2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Process Development: Powder Bed Fusion IV
Program Organizers: Joseph Beaman, University of Texas at Austin

Tuesday 1:30 PM
August 13, 2024
Room: 616 AB
Location: Hilton Austin

Session Chair: Maryam Tilton, University of Texas at Austin

1:30 PM
Enhanced Energy Absorption for Fiber Laser Powder Bed Fusion of Thermoplastic Polyurethane (TPU): Aakil Raj Lalwani¹; Christian Budden¹; Anna Paszkowska¹; Venkata Nadimpalli¹; Anders Daugaard¹; David Pedersen¹; ¹Technical University of Denmark
    Commercial Laser Powder Bed Fusion (LPBF) systems for polymers incorporated with fiber or diode lasers produce parts which have a color of either dark grey or black. Due to the wavelength of these lasers being in between 400nm to 2500nm absorptivity for most nature/white polymer powders available on the market is very low and hence a black optical absorber is incorporated into the material to allow for processing. This work focuses on moving away from black optical absorbers and incorporating an optical absorber which provides a green hue instead. The material used was a thermoplastic polyurethane (TPU) and parts were manufactured using an Open Architecture LPBF system using a 1080nm fiber laser. The process parameters were optimized, and specimens manufactured were tested for their mechanical properties. The current optical absorber can allow for printing with more materials and producing well-formed greenish parts allowing for post-coloring, if needed.

1:50 PM
Experimental and Computational Investigation in the Resonant Vibration of 3D-printed PLA Thin Rectangular Plates: Mitchell Dutczak¹; John Shelton¹; ¹Northern Illinois University
    As designers and engineers continue to explore innovative applications for 3D printed materials, it is important to ensure that these fabricated parts possess mechanical resonant frequencies that match those fabricated from traditional processes. The objective of this investigation is to determine the relationship between 3D printing layer height and the vibrational response for fused deposition modeled (FDM), polylactic acid (PLA), 3D-printed, thin rectangular plates. Experimental and computational analyses are performed to describe the free vibration of centrally clamped plates with free edge boundary conditions on all four sides indicated (FFFF). It is concluded that by decreasing the fabrication layer height, an approximately 3% deviation in the accepted resonant frequency in the 3D printed rectangular plate is approached. It is believed that as the layer height decreases, the number of connections in the plates increases, resulting in the increase of homogenous tendencies within the plate body.

2:10 PM
Measuring Thermomechanical Response of Large-Format Printed Polymer Composite Structures via Digital Image Correlation: Tyler Corum¹; Johnna O'Connell¹; James Brackett¹; Ahmed Hassen²; Chad Duty¹; ¹University of Tennessee; ²Oak Ridge National Laboratory
    Large-format additive manufacturing (LFAM) can create large structures typically measuring several meters in scale. Fiber reinforced polymers (FRPs) are commonly used in these structures to reduce distortion experienced during printing, however, FRPs introduce highly anisotropic thermomechanical properties across a nonhomogeneous microstructure, which can result in critical distortion during tooling. Measuring the thermomechanical response of LFAM structures requires a more representative approach than traditional techniques, such as thermomechanical analysis (TMA), as they assume homogenous microstructure throughout the sample. This study compared coefficient of thermal expansion (CTE) values from LFAM structures made of 20% by weight carbon fiber reinforced acrylonitrile butadiene styrene (CF-ABS) measured using TMA and the digital image correlation oven (DIC Oven). The DIC Oven also quantified global effects of different ply orientations on thermomechanical response, which cannot be captured by TMA. This work also developed a model to predict distortion that accounts for the nonhomogeneous anisotropy of LFAM structures.

2:30 PM
Processing of Recycled PEKK-CF in Powder Bed Fusion: Karl Freihart¹; Aarif Shaik¹; Sybille Fischer¹; ¹EOS GmbH Electro Optical Systems
    Ecological and economical demands are driving developments of sustainable solutions in the AM market, especially in the field of industrial applications. One open key point is the consideration of end-of-life scenarios for AM parts. This research evaluates recyclability of parts made from high temperature PAEK materials manufactured by laser sintering. In a first step, aging mechanisms of commercial PAEK materials in Powder Bed Fusion are evaluated. Secondly, parts made from carbon-fiber reinforced PEKK are micronized into powder and employed as feedstock for powder-based additive manufacturing. Basic part properties of laser sintered specimen produced with different content of recycled material are presented. Overall, technical feasibility of recycling of PAEK parts in powder bed fusion can be shown, whilst qualification for serial applications still has to be performed.

2:50 PM
Reduction of Aging Mechanisms in a Polyamide 66 Material for Use in the Laser-based Powder Bed Fusion Process: Joseph Hofmann¹; Andreas Wegner²; Katrin Wudy¹; ¹Technical University of Munich; ²AM POLYMERS GmbH
    In laser-based powder bed fusion, aging mechanisms caused by prolonged thermal exposure affect polymers. Therefore, new material is often blended with used powder to maintain acceptable component properties and save costs. However, this method is limited for high-performance plastics with high processing temperatures (> 200 °C), like PEEK. Filled polyamide 66 compounds with lower processing temperatures, lower service temperatures but comparable mechanical properties represent a promising alternative for aerospace and automotive components. This study examines processed and artificially aged PA66 powder using a vacuum-drying oven to understand the aging mechanisms during processing. An analysis of the thermal and rheological properties of neat PA66 and filled compounds revealed significantly decreased aging effects at lower storage temperatures and oxygen levels. Furthermore, a novel filled and modified PA66 compound was investigated, balancing thermal oxidation and post-condensation effects while maintaining high mechanical properties (tensile strength > 70 MPa) when using 50 % recycled material.

3:10 PM
Integrating Automated Assembly and 3D Printing for the Manufacture of Miniature Pipe Inspection Robots: Matthew Shuttleworth¹; Mateusz Gora¹; Alexander Brown¹; Elliott Leslie¹; Damian Crosby²; Lutong Li²; Andrew Weightman²; Robert Richardson¹; Robert Kay¹; ¹University of Leeds; ²University of Manchester
    Miniature robots consist of actuators, sensors and microprocessors combined into centimetre scale housing. In swarms they can have applications from infrastructure inspection to search and rescue. Traditionally, components are hand assembled and affixed using fasteners and wiring harnesses, applying design constraints, and limiting minimum size of potential devices. Through the hybridisation of multi-material 3D printing and an array of ancillary tools including grippers, clamps and screw delivery systems, this work demonstrates the ability for one machine to print and assemble, miniature robots without operator intervention. The footprint of the platform is minimised, while maintaining a 250 x 200mm build area by using an intelligent tool changing mechanism that enables inactive tools to be stored when not in use. Complex assembly operations can be performed by integrating repositionable grippers and a bed-mounted, rotatable clamp. These were used to manufacture a miniature pipe inspection robot, with 0.2mm precision.