2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Applications: Finishing Techniques and Partameters
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 8:00 AM
August 16, 2023
Room: 417 AB
Location: Hilton Austin
8:00 AM
Effect of Printing Parameters on the Internal Geometry of Products Manufactured by Fused Filament Fabrication (FFF): Benjamin Moreno Nunez1; Cecilia Trevino-Quintanilla2; Juan Espinoza-Garcia1; Enrique Cuan-Urquizo2; Esmeralda Uribe-Lam1; 1School of Engineering and Sciences, Tecnologico de Monterrey, QRO; 2Institute of Advanced Materials for Sustainable Manufacturing, Tecnologico de Monterrey, QRO
The internal geometry of a 3D printed product determines its mechanical properties. In Fused Filament Fabrication (FFF) the filaments that build up the internal geometry suffer from variation that have not been sufficient studied. This research focused on identifying the parameters that most affect the filaments and finding the optimum values to reduce their variations. To detect the printing parameter effects on FFF products it was used a fractional factorial design and the results were analyzed using statistics with a specialized statistical software (MINITAB), been the layer height the parameter that most affect the extruded filament width. Additionally, a response optimization was done to obtain six regression models that can predict the width of extruded filaments based on the printer and material used, the printing parameters and interactions that most affect the FFF product.
8:20 AM
Assessing the Impact of Melt Pool Variability on Fatigue Life in Laser Powder Bed Fusion: Justin Miner1; Tharun Reddy1; Austin Ngo2; Christian Gobert1; Jack Beuth1; Anthony Rollett1; John Lewandowski2; Sneha Narra1; 1Carnegie Mellon University; 2Case Western Reserve University
Stress intensities created by sharp, lack-of-fusion (LOF) defects, hinder fatigue life of laser powder bed fusion components. LOF defects result from insufficient melt pool overlap which depends on process parameters, layer thickness and hatch spacing. The delineation between parameters producing parts with and without LOF defects is the LOF boundary. However, recent studies hypothesize that infrequent LOF defects can occur outside of the LOF region through melt pool instabilities. To evaluate this problem, this work utilizes spectral analysis of single and multi-tracks and computed tomography of the bulk samples to evaluate the geometric variability of melt tracks produced within the process window as determined by melt pool geometry-based LOF modeling. The results suggest that melt pool variation generates LOF defects within the process window near the LOF boundary. Because of the impact of LOF pores on fatigue life, a conservative process window accounting for melt pool geometric variation is needed.
8:40 AM
Comparison of Surface Texture from Various Surface Morphology Techniques for Evaluating As-built Ti6Al4V Laser Powder Bed Fusion: Alex De La Cruz1; Luke Weston2; Thao Gibson3; Fank Medina1; Edel Arrieta1; Mark Benedict2; 1University of Texas El Paso; 2Air Force Research Laboratory; 3University of Dayton Research Institute
Without post-processing, AM components contain a variety of flaws, such as surface roughness and porosity. Surface roughness is a flaw present for every as-built AM surface that serves as an array of sites for material failure to initiate. Common surface roughness measurements involve the use of optical and contact stylus profilometry. However, x-ray Computed Tomography (xCT) is already the most widely used method of analyzing AM parts for porosity, inclusions, and a variety of other flaws.In this study, we compared three surface characterization technologies, xCT, optical profilometry, and contact stylus profilometry. The comparison of these technologies is being done on as-built Laser Powder Bed Fusion (L-BPF) Ti6AI4V four-point bending fatigue samples. Preliminary results show Sa, Sz, Sv, and Sku values are comparable between the three methods.
9:00 AM
Fatigue Endurance Investigation of Post-processed Surfaces of L-PBF Ti-6Al-4V under Flexural Stress: Cristian Banuelos1; Brandon Ramirez1; Alex De la Cruz1; Shadman Nabil1; Edel Arrieta1; Francisco Medina1; Ryan Wicker1; 1W.M. Keck Center for 3D Innovation
Numerous research works can be found focusing on fatigue properties of AM components, however most of this literature is focused on uniaxial testing. Because the very few actual components under uniaxial loading conditions found in any application, it is also important to investigate fatigue performance under loads that produce combined stresses, such as bending. This project investigates the fatigue endurance of LPBF Ti-6Al-4V specimens subjected to five different surface finishing prost-processes (milled, ground, polished and abrasive media). The test consisted of a force-controlled cyclic load applied on the specimen in 4-point bending setup until fracture. The study incorporated mechanical and optical techniques to measure and quantify the characteristic surface roughness of the post-processes. Additionally, failure mechanisms are discussed on fractographs. The data analyses suggested that internal defects commonly present in additively manufactured parts had a more significant impact on the fatigue life than surface roughness of post-processed parts.
9:20 AM Cancelled
Investigating the Effects of Chemical Smoothing on Mechanical Properties and Surface Roughness of Additive Manufactured Polymer Parts: Paul Oehlmann1; 1BMW Group
The surface of laser-based powder bed fusion of polymer parts (PBF-LB/P) is known for its rough texture and external appearance, whereby the surface roughness has a significant influence on the mechanical properties. Chemical smoothing with solvents is a well-known method for influencing the surface texture of PBF-LB/P components. Due to the further development and industrialization of the process, the post-processing method is becoming increasingly attractive for the use in the automotive industry. Chemical smoothing reduces the surface roughness and seals the surface, which leads to a change in the functional properties. Due to the significant increase in elongation at break at a near constant tensile strength after smoothing, this post-processing method has the potential to expand the range of applications for PBF-LB/P parts in the automotive industry. This paper is investigating the influence of the chemical smoothing process on the mechanical properties and surface roughness of polyamide 12 (PA12) parts.
