The current severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) pandemic has highlighted the need for personal protective equipment, specifically filtering facepiece respirators like N95 masks. While it is common knowledge that polypropylene (PP) is the industry standard material for filtration media, trial and error is often required to identify suitable commercial precursors for filtration media production. This work aims to identify differences between several commercial grades of PP and demonstrate the development of N95 filtration media with the intent that the industry partners can pivot and help address N95 shortages. Three commercial grades of high melt flow index PP were melt blown at Oak Ridge National Laboratory and broadly characterized by several methods including differential scanning calorimetry (DSC), X-ray diffraction (XRD), and neutron scattering. Despite the apparent similarities (high melt flow and isotacticity) between PP feedstocks, the application of corona charging and charge enhancing additives improve each material to widely varying degrees. From the analysis performed here, the most differentiating factor appears to be related to crystallization of the polymer and the resulting electret formation. Materials with higher crystallization onset temperatures, slower crystallization rates, and larger number of crystallites form a stronger electret and are more effective at filtration.

Biomimetic model organisms could be useful surrogates for live animals in many applications if the models have sufficient biofidelity. One such application is for use in field and laboratory tests of fish mortality associated with passage through hydropower turbines. Laboratory trials suggest that blade strikes are especially injurious and often causes mortality when fish are struck by thinner blades moving at higher velocities. Dose-response relationships have been created from these data, but the exact relationship between fish mortality and the actual forces enacted on fish during simulated blade strike testing remains unknown. Here, we describe the methods used to create a prototype biomimetic model fish composed of ballistic gelatin and covered with a surrogate skin to better approximate the biomechanical properties of a fish body. Frozen fish were scanned with high-fidelity laser scanners, and a 3D-printed, reusable mold was created from which to cast our gelatin model. Computed tomography scan data, imaged directly or taken from online data repositories, were also successfully used to create CAD models for use in additive manufacturing of molds. One 3-axis accelerometer was embedded into the gelatin to compare accelerometer data to dose-response data from previous laboratory research on live fish. The resulting model (i.e., Gelfish) had a statistically indistinguishable tissue durometer to that of real fish tissue and preliminary blade strike impact testing suggested its overall flexibility was similar to that of live fish. Gelfish was designed with biofidelity as its guiding principle and our results suggest initial experimentation was successful. Future research will include replication of initial Gelfish test results, quantitative measurement of model flexibility relative to real fish, and inclusion of surrogate skeletal structures to enhance biofidelity. Use of more sophisticated sensors would also better quantify the physical forces of blade strike impact and help determine how said forces correlate with rates of mortality observed during tests on live fish.

Oak Ridge National Laboratory’s Manufacturing Demonstration Facility is developing a system that will deposit and embed conductive and resistive elements within a printed bead of material. The system was implemented on a Big Area Additive Manufacturing (BAAM) system using a co-extruding nozzle. It has already been demonstrated that BAAM is useful for the tooling industry, but this could be a great improvement on an established application of BAAM parts. This system will provide the ability to control and monitor the surface of additively manufactured (AM) parts. It will also enable self-heating surfaces of AM parts, which is particularly useful in tooling applications. This system could even be used in the future for embedding other materials not found in pellet form in BAAM parts. This work will cover the development of the co-extrusion system and its integration with the dual-port nozzle and the BAAM system. Introduction Traditionally, mold and tool making has not been a fast process. It can take months to handcraft and shape molds into the correct form. In some conventional molds, heat conducting wire is laid in the surface of the mold and a coating is applied over it. This requires many hours of costly manual labor. Mold and tool making can also be quite wasteful because they are often made from a large piece of material that is machined or carved into the proper shape. For these reasons, the tooling industry is one of the primary target applications of large-scale additive manufacturing [1]. Big area additive manufacturing can make large parts quickly because of its high deposition rate of nearly 80lbs/hour. One of the strong suits of AM is the ability to manufacture near net shape parts, which results in much less excess material that needs to be removed and wasted. The plastics used in this process are typically easy to machine, and surface machining is all that is frequently required to make high quality molds. This helps to decrease the material losses in the tooling industry while creating an accurate part. AM has been utilized in the tooling industry, but there are some problems with its application. Molding processes frequently utilize heated molds to provide proper curing of parts, which is typically done by running wires on the surface of molds. However, the addition of conductive elements to the material used for the surface layers of additively manufactured molds would provide more consistent and efficient heat to the tool and mold areas where heat is needed. The goal of this project was to see if this process could be automated during the AM process. Once this technology is fully developed, it will provide an avenue for the deposit of other filament-like elements within a bead in any area of a BAAM printed part. Wire Co-Extrusion System The system was developed on a BAAM system and is comprised of a spool for material, a Midwest Motion Products DC motor and gearbox, a custom wire feed system, a wire feeding tube, 1549 Solid Freeform Fabrication 2019: Proceedings of the 30th Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference

