An Empirical Study Linking Additive Manufacturing Design Process to Success in Manufacturability

This paper characterizes engineering designers’ abilities to re-design a component for additive manufacturing, employing screen capture methods. Additive Manufacturing has garnered significant interest from a wide range of industries, academia and government stakeholders due to its potential to reform and disrupt traditional manufacturing processes. The technology offers unprecedented design freedom and customization along with its ability to process novel and high strength alloys in promising lead times. To harness the maximum potential of this technology, designers are often tasked with creating new products or re-design existing portfolios of traditionally manufactured parts to achieve lightweight designs with better performance. To date, few studies explore the correspondence between design behaviors and manufacturability of final product within an Additive Manufacturing context. This paper presents empirical data from the design processes of six graduate student engineering designers as they re-design a traditionally designed part for additive manufacturing. Behaviors through the design task are compared between the study participants with a quantitative measure of the manufacturability and quality of each design. Results indicate opportunities for further research and best practices in design for Additive manufacturing and engineering education practitioners across multiple disciplines.Mechanical Engineerin

A Surface Modification Decision Tree to Influence Design in Additive Manufacturing

Additive manufacturing (AM) presents a very different set of design challenges to traditional manufacturing. Layer-wise building brings about issues with residual stresses and support requirements which lead to failures during processing of poorly-designed parts. Additionally, there is a need for post-processing due to poor part quality, which adds another process to the chain with its own unique design limitations. This paper discusses the issues surrounding designing for AM and the subsequent post-processing. A future vision is proposed for the selection of post-processes and the relative design adjustments to accommodate the chosen techniques. A decision tree is presented as a framework for process selection based on part requirements. Although at present, the data necessary to realise this vision is incomplete, with further research into the capabilities and design constraints of different post-processes, this approach could provide a systematic method for integrating design for post-processing with AM design

Study of Infill Print Parameters on Mechanical Strength and Production Cost-Time of 3D Printed ABS Parts

The ever-growing adoption of Additive Manufacturing (AM) can be attributed to lowering prices of entry-level extrusion-based 3D Printers. It has enabled using AM for mainstream DIY, STEM education, prototypes and often, to produce custom complex commercial products. With the growing number of available printers and newer materials, the influence of print parameters specifically infill patterns on the mechanical strength and print costs need to be investigated. This study presents the correlation of infill pattern selection and several mechanical properties along with final part cost and production time. Infill with varying design parameters are analyzed with respect to mechanical properties determined using ASTM standards, fabrication cost and time. Relevant applications are presented for all the varied infill designs. Findings from this study will help formulate criteria for relevant economically sound infill design pattern for real world applications.Mechanical Engineerin

A Novel Approach to Visualize Liquid Aluminum Flow to Advance Casting Science

Turbulent filling of molten metal in sand-casting leads to bi-films, porosity and oxide inclusions which results in poor mechanical properties and high scrap rate of sand castings. Hence, it is critical to understand the metal flow in sand-molds, i.e., casting hydrodynamics to eliminate casting defects. While multiple numerical methods have been applied to simulate this phenomenon for decades, harsh foundry environments and expensive x-ray equipment have limited experimental approaches to accurately visualize metal flow in sand molds. In this paper, a novel approach to solve this challenge is proposed using Succinonitrile (SCN) as a more accurate metal analog in place of water. SCN has a long history in solidification research due to its BCC (Body-Centered-Cubic) crystal structure and dendrite-like solidification (melting temperature ~60 °C) like molten aluminum. However, this is the first reported study on applying SCN through novel casting hydrodynamics to accurately visualize melt flow for casting studies. This paper used numerical simulations and experiments using both water and SCN to identify the critical dimensionless numbers to perform accurate metal flow analog testing. Froude’s number and wall roughness were identified as critical variables. Experimental results show that SCN flow testing was more accurate in recreating the flow profile of molten aluminum, thus validating its utility as a metal analog for metal flow research. Findings from this study can be used in future metal flow analysis such as: runner, in-gate and integrated filling-feeding-solidification studies

Investigation of Wear Behavior of Centrifugal Disc Finishing on Additively Manufactured Ti6Al4V Samples

