2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Process Development: Material Extrusion II
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 8:15 AM
August 15, 2023
Room: 412
Location: Hilton Austin
Session Chair: David Espalin, University of Texas El Paso
8:15 AM
Mechanically Bonding and Thermally Releasing Print Surface for Big Area Additive Manufacturing: Eric Weflen1; Frank Peters1; Matthew Frank1; 1Iowa State University
Part retention and removal are challenges for Big Area Additive Manufacturing (BAAM) systems, increasing production costs and impacting part quality. A part should remain locked to the print surface during processing and then be released for removal when processing is completed. However, a method for releasing large, multi-meter parts from the print surface on BAAM systems is nonexistent. This work presents a print surface with a mechanically bonding interfacial structure that locks the part to the print surface during processing and then thermally releases the part for removal. Design and process parameters were evaluated, and a model was developed as a design guide for industry implementation. A demonstration casting pattern was produced in a hybrid manufacturing machining center by iterating between polymer pellet-fed material extrusion and surface machining. The viable applications of BAAM can be expanded by improving the process and reducing costs.
8:35 AM
Inexpensive Mechanistic-Knowledge-Agnostic Machine Learning in Additive Manufacturing: Jeremy Cleeman1; Rajiv Malhotra1; 1Rutgers University
Machine Learning (ML) enables deployable modeling of parametric effects in additive manufacturing. Multi-Fidelity Learning (MFL) reduces the cost of training such a ML model by initially training it on a large amount of low-fidelity (LF) modeling data and then fine-tuning it based on a small high-fidelity (HF) experimental dataset. But current approaches for generating the LF data incur high model development cost (≈ decades) due to the need for deep mechanistic understanding of the process. We address this issue by pushing the boundary of the functional similarity necessary between the LF and HF data. This capability is demonstrated for two problems in Fused Filament Fabrication, i.e., predicting the printed road’s size and modeling the compression induced by an emerging in-situ rolling technique. We envision that our approach will enable accelerated and inexpensive understanding and adoption of new aspects or performance metrics in additive manufacturing despite limited mechanistic knowledge.
8:55 AM
In-situ Process Monitoring System for Large Format Thermoplastic Additive Manufacturing: James Haley1; Adam Stevens1; Phillip Chesser1; James Tobin1; Celeste Atkins1; Alex Roschli1; Brian Post1; 1Oak Ridge National Laboratory
An in-situ process monitoring system was developed to track geometric and thermal data during large-format thermoplastic additive manufacturing (LFAM). The monitoring system is designed to repeatably mount near the nozzle and consists of dual stereoscopic depth cameras and eight thermal cameras. The data streams are gathered and combined utilizing a Robot Operating System (ROS) framework to synthesize top-down bead width and temperature information unobstructed by the nozzle and used for print validation. We present the hardware and software design for this system, as well as performance validation.
9:15 AM
Distributed Optical Fiber Testing for Additive Manufacturing: Brian Hlifka1; Edward Kinzel1; 1University of Notre Dame
This paper explores the use of optical fiber for in-situ inspection of additive manufacturing. Single-mode SMF-28 optical fiber can be placed on the build plate to monitor the printing process or embedded in the part itself. Distributed measurements using optical backscattering reflectometry (OBR) resolve the strain along the optical fiber as well as the temperature. OBR-enabled sensing is demonstrated for the fused filament fabrication (FFF) process. The small diameter (0.25 mm) of SMF-28 lends itself to embedding in FFF prints this enables laying the fiber into the part which provides continued sensing for the parts in use. Knowledge of the process and the fiber arrangement allows heating from the deposition head to be distinguished from stress-driven strain. Calibration of the fiber arrangement is discussed as well as a comparison with process modeling.
9:35 AM Cancelled
An Extrusion-based 3D Printing Method for Direct Deposition of Photopolymers: Rencheng Wu1; Chao Sui1; Zachary Hyden2; Wan Shou1; Zhenghui Sha1; Wenchao Zhou1; 1University of Arkansas; 2AMBOTS
Photopolymer 3D printing methods, such as stereolithography (SLA), digital light processing (DLP), and inkjet 3D printing, suffer from various limitations, such as the need of a resin tank and postprocessing, or high equipment cost. This paper introduces a novel extrusion-based method for direct deposition photopolymer printing (DDPP) that resembles fused deposition modeling (FDM), one of the most widely used 3D printing methods. The proposed DDPP method uses a gear pump to continuously extrude photopolymer resin and instantly cure the photopolymer while printing. Specifically, we have addressed the challenges associated with the system reliability issues, such as dripping, spreading, and shrinkage, via a systematic design of curing mechanism, synchronizing control, and slicing under various resin material scenarios. The performance of the developed DDPP system is experimentally evaluated, which shows promise as an easy and low-cost alternative for printing photopolymers.
9:55 AM Break
10:25 AM
Beyond Throughput-resolution-flexibility Tradeoffs with Mutliplexed Fused Fabrication: Jeremy Cleeman1; Rajiv Malhotra1; 1Rutgers University
Low build time in Material Extrusion Additive Manufacturing (MatEx) is key to economically scalable printing of both large and small parts. A common approach used to overcome this issue today is to print larger roads at the cost of reduced geometric resolution and greater waste. The alternative approach of parallelization is limited by issues with geometric complexity, high cost, and machine design. We develop a new paradigm for parallelized MatEx of thermoplastics called Multiplexed Fused Filament Fabrication (MF3). MF3 simultaneously prints the same part or multiple parts with multiple FFF extruders without controlling each extruder’s motion, based on a continuous filament retraction and advancement strategy. MF3 can print non-periodic 3D structures, larger or smaller parts, unitary or distinct parts or a mixture of both, on the same machine, at a high throughput-resolution combination, without the limits of existing parallelization techniques.
10:45 AM
Calibration Method for Combined Structured Light and Additive Manufacturing Systems: William Keller1; Jack Girard1; Song Zhang1; 1Purdue University
The combination of 3D imaging and additive manufacturing systems has given rise to novel in-situ monitoring and error correction techniques allowing for increased efficiency and reduced operational costs. A novel method of the coordinate system calibration for a fused filament fabrication printer and digital fringe projection (DFP) scanner was developed. A single layer rhombus outline is printed with known G-code coordinate corners. The shape is scanned and a series of image processing and DFP techniques yields the corner locations in scanner coordinates. The number of scanner and G-code data points are increased using linear interpolation between the corners to improve accuracy. The transformation matrix is calculated. With this, scanned data can easily be compared to the ideal print geometry leading to improved monitoring and correction. Preliminary results indicate the calibration method has acceptable accuracy. When used in underfill correction techniques this method has proved to be effective and reliable.
11:05 AM
Investigation of Instrumenting Robocasting Printer for Ceramic Slurries: Jason McCleary1; David Espalin1; 1University of Texas at El Paso
Robocasting has multiple steps from ceramic slurry preparation to sintering that can impact the end part quality. In-situ monitoring and process controls can aid in minimizing differences in the quality of printed parts. The study and impact of different parameters during the printing process and a parameter database will improve the quality between green bodies and sintered parts. This paper discusses implementation of a CMOS camera, dynamic pressure sensor, and 2D laser scanner into a custom-built robocasting printer for in process monitoring. Single line beads and single layer samples were printed and analyzed by measuring the dimensions and pressure changes during printing. Results show that the printer with sensors detected the location of defects and changes in printed samples.