Rapid Manufacturing in Minutes: The Development of a Mask Projection Stereolithography Process for High-Speed Fabrication

2012 ◽  
Author(s):  
Yayue Pan ◽  
Chi Zhou ◽  
Yong Chen
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Film Coating ◽  
Thin Layers ◽  
Projection System ◽  
Order Of Magnitude ◽  
Cross Links ◽  
Projection Stereolithography ◽  
Direct Digital Manufacturing

The purpose of this paper is to present a direct digital manufacturing (DDM) process that is an order of magnitude faster than other DDM processes currently available. The developed process is based on a mask-image-projection-based Stereolithography process (MIP-SL), during which a Digital Micromirror Device (DMD) controlled projection light cures and cross-links liquid photopolymer resin. In order to achieve high-speed fabrication, we investigated the bottom-up projection system in the MIP-SL process. A set of techniques including film coating and the combination of two-way linear motions have been developed for the quick spreading of liquid resin into uniform thin layers. The process parameters and related settings to achieve the fabrication speed of a few seconds per layer are presented. Additionally, the hardware, software, and material setups developed for fabricating given three-dimensional (3D) digital models are presented. Experimental studies using the developed testbed have been performed to verify the effectiveness and efficiency of the presented fast MIP-SL process. The test results illustrate that the newly developed process can build a moderately sized part within minutes instead of hours that are typically required.

A Fast Mask Projection Stereolithography Process for Fabricating Digital Models in Minutes

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Yayue Pan ◽  
Chi Zhou ◽  
Yong Chen
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Thin Layers ◽  
Digital Models ◽  
Projection System ◽  
Order Of Magnitude ◽  
Projection Stereolithography ◽  
Direct Digital Manufacturing ◽  
3D Digital Models

The purpose of this paper is to present a direct digital manufacturing (DDM) process that is an order of magnitude faster than other DDM processes that are currently available. The developed process is based on a mask-image-projection-based stereolithography (MIP-SL) process, in which a digital micromirror device (DMD) controls projection light to selectively cure liquid photopolymer resin. In order to achieve high-speed fabrication, we investigate the bottom-up projection system in the MIP-SL process. A two-way linear motion approach has been developed for the quick spreading of liquid resin into uniform thin layers. The system design and related settings for achieving a fabrication speed of a few seconds per layer are presented. Additionally, the hardware, software, and material setups for fabricating three-dimensional (3D) digital models are presented. Experimental studies using the developed testbed have been performed to verify the effectiveness and efficiency of the presented fast MIP-SL process. The test results illustrate that the newly developed process can build a moderately sized part within minutes instead of hours that are typically required.

scholarly journals Investigation of Flow Behavior around Corotating Blades in a Double-Spindle Lawn Mower Deck

2005 ◽  
Vol 2005 (1) ◽  
pp. 77-89 ◽  
Author(s):  
W. Chon ◽  
R. S. Amano
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Video Camera ◽  
Sound Level ◽  
Lawn Mower ◽  
Level Meter

When the airflow patterns inside a lawn mower deck are understood, the deck can be redesigned to be efficient and have an increased cutting ability. To learn more, a combination of computational and experimental studies was performed to investigate the effects of blade and housing designs on a flow pattern inside a1.1mwide corotating double-spindle lawn mower deck with side discharge. For the experimental portion of the study, air velocities inside the deck were measured using a laser Doppler velocimetry (LDV) system. A high-speed video camera was used to observe the flow pattern. Furthermore, noise levels were measured using a sound level meter. For the computational fluid dynamics (CFD) work, several arbitrary radial sections of a two-dimensional blade were selected to study flow computations. A three-dimensional, full deck model was also developed for realistic flow analysis. The computational results were then compared with the experimental results.

Numerical and Experimental Investigation of Secondary Flow in a High Speed Compressor Stator

1995 ◽  
Author(s):  
Y. Ohkita ◽  
H. Kodama ◽  
O. Nozaki ◽  
K. Kikuchi ◽  
A. Tamura
Keyword(s):  
Numerical Simulation ◽  
Experimental Investigation ◽  
Shear Flow ◽  
Secondary Flow ◽  
Total Pressure ◽  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Performance Recovery

A series of numerical and experimental studies have been conducted to understand the mechanism of loss generation in a high speed compressor stator with inlet radial shear flow over the span. In this study, numerical simulation is extensively used to investigate the complex three-dimensional flow in the cascades and to interpret the phenomena appeared in the high speed compressor tests. It has been shown that the inlet radial shear flow generated by upstream rotor had a significant influence on the stator secondary flow, and consequently on the total pressure loss. Redesign of the stator aiming at the reduction of loss by controlling secondary flow has been carried out and the resultant performance recovery was successfully demonstrated both numerically and experimentally.

