Abstract: In this presentation, I plan to walk the audience through the journey of metal Additive as both an enabler and a disruptor simultaneously. We at the GE Aviation in the early years of 2010/2011 were facing a challenge to create the most reliable and most efficient engine for the commercial narrow body planes, namely the A320neo and 737max as well as the C919. Through this challenge we found a solution that actually pointed us to a new technology and industry now known as Additive Manufacturing. I will narrate the successes and failures of this journey plus how it lead us to create a new vertical inside GE by acquiring the Concept Laser, Arcam and GeonX companies in addition to the original Morris technology. I will also highlight the challenges one faces between prototyping and going to a full production as well as what is takes to create an ecosystem that supports the journey and the successful launch of printing engine and components for cost, performance, time to market and vertical integration. I then plan to close the talk by addressing what we have done to enable the academia and the school systems to have access and expose students to the 3-D printing.

Abstract: As the Additive Manufacturing (AM) industry moves towards series industrial production, the need for standards covering all aspects of the technology becomes ever more prevalent. While some standards and specifications for the various aspects of AM process chain exist and continue to evolve, many such standards still need to be matured or are under consideration/development within standards development organizations (SDOs). A resource to aid in the identification and development and approval of AM standards is a framework that has introduced a comprehensive structure to target various aspects of the AM space, including feedstock materials, design, process/equipment, testing, safety, and finished parts properties. The approach will also enable the development of application-specific standards to address the needs of the various industries. This presentation will discuss the state of the AM standards including gaps, challenges, opportunities and insight based on a recent initiative to establish global center of excellence to support research and development and close the standardization gaps that exist. Potential collaboration opportunities with the stakeholders and technical considerations in support of ongoing/future standards development will also be discussed.

Abstract: Titanium alloys are utilized extensively in the aerospace industry within many scenarios including those that involve tribological loadings (slat tracks, landing gear components, etc.). Unfortunately, titanium is not regarded as a material with high wear resistance ensuring the need for frequent component replacement at significant cost. The application of wear resistant coatings to the titanium substrate is one concept that has been exploited to mitigate this issue. Moving in this direction, the objective of this research was to develop durable coatings that could be applied through laser powder fed deposition (a.k.a. direct energy deposition (DED)). The core material system of interest was a metal matrix composite comprised of Ti64+TiC. Two concepts were considered in feedstock preparation. In one, gas atomized AncorTi-64 powder was mixed with TiC particulate. In the second, the AncorTi-64 powder was mixed with two sources of graphite powder such that the TiC would be grown in-situ during laser ablation. Experimental variables included laser power and scan speed, TiC concentration in the MMC product, and particle size of the graphite additions. All coatings were characterized to assess the resultant microstructure (Optical microscopy, SEM, X-ray diffraction), superficial hardness, and residual stress. It was discovered that the TiC formed in-situ maintained a very distinct morphology that was dependent on the processing parameters employed. Hardness was seen to largely depend on the weight percent of TiC within the coating, and if this TiC was deposited directly, or grown in-situ.

Abstract: Although this family of materials presents interesting mechanical and physical characteristics that are key to the transport industry, the number of studies on aluminum and its alloys built with Additive Manufacturing (AM) is still minor compared to other materials such as Ti-6Al-4V and stainless steels. Directed Energy Deposition (DED) is a sub-category within AM processes that offers unique possibilities thanks to the clever design of its deposition process. Indeed, DED is particularly well suited to add new complex features to existing parts, to vary the chemical composition in function of the XYZ coordinates within a build and to repair surface defects or worn parts. The latter is quite interesting for the manufacturing industry since it enables significant cost savings and is the focus of this study. In this work two different applications were studied: 1) the complete construction of samples made of A357 and 2) the repair of tensile half-specimens made of cast A357 with DED. Samples were characterized in terms of tensile properties, microstructure, crystallographic textures as well as grain size using SEM, EBSD and image analysis.