9:40 AM Break
10:10 AM
Improving Fatigue Performance of PBF Metals using Self-terminating Etching Processes: Subbarao Raikar1; Steven DiGregorio1; Owen Hildreth1; 1Colorado School of Mines
The poor surface finish of Ti-6Al-4V (Ti64) and GRCop42 parts fabricated from Powder Bed Fusion has detrimental effects on their fatigue performance. With the help of post-processing techniques, the surface finish needs to be improved before the parts are operation ready for better fatigue performance. Self-terminating etching process (STEP) is one such post-processing technique that decreases the surface roughness by as much as 8× and increases the fatigue life by 340% compared to as-printed specimens for Ti64. In this work, we study the fatigue performances of Ti64 using sulfur-based STEP and GRCop42 using iodine-based STEP for surface finishing. The PBF specimens are studied in as-printed, stress-relieved, and post-STEP conditions by characterizing the surface roughness and microstructure.
10:30 AM
Investigating the Effects of Thermal Post-processing Parameters on Interfacial Delamination of Bimetallic 3D Printed Parts: Erik Inman1; Chaitanya Mahajan2; Srikanthan Ramesh1; 1Oklahoma State School of Industrial Engineering and Management; 2Kettering University
The rise of heated metal filament extrusion 3D printing has simplified on demand production of unique and supply chain restricted parts. This process involves layer-by-layer material deposition to produce a 3D part, which is then thermally debound, leaving a porous metal part. A secondary thermal sintering heat cycle is then used to create a solid, finished product. While this process is readily deployable, the concept of bimetallic printing presents an opportunity for innovation. Bimetallic Copper (Cu) and Stainless Steel (SS 316L) parts can be produced using a dual extrusion system. One of the challenges in printing bimetallic parts that this study seeks to address is interfacial delamination during thermal sintering. The study intends to develop predictable and functional sintering parameters of Cu/SS 316L bimetallic 3D printed parts. Material coalescence and the delamination interface will be characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and microcomputed tomography (Micro CT) equipment.
10:50 AM
Mechanical Surface Treatment of Polymer Parts Produced by FFF: Stefan Dietrich1; Benjamin Karcher1; Uwe Popp2; Julian Scholz2; 1KIT; 2Apium Additive Technologies GmbH
The surface structure in the form of waviness and roughness as well as near surface density of FFF parts represents a major issue with respect to mechanical performance especially under fatigue loading. Mechanical surface treatments like shot peening or rolling are commonly used techniques, especially for metal components, to reduce surface roughness, increase surface densification and create beneficial residual stress states in the surface layer. In this study, a rolling process has been applied intermittently with the layer-wise FFF process and the effect on the surface state has been investigated using laser scanning and optical microscopy as well as micro-computed tomography. A process window with different rolling tools and rolling paths has been identified and analysed. The results show clearly advantageous properties regarding an improved surface roughness, with a higher densification gradient in the first perimeter tracks of the FFF extrusion strategy as well as sharper corners being realized.
11:10 AM
Optimizing the Surface Texture and Chemistry of Laser Powder Bed Fusion (LPBF) Haynes
282 for Increased Solar Absorptance: Junwon Seo1; Andrea Ambrosini2; Erfan Rasouli3; Ansel Blumenthal2; Vinod Narayanan3; Anthony Rollett1; 1Carnegie Mellon University; 2Sandia National Laboratories; 3University of California, Davis
The topology and chemistry of surfaces play a crucial role in dictating the overall properties of the material, especially for samples with high surface-to-volume ratios. The ability to control the surface characteristics becomes useful for additive manufacturing since the process can be used to fabricate complex geometries with a high surface area. In this research, we investigate ways to induce various textures and chemistry on the surface of Haynes 282 fabricated by LPBF. Samples are fabricated with various combinations of infill and contour parameters as well as different CAD geometries and are gone through post-processing steps. Topological features are extracted by applying computer vision techniques to optical profilometer measurements and computed tomography data, whereas diffraction experiments are utilized to obtain the chemical information of various surfaces. We show that our methods are effective in modifying surface characteristics by measuring the optical absorptance of the samples.
11:30 AM
Complex Laser Beam Shaping for Improved Process Control in Metal Additive Manufacturing: Thej Tumkur1; John Roehling1; Gabe Guss1; Kaila Bertsch1; Manyalibo Matthews1; 1Lawrence Livermore National Lab
Process instabilities in laser powder bed fusion additive manufacturing (AM), arise from insufficient optothermal control induced by Gaussian beams at the melt pool scale. We incorporate laser beams shaped in amplitude, phase and polarization, to deliver controlled and modulated optothermal profiles on the powder bed. Unique optical properties of such beams (such as non-diffractive propagation and phase singularities) result in an improved combination of reduced spatter, keyholing and porosity, and results in improved tensile properties across a broad scan parameter range, compared to conventional beams. We employ Multiphysics simulations and highspeed imaging for feedback and validation for printing SS 316 and Inconel 625. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-846873