Modelling mechanically stable muscle architectures

1992 ◽  
Vol 336 (1277) ◽  
pp. 275-292 ◽  
Keyword(s):  
Pressure Distribution ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Muscle Fibres ◽  
Pressure Measurements ◽  
Muscle Belly ◽  
Longitudinal Plane ◽  
Order Of Magnitude ◽  
Volume Problem

This paper presents a planar architectural model for an activated skeletal muscle, with mechanical equilibrium throughout the muscle belly. The model can predict the shape of the muscle fibres and tendinous sheets as well as the internal pressure distribution in the central longitudinal plane (perpendicular to the tendinous sheets) of uni- and bipennate muscle bellies. Mechanically stable solutions for muscle architectures were calculated by equating the pressure developed by curved muscle fibres with the pressure under a curved tendinous sheet. The pressure distribution under a tendinous sheet is determined by its tension, its curvature and the tensile stress of the attached muscle fibres. Dissections showed a good resemblance of the architecture of embalmed muscles with those from our simulations. Calculated maximum pressures are in the same order of magnitude as pressure measurements from the literature. Our model predicts that intramuscular blood flow can be blocked during sustained contraction, as several experimental studies have indeed demonstrated. The volume fractions of muscle fibres and interfibre space in the muscle belly were also calculated. The planar models predict a too low volume fraction for the muscle fibres (about 45% for the bipennate models with a straight central aponeurosis, and about 60% for the simulated unipennate muscle). It is discussed how, in a real muscle, this volume problem can be solved by a special three-dimensional arrangement of muscle fibres in combination with varying widths of the tendinous sheets.

Numerical and Experimental Investigation of Secondary Flow in a High-Speed Compressor Stator

1997 ◽  
Vol 119 (2) ◽  
pp. 169-175
Author(s):  
Y. Ohkita ◽  
H. Kodama ◽  
O. Nozaki ◽  
K. Kikuchi ◽  
A. Tamura
Keyword(s):  
Numerical Simulation ◽  
Experimental Investigation ◽  
Shear Flow ◽  
Secondary Flow ◽  
Total Pressure ◽  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Performance Recovery

A series of numerical and experimental studies have been conducted to understand the mechanism of loss generation in a high-speed compressor stator with inlet radial shear flow over the span. In this study, numerical simulation is extensively used to investigate the complex three-dimensional flow in the cascades and to interpret the phenomena that appeared in the high-speed compressor tests. It has been shown that the inlet radial shear flow generated by the upstream rotor had a significant influence on the stator secondary flow, and consequently on the total pressure loss. Redesign of the stator aiming at the reduction of loss by controlling secondary flow has been carried out and the resultant performance recovery was successfully demonstrated both numerically and experimentally.

High-Speed, High-Resolution 3D Imaging Using Projector Defocusing

2011 ◽  
pp. 121-140
Author(s):  
Song Zhang ◽  
Yuanzheng Gong
Keyword(s):  
High Speed ◽  
3D Imaging ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Projection System ◽  
Digital Fringe Projection ◽  
System Nonlinearity ◽  
Projection Techniques ◽  
Fringe Patterns ◽  
3D Scene

With the advance of software and hardware, three-dimensional (3D) scene digitization becomes increasingly important. Over the years, numerous 3D imaging techniques have been developed. Among these techniques, the methods based on analyzing sinusoidal structured (fringe) patterns stand out due to their achievable speed and resolution. With the development of digital video display technologies, digital fringe projection techniques emerge as a mainstream for 3D imaging. However, developing such a system is not easy especially when an off-the-shelf projector is used. The major challenging problems are: (1) the projection system nonlinearity; (2) the precise synchronization requirement; and (3) the projection system speed limit. This chapter will present an alternative route for 3D imaging while reducing these problems. The fundamentals of the proposed technique will be introduced, the analytical and experimental results will be shown, and its advantages and limitations will be addressed.

Computational Modeling of a Solar Thermoelectric Generator

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Chukwunyere Ofoegbu ◽  
Sandip Mazumder
Keyword(s):  
Solar Energy ◽  
Computational Model ◽  
Peak Power ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Atmospheric Conditions ◽  
Absorber Plate ◽  
Thermoelectric Effects ◽  
Order Of Magnitude ◽  
Solar Thermoelectric Generator

