Browsing by Author "Espalin, David"

Now showing 1 - 19 of 19

3D Printing of Electro Mechanical Systems
(University of Texas at Austin, 2013) Aguilera, Efrain; Ramos, Jorge; Espalin, David; Cedillos, Fernando; Muse, Dan; Wicker, Ryan; MacDonald, Eric
Recent research has focused on the fabrication freedom of 3D printing to not only create conceptual models but final end-use products as well. By democratizing the manufacturing process, products will inevitably be fabricated locally and with unit-level customization. For 3D printed end-use products to be profoundly meaningful, the fabrication technologies will be required to enhance the structures with additional features such as electromechanical content. In the last decade, several research groups have reported embedding electronic components and electrical interconnect into 3D printed structures during process interruptions. However, to date there appears to be an absence of fabricated devices with electromechanical functionality in which moving parts with electronic control have been created within a single Additive Manufacturing (AM) build sequence. Moreover, previously reported 3D printed electronics were limited by the use of conductive inks, which serve as electrical interconnect and are commonly known for inadequate conductivity. This paper describes the fabrication of a high current (>1 amp) electromechanical device through a single hybrid AM build sequence using a uPrint Plus, a relatively low cost 3D. Additionally, a novel integrated process for embedding high performance conductors directly into the thermoplastic FDM substrate is demonstrated. By avoiding low conductivity inks, high power electromechanical applications are enabled such as 3D printed robotics, UAVs and biomedical devices.
Analysis of Bonding Methods for FDM-Manufactured Parts
(University of Texas at Austin, 2010-09-23) Espalin, David; Arcaute, Karina; Anchondo, Eric; Adame, Arturo; Medina, Francisco; Winker, Rob; Hoppe, Terry; Wicker, Ryan
The fused deposition modeling (FDM) additive manufacturing (AM) technology has been valuable for producing a variety of concept models, functional prototypes, end-use parts and manufacturing tools using a range of durable thermoplastic materials. The largest individual component that can be produced in FDM depends on the dimensions of the build chamber for the specific FDM system being used, with a maximum build chamber size available of 914 x 610 x 914 mm. This limitation is not unique to FDM as all AM systems are constrained by a build chamber. However, by using thermoplastic materials, individual components can be bonded together using different methods to form a single piece. Bonding can be used to help reduce building time and support material use, and also allows for the fabrication and assembly of final products larger than the build chamber. This work investigated different methods for bonding FDM-manufactured parts, including the use of five different adhesives and solvents as well as two different welding techniques (hot air welding and ultrasonic welding). The available FDM materials investigated included acrylonitrile butadiene styrene (ABSi, ABS-M30, ABS-M30i), polycarbonate (PC, PC-ABS, PC-ISO), polyphenylsulfone (PPSF), and ULTEM 9085. Bonding strengths were characterized by comparing ultimate tensile strengths at break and analyzing the mode of failure. Overall, the bonding method of hot air welding produced the strongest bond for all the materials investigated except for ULTEM 9085 for which the strongest bond was achieved with the two-part epoxy adhesive Hysol E-20HP.
Analysis of Sealing Methods for FDM-fabricated Parts
(University of Texas at Austin, 2011-08-17) Mireles, Jorge; Adame, Arturo; Espalin, David; Medina, Francisco; Winker, Rob; Hoppe, Terry; Zinniel, Bob; Wicker, Ryan
As a result of the layer-by-layer deposition characteristics of Additive Manufacturing (AM) processes, fabricated parts exhibit limiting qualities and have yet to achieve the requirements for end-use applications. Specifically, the use of AM-fabricated parts in fluid pressure applications is limited due to part porosity as well as non-optimized building variables (e.g., build orientation and material properties). In an effort to extend the use of AM in more applications involving fluid pressure, parts manufactured with Fused Deposition Modeling (FDM) were sealed with a variety of sealants and tested under applied pressure. Eleven sealants with diverse chemical properties were applied to multiple geometries of FDM-fabricated pressure caps through brushing or vacuum infiltration. The caps were installed on pressure vessels and subsequently tested while safety precautions were taken to avoid catastrophic failure (i.e., exploding) caused by pressure differentials. Results of the testing provides a sealing method using BJB TC-1614 that enables FDM-fabricated parts to withstand pressures up to ~276 kPa (40psi) through brushing and ~138 kPa (20 psi) through vacuum infiltration. Other noteworthy sealants (Minwax Sanding Sealer, Minwax Polyurethane Oil Based, PRO Finisher Water-Base Polyurethane) that are readily available to consumers and easy to apply (i.e. no mixing ratios to follow, long working times) also had notable results by withstanding pressures up to ~207 kPa (30 psi). In addition, an analysis on dimensional changes was performed to determine the absolute difference between as-built and surface-treated parts. Parts that were infiltrated with BJB TC-1614 showed less dimensional changes (average absolute change of 0.104 mm) than parts that were brushed (average absolute change of 0.231 mm) however one-part sealants had smaller dimensional changes (maximum absolute change for one-part sealants of 0.065 mm for infiltration and 0.171 for brushing) with noteworthy results in pressure testing. Benefits of filling voids within FDM-manufactured parts enables end-use applications such as hermetic housings for biomedical devices and pipes/covers for thermodynamic systems such as heat exchangers.
