Browsing by Subject "in-situ"
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Item Additive Manufacturing of Alumina Components by Extrusion of In-Situ UV-Cured Pastes(University of Texas at Austin, 2018) Tsui, Lok-kun; Maines, Erin; Evans, Lindsey; Keicher, David; Lavin, JudithAdditive manufacturing of ceramic materials is an attractive technique for rapid prototyping of components at small scales and low cost. We have investigated the printing of alumina pastes loaded at 70-81.5 wt% solids in a UV curable resin. These can be deposited by extrusion from a syringe head on a Hyrel System 30M printer. The print head is equipped with an array of UV LEDs, which solidify the paste without the need for any applied heating. Parameters optimized include print speed, layer height, applied force, and deposition rate. Using A15 alumina and submicron A16 powder precursors, we can achieve bulk densities of 91% and 96% of theoretical density respectively. The influence of dispersants and surfactants added to the powder on the rheology of the pastes, the print process parameters, and the quality of the final components are also investigated.Item Characterization of In-Situ Conductive Paste Extrusion on PolyJet Substrates(University of Texas at Austin, 2014) Perez, K. Blake; Williams, Christopher B.The integration of Direct Write technologies into Additive Manufacturing system enables the in-situ deposition of conductive traces during part printing, and thus the creation of parts with embedded electronics. In this paper, the authors detail their research of integrating an extrusion-based direct write system into a PolyJet material jetting system to create multimaterial products with structurally integrated, functional electronics. An investigation of the dispensing (e.g. orifice diameter, dispense pressure, and toolhead speed), drying (e.g., time and temperature), and substrate parameters (e.g., VeroWhitePlus and TangoBlackPlus) on the geometry of the deposited trace is presented. Additionally, the adhesive compatibility of the conductive material on both rigid and elastomeric PolyJet substrate surfaces is investigated by measuring wet and dry contact angles.Item The Effect of Powder on Cooling Rate and Melt Pool Length Measurements Using In-Situ Thermographic Techniques(University of Texas at Austin, 2017) Heigel, J.C.; Lane, B.M.High-speed thermal cameras enable in situ measurement of the temperatures in and around melt pools generated during powder bed fusion processes. These measurements can be used to validate models, to monitor the process, and to understand the microstructure formed during the process. Unfortunately, pre-placed powder layers complicate the measurement due to spatter and irregular surfaces that impact emissivity. The objective of this work is to present high speed thermographic measurements of single and multiple scan tracks on substrates with and without pre-placed powder and to analyze and compare the impacts of powder on melt pool length and cooling rate measurements.Item Evaluation of a Feed-Forward Laser Control Approach for Improving Consistency in Selective Laser Sintering(University of Texas at Austin, 2019) Phillips, T.; Fish, S.; Beaman, J.Selective Laser Sintering (SLS) is a popular industrial additive manufacturing technique for creating functional polymer components. One of the biggest limitations today with SLS is its poor mechanical consistency when compared with traditional manufacturing techniques, inhibiting the use of SLS among structurally critical components. Evaluation of the SLS process has revealed that the quality of components is strongly affected by the thermal history during the build process and poor control over this can lead to premature part failure. This paper will discuss a novel technique of improving in-situ thermal control by implementing a feed-forward laser controller that uses dynamic surrogate modelling to predict optimal laser power to achieve desired thermal characteristics. Thermal and destructive testing results will be presented showing that the described laser power controller is capable of decreasing the standard deviations of post sintering temperature by up to 57% and ultimate flexural strength by up to 45%.Item Experimental Implementation and Investigation of Real-Time Metrology for Exposure Controlled Projection Lithography(University of Texas at Austin, 2016) Zhao, Xiayun; Wang, Jenny M.; Zhao, Changxuan; Jariwala, Amit; Rosen, David W.Exposure Controlled Projection Lithography (ECPL) is a stereolithography based process, curing photopolymer parts on a stationary substrate. To improve the process accuracy with closed-loop control, an in-situ interferometric curing monitoring and measurement (ICM&M) system was developed to infer the output of cured height. The previously reported ICM&M method incorporated a sensor model and online parameter estimation algorithms based on instantaneous frequency. In this paper, to validate the ICM&M method, an application program was created in MATLAB to integrate the ECPL and ICM&M systems and to acquire and analyze interferograms online. Given the limited computing power, the interferogram analysis is performed offline. Experiments were performed curing square samples by varying exposure time and intensity. They show that the ICM&M can provide a cost-effective metrology for cured heights with excellent