ORNL worked with GE Renewable Energy to develop additive manufacturing capabilities that enable the manufacture of large cement structures on-site. This project resulted in the testing and definition of the materials and deposition functions necessary for an on-site additive manufacturing system. Test articles were manufactured using a medium-scale prototype system, and mechanical testing of the samples was performed.

Additive Manufacturing (AM) has the potential to offer many benefits over traditional manufacturing methods in the fabrication of complex parts with advantages such as low weight, complex geometry, and embedded functionality. In practice, today’s AM technologies are limited by their slow speed and highly directional properties. To address both issues, we have developed a reactive mixture deposition approach that can enable 3D printing of polymer materials at over 100X the volumetric deposition rate, enabled by a greater than 10X reduction in print head mass compared to existing large-scale thermoplastic deposition methods, with material chemistries that can be tuned for specific properties. Additionally, the reaction kinetics and transient rheological properties are specifically designed for the target deposition rates, enabling the synchronized development of increasing shear modulus and extensive cross linking across the printed layers. This ambient cure eliminates the internal stresses and bulk distortions that typically hamper AM of large parts, and yields a printed part with inter-layer covalent bonds that significantly improve the strength of the part along the build direction. The fast cure kinetics combined with the fine-tuned viscoelastic properties of the mixture enable rapid vertical builds that are not possible using other approaches. Through rheological characterization of mixtures that were capable of printing in this process as well as materials that have sufficient structural integrity for layer-on-layer printing, a “printability” rheological phase diagram has been developed, and is presented here. We envision this approach implemented as a deployable manufacturing system, where manufacturing is done on-site using the efficiently-shipped polymer, locally-sourced fillers, and a small, deployable print system. Unlike existing additive manufacturing approaches which require larger and slower print systems and complex thermal management strategies as scale increases, liquid reactive polymers decouple performance and print speed from the scale of the part, enabling a new class of cost-effective, fuel-efficient additive manufacturing.

Oak Ridge National Laboratory (ORNL) worked with concrete block manufacturer, NRG Insulated Block, to demonstrate additive manufacturing of a multi-component block mold for its line of insulated blocks. Solid models of the mold parts were constructed from existing two-dimensional drawings, and the parts were fabricated on a Stratasys Fortus 900 using ULTEM™ 9085. Block mold parts were delivered to NRG and installed on one of their fabrication lines. While form and fit were acceptable, the blocks made from the molds collapsed when extruded from the printed molds during NRG’s testing. However, the project demonstrated significant time and cost reductions and achieving proper functionality through the use of different additive manufacturing techniques.

Additive manufacturing (AM), commonly referred to as 3D printing, was originally used for rapid prototyping. However, research into new technologies has allowed AM to become applicable far beyond prototype fabrication. Oak Ridge National Laboratory (ORNL), sponsored by the Office of Naval Research, has designed and developed an anthropomorphic seven degree-of-freedom (DOF) dual arm hydraulic manipulator using metal AM technologies. The titanium manipulators are designed for subsea use. All electrical and fluidic passageways are printed into each arm. The novel, cam-based design uses low-flow, energy-efficient valves. The hydraulic power unit is built into the base of the hydraulic arms’ mount. This article will detail the novel AM design of the hydraulic manipulator system. It will cover the manipulators’ pitch and rotary link designs, custom valves, hydraulic power unit, and the motivation for a dual arm design. This article will also describe lessons learned throughout the project and draw conclusions for future applications.

Big Area Additive Manufacturing (BAAM) is an additive manufacturing (AM) technique that rapidly deposits polymer to fabricate large components. However, the increase in deposition rates leads to a decrease in resolution and a consequent decline in part surface finish. A novel technique has been developed where the nozzle diameter can be changed mid-print using a poppet nozzle selector. With this technique, a course resolution can be employed to rapidly fabricate the interior of a part, while a fine resolution can be used on the surface. This allows for improved surface quality and resolution without significantly increasing print time. This work will explain the development of the selectable nozzle and integration with the BAAM system to produce selective high-resolution surfaces on parts.