Effect of Porosity on Electrical Insulation and Heat Dissipation of Fused Deposition Modeling Parts Containing Embedded Wires
(University of Texas at Austin, 2018) Billah, Kazi Md Masum; Coronel, Jose Luis Jr; Wicker, Ryan B.; Espalin, David
While the effects of porosity on the mechanical strength of fused deposition modeling (FDM) parts have been thoroughly investigated, there exists a need for evaluating electrical and thermal properties. This work describes the method of determining the effect of porosity that resembles 3D printed electronics. In addition to mechanical strength, determination of desirable limit of electrical insulation and heat dissipation will allow the additive manufacturing community to fabricate power electronics components with reduced cost and improved performance. For experimentation, three different sets of coupons were fabricated using Polycarbonate (PC) thermoplastic with embedded bare copper wire. Characterization included high electrical stresses and thermal testing to determine the effect of porosity on insulation and heat dissipation, respectively. During electrical characterization, higher wire density resulted in reduced breakdown strength. In thermal test, the comparisons between as fabricated and heat-treated specimen showed that heat dissipation increased by an average of 30 % to 40 %.
Folding Endurance Appraisal for Thermoplastic Materials Printed in Fusion Deposition Technology
(University of Texas at Austin, 2016) Balderrama-Armendariz, Cesar O.; MacDonald, Eric; Valadez, Esdras D.; Espalin, David
The anisotropic behavior of the fusion deposition modeling (FDM) machines could change the mechanical properties of the materials in the layer by layer technology. In general, the tensile, compressive and flexural strength are decreased against molded plastics. Some lasting products need the iteration of low flexural strength and high elongation to obtain an effective flexibility to bend in repetitive movements. The present work provides an analysis of the capacity of several selected thermoplastics materials such as Nylon (PA), Polyethylene Terephthalate (PETG), Polylactide (PLA), Polyurethane (TPU) and Polypropylene (PP) in order to test the maximal load capacity and the number of folding cycles sustained in perpendicular direction of movement. Results demonstrate that those of similar to injected molded products, PP and TPU materials surpass one million of cycles in the folding test. Yet, in axial load they have lower strength against the other considered materials.
Fused Deposition Modeling of Metals
(University of Texas at Austin, 2012-08-22) Mireles, Jorge; Espalin, David; Roberson, David; Zinniel, Bob; Medina, Francisco; Wicker, Ryan
Studies have been conducted to improve previous work performed in developing a Fused Deposition Modeling for metals (FDMm) system used for applications in electronics and fabrication of 3-dimensional metallic structures. A FDM 3000 system was modified to achieve controlled deposition of eutectic Bi58Sn42 and non-eutectic Sn60Bi40 materials. Toolpath command modifications were required to achieve controlled deposition of metals. Results are presented which include a redesigned metal deposition head, computer modeling of fluid flow, and finally examples of the successful deposition of metal alloys. Additionally, FDMm-fabricated metal samples were prepared and analyzed using optical and scanning electron microscopy. Controlled deposition of metals using FDMm allows for parts that can be used for jigs and fixtures, electroforming mandrels, encapsulation molds, dies, electronic joining applications, as well as printing 3-dimensional electronic circuitry.