accuracy and reliability, and decent capability of estimating lateral dimensions. The offline ICM&M is a convincing demonstration and benchmark for the real-time ICM&M metrology.Item IN-SITU DEFECT DETECTION FOR LASER POWDER BED FUSION WITH ACTIVE LASER THERMOGRAPHY(University of Texas at Austin, 2023) Breese, P.P.; Becker, T.; Oster, S.; Metz, C.; Altenburg, S.J.Defects are still common in metal components built with Additive Manufacturing (AM). Process monitoring methods for laser powder bed fusion (PBF-LB/M) are used in industry, but relationships between monitoring data and defect formation are not fully understood yet. Additionally, defects and deformations may develop with a time delay to the laser energy input. Thus, currently, the component quality is only determinable after the finished process. Here, active laser thermography, a nondestructive testing method, is adapted to PBF-LB/M, using the defocused process laser as heat source. The testing can be performed layer by layer throughout the manufacturing process. We study our proposed testing method along experiments carried out on a custom research PBF-LB/M machine using infrared (IR) cameras. Our work enables a shift from post-process testing of components towards in-situ testing during the AM process. The actual component quality is evaluated in the process chamber and defects can be detected between layers.Item In-Situ Layer-Wise Quality Monitoring for Laser-Based Additive Manufacturing Using Image Series Analysis(University of Texas at Austin, 2019) Esfahani, Mehrnaz Noroozi; Bian, Linkan; Tian, WenmengQuality assurance has been one of the major challenges in laser-based additive manufacturing (AM) processes. This study proposes a novel process modeling methodology for layer-wise in-situ quality monitoring based on image series analysis. An image-based autoregressive (AR) model has been proposed based on the image registration function between consecutively observed thermal images. Image registration is used to extract melt pool location and orientation change between consecutive images, which contains sensing stability information. Subsequently, a Gaussian process model is used to characterize the spatial correlation within the error matrix. Finally, the extracted features from the aforementioned processes are jointly used for layer-wise quality monitoring. A case study of a thin wall fabrication by a Directed Laser Deposition (DLD) process is used to demonstrate the effectiveness of the proposed methodology.Item In-Situ Optical Emission Spectroscopy during SLM of 304L Stainless Steel(University of Texas at Austin, 2018) Lough, Cody S.; Escano, Luis I.; Qu, Minglei; Smith, Christopher C.; Landers, Robert G.; Bristow, Douglas A.; Chen, Lianyi; Kinzel, Edward C.This paper demonstrates the potential of in-situ Optical Emission Spectroscopy (OES) to monitor the Selective Laser Melting (SLM) process. A spectrometer is split into the beam path of a home-built SLM system to collect visible light emitted from the melt pool and plume. The inline configuration allows signal collection regardless of the laser scan location. The spectral data can be used to calculate the temperature of the vapor plume and correlated with the melt-pool size. The effects of varying the atmosphere and pressure on the OES signal are also explored. These results demonstrate that OES can provide useful feedback to the SLM process for process monitoring and part validation. The challenges implementing OES in-line on a commercial SLM platform are discussed.Item Novel Machine and Measurement Concept for Micro Machining by Selective Laser Sintering(University of Texas at Austin, 2014) Erler, M.; Streek, A.; Schulze, C.; Exner, H.Laser sintering has been established in solid freeform fabrication to produce individual micro parts and small batches. However, the achievable resolution and accuracy of this technology seems to be not sufficient to meet prospective demands in micro production, i.e. micro system technology, aerospace or innovative medical applications. As a modification of the technology, laser micro sintering (LMS) was developed to overcome this limitation. In general, the results obtained in LMS demonstrated already the high potential of this additive manufacturing process in micro production. The limited dimensions of the micro parts and even the reproducibility, due to the special process requirements regarding the applied powder particles sizes in the µm-ranges, inhibits the implementation as an industrial manufacturing process. Therefore a novel concept of setups, suitable for an industrial demand of selective laser sintering with noticeable higher resolutions has to be proven. As a first, a novel machinery setup for a high resolution selective laser sintering has been studied in this work. To achieve a sufficient repeatability of the sintering process, a new method for in-situ analyzing and measuring is implemented and allows the verification the homogeneity and thickness first: of the deposited powder layers and second: of the resulting sinter structure. As an innovative feature the measurement system has to be applied as an in-situ method for direct process controlling in a future use. Accordingly, the possibility to recognize structural defects during generation of sintered bodies are presented and comparably analyzed by cross sections of the