Abstract: Although Additive Manufacturing (AM) promises low wastage or attractive buy to fly ratios, the widely used Ti6Al4V powders inherently suffer from powder recyclability issues as feedstock powders degrade both in quality and form over ongoing builds in Selective Laser Melting (SLM) AM processes. Previous studies indicate negligible degradation in terms of Particle Size Distribution (PSD) and flowability but a major issue is the rising amounts of interstitial elements like Oxygen and Nitrogen with ongoing builds which gradually render the powder useless by crossing standard specifications. There exists a significant lack of data and know-how on powder recycling so a physicochemical approach is made on understanding how the powders gain these interstitial elements in an SLM AM machine over time during standard operations. A detailed understanding of the changing surface chemistries of the re-used powders over multiple machine runs is studied to facilitate a predictive model of Oxygen and Nitrogen uptake of the powder bed. The model will consider powder characteristics of the bed and the process parameters for the SLM AM machine as input to chart out a gain of these interstitials. Once validated, the model can be calibrated for specific SLM AM systems to provide a logical prediction of the condition of the powders and the disposal limit. This aims to provide manufacturers a controlled powder recycling policy over the existing mal-practice of disposing of the powders after an arbitrary number of re-use.

Abstract: This presentation will catalogue my journey through time where I have been looking at medical uses for AM. I believe that we are finally approaching a watershed moment where AM will become commonplace rather than on the periphery of medical treatments. To many it is surprising that it has taken so long to reach this point when we realise that some clinicians have been using the technology for more than 20 years.

Abstract: The behavior of the melt pool in AM affects the temperature history, pore formation and grain size, which in turn, impacts on the mechanical properties of the final built part and residual deformation. Hence, there is a need to development a quantitative link between the process parameters and heat transport at a range of length scales. The evolution of temperature during an EB-based powder-bed process has been investigated at the meso-scale using the Finite Volume based code Flow-3DTM. 2D and 3D thermal-fluid models has been developed to explore the relative importance of the factors affecting the liquid pool profile and the transport of heat within it. The thermal fluid model includes the following phenomena: a free upper surface, a moving surface-based heat flux (Gaussian Distribution), diffusive heat transfer, advective heat transfer, radiation heat loss, evaporation heat loss, recoil pressure due to evaporation, buoyancy forces and Marangoni forces. The results of a parameter sensitivity analysis using the 2D model are presented and indicate that, in addition to the beam parameters, the evaporation heat loss has a significant effect on temperature helping to moderate peak temperatures. Phenomena that have a significant effect on melt pool also include the surface tension and its temperature dependency and the recoil pressure due to evaporation (free surface shape). The results of a preliminary 3D analysis are also presented for comparison.

Abstract: Volumetric energy density (VED) is a commonly used expression for optimizing process parameters in powder bed laser fusion (PBLF). However, VED has shown to have certain limitations, particularly in predicting melt pool dynamics of PBLF. Melt pool geometry is dependent on the melting mode related to lack of fusion mode, conduction mode, or keyhole mode. These melting modes have a significant effect on the microstructure and mechanical properties in additively manufactured metallic materials. In laser welding, a dimensionless model for predicting melt pool geometry and melting mode has been developed based on numerical modelling and empirical observations. This model presents melt pool geometry as a function of normalized enthalpy. The expression for normalized enthalpy is derived from material parameters in addition to laser parameters thereby making the model material independent. The normalized enthalpy model has been successfully applied to PBLF of materials like 316L stainless steel and Inconel 625. This work studies the applicability of the model to Ti-6Al-4V processed by PBLF. Previous research has studied melt pool geometry on a base plate, which has been shown to have different melting characteristics when compared to a solid part. This work studies Ti-6Al-4V melt pool characteristics based on weld lines printed on built artifacts manufactured during the PBLF process. Additionally, the effect of varying artifact-processing parameters on the melt pool of weld lines is investigated by analyzing the effect of surface roughness and microstructure of artifacts on melt pool geometry.