Fused Deposition Modeling of Polymethylmethacrylate for Use in Patient-Specific Reconstructive Surgery
(University of Texas at Austin, 2009-09) Espalin, David; Arcaute, Karina; Rodriguez, David; Medina, Frank; Posner, Matthew; Wicker, Ryan
facial reconstruction and as bone cement and antibiotic-impregnated spacers in orthopaedics. The polymerization of PMMA in-situ causes tissue necrosis and other complications due to the long surgical times associated with mixing and shaping the PMMA. PMMA is a thermoplastic acrylic resin suitable for extrusion in FDM thus 3D anatomical models can be fabricated prior to surgery directly from medical imaging data. The building parameters required for successful FDM fabrication with medical-grade PMMA filament (1/16”Ø) were developed using an FDM 3000. It was found that a liquefier and envelope temperature of 235ºC and 55ºC, respectively, as well as increasing the model feed rate by 60%, were necessary to properly and consistently extrude the PMMA filament. Scaffolds with different porosities and fabrication conditions (tip wipe frequency and layer orientation) were produced, and their compressive mechanical properties were examined. Results show that both the tip wipe frequency (1 wipe every layer or 1 wipe every 10 layers) and layer orientation (transverse or axial with respect to the applied compressive load) used to fabricate the scaffolds, as well as the porosity of the scaffold had an effect on the mechanical properties. The samples fabricated with the high tip frequency had a larger compressive strength and modulus (Compressive strength: 16 ± 0.97 vs. 13 ± 0.71 MPa, Modulus: 370 ± 14 vs. 313 ± 29 MPa, for samples fabricated in the transverse orientation with 1 tip wipe per layer or 1 tip wipe per 10 layers, respectively). Also, the samples fabricated in the transverse orientation had a larger compressive strength and modulus than the ones fabricated in the axial orientation (Compressive strength: 16±0.97 vs. 13±0.83 MPa, Modulus: 370±14 vs. 281±22 MPa, for samples fabricated with 1 tip wipe per layer, in the transverse and axial orientation, respectively). Overall, the compressive strain for the samples fabricated with the four different conditions ranged from 8 – 12%. In regards to the porosity of the samples, in general, the stiffness, yield strength and yield strain decreased when the porosity increased (Compressive strength: 12±0.71 – 7±0.95 MPa, Modulus: 248±10 – 165±16 MPa, Strain: 7±1.5 – 5±1% for samples with a porosity ranging from 55 – 70%). The successful FDM fabrication of patient-specific, 3D PMMA implants with varying densities, including the model of a structure to repair a cranial defect and the model of a femur, was demonstrated. This work shows that customized structures with varying porosities to achieve tailored properties can be designed and directly fabricated using FDM and PMMA.
Hybrid Manufacturing with FDM Technology for Enabling Power Electronics Component Fabrication
(University of Texas at Austin, 2018) Coronel, Jose L. Jr; Billah, Kazi Md Masum; Acosta Carrasco, Carlos F.; Barraza, Sol A.; Wicker, Ryan B.; Espalin, David
The introduction of Kapton coated wires within a printed substrate presents the opportunity to design and fabricate power electronics components. Preventing dielectric breakdown of the printed substrate, the ultrasonic embedding approach enables complex geometrical embedding through customized software. This work presents the effective embedding of large diameter (14 AWG) kapton coated litz wire into polycarbonate (PC) substrate. Custom software allowed for generation of embedding toolpaths directly from the CAD model of the designed coupon. Results showed the most successful embedding paths were circular pre-formed cavities. Through characterization of a myriad of printed samples, an approach was developed for embedding large diameter wire. Through the use of the Foundry Multi3D System, the increased complexity of embedded electronic parts can further impulse the implementation of hybrid additive manufacturing in large scale applications.
Improving Tensile Mechanical Properties of FDM-Manufactured Specimens via Modifying Build Parameters
(University of Texas at Austin, 2013-08-16) Shojib Hossain, Mohammad; Ramos, Jorge; Espalin, David; Perez, Mireya; Wicker, Ryan
In this paper, the focus was on improving tensile mechanical properties of FDMmanufactured parts by adjusting FDM processing parameters and analyzing stress concentration features between adjacent roads of material. FDM processing parameters are specified by the user via Insight – the file preparation software for most FDM machines. Even though Insight gives the impression that adjacent roads are to be deposited and connected throughout, an optical imaging observation of the deposited material revealed that adjacent roads are not consistently connected forming voids that reduce mechanical performance. Therefore, this work reports the tensile mechanical properties of specimens built using three sets of parameters: standard/default parameters, an Insight revision method, and a visual feedback method. When compared to the default build parameters, the experimentally determined, visual feedback approach produced specimens, in some cases, exhibiting as high as 19% improvement in ultimate tensile strength.