respective specimens.Item Overview of In-Situ Temperature Measurement for Metallic Additive Manufacturing: How and then What(University of Texas at Austin, 2019) Li, Dian; Liu, Ruikai; Zhao, XiayunAdditive manufacturing (AM) is important in industrial and economical domains but still lacking process accuracy. In-situ measurement and process control can offer an effective solution. In AM based on metals, the temperature field of melting pool has critical impacts on phase transformation and mechanical properties. Researchers have developed various approaches to track real-time temperature during ultrahigh temperature in AM. Nevertheless, large temperature gradient around the energy source demands a capable measurement system and method due to the limitations of the conventional infrared cameras and pyrometers. This study will explore the deficiency and improvement of the existing approaches with a focus on the cutting-edge methods of AM process temperature measurement, along with a critical thinking about the follow-up usage of the collected data. Specifically, it will report the status and trends in employing various machine learning and advanced control techniques with the in-situ sensor data for process qualification purposes.Item PEEK High Performance Fused Deposition Modeling Manufacturing with Laser In-Situ Heat Treatment(University of Texas at Austin, 2018) Luo, M.; Tian, X.; Shang, J.; Zhu, W.; Li, D.Because of the thermal resistance, high mechanical properties, biocompatibility, PEEK have increasingly extended their application in medicals, aircraft, industrial fields and so on. In FDM, a low crystallinity can be got to limit volume contraction to avoid weak interlaminar bonding, which results in the conflict between high interlaminar bonding and crystallinity. In this study, a CO2 laser device was adopted to improve both the interlaminar shear strength and the crystallinity of PEEK part synchronously in FDM. A series of test was then successively implemented. And after the observation and the analysis of the results, an obvious improvement was got that its interlaminar shear strength could improve over 45%, while its crystallinity could improve over double times for PEEK. Additionally, the process suggests a much potential in developing the gradient distribution of the crystallinity or stiffness in multi-function integration manufacturing for PEEK-like semi-crystalline materials.Item Prokaryotic Suppression Subtractive Hybridization Pcr Cdna Subtraction, A Targeted Method To Identity Diferentially Expressed Genes(2008-01) De Long, Susan K.; Kinney, Kerry A.; Kirisits, Mary Jo; De Long, Susan K.; Kinney, Kerry A.; Kirisits, Mary JoMolecular biology tools can be used to monitor and optimize biological treatment systems, but the application of nucleic acid-based tools has been hindered by the lack of available sequences for environmentally relevant biodegradation genes. The objective of our work was to extend an existing molecular method for eukaryotes to prokaryotes, allowing us to rapidly identify differentially expressed genes for subsequent sequencing. Suppression subtractive hybridization (SSH) PCR cDNA subtraction is a technique that can be used to identify genes that are expressed under specific conditions (e.g., growth on a given pollutant). While excellent methods for eukaryotic SSH PCR cDNA subtraction are available, to our knowledge, no methods previously existed for prokaryotes. This work describes our methodology for prokaryotic SSH PCR cDNA subtraction, which we validated using a model system: Pseudomonas putida mt-2 degrading toluene. cDNA from P. putida mt-2 grown on toluene (model pollutant) or acetate (control substrate) was subjected to our prokaryotic SSH PCR cDNA subtraction protocol to generate subtraction clone libraries. Over 90% of the sequenced clones contained gene fragments encoding toluene-related enzymes, and 20 distinct toluene-related genes from three key operons were sequenced. Based on these results, prokaryotic SSH PCR cDNA subtraction shows promise as a targeted method for gene identification.Item Real-Time Process Measurement and Feedback Control for Exposure Controlled Projection Lithography(University of Texas at Austin, 2017) Zhao, Xiayun; Rosen, David W.The Exposure Controlled Projection Lithography (ECPL) is an additive manufacturing process that can cure microscale photopolymer parts on a stationary substrate with patterned ultraviolet beams underneath. An in-situ interferometric curing monitoring and measuring (ICM&M) system is developed to measure the ECPL process output of cured height profile. This study develops a real-time feedback control system that utilizes the online ICM&M feedback for automatically and accurately cure a part of targeted height. The experimental results directly validate the ICM&M system’s real-time capability in capturing the process dynamics and in sensing the process output, and evidently demonstrate the feedback control system’s satisfactory performance in achieving the desired height despite the presence of ECPL process uncertainties, ICM&M noises, and computing interruptions. A comprehensive error analysis is reported, implying a promising submicron control with enhanced hardware. Generally, the study establishes a paradigm of improving additive manufacturing with a real-time closed-loop measurement and control system.