2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Process Development: Material Extrusion I
Program Organizers: Joseph Beaman, University of Texas at Austin
Monday 1:30 PM
August 14, 2023
Room: 412
Location: Hilton Austin
Session Chair: Anthony Rollett, Carnegie Mellon University
1:30 PM
Testing Protocol Development for Fracture Toughness of Parts Built with Big Area Additive Manufacturing: Juan Pablo Garcia Chavira1; Luis Camacho1; David Espalin2; 1University of Texas at El Paso; 2UTEP - W.M. Keck Center for 3D Innovation
Mechanical testing of additively manufactured parts has largely relied on existing standards developed for traditional manufacturing. While this approach leverages the investment made on current standards development, it inaccurately assumes that mechanical response of AM parts is identical to that of parts manufactured through traditional processes. When considering thermoplastic, material extrusion AM, differences in response can be attributed to an AM part’s inherent inhomogeneity caused by porosity, interlayer zones, and surface texture. Additionally, interlayer bonding of parts printed with large-scale AM is difficult to adequately assess as much testing is done such that stress is distributed across many layer interfaces; therefore, the lack of AM-specific standard to assess interlayer bonding is a significant research gap. To quantify interlayer bonding via fracture toughness, double cantilever beam (DCB) testing has been used for some AM materials, and DCB has been generally used for a variety of materials including metal, wood, and laminates. Mode I DCB testing was performed on thermoplastic matrix composites printed with Big Area Additive Manufacturing (BAAM). Of particular interest was the crack shape and deflection speed during testing. Results discuss the differences when using two crack types and three deflection speeds.
1:50 PM
Strengthening FFF Parts via Annealing with Structured Dual Material Filaments and Dissolvable High-temperature Shells: Ryan Dunn1; Eric Wetzel1; 1US Army Research Laboratory
Thermal annealing is an established method for strengthening polymer interfaces, including the weak interlaminar bonds produced by fused filament fabrication (FFF). However, highly effective annealing takes place at temperatures where the polymer will deform. By printing models with an added shell composed of a dissolvable high-temperature polymer, annealing can be achieved without deformation. Because the shell is dissolvable none of the model's geometry is replaced with temperature resistant polymer allowing the resulting part to fully benefit from annealing. Annealing can also take place during the dual-material print, or in a printer's heated build chamber post-print, reducing the time and equipment requirements for this process. Applications are discussed, as well as numerical improvements in mechanical properties such as fracture toughness and impact strength.
2:10 PM
Static Mixing Nozzles for Long and Short Fiber Additive Extrusion Processes: Tyler Smith1; Katie Copenhaver1; Chase Joslin1; John Lindahl1; Chris Hershey1; Meghan Lamm1; James Brackett1; Vipin Kumar1; Jim Tobin1; Brittany Rodriguez1; Ahmed Hassen1; Vlastimil Kunc1; 1Oak Ridge National Laboratory
Additive Manufacturing is conventionally used to create structures through extruding plastic or metal layer by layer. In the case of polymer processes, fibers are typically added to increase stiffness and reduce warping during building. The of the fiber exiting the nozzle can impact the overall mechanical properties of the structure. Using Long Fiber Pellets can increase the starting length of the pellets to help increase the average fiber length coming out from the extruder. However, extruded long fiber materials tend to have low fiber alignment and high porosity leading to poor mechanical properties. By using a blend of materials and a static mixing nozzle, consolidated beads can be created to produce more stable and solid structures while added a fixed amount of long fiber into the extruded bead to increase mechanical performance.
2:30 PM
Self-heating Tooling on BAAM using Co-extruded Heating Wires: Jesse Heineman1; 1Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) has developed a wire co-extrusion module that enables wires to be embedded inside the selected polymer beads during fused deposition modeling (FDM) manufacturing. The FDM machine used for this research is the Big Area Additive Manufacturing (BAAM) machine from Cincinnati Incorporated, which has a build volume of 7’ x 20’ x 6’ high. The composite tooling industry relies heavily on applied heat to improve the curing rate and final mechanical properties of composite parts. However, as the size of the tools get larger, the cost and practicality of autoclave tooling becomes prohibitively expensive. This method of manufacturing aims to reduce the cost and delivery time of large-scale self-heated tooling. This paper will include details about the custom hardware and software developed by ORNL for this process, as well as the results from initial heating trials of a demonstration tool.
