Build Material Research Articles

3-D-Printed Microwave and THz Devices Using Polymer Jetting Techniques

3-D additive manufacturing (AM) offers unprecedented flexibility in the realization of complicated 3-D structures. Polymer jetting is one of the promising 3-D AM techniques that utilizes photosensitive polymers as the build material and is capable of precisely printing electromagnetic (EM) components up into the THz range. In this paper, important design and implementation aspects of polymer-jetting-based 3-D-printed EM components are discussed. A number of 3-D-printable polymer materials and their broadband EM characterization from GHz to THz are introduced. Design methodologies specific for 3-D-printed antennas and other EM components are presented. As examples, various 3-D-printed devices operating from GHz to THz frequency, including electromagnetic crystals (EMXT), waveguide, horn antenna, gradient index (GRIN) lenses, as well as 3-D AM-enabled new designs, such as millimeter wave (mmW)/THz, reflect array antennas, computer-generated THz holograms, and so on are reviewed. Moreover, current limitations and possible future improvements of the polymer jetting technique for EM applications are discussed. This type of 3-D AM technique is likely to enable many novel antenna and circuit architectures as well as various interesting 3-D metamaterial structures.

Performance evaluation of ProJet multi-material jetting 3D printer

ABSTRACTThe purpose of this paper is to quantitatively evaluate the performance of a multi-material jetting 3D printer, ProJet 5500X, especially the capability for micro manufacturing. Unlike other single material 3D printer, ProJet 5500X uses photopolymers as the build material and wax as the support material. The building performance was evaluated by building a modified version of the standard benchmark model with a high-resolution printing mode. The dimensional error, forming quality and surface roughness of the printed parts have been measured and analysed using a microscope, a 3D coordinate measuring machine and a surface profilometer. Using wax as the support material, fine features as small as 0.25 mm, lateral features and sharper edges could all be properly built, despite the rough side surfaces observed in the printed part. Identical features (3 mm pins) were precisely built with an accuracy of 15 µm. The research provides first-hand detailed performance knowledge in the ProJet system for understanding the working principle and comparison with other 3D printing systems.

Additive Technology: Update on Current Materials and Applications in Dentistry.

Additive manufacturing or 3D printing is becoming an alternative to subtractive manufacturing or milling in the area of computer-aided manufacturing. Research on material for use in additive manufacturing is ongoing, and a wide variety of materials are being used or developed for use in dentistry. Some materials, however, such as cobalt chromium, still lack sufficient research to allow definite conclusions about the suitability of their use in clinical dental practice. Despite this, due to the wide variety of machines that use additive manufacturing, there is much more flexibility in the build material and geometry when building structures compared with subtractive manufacturing. Overall additive manufacturing produces little material waste and is energy efficient when compared to subtractive manufacturing, due to passivity and the additive layering nature of the build process. Such features make the technique suitable to be used with fabricating structures out of hard to handle materials such as cobalt chromium. The main limitations of this technology include the appearance of steps due to layering of material and difficulty in fabricating certain material generally used in dentistry for use in 3D printing such as ceramics. The current pace of technological development, however, promises exciting possibilities.

An Approach towards Economized 3D Printing

The growing demand for advanced manufacturing processes calls for reduction in manufacturing cost and manufacturing time. Fused Deposition Modelling (FDM) is one of the rapidly developing rapid Prototyping (RP) process. In this work an effort has made to make FDM process cost effective by replacing solid model with shelled model in-filled with user-defined parametric cellular structures. This approach helps in keeping a balance between material usages, build time and mechanical properties. The proposed method is implemented on a few specimens and results signify that 20-30% expensive build material as well as build time can be saved by this approach. The whole algorithm is based on .STL format, and is coded in MATLAB providing a versatile and widely acceptable platform.

A design of experiments approach to optimise tensile and notched bending properties of fused deposition modelling parts

As additive manufacturing expands from rapid prototyping into rapid production, it is becoming more important to consider the mechanical performance of candidate products in addition to their functional attributes as a prototype. This study demonstrates how a design of experiments approach can be used to optimise the tensile and notched bending properties of the materials used in the process, while also considering the time of production and material efficiency. Such an approach can allow manufacturers to optimise the build in terms of the time, cost and material properties according to the requirements of the product. The main conclusion of this study was that when considering the significant contributors, similar build parameters result in optimised properties for both specimen types. It was also found that the layer height, being insignificant to the mechanical properties of both specimens, was critical to the cost control in terms of build time and material usage. Thus, the maximum layer height could be used to incorporate cost control into the design without affecting final performance.