Abstract: The paper analytically coupling the mass and heat transfer of powder-bed additive manufacturing (LPB-AM), in which the schematic particle distribution was considered and incorporated into the final powder-bed temperature field prediction. The model can perform an efficient prediction of the melt pool dimension, process heating/cooling rate, 3D profiles of simple multi-track structure, and have the potential to be employed for fast process optimization and controller design. The analytical predicted melt pool dimensions were compared with that of a developed numerical model, which agrees well with the numerical results. Sensitivity analysis of the built model shows that the laser power and laser absorptivity have the largest positive effect on the melt pool geometry, whereas the material thermal conductivity has the largest negative effect on the melt pool geometry.

Abstract: The relationship between process parameters and properties of the printed parts is one of the main challenges in laser powder-bed fusion (LPBF) additive manufacturing. Unlike conventional manufacturing processes, LPBF involves a large number of input process parameters (~100). It is important to identify the most significant process parameters to achieve the best as-build part quality. This is not possible by using conventional (factorial, fractional factorial) experimental design approaches as they require a huge number of runs. In this paper, Plackett-Burman experimental design is used to identify the most significant parameters that affect the surface roughness of printed LPBF Hastelloy X parts. Results from experimental design show that the skin thickness, geometry and layer thickness are the most significant process parameters affecting the surface roughness of LPBF Hastelloy X parts.

Abstract: The cooling system of plastic injection mold plays a critical role. It not only affects part quality but also the cycle time of injection molding process. Traditionally, due to the limitations of conventional drilling methods, the cooling system of injection mold usually consists of simple parallel straight channels. It seriously limits the mobility of cooling fluid, which causes the low cooling efficiency for parts with complex free-form surfaces. In this research, an innovative design method for the cooling system of the injection mold is provided by using conformal porous structure. The size and shape of each cell in the porous structure are varied according to the shape of injection molded part. A case study is provided at the end of this paper to further illustrate the efficiency of the proposed method. Comparing to the porous structures designed by the existing method, the proposed method can efficiently reduce the peak temperature as well as decrease the pressure drop of cooling systems.

Abstract: Print recipes are generally machine-specific requiring new optimization efforts to move to a different manufacturing system. Reduced parameters such as energy density and interaction time provide scaling rules for spot size. No such guidelines are currently available for the additional degree of freedom associated with point distance in modulated laser systems. In this work a recipe for water atomized pure iron from the continuous laser based EOS M 290 is translated to the Renshaw AM 400 modulated laser system. Using the surface energy density, volumetric energy density and interaction time from the EOS recipe, on the Renishaw we experimentally varied 1) apparent velocity, 2) hatch spacing, and 3) point distance. The experiment design takes the form of a 2^3 factorial. Scaling functions are considered to interpret datasets. Quantitative merit functions include surface roughness part density and pore distribution by computed tomography. The results are discussed both respect to recipe robustness and process speed.

Abstract: Binder jetting additive manufacturing (AM) was deployed to processing of pure iron powder. Surface morphology, particle size distribution, flow properties, and thermal behavior of water atomized pure iron powders were fully characterized using scanning electron microscopy (SEM), particle dynamic image analysis via Camsizer XT, FT4-Powder Rheometer, and Simultaneous Thermal Analysis respectively. A statistical process parameter optimization approach was applied to increase the green part density of manufactured samples. Cylindrical parts were fabricated and the effect of design parameters such as powder spreading/compaction, binder level, and layer thickness on the quality of green and sintered samples was examined using X-ray computed tomography (XCT). The potential application and future research work will be outlined based on the characterization results.

Abstract: A pattern is emerging among companies adopting metal-based additive manufacturing (AM). In the first stage, they use AM to replicate an existing part to understand the technology’s costs and capabilities. This starts to give them insight into the process and allows them to move onto the second stage wherein they adapt their designs for AM to reap more of its benefits—leveraging the design and material freedoms that AM affords. Finally, companies will shift to optimizing for AM as they gain confidence in the process while learning how to capitalize on AM to its full potential. These three stages can be effective when designing for AM, but only if expectations are carefully managed at each stage. Automotive, aerospace, and consumer product examples from Penn State’s Center for Innovative Materials Processing through Direct Digital Deposition (CIMP-3D) are presented to illustrate the benefits and drawbacks of each stage.

