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Design for Additive Manufacturing: A Method to Explore Unexplored Regions of the Design Space
Additive Manufacturing (AM) technologies enable the fabrication of parts and devices that
are geometrically complex, have graded material compositions, and can be customized. To take
advantage of these capabilities, it is important to assist designers in exploring unexplored regions
of design spaces. We present a Design for Additive Manufacturing (DFAM) method that
encompasses conceptual design, process selection, later design stages, and design for
manufacturing. The method is based on the process-structure-property-behavior model that is
common in the materials design literature. A prototype CAD system is presented that embodies
the method. Manufacturable ELements (MELs) are proposed as an intermediate representation
for supporting the manufacturing related aspects of the method. Examples of cellular materials
are used to illustrate the DFAM method.Mechanical Engineerin
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On the Use of Angled, Dynamic Laser Beams to Improve Stereolithography Surface Finish
Improved surface finish of Stereolithography (SLA) parts is an important goal for furthering
the resolution of the technology. In order to improve the surface finish, a dynamic laser beam
with changing angle, beam size, beam shape, and irradiance distribution is proposed. In this
paper, an analytical irradiance model of an angled, dynamic laser beam in the SLA process is
presented. This model is used to simulate cured shapes of SLA builds. Simulated build shapes
are compared to established SLA analytical models and conclusions are drawn on the accuracy
of the developed model.Mechanical Engineerin
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Use of Parameter Estimation for Stereolithography Surface Finish Improvement
In order to improve Stereolithography (SLA) surface finish, a systematic approach based on
estimation of process parameters is needed. In this paper, the exposure on a desired SLA build
surface is formulated as a function of process parameters. The deviation of exposure on this
surface from the critical exposure, which is the threshold that determines curing in the SLA
process, is formulated using least squares minimization. By applying inverse design techniques,
SLA process parameters that satisfy this least squares minimization are determined. Application
of parameter estimation formulation to important SLA geometries is presented and the results,
including surface finish improvement, are discussed.Mechanical Engineerin
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Compensation Zone Approach to Avoid Z Errors in Mask Projection Stereolithography Builds
Print-through results in unwanted polymerization occurring beneath a part cured using
Mask Projection Stereolithography (MPSLA) and thus creates error in its Z dimension. In this
paper, the "Compensation zone approach" is proposed to avoid this error. This approach entails
modifying the geometry of the part to be cured. A volume (Compensation zone) is subtracted
from underneath the CAD model in order to compensate for the increase in the Z dimension that
would occur due to Print-through. Three process variables have been identified: Thickness of
Compensation zone, Thickness of every layer and Exposure distribution across every image used
to cure a layer. Analytical relations have been formulated between these process variables in
order to obtain dimensionally accurate parts. The Compensation zone approach is demonstrated
on an example problem.Mechanical Engineerin
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Process Planning Based on User Preferences
Typical approaches to adaptive slicing in previous literature have typically used surface finish
requirements to control the slicing process. As a result, slice schemes improve the part's surface
quality, but do not enable explicit trade-offs between finish and build time. The purpose of this
article is to present a process planning method that enables the preferences of the user for surface
finish, build time, and accuracy to control how trade-offs are made in a process plan. A multiobjective goal formulation is used by this method to evaluate how well user preferences are met by
a process plan. This method consists of three modules, for determining part orientation, for slicing
the part, and for determining other parameter values. An example with several scenarios
representing different user preferences is provided to illustrate the process planning method.Mechanical Engineerin
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Manufacturing Metallic Parts with Designed Mesostructure via Three-Dimensional Printing of Metal Oxide Powder
Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer
high strength accompanied by a relatively low mass. In this paper, the authors investigate the use of ThreeDimensional Printing (3DP) to manufacture metallic cellular materials by selectively printing binder into a
bed of metal oxide ceramic powder. The resulting green part undergoes a thermal chemical post-process in
order to convert it to metal. As a result of their investigation, the authors are able to create cellular
materials made of maraging steel that feature wall sizes as small as 400 µm and angled trusses and channels
that are 1 mm in diameter.Mechanical Engineerin
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An Ejection Mechanism Design Method for AIM Tools
One of the key advantages of AIM tooling is time savings when producing small batch
production quality parts. However, designing suitable ejection mechanisms is becoming a
bottleneck. There are two goals of this paper. First, a model is presented that effectively
characterizes the stresses on the mold core and part during injection molding. Second, a method
is described for ejection system design. Our approach consists of a combination of analytical,
computational, and physical experiments. The ejection system design method will first determine
the feasibility of ejection for a particular part geometry, then will determine the number, sizes,
and locations of ejector pins. Each phase of the method will be formulated into a Compromise
Decision Support Problem, a multi-objective optimization problem formulation. An example will
be presented to provide an idea of the robustness and the limitations of the method. Preliminary
results indicate that this methodology is sound for a simple geometry.Mechanical Engineerin
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Printing High Viscosity Fluids using Ultrasonic Droplet Generation
A new printing technology based on ultrasonic actuation (~1 MHz) is presented that has the
potential to print high viscosity fluids. In this paper, we describe the print-head’s operating
principles and construction. Acoustic focusing in the nozzles produces high pressure gradients
that help eject the fluid which, under the proper conditions, forms droplets. Two types of models
are presented to attempt to predict print-head behavior over a range of conditions. The first
model borrows from simple fully developed, laminar flows to estimate printing conditions based
on fluid properties, as well as printing pressures. The second model captures the dynamic
behavior of the print-head to estimate cavity resonances that lead to acoustic focusing and
potentially droplet generation. We report on experiments with several types of fluids that
demonstrate the technology’s potential.Mechanical Engineerin
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Design Synthesis of Adaptive Mesoscopic Cellular Structures with Unit Truss Approach and Particle Swarm Optimization Algorithm
Cellular material structures have been engineered at the mesoscopic scale for high performance
and multifunctional capabilities. However, the design of adaptive cellular structures - structures with
cellular configurations, sizes, and shapes designed for a specific geometric and loading context - has
not been sufficiently investigated. In this paper, the authors present a design synthesis method with the
use of unit truss approach and particle swarm optimization algorithm to design adaptive cellular
structures. A critical review is presented to show the pros and cons of the new design synthesis method
and an existing homogenization method. The research extends the application of additive
manufacturing in the design of new materials for high performances and benefits its long-term growth.Mechanical Engineerin
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A Process Planning Method and Data Format for Achieving Tolerances in Stereolithography
When building parts in a stereolithography apparatus (SLA), the user is faced with many decis!ons
regarding the setting of process variables. To 'achieve a set of tolera~ces as closely as pOSSIble,
relationships between part geometry, tolerances, and process v~nables ~ust be understood
quantitatively. This paper presents a method for SLA process plannIng that IS based on response
surface methodology and multi-objective optimization, where the response surfaces capture these
relationships. These response surfaces were generated by extensive design-of-experiment studies
for a variety of geometries. An annotated STL data format is also presented that enables the
inclusion of tolerance and surface information in fatetted representations. Application of the data
format and process planning method is illustrated on one part.Mechanical Engineerin
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