230 research outputs found
Recommended from our members
Design of Experiments Approach for Statistical Classification of Stereolithography Manufacturing Build Parameters: Effects of Build Orientation on Mechanical Properties for ASTM D-638 Type I Tensile Test Specimens of DSM Somos® 11120 Resin
A statistical design of experiments (DOE) approach was used to determine if specific build
orientation parameters impacted mechanical strength of fabricated parts. A single platform (10-
inch by 10 inch cross-section) on the 3D Systems Viper si2 machine was designed to hold 18,
ASTM D-638 Type I samples built in six different orientations (called Location) with three
samples built for each location. The DOE tested four factors: Location, Position, Axis, and
Layout. Each sample within a Location was labeled as Positions 1, 2, or 3 depending on the
distance from the center of the platform with Position 1 being the closest to the center. Samples
were fabricated parallel with the x-axis, y-axis, or 45o
to both axes (called Axis 1, 2, and 3,
respectively) and were fabricated either flat or on an edge relative to the x-y plane (called Layout
1 and 2, respectively). The results from the statistical analyses showed that Axis, Location, and
Position had no significant effect on UTS or E. However, Layout (or whether a sample was built
flat or on an edge) was shown to have a statistically significant effect on UTS and E (at a 95%
level of confidence). This result was not expected since a comparison of the average UTS for
each Layout showed only a 1.2% difference (6966 psi versus 7050 psi for samples built flat and
on an edge, respectively). Because of the small differences in means for UTS, the statistical
differences between Layout most likely would not have been identified without performing the
DOE. Furthermore, Layout was the only factor that tested different orientations of build layers
(or layer-to-layer interfaces) with respect to the sample part, and thus, it appears that the
orientation of the build layer with respect to the fabricated part has a significant effect on the
resulting mechanical properties. This study represents one of many to follow that is using
statistical analyses to identify and classify important fabrication parameters on mechanical
properties for layer manufactured parts. Although stereolithography is the focus of this work, the
techniques developed here can be applied to any layered manufacturing technology.Mechanical Engineerin
My Baseball Season that was Canceled
My experience posted describes my experience from my baseball season that was canceled because of COVID-19
Recommended from our members
Hydrogels in Stereolithography
The use of stereolithography (SL) for fabricating complex three-dimensional (3D) tissue
engineered scaffolds of aqueous poly(ethylene glycol) (PEG) hydrogel solutions is described.
The primary polymer used in the study was PEG-dimethacrylate (PEG-dma) with an average
molecular weight (MW) of 1000 in distilled water with the photoinitiator Irgacure 2959 (I-2959).
Successful layered manufacturing (LM) with embedded channel architecture required
investigation of the photopolymerization characteristics of the PEG solution (measured as
hydrogel thickness or cure depth) as a function of photoinitiator concentration and laser energy
dosage for a specific photoinitiator type and polymer concentration in solution. Hydrogel
thickness was a strong function of PI concentration and energy dosage. Curves of hydrogel
thickness were utilized to successfully plan, perform, and demonstrate layered manufacturing of
highly complex hydrogel scaffold structures, including structures with internal channels of
various orientations. Successful fabrication of 3D, multi-layered bioactive PEG scaffolds
containing cells was accomplished using a slightly modified commercial SL system (with 325
nm wavelength laser) and procedure. Human dermal fibroblast (HDF) cells were encapsulated in
PEG hydrogels using small concentrations (~ 5 mg/ml) of acryloyl-PEG-RGDS (MW 3400)
added to the photopolymerizable PEG solution to promote cell attachment. HDF cells were
combined with the PEG solution, photocrosslinked using SL, and successfully shown to survive
the fabrication process. The combined use of SL and photocrosslinkable biomaterials such as
PEG makes it possible to fabricate complex 3D scaffolds that provide site-specific and tailored
mechanical properties (i.e., multiple polymer materials) with a polymer matrix that allows
transport of nutrients and waste at the macroscale and facilitates cellular processes at the
microscale through precisely placed bioactive agents.Mechanical Engineerin
Recommended from our members
Effect of Surface Preparation Methods on Mechanical Properties of 3D Structures Fabricated by Stereolithography and 3D Printing for Electroless Ni Plating
Stereolithography (SL) and 3D Printing (3DP) are useful technologies for
three-dimensional prototyping applications, providing highly accurate and detailed part
geometries with high quality surface finishes. It is desired to improve the materials
performance of the existing photocurable SL and 3DP resins for rapid tooling and other
functional applications by applying a nickel (Ni) coating. In this work, surface
preparation methods for electroless plating of commercial photopolymer resins such as
NanoFormTM15120 (NanoForm) and Objet FullCure®840 (Veroblue) were explored in
order to enhance the structural integrity of RP components. This study examined
different surface preparation methods (chemical etching) and their effect on the surface
morphology and mechanical strength of the polymers. It was observed that surface
preparation of the resins significantly affected the mechanical properties and Ni plating of
the substrate polymers. This is a critical step, since the Ni film takes on the surface
structure of the substrate.Mechanical Engineerin