In-situ Electrical Resistance Measurements for Soldering Studies in Hybrid AM
(University of Texas at Austin, 2023) Pustinger, Alexander P.; Corral, Joselin; Villegas, Arianna; Espalin, David
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof: The views and opinions of-authors expressed herein do not necessarily state or reflect those of the-United States Government or any agency thereof.
Installation and Thermal Feedback from a Multi-wavelength Pyrometer in Electron Beam Melting
(University of Texas at Austin, 2014) Mijares, Jonathan; Mireles, Jorge; Gaytan, Sara M.; Espalin, David; Carter, William T.; Wicker, Ryan B.
The purpose of this paper is to outline and discuss the installation and use of a multi-wavelength pyrometer for process temperature monitoring in Electron Beam Melting (EBM). A multi-wavelength pyrometer was externally mounted atop an EBM system to observe and record surface temperatures during the fabrication process. The multi-wavelength pyrometer is a non-contact device capable of measuring the temperature of an object without the need of knowing the object’s emissivity. Temperature data from the EBM system thermocouple and the multi-wavelength pyrometer were compared, and it was determined that the pyrometer measurements were reasonable. During fabrication, the multi-wavelength pyrometer allowed the characterization of the EBM process that consisted of various steps during fabrication (e.g. heating of the build platform, powder deposition, and melting). Measurement of surface temperatures during fabrication can be useful for parameter development of novel materials, prediction of resulting microstructural architectures, and ultimately as feedback used in a closed-loop control system, allowing full spatial and temporal control of melting and microstructure.
Integration of a Thermal Imaging Feedback Control System in Electron Beam Melting
(University of Texas at Austin, 2012-08-15) Rodriguez, Emmanuel; Medina, Francisco; Espalin, David; Terrazas, Cesar; Muse, Dan; Henry, Chad; MacDonald, Eric; Wicker, Ryan B.
A thermal imaging system using an infrared (IR) camera was incorporated in the fabrication process of an Arcam A2 Electron Beam Melting system to provide layer-by-layer feedback and ensure quality and defect free products. Using the IR camera, build chamber surface temperature profiles were imaged and analyzed, providing information used to modify build settings for the next build layer. Individual part temperatures were also monitored and modified to achieve a more uniform bed temperature. The thermal imaging information can also be used as a quality control tool to detect imperfections during the build. Results from the integration of the camera in the system as well as use of the thermal images in process monitoring and control is described.
Laser Powder Bed Fusion Fabricated and Characterization of Crack-Free Aluminum Alloy 6061 Using In-Process Powder Bed Induction Heating
(University of Texas at Austin, 2017) Uddin, Syed Zia; Espalin, David; Mireles, Jorge; Morton, Philip; Terrazas, Cesar; Collins, Shane; Murr, Lawrence E.; Wicker, Ryan
A parameter development study for pre-alloyed aluminum alloy 6061 (AA6061) was carried out using an open-architecture powder bed laser melting (LM) technology with capabilities of induction heating for raising the powder bed temperature. Cube specimens (10 mm on each side) were used for parameter development with variation in laser power and scanning speed, whereas layer thickness, hatch spacing and powder bed temperature were empirically determined. While higher relative densities were achieved when using induction heating (as compared to specimens fabricated without induction heating), the key difference in the experiments was the ability to fabricate specimens without cracks when using induction heating. That is, crack-free AA6061 parts were fabricated with the highest relative density measured of 98.7%. Micrographs of specimens fabricated with the induction heating demonstrated the lack of melt pool and melt track features, which are normally only achieved with post-processing heat treatments. This research was important in its approach of using high temperature heating of the powder bed prior to laser scanning to produce crack-free AA6061 parts. Further investigations are ongoing to explore and optimize this fabrication process.
Measurement Systems Comparison on Various Feature Sizes of FDM Parts
(University of Texas at Austin, 2014) Fly, David E.; Gradowski, Anita; Espalin, David; Winker, Rob; Rask, Josh
12 identical FDM parts were produced in ABSM30, each having 16 features for replicated measurements. Half the features were positive (posts), half were negative (holes). Half of all features were rectangular, half were round. Two different CMMs with 1.5mm touch probes were compared, one CMM additionally used a laser, and manual measurements were taken with gauges and calipers. All features were measured using these 4 measurement systems. All measurements were compared against the theoretical feature size to generate a percent error value. The laser values were notably different than both probe values. The manual measurements were similar to one of the two CMM probes. Positive versus negative features were significantly different in 7 of 8 cases. Feature size and measurement error were inversely proportional. The largest features had the least amount of error in all cases while the features below 6mm had the most error and high variation.