Abstract: Additive Manufacturing (AM) is becoming a very reliable technology to manufacture custom and complex components. The technology has made an exponential growth in the last decade, with many applications and industrial usage. Still, AM needs to improve in areas like Design for AM, geometric deviation modeling and control, and metrological aspects. Regarding geometric deviation, a lot of models and geometric control methodologies are present in literature. However, most of them are limited to plus/minus dimensioning or just one or two Geometric Dimensioning and Tolerancing (GD&T) characteristics, e.g., flatness, cylindricity, etc. This article focusses on the geometric deviation modeling and tolerancing from the GD&T point of view, since GD&T focusses on component’s form and shape along with dimensions. Different methodologies are reviewed which focus on the geometric deviation based AM process modeling, error minimization, accuracy control, form error minimization, etc. These are categorized based on the process stage of the AM: Pre-processing geometric control, in process control and Post processing control. A critical analysis of all the methods based on the GD&T characteristics done and pros-cons brought forward. Finally, a new geometric deviation modeling and control methodology is presented based on analytical modeling of the process and quantifying its effects on GD&T features. A simple case study is presented to validate the new methodology and it’s potential. Geometric compensation based on the new methodology and experiential validation is planned at a later stage to quantify and eradicate the geometric error as much as possible.

Abstract: We examine three-dimensional metallic lattices with regular octet and rhombicuboctahedron units fabricated with geometric imperfections via Selective Laser Sintering. We use X-ray computed tomography to capture morphology, location, and distribution of process-induced defects with the aim of studying their role in the elastic response, damage initiation, and failure evolution under quasi-static compression. Testing results from in-situ compression tomography show that each lattice exhibits a distinct failure mechanism that is governed not only by cell topology but also by geometric defects induced by additive manufacturing. Extracted from X-ray tomography images, the statistical distributions of three sets of defects, namely strut waviness, strut thickness variation, and strut oversizing, are used to develop numerical models of statistically representative lattices with imperfect geometry. Elastic and failure responses are predicted within 10% agreement from the experimental data. In addition, a computational study is presented to shed light into the relationship between the amplitude of selected defects and the reduction of elastic properties compared to their nominal values. The evolution of failure mechanisms is also explained with respect to strut oversizing, a parameter that can critically cause failure mode transitions that are not visible in defect-free lattice.

Abstract: Selective Laser Melting (SLM) is a rapid manufacturing technique in which geometrically complex parts can be made by selectively melting layers of powder. In order to estimate the dimensions of the melt pool cross-sections during this process, three-dimensional finite element simulations of heat transfer are performed. The models, adopting four different volumetric heat sources, are employed to simulate the processes of laser melting single tracks on a single layer of stainless steel 17-4PH powder. Then prediction results, such as the melt-pool dimensions, the temperature distributions, and the temperature gradients, are summarized and compared, and the simulation results are validated with the experimental results. This work is intended for presenting a relatively comprehensive study about the influences of heat-source models on the heat-transfer-simulation results. Recommendations on choosing a heat source model for selective laser melting are given and explained.

Abstract: We examine three-dimensional metallic lattices with regular octet and rhombicuboctahedron units fabricated with geometric imperfections via Selective Laser Sintering. We use X-ray computed tomography to capture morphology, location, and distribution of process-induced defects with the aim of studying their role in the elastic response, damage initiation, and failure evolution under quasi-static compression. Testing results from in-situ compression tomography show that each lattice exhibits a distinct failure mechanism that is governed not only by cell topology but also by geometric defects induced by additive manufacturing. Extracted from X-ray tomography images, the statistical distributions of three sets of defects, namely strut waviness, strut thickness variation, and strut oversizing, are used to develop numerical models of statistically representative lattices with imperfect geometry. Elastic and failure responses are predicted within 10% agreement from the experimental data. In addition, a computational study is presented to shed light into the relationship between the amplitude of selected defects and the reduction of elastic properties compared to their nominal values. The evolution of failure mechanisms is also explained with respect to strut oversizing, a parameter that can critically cause failure mode transitions that are not visible in defect-free lattice.