Solar thermoelectric generators (STEGs) convert solar energy to electricity. The solar energy is first used to heat an absorber plate that serves as the high temperature reservoir. Power is generated by connecting the hot reservoir and cold (ambient) reservoirs with a pair of p- and n-doped thermoelectric legs. Experimental studies have shown that the efficiency of a STEG can reach values of about 5% if the entire setup is placed in near-vacuum conditions. However, under atmospheric conditions, the efficiency decreases by more than an order of magnitude, presumably due to heat loss from the absorber plate by natural convection. A coupled fluid–thermal–electric three-dimensional computational model of a STEG is developed with the objective of understanding the various loss mechanisms that contribute to its poor efficiency. The governing equations of mass, momentum, energy, and electric current, with the inclusion of thermoelectric effects, are solved on a mesh with 60,900 cells, and the power generated by the device is predicted. The computational model predicts a temperature difference (ΔT) of 16.5 K, as opposed to the experimentally measured value of 15 K. This corresponds to a peak power of 0.031 W as opposed to the experimentally measured peak power of 0.021 W. When only radiative losses are considered (i.e., perfect vacuum), the ΔT increases drastically to 131.1 K, resulting in peak power of 1.43 W. The predicted peak efficiency of the device was found to be 0.088% as opposed to the measured value of 0.058%.

Experimental studies of stability and transition in high-speed wakes

1999 ◽  
Vol 392 ◽  
pp. 1-26 ◽  
Author(s):  
V. I. LYSENKO
Keyword(s):  
Mach Number ◽  
Flat Plate ◽  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Wave Structure ◽  
Plate Length ◽  
Stage Of Development ◽  
Laminar Wake ◽  
Tollmien Schlichting

The investigation undertaken deals with the development of disturbances in a supersonic wake (free viscous layer and regular wake) behind a flat plate both in its linear and nonlinear stages. The influence of a number of factors (Mach and Reynolds numbers, temperature factor, thickness of the plate, length of its stern) on the wake stability and transition was studied. The development of the artificial disturbances in a wake at Mach number M∞ = 2 was investigated also.It was found that compressibility of the flow (increasing Mach number) stabilizes the wake disturbances – their amplification rates decrease, and the transition point moves away from the model plate. Cooling of the model surface at M∞ ≈ 7 has a destabilizing influence on the development of disturbances in the wake. With increase of unit Reynolds number the beginning of transition in the wake moves forward to a rear critical point. It was confirmed that a distinctive maximum in the spectral distribution of fluctuations appears, corresponding to Strouhal number (based on frequency of this maximum) of 0.3. With the growth of the model thickness the disturbance amplification rates in the wake increase, which results in earlier transition of a laminar wake into turbulent one. With the growth of length of the plate stern, the position of the wake transition moves back accordingly, while the wake stability increases a little (though very unsignificantly). In the nonlinear stage of development of disturbances, the occurrence of a triad of waves, satisfying the resonant correlation of frequencies, and the growth of harmonics are observed. A monochromatic packet of waves of Tollmien–Schlichting type, rather narrow (in the transversal coordinate) in the boundary layers on a flat plate with an opposite wedge at the stern, was found to extend in the wake. The wake disturbances have a complex wave structure. At the Mach number of free flow 2.0, the three-dimensional disturbances are the most unstable in the wake.

Three-dimensional blood vessel reconstruction using a high-speed X-ray rotational projection system

1994 ◽  
Vol 25 (8) ◽  
pp. 83-94 ◽  
Author(s):  
Yoshiki Kawata ◽  
Noburu Niki ◽  
Hitoshi Satoh ◽  
Tatsuo Kumazaki
Keyword(s):  
Blood Vessel ◽  
High Speed ◽  
Three Dimensional ◽  
Projection System ◽  
X Ray ◽  
Vessel Reconstruction

scholarly journals Numerically Investigating the Effects of Cross-Links in Scaled Microchannel Heat Sinks

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Minh Dang ◽  
Ibrahim Hassan ◽  
Sung In Kim
Keyword(s):  
Pressure Drop ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Heat Sinks ◽  
Straight Channel ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
Cross Links ◽  
Channel Configuration

Thermal management as a method of heightening performance in miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and the industry. One of the current challenges is to design heat sinks with uniform flow distribution. A number of experimental studies have been conducted to seek appropriate designs for microchannel heat sinks. However, pursuing this goal experimentally can be an expensive endeavor. The present work investigates the effect of cross-links on adiabatic two-phase flow in an array of parallel channels. It is carried out using the three-dimensional mixture model from the computational fluid dynamics software, FLUENT 6.3. A straight channel and two cross-linked channel models were simulated. The cross-links were located at 1/3 and 2/3 of the channel length, and their widths were one and two times larger than the channel width. All test models had 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The results showed that the trend of flow distribution agrees with experimental results. A new design, with cross-links incorporated, was proposed and the results showed a significant improvement of up to 55% on flow distribution compared with the standard straight channel configuration without a penalty in the pressure drop. Further discussion about the effect of cross-links on flow distribution, flow structure, and pressure drop was also documented.

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