A Comparative Study for Weldability Prediction of AHSS Stackups

Resistance welding is the most commonly implemented method to join steel sheets in the automobile industry. To increase the efficiency and to maintain or reduce the weight of vehicles, advanced high-strength steel (AHSS) has been developed as a build material for vehicular structures. This paper aims to exploit the ability of prediction for nugget sizes in resistance spot welding by using support vector regression (SVR) and artificial neural network (ANN) model. In this study, the nugget size will be predicted according to parameters in resistance spot welding, such as welding current, welding time and welding force, etc. using machine learning methods. In addition to considering important process parameters for resistance spot welding, some design parameters, such as the thickness of the materials and the coating, are also considered. As the experimental results, SVR shows better performance in the prediction of nugget size when compared to ANN.

Phase-field simulation of microstructure evolution of Ti–6Al–4V in electron beam additive manufacturing process

Electron beam additive manufacturing (EBAM) is a relatively new technology to produce metallic parts in a layer by layer fashion by melting and fusing the metallic powders. Ti–6Al–4V is one of the most used industrial alloys used for aerospace and biomedical application. EBAM is a rapid solidification process and the properties of the build material depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be an important factor for process optimization. In this study, a phase field model is developed for microstructure evolution of Ti–6Al–4V powder in EBAM process. FORTRAN code is used to solve the phase field equations, which incorporates the temperature gradient and solidification velocity as the simulation parameters. The effect of temperature gradient and the beam scan speed on microstructure is investigated through simulation. The simulation results are compared with the analytical model and experimental findings by measuring the spacing evolution under the solidification condition

Study of Support Structure in Solid Based Rapid Prototyping Technique – FDM Approach

Support structure plays a vital role in Rapid Prototyping system in producing quality and dimensional accurate prints for a product having bridges or overhangs in a Rapid Prototyping product. The paper reports the selection of best support structure for any given model based on build time, material requirement and quality output of the prints. It also discusses the effects of introducing raft layers on a given model. A CAD model in STL (stereo lithography) format is an input to the Rapid Prototyping system. The CAD data is sliced for 3 different support structures by keeping constant printing parameters. Based on the build time, material consumption and part quality obtained, thebest support structure of any given model is experimentally found.

Microstructure Characteristics of Inconel 625 Superalloy Manufactured by Selective Laser Melting

Selective laser melting (SLM), an additive manufacturing process, is capable of manufacturing metallic parts with complex shapes directly from computer-aided design (CAD) models. SLM parts are created on a layer-by-layer manner, making it more flexible than traditional material processing techniques. In this paper, Inconel 625 alloy, a widely used material in the aerospace industry, were chosen as the build material. Scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) and X-ray diffraction (XRD) analysis techniques were employed to analyze its microstructure. It was observed that the molten pool was composed of elongated columnar crystal. Due to the rapid cooling speed, the primary dendrite arm space was approximately 0.5 μm and the hardness of SLM state was very high (343 HV). The inverse pole figure (IPF) indicated that the growing orientation of the most grains was due to the epitaxial growth and heat conduction. The XRD results revealed that the austenite structure with large lattice distortion was fully formed. No carbides or precipitated phases were found. After heat treatment the grains grew into two microstructures with distinct morphological characters, namely, rectangular grains and limited in the molten pool, and equiaxed grains along the molten boundaries. Upon experiencing the heat treatment, MC carbides with triangular shapes gradually precipitated. The results also identified that a large number of zigzag grain boundaries were formed. In this study, the grain formation and microstructure, and the laws of the molten pool evolution were also analyzed and discussed.

Phase-Field Modeling of Microstructure Evolution in Electron Beam Additive Manufacturing

In this study, the microstructure evolution in the powder-bed electron beam additive manufacturing (EBAM) process is studied using phase-field modeling. In essence, EBAM involves a rapid solidification process and the properties of a build partly depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of microstructure evolution in EBAM is of importance for its process optimization. Phase-field modeling was applied to study the microstructure evolution and solute concentration of the Ti-6Al-4V alloy in the EBAM process. The effect of undercooling was investigated through the simulations; the greater the undercooling, the faster the dendrite grows. The microstructure simulations show multiple columnar-grain growths, comparable with experimental results for the tested range.

The Mechanical Characteristics of 3D Printed Parts According to the Build Orientation

This article is focused on a production of mechanically resistant physical models using Rapid Prototyping technology. There are two tested materials, ABS is the first build material and ABS-like is the second build material with similar properties. The article describes the production of a testing component - element for tensile tests by two RP technologies. The first technology is FDM (Fused Deposition Modeling) and the second PolyJet Matrix. Further the article describes the description and evaluation of the tensile tests.