Abstract: The research group at the Advanced Materials and Processing Laboratory, University of Alberta, has developed a methodology to formulate and quantify the solidification paths of alloys. The methodology is based on the quantification of a solidified microstructure for its various phase fractions. This measured data is combined with well-established solidification models to yield undercooling temperatures of individual phases. The thermal history and undercooling of different phases in the solidified alloy are estimated for a wide range of cooling rates (from 0.5 K/min to 104 K/s). A detailed quantitative analysis of eutectic structures also reveals solidification conditions that yield optimum properties. In this presentation, the methodology will be described using examples of Al-Cu, Al-Cu-Sc alloys as well as Al-Si.

Abstract: The study of multi-functional nanoscale materials (graphene, nanotubes, nanowires) has inspired novel applications in manufacture of products with highly desirable mechanical and electrical properties. Developing additive manufacturing techniques for 3D carbon nanomaterial structures could lead to a manufacturing process that facilitates rapid prototyping and promotes ubiquitous usage of nanomaterials in flexible sensors, actuators, and energy devices. Graphene oxide dispersions in water exhibit 4 distinct regions of rheological behavior varying with dispersion concentration: viscoelastic liquid, transition state consisting of viscoelastic liquid and viscoelastic soft solid, viscoelastic soft solid, and viscoelastic gel. The transition state rheology is ideal for inkjet printing, while the viscoelastic gel is ideal for direct ink writing. Binder jetting and direct ink writing are ideal tools for investigating the use of graphene oxide dispersions in additive manufacturing. Shear forces induced by extrusion from thin microscale nozzles in both techniques is also known to facilitate alignment of crystalline carbon nanomaterials, imparting improved mechanical properties and electrical conductivity to the printed structure. A study of the full range of rheological behaviors of graphene oxide dispersions as additive manufacturing materials and their resulting 3D structural properties motivates the design and build of a hybrid binder jetting and direct ink writing 3D printer. Simple models of binder jetting printers and direct ink writing printers are proposed, discussing the overlapping subassemblies that enable the building of a functional hybrid. Performance metrics are presented for the direct ink writing of a cellulose nanofiber (CNF)/ Graphene oxide composite.

Abstract: Additive manufacturing (AM) is a promising technology that enables the production of complex parts with a unique freedom in design and short lead times. Variety of metallic materials can be processed through additive manufacturing. However, for application requiring high strength and high temperature resistance Ni-base superalloys are the primary choice of material. While there are variety of Ni-base superalloys that can be produced through AM, most high strength alloys are prone to cracking and considered unweldable. The objective of the project is to better understand the factors affecting these manufacturing difficulties. Traditional studied avenues include process parameters and alloy composition. This presentation will focus on investigating the solidified microstructure for Rene 41 (similar to Udimet 520), material that will be used as reference for this project.

Abstract: The long-term objective of this research is to design, develop, and process aluminum alloys for laser powder bed additive manufacturing (LPB-AM) that offer enhanced in-service thermal stability. In doing so, alloys strengthened by a distribution of thermally stable aluminide dispersoids within the microstructure are emphasized. Early stage efforts have addressed systematic additions of iron and nickel. Powders of Al-1Fe, Al-1Ni, and Al-1Fe-1Ni were inert gas atomized for this purpose. Each powder was characterized extensively to assess key attributes (particle size distribution, dynamic angle of repose, microstructure, flow, apparent density, etc.) and then processed via LPB-AM. Each build was then examined to determine finished product density and the general nature of the final microstructure (SEM/EDS, EBSD, XRD).