Recommended from our members
Multi-Material Stereolithography: Spatially-Controlled Bioactive Poly(Ethylene Glycol) Scaffolds for Tissue Engineering
Challenges remain in tissue engineering to control the spatial and temporal mechanical and
biochemical architectures of scaffolds. Unique capabilities of stereolithography (SL) for
fabricating multi-material spatially-controlled bioactive scaffolds were explored in this work. To
accomplish multi-material builds with implantable materials, a new mini-vat setup was designed,
constructed and placed on top of the existing build platform to allow for accurate and selfaligning X-Y registration during fabrication. Precise quantities of photocrosslinkable solution
were added to and removed from the mini-vat using micro-pipettes. The mini-vat setup allowed
the part to be easily removed and rinsed and different photocrosslinkable solutions could be
easily removed and added to the vat to aid in multi-material fabrication. Two photocrosslinkable
hydrogel biopolymers, poly(ethylene glycol dimethacrylate) (PEG-dma, molecular wt 1,000) and
poly(ethylene glycol)-diacrylate (PEG-da, molecular wt 3,400), were used as the primary
scaffold materials, and controlled concentrations of fluorescently labeled dextran or bioactive
PEG were prescribed and fabricated in different regions of the scaffold using SL. The
equilibrium swelling behavior of the two biopolymers after SL fabrication was determined and
used to design constructs with the specified dimensions at the swollen state. Two methods were
used to measure the spatial gradients enabled by this process with multi-material spatial control
successfully demonstrated down to 500-µm. First, the presence of the fluorescent component in
specific regions of the scaffold was analyzed with fluorescent microscopy. Second, human
dermal fibroblast cells were seeded on top of the fabricated scaffolds with selective bioactivity,
and phase contrast microscopy images were used to show specific localization of cells in the
regions patterned with bioactive PEG. The use of multi-material SL and the relative ease of
conjugating different bioactive ligands or growth factors to PEG allows for the fabrication of
tailored three-dimensional constructs with specified spatially-controlled bioactivity.Mechanical Engineerin
Recommended from our members
Development of an Automated Multiple Material Stereolithography Machine
An automated Multiple Material Stereolithography (MMSL) machine was developed by
integrating components of a 3D Systems 250/50 stereolithography (SL) machine in a separate
stand-alone system and adapting them to function with additional components required for
MMSL operation. We previously reported retrofitting a 250/50 SL machine with multiple vats
to accommodate multiple material fabrication for building a wide variety of multi-material
models (Wicker et al., 2004). In the MMSL retrofit, spatial constraints limited the multiple vats
located circumferentially on a vertical rotating vat carousel to cross-sectional areas of
approximately 4.5-inches by 4.5-inches. The limited build size of the retrofitted 250/50
motivated the full development of a new system with multiple material build capabilities
comparable to the build envelope of the original 250/50 machine. The new MMSL machine
required fabrication of a large system frame, incorporating various 250/50 components and
software, and adding a variety of new components and software. By using many existing
components and software, the previous engineering development of 3D Systems could be
directly applied to this new technology. Components that were transferred from an existing
250/50 to the MMSL machine included the complete optical system (including the optics plate
with laser, mirrors, beam expander, scanning mirrors, and focusing lens), the rim assembly
(including the laser beam profilers), the associated controllers (computer system, scanning mirror
controller, power supply-vat controller) and the wiring harness. In addition to the new frame, the
MMSL machine required the development of a new rotating vat carousel system, platform
assembly, multi-pump filling/leveling system, and a custom LabVIEW® control system to
provide automated control over the MMSL process. The overall operation of the MMSL system
was managed using the LabVIEW® program, which also included controlling a new vat leveling
system and new linear and rotational stages, while the 3D Systems software (Buildstation 4.0)
was retained for controlling the laser scanning process. As a demonstration of MMSL
technology, simple multi material parts were fabricated with vertically and horizontally oriented
interfaces. The fully functional MMSL system offers enormous potential for fabricating a wide
variety of multiple material functional devices.Mechanical Engineerin
Recommended from our members
Expanding Rapid Prototyping for Electronic Systems Integration of Arbitrary Form
An innovative method for rapid prototyping (RP) of electronic circuits with components
characteristic of typical electronics applications was demonstrated using an enhanced version of
a previously developed hybrid stereolithography (SL) and direct write (DW) system, where an
existing SL machine was integrated with a three-axis DW fluid dispensing system for combined
arbitrary form electronic systems manufacturing. This paper presents initial efforts at embedding
functional electronic circuits using the hybrid SL/DW system. A simple temperature-sensitive
circuit was selected, which oscillated an LED at a frequency proportional to the temperature
sensed by the thermistor. The circuit was designed to incorporate all the required electronic
components within a 2.5” x 2” x 0.5” SL part. Electrical interconnects between electronic
components were deposited on the SL part with a DW system using silver conductive ink lines.