Multi-Material, Multi-Technology FDM System
(University of Texas at Austin, 2012-08-15) Espalin, David; Ramirez, Jorge; Medina, Francisco; Wicker, Ryan
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.
Ranking Model for 3D Printing
(University of Texas at Austin, 2013) Perez, Mireya A.; Ramos, Jorge; Espalin, David; Hossain, Mohammad S.; Wicker, Ryan B.
The capabilities of desktop additive manufacturing (AM) machines were evaluated based on the ability to produce a standard component. This work also developed a model/method for evaluating and ranking AM technologies based on select criteria that can facilitate purchasing decisions. A standard part was adapted and printed on each machine, and evaluated in various ways to provide machine-specific input data for the model. The research highlights the differences between AM units and suggests a method by which to evaluate the differences. With the rapid proliferation of desktop additive manufacturing units, a quantitative ranking system was developed to rate these units so that the consumer, for example, can use this model to assist with decision making during purchase. Although the focus of the work was on desktop systems, the approach can be applied across other AM technologies.
Sterilization of FDM-Manufactured Parts
(University of Texas at Austin, 2012-08-15) Perez, Mireya; Block, Michael; Espalin, David; Winker, Rob; Hoppe, Terry; Medina, Francisco; Wicker, Ryan
Fused Deposition Modeling (FDM) can be used to produce an array of medical devices; however, for such devices to be practical, they must be manufactured using sterilizable materials. Nine FDM materials were tested using four methods of sterilization: autoclave, ethylene oxide, hydrogen peroxide, and gamma radiation. Sterility testing was performed by incubating the samples in Tryptic Soy Broth for 14 days. The majority of the materials were sterilizable by all four methods while deformations were caused by autoclaving. Results from this research will allow medical staff to sterilize an FDM-manufactured device using a suitable method.
Thermal Analysis of Thermoplastic Materials Filled with Chopped Fiber for Large Area 3D Printing
(University of Texas at Austin, 2019) Billah, Kazi Md Masum; Lorenzana, Fernando A.R.; Martinez, Nikki L.; Chacon, Sarah; Wicker, Ryan B.; Espalin, David
At room temperature, material extrusion, in the context of large area fabrication, requires thermally stable materials and, as a result, fillers are included to tailor the thermal behavior. This research investigated the thermophysical properties of neat ABS and short carbon fiber (CF) reinforced ABS. Thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis were carried out to determine the thermophysical properties. The addition of CF (20 wt. %) to an ABS matrix caused the glass transition temperature to change slightly (110 °C to 105 °C). Also, the CF within the ABS matrix reduced the thermal stability by decreasing the degradation on set temperature by (323 °C to 253 °C). Thermal deformation analysis showed that large area pellet extruded AM machine produces highly anisotropic materials. Thermomechanical analysis results showed that the coefficient of thermal expansion (CTE) reduced 4 times in the perpendicular to the extruded direction. The dataset and knowledge from the thermal analysis can be useful to design optimized printing parameters for highly filled thermoplastics used in large area 3D printing machines.
Ultrasonic Embedding of Continuous Carbon Fiber into 3D printed Thermoplastic Parts
(University of Texas at Austin, 2019) Billah, Kazi Md Masum; Coronel, Jose L. Jr.; Chacon, Sarah; Wicker, Ryan B.; Espalin, David
A novel multimaterial fabrication process was developed to embed continuous bundles of carbon fiber (CF) into polycarbonate (PC) substrates using ultrasonic energy. Continuous CF possesses superior reinforcement properties compared to that of chopped or short fibers. In this research, dry continuous CF bundles were impregnated with a PC solution prior to embedding. Three printing raster orientations were studied (0°, 45°, and 90°), where three layers of CCF were embedded within each test specimen. Characterizations including tensile, flexural, and dynamic mechanical analysis were carried out to investigate reinforcement related properties. Results showed an increase in ultimate tensile strength between neat PC (37 MPa) and CF reinforced specimens (141 MPa). An automated ultrasonic embedding process allowed for the selective deposition of CF, regardless of the raster orientation. Future development of continuous CF reinforced parts could enable smart part fabrication, with applications in structural health monitoring, microwave shielding, and thermal management.