As-built Additively Manufactured (AM) metallic parts require secondary processing in most applications to improve surface finish and mechanical strength. Mass Finishing (MF) processes are gaining popularity as effective and economical surface improvement methods for metal AM parts. This study investigates the wear behavior of post-processing both Laser Powder Bed Fusion (LPBF) and Electron Beam Melting (EBM) fabricated Ti6Al4V parts via Centrifugal Disc Finishing (CDF). Both AM orientation-based surface finish and wear behavior are compared for better understanding on key mechanisms of AM+MF hybrid manufacturing system. The areal surface roughness results showed that wear rate on side surfaces were higher than top surfaces for both LPBF and EBM samples in CDF. In addition, LPBF samples exhibited higher material removal than EBM samples based on weight loss measurements.Mechanical Engineerin

Measurement of Metal Velocity in Sand Casting during Mold Filling

Melt turbulence during mold filling is detrimental to the quality of sand castings. In this research study, the authors present a novel method of embedding Internet of Things (IoT) sensors to monitor real-time melt flow velocity in sand molds during metal casting. Cavities are incorporated in sand molds to position the sensors with precise registration. Capacitive and magnetic sensors are embedded in the cavities where melt flow velocity is calculated by using an oscillator, the frequency of which is sensitive to changes in the close field permittivity, and change in magnetic flux, respectively. Their efficiency is investigated by integrating the sensors into 3D sand-printing (3DSP) molds for conical-helix and straight sprue configurations to measure flow velocities for aluminum alloy 319. Experimental melt flow velocities are within 5% of estimations from computational simulations. A major benefit of 3DSP is the geometrical freedom for complex gating systems necessary to reduce turbulence and access to mold volume for sensor integration during 3DSP processing. Findings from this study establish the opportunity of embedding IoT sensors in sand molds to monitor metal velocity in order to validate simulation results (2–5% error), compare gating systems performance, and improve foundry practice of manual pouring as a quality control system

Effect of Prior Surface Textures on the Resulting Roughness and Residual Stress during Bead-Blasting of Electron Beam Melted Ti-6Al-4V

The finishing of additive manufactured (AM) components is crucial for endowing them with fatigue resistance. Unfortunately, current AM processes naturally promote anisotropic surface characteristics that make it challenging to optimize finishing processes. In this study, bead-blasting is explored as a process for finishing Electron Beam Melted (EBM) Ti-6Al-4V. The effects of anisotropic roughness characteristics on the mechanics of bead-blasting are delineated using surface texture measurements via optical profilometry and residual stress measurements via X-ray diffraction. As-received surfaces resulting from AM, as well as those that have been Electrical Discharge Machined (EDM), are studied. It is seen that pre-processed roughness textures heavily influence the final textures and residual stresses. These linkages are quantified using a plasticity index as the governing metric—a rougher surface features a larger plastic index, which results in comparatively greater evolution of its texture characteristics than a smoother surface after equivalent bead-blasting treatments. The mechanics of this evolution are delineated using energy-controlled indentation as a model representing a single impact in bead-blasting. It is seen that rougher surfaces featuring complex textures in as-received states also produce complex stress states featuring a greater level of locally tensile stresses during indentation compared with smoother surfaces. Approaches to address these complications are proposed that can potentially transform a printed, non-functional surface into one that is optimized for fatigue resistance

Sliding Contact Wear Damage of EBM built Ti6Al4V: Influence of Process Induced Anisotropic Microstructure

Process-induced directional microstructure is identified as one of the key factors of anisotropic mechanical properties. This directional property significantly affects surface contact fatigue and corrosion of electron beam melting (EBM) built biomedical implants. In the current study, material removal on EBM built titanium (Ti6Al4V) subjected to reciprocating motion of commercially pure titanium spherical slider is investigated to identify the influence of the process-induced layered structure and environments on wear damage. Specimens developed by two different build orientations are mechanically stimulated using different sliding directions with nominally elastic normal load in dry, passivating, and synovial environments. It was noticed that EBM orientation significantly changes wear behavior in ambient environment. Wear resistance of mill-annealed Ti6Al4V was improved in passivating environment. Implications to improve useful life of orthopedic implants are discussed