2:50 PM
Real-time Image-based Quality Control for Bio-additive Manufacturing through Layer-by-layer Analysis: Casey Tran1; Camila Ceballos-Santa2; Chaitanya Mahajan1; Sri Ramesh3; Iris Rivero2; Satyajayant Misra1; 1New Mexico State University; 2Rochestor Institute of Technology; 3Rochester Institute of Technology
Achieving precise geometric quality control in bio-additive manufacturing is crucial for fabricating functional tissue constructs with high fidelity. However, this can be challenging, especially when dealing with hydrogels that are difficult to 3D scan accurately. To detect any inaccuracies in the printed construct, we developed a real-time monitoring framework for extrusion-based printing processes that generates layer-by-layer nominal images of the tool path and computes the MSE/SSIM similarity score of the actual printed construct for geometrical variations. The proposed monitoring system represents a significant step towards ensuring quality control and process efficiency in bio-additive manufacturing, with implications for tissue engineering and regenerative medicine. Future research will focus on optimizing the system design and improving the accuracy of monitoring algorithms, especially in accounting for layer thickness and hydrogel material rheology, and a feedback system to correct the next layer or cancel the print given detected anomalies.
3:10 PM Break
3:40 PM
Printing Parameter Optimization of Extruded Metal Paste by Response Surface Technique: Marshall Norris1; Ismail Fidan1; 1Tennessee Tech University
This research is focused on optimizing printing parameters using the response surface (RS) methodology. When printing parameters are not optimized, the resulting prints contain an unacceptable surface finish, porosity, or the print fails entirely as the lower portion of the print will not be able to withstand the weight of consecutive layers. Printing parameters, layer height, and percent infill were adjusted for the study while material flow rate and print head speed were held constant. RS is a statistical based eigenvalue process that uses data points on a three-dimensional curve to predict and identify local maxima or minima. For this study, RS was used to identify the inflection point where surface finish is optimized. A starting point for the parameters begins with rheological characterization of the paste and geometric modeling (or brute force approach). Once the parameters are able to produce an acceptable surface finish, the RS approach was used to refine printing parameters.
4:00 PM
Parametric Analyses of Impact of Deposition Pressure on Multi-axis Free-form Fabrication.: Aditya Thakur1; Jan Eine1; Niklas kyriazis1; 1Institute of Space System (IRAS)
Additive manufacturing is being explored as one of the promising in-space manufacturing techniques. The presence of µgravity enables fabrication of support-free spare structures with ease. Sparse structures (e.g. trusses) are attractive for space applications as they can be tailored for specific load paths. Previous studies have identified positive correlation between the deposition pressure and inter-layer adhesion in 3Dprinting. However, excessive deposition pressures negatively influence the in-orbit printing accuracy. Therefore, a parametric investigation was conducted to determine optimal deposition pressure to fabricate mechanically sound trusses in orbit. Support-free arches with varying nodal deposition pressures were 3Dprinted using multi-axis robotic arms with integrated force sensors. Mechanical testing of these arches concluded that the strength improvement plateaus. It registers no significant increase in joint strength after a certain deposition pressure, characterized by the properties of the extrude. Integration of a force-feedback facilitates printing of complex, multi-layered, support-free trusses in a free-floating space environment.
4:20 PM
Non-linear Dynamic Modelling of Cartesian-frame FFF 3-D Printer Gantry for Predictive Control: Maharshi Arindom Sharma1; Albert Patterson1; 1Texas A&M University
This paper addresses the dynamic modelling of an FFF 3-D printer gantry (2-D) to reduce manufacturing defects from extruder carriage error. Physical examples of vibration errors are presented with observations about the machine-related causes of these errors. A six-dimensional non-linear dynamic model of the printer gantry was derived using Newton-Euler method. The Lagrangian dynamic model was derived to get additional insight on energy transfer aspects and model validation. A state-space model of the full system was developed for positioning and control. A detailed case-study of an example printer was completed in Matlab-Simulink to demonstrate the system model with comparisons from the analytical model and some physical characterization on a printer. Finally, a few examples of passive control designs were illustrated for predictive control. It was concluded that dynamics-based predictive control is a promising, realistic, and practical approach to controlling the dynamic error and dimensional error commonly seen with FFF machines.