An Optimization Approach for Components Built by Fused Deposition Modeling with Parametric Internal Structures

Additive manufacturing processes are employed to create physical models from three-dimensional (3D) computer-aided design (CAD) math data. A solid model or water-tight surface model is used as the input, which is sliced into layers, and travel paths are created for each layer. The object is built by layer by layer stacking, with supporting structures for overhanging geometry and undercuts being created where necessary (process dependent). Fused deposition modeling (FDM) is an additive fabrication process that builds a part from extruded filaments of a melted thermoplastic. Several studies have focused on the depositing parameters; however, none of them have characterized internal support structures in different geometrical arrangements. The incorporation of reconfigurable parametric internal matrix structures based on primitive elements will balance the mechanical properties, the material usage and the build time. Parametric internal structures are designed, and compressive test components built and tested both experimentally and using simulation tools to depict the compressive characteristics. Extensive physical testing is done as the components built by the FDM process have anisotropic properties. The material usage, build time, and loading characteristics are captured for a variety of parametric structures (solid, shell, orthogonal, hexagonal, pyramid) build orientations, and internal densities (loose, compact). From this data, a model is developed that serves as a predictive tool to: (i) estimate the mechanical properties and (ii) calculate the build time and materials utilized based on various internal structural configurations for the component's application. A model that generates an optimal solution (minimum material, minimum build time, etc.) needs to be developed. Using the collected data as a foundation, an optimization model that considers the build time, material usage, surface finish, interior geometry, strength characteristics, and related parameters is presented and can be used to assist designers making informed decision with respect to strength, material usage and time, etc. is developed using the Genetic Algorithm approach.

Optimization of FDM Prototypes Mechanical Properties with Path Generation Strategy

This paper present result of a study evaluating the influence of path generation strategy on mechanical properties of Fused Deposition Modeling (FDM) prototypes. Several scientific studies were researching the problematic of path generation and internal structure of FDM prototypes. Mostly the influence on mechanical properties was observed. This paper is aimed on determine the influence of outline number and internal air-gap on tensile strength of parts built from ULTEM 9085. For this two variables was determined the influence on built time and consumption of modeling material. Result show that proper model orientation when the orientation of load is known, can help to reduce the build time and material consumption.

Microstructure simulation of Ti-6Al-4V biomaterial produced by electron beam additive manufacturing process

Ti-6Al-4V is one of the most promising biomaterial compared to other alloys used for biomedical application. Electron Beam Additive Manufacturing (EBAM) process is a rapid solidification process and the properties of the material depends on the solidification behaviour as well as the microstructure of the build material. Thus, the prediction of part microstructures during the process may be an important factor for process optimisation. In this study, a phase field model is developed for microstructure evolution of Ti-6Al-4V biomaterials produced by EBAM process. The simulation results are compared with the analytical model and experimental findings by measuring the spacing evolution under the solidification condition.

INFLUENCE OF PROCESS PARAMETERS ON DIMENSIONAL ACCURACY OF PARTS MANUFACTURED USING FUSED DEPOSITION MODELLING TECHNOLOGY

The paper presents the results of experimental study – part of research of additive technology using thermoplastics as a build material, namely Fused Deposition Modelling (FDM). Aim of the study was to identify the relation between basic parameter of the FDM process – model orientation during manufacturing – and a dimensional accuracy and repeatability of obtained products. A set of samples was prepared – they were manufactured with variable process parameters and they were measured using 3D scanner. Significant differences in accuracy of products of the same geometry, but manufactured with different set of process parameters were observed.

A Novel Approach for Assured Sterility of Medical Devices

A Novel Approach for Assured Sterility of Medical Devices

Evaluation of Parts Produced by a Novel Additive Manufacturing Process

Rapid prototyping refers to building three dimensional parts in a tool-less, layer by layer manner using the CAD geometry of the part. Additive Manufacturing (AM) is the name given to the application of rapid prototyping technologies to produce functional, end use items. Since AM is relatively new area of manufacturing processes, various processes are being developed and analyzed for their performance (mainly speed and accuracy). This paper deals with the design of a new benchmark part to analyze the flatness of parts produced on High Speed Sintering (HSS) which is a novel Additive Manufacturing process and is currently being developed at Loughborough University. The designed benchmark part comprised of various features such as cubes, holes, cylinders, spheres and cones on a flat base and the build material used for these parts was nylon 12 powder. Flatness and curvature of the base of these parts were measured using a coordinate measuring machine (CMM) and the results are discussed in relation to the operating parameters of the process.The result show changes in the flatness of part with the depth of part in the bed which is attributed to the thermal gradient within the build envelope during build.