Purpose This paper aims to investigate the deposited structure and mechanical performance of printed materials obtained during initial development of the Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory. Issues unique to large-scale polymer deposition are identified and presented to reduce the learning curve for the development of similar systems. Design/methodology/approach Although the BAAM’s individual extruded bead is 10-20× larger (∼9 mm) than the typical small-scale systems, the overall characteristics of the deposited material are very similar. This study relates the structure of BAAM materials to the material composition, deposition parameters and resulting mechanical performance. Findings Materials investigated during initial trials are suitable for stiffness-limited applications. The strength of printed materials can be significantly reduced by voids and imperfect fusion between layers. Deposited material was found to have voids between adjacent beads and micro-porosity within a given bead. Failure generally occurs at interfaces between adjacent beads and successive layers, indicating imperfect contact area and polymer fusion. Practical implications The incorporation of second-phase reinforcement in printed materials can significantly improve stiffness but can result in notable anisotropy that needs to be accounted for in the design of BAAM-printed structures. Originality/value This initial evaluation of BAAM-deposited structures and mechanical performance will guide the current research effort for improving interlaminar strength and process control.

Tooling is a primary target for current additive manufacturing (AM), or 3D printing, technology because of its rapid prototyping capabilities. Molds of many sizes and shapes have been produced for a variety of industries. However, large tooling remained out of reach until the development of large-scale composite AM manufacturing processes like the Big Area Additive Manufacturing (BAAM) system. The Department of Energy’s Oak Ridge National Laboratory (ORNL) worked with TPI Composites to use the BAAM system to fabricate a wind turbine blade mold. The fabricated wind turbine blade mold was produced in 16 additively manufactured sections, was 13 meters long, had heating channels integrated into the design, and was mounted into a steel frame post fabrication. This research effort serves as a case study to examine the technological impacts of AM on wind turbine blade tooling and evaluate the efficacy of this approach in utility scale wind turbine manufacturing.

Oak Ridge National Laboratory (ORNL) has been utilizing the ARCAM electron beam melting technology to additively manufacture complex geometric structures directly from powder. Although the technology has demonstrated the ability to decrease costs, decrease manufacturing lead-time and fabricate complex structures that are impossible to fabricate through conventional processing techniques, certification of the component quality can be challenging. Because the process involves the continuous deposition of successive layers of material, each layer can be examined without destructively testing the component. However, in-situ process monitoring is difficult due to metallization on inside surfaces caused by evaporation and condensation of metal from the melt pool. This work describes a solution to one of the challenges to continuously imaging inside of the chamber during the EBM process. Here, the utilization of a continuously moving Mylar film canister is described. Results will be presented related to in-situ process monitoring and how this technique results in improved mechanical properties and reliability of the process.

Abstract Lockheed Martin and Oak Ridge National Laboratory (ORNL) are working on an additive manufacturing (AM) system (Big Area Additive Manufacturing, or BAAM) capable of producing components measured not in terms of inches or feet, but multiple yards in all dimensions. The highly automated system has the potential to manufacture parts completely unbounded in size.

The Stack Characterization System (SCS) is a collaborative project with the Robotics and Energetic Systems Group (RESG) at Oak Ridge National Laboratory (ORNL) and the Applied Research Center (ARC) at Florida International University (FIU). The SCS is a robotic system that will be deployed into off-gas stacks located around the central campus at ORNL. The system will consists of surveying equipment capable of taking surface contamination samples, radiation readings, core samples and transmit live video to its operators. Trade studies were conducted on varying concrete materials to determine the best way of retrieving loose contamination from the surface. The studies were performed at the ARC facility by FIU students, where traditional cloth wipes were compared to adhesive material. The adhesive material was tested on the RESG’s smear sampler to record how much loose surface material could be retrieved. The FIU students completed a summer internship during which conceptual designs were created for a deployable radiation detector and core drill capable of retrieving multiple core samples.

Needle insertion is pervasive in almost all medical activities. The development of compact, lightweight automated tools for needle insertion with the reliability of an expert needle-inserting nurse could significantly reduce the risk to both civilian and military patients. Such tools could open the door to many advanced concepts for future medicine by being an "enabler" of one of the first actions in almost all procedures. The purpose of this paper is to discuss two force-based devices that address the needle insertion problem: a compliance-sensing system that mimics the nurse palpation to determine the best needle insertion point across a vein, and a needle insertion device that uses force-based profiles during insertion to achieve successful catheterization without puncturing the vein back wall. The methodologies and implementation approaches for the two enabling systems are described. Experimental data obtained with training pads and phantom arms are presented and discussed.