Several inks were deposited, cured, and tested on a variety of SL resin substrates, and the E 1660
ink (Ercon Inc, Wareham, MA) was selected due to its measured lowest average resistivity on
the SL substrates. The finished circuit was compared with Printed Circuit Board (PCB)
technology for functionality. The electronic components used here include a low voltage battery,
LM 555 timer chip, resistors, a thermistor, capacitors, and Light Emitting Diodes (LEDs). This
circuit was selected because it (1) represented a simple circuit combining many typically used
electronic components and thus provided a useful demonstration for integrated electronic
systems manufacturing applicable to a wide variety of devices, and (2) provided an indication of
the parasitic resistances and capacitances introduced by the fabrication process due to its
sensitivity to manufacturing variation. The hybrid technology can help achieve significant size
reductions, enable systems integration in atypical forms, a natural resistance to reverse
engineering and possibly increase maximum operating temperatures of electronic circuits as
compared to the traditional PCB process. This research demonstrates the ability of the hybrid
SL/DW technology for fabricating combined electronic systems for unique electronics
applications in which arbitrary form is a requirement and traditional PCB technology cannot be
used.Mechanical Engineerin
Recommended from our members
Integration of Direct-Write (DW) and Ultrasonic Consolidation (UC) Technologies to Create Advanced Structures with Embedded Electrical Circuitry
In many instances conductive traces are needed in small, compact and enclosed areas.
However, with traditional manufacturing techniques, embedded electrical traces or antenna
arrays have not been a possibility. By integrating Direct Write and Ultrasonic Consolidation
technologies, electronic circuitry, antennas and other devices can be manufactured directly into a
solid metal structure and subsequently completely enclosed. This can achieve a significant
reduction in mass and volume of a complex electronic system without compromising
performance.Mechanical Engineerin
Recommended from our members
Multi-Material, Multi-Technology FDM System
A multi-material, multi-technology FDM system was developed and constructed to
enable the production of novel thermoplastic parts. Two legacy FDM systems were modified
and installed onto a single manufacturing system to allow the strategic, spatially controlled
thermoplastic deposition of multiple materials during the same build. Additionally, a build
process variation utilizing more than two extrusions tips was employed to deposit
thermoplastic materials using variable layer thicknesses and road widths. The hardware and
control software is discussed as well as the potential applications of multi-material polymeric
parts. Benefits of multiple material FDM include: 1) achieving aesthetic requirements by
using polymers of different colors, and 2) attaining desired properties (e.g., bulk
tensile/compressive/flexural strength, weight, thermal conductivity) by strategically
combining layers and regions within layers of polymers that display different properties.
Parts produced using the build process variation exhibited internal road with 1200 ± 39µm
road width and 497 ± 11µm layer height while the contours measured 269 ± 18µm road width
and 133 ± 3µm layer thickness. Additionally, for a 50.8mm by 50.8mm square section
(25.4mm tall), the build process variation required 4.0 hours to build while the original
strategy required 6.2 hours constituting a 35% reduction in build time.Mechanical Engineerin
- …