Direct laser deposition with different types of 316L steel particle: A comparative study of final part properties

This article investigates the role that particle size and morphology have in determining the final characteristics of a part produced by direct laser deposition. 316L stainless steel in the form of traditional gas-atomised powder and metal shavings in two size ranges were deposited into multiple-layer thin-walled parts at different process parameters. The walls were characterised, considering properties such as geometry, microstructure, composition, physical and corrosive properties and results matched to the type of build material. Results showed that using particles of >150 µm, equivalent spherical diameter offered few functional advantages, leading to a process with lower deposition efficiency and part with lower mechanical properties. Using machined shavings increases deposition efficiency and can reduce gas porosity compared with powder in the same size range, but also results in higher surface oxidation, thought to be due to higher oxidation on the original shavings. This is a barrier for some applications, but the deposition of machined shavings offers significant economic advantages.

Influence of path generation strategy on tensile properties of FDM prototypes

This paper presents the results of a study evaluating the influence of path generation strategy of Fused Deposition Modeling (FDM) prototypes on mechanical properties of material. Several scientific studies were researching the problematic of path generation and internal structure of FDM prototypes. Mostly the influence on mechanical properties was observed. The presented study focuses on assessment of mechanical property of part fabricated using fused deposition modeling (FDM) technology in uniaxial tensile test. In this study standardized uniaxial tensile test (STN ISO 527-2) was used to determine tensile properties of specimens from ULTEM 9085. As the relation between mechanical property and process parameters is difficult to establish, attempt has been made to derive the empirical model between the processing parameters and mechanical properties using statistical methods. One of the parameter in path generation was the positive air-gap between fibres in internal raster. In actual practice, the parts are subjected to various types of loadings. Result show that proper model orientation when the orientation of load is known, can help to reduce the build time and material consumption.

Selecting Digital Deposition Methods to Meet 2D and 3D Application Requirements

The paper outlines methods for effectively selecting digital deposition technologies for 2D printing and 3D deposition when there are dozens of technologies from which to choose. We present a matrix of parameters for comparing and evaluating the costeffectiveness, performance capabilities and characteristics of currently available digital print and deposition technologies against the performance requirements of applications. The paper specifically cites 2D and 3D applications including folding carton production and plastic parts manufacturing requirements. The matrix structure provides researchers and technology developers with a flexible tool for fine-tuning the print and deposition technology selection process. This paper also examines how developers can use the matrix for integrating digital deposition technology into complex manufacturing assembly processes. Due to the space limitations that this publication affords, we provide the matrix in outline form with a few examples. Our research group has compiled a comprehensive matrix.The digitally controlled deposition methods covered in this presentation include: the various forms of inkjet, inkjet-like methods, Inkjet Liquid Binding Powder (IJLBP), syringe deposit / Robo-casting (RC), aerosol deposit, pump dispensing, Electron Beam Freeform Fabrication (EB3F), Shape Deposition Manufacturing (SDM), and Fused Deposition Modeling (FDM)/Fused Filament Fabrication (FFF). We have focused for this presentation on methods where a digitally controlled process deposits material on a substrate or a particulate build material. In this report we do not cover spread-coating methods using radiation curing, such as laser electro-photography, stereolithography (SLA), selective laser sintering (SLS), Selective Laser Melting (SLM), Electron Beam Melting (EBM), and Solid Ground Curing (SGC). Nor do we cover laminating build methods, such as Laminated Object Manufacturing (LOM). Our group covers these other technologies in an upcoming report. The matrix structures of all these reports will facilitate comparison of print, deposition and build methods against application requirements.We focus on the characteristics of the deposition methods that address application requirements. These encompass both the way the deposition method performs and what it can deposit. Performance factors include the rate at which it can deposit amounts of specific materials, the accuracy and consistency of deposition placement, deposition resolution, the pH and deposit material device tolerances, material viscosity ranges necessary for deposition, system temperature controls and tolerances, operating, deposition material velocity, grey-scale capabilities, and device performance life. Users would also need capital and operation costs in selecting deposition systems. Operating costs will, however, vary greatly depending upon particular use. We therefore have not included operating costs in the current presentation matrix. Deposited material characteristics include viscosity, surface tension, and method to dry, solidify, polymerize, cure or fix. Performance requirements for deposited films and builds include abrasion and chemical resistance, tensile strength, and market acceptance of output appearance.