Fused deposition modeling with polypropylene

This paper addresses the potential of polypropylene (PP) as a candidate for fused deposition modeling (FDM)-based 3D printing technique. The entire filament production chain is evaluated, starting with the PP pellets, filament production by extrusion and test samples printing. This strategy enables a true comparison between parts printed with parts manufactured by compression molding, using the same grade of raw material. Printed samples were mechanically characterized and the influence of filament orientation, layer thickness, infill degree and material was assessed. Regarding the latter, two grades of PP were evaluated: a glass-fiber reinforced and a neat, non-reinforced, one. The results showed the potential of the FDM to compete with conventional techniques, especially for the production of small series of parts/components; also, it was showed that this technique allows the production of parts with adequate mechanical performance and, therefore, does not need to be restricted to the production of mockups and prototypes.     

Modelling and estimation of tensile behaviour of polylactic acid parts manufactured by fused deposition modelling using finite element analysis and knowledge-based library

With the rise of the Fused Deposition Modelling (FDM) industry, a better understanding of the relationship between FDM process parameters and mechanical behaviour —especially tensile behaviour —of designed parts is needed to enable development of industry specifications. To optimise and control the deposition process, modelling and predicting the mechanical behaviour of a manufactured part under various process parameters is required. Existing numerical modelling approaches either require input of extensive experimental data or lack cross-validation. In this paper, the mechanical behaviour of polylactic acid manufactured parts under tensile conditions was studied both experimentally and numerically, and the effects of printing pattern and infill density on ultimate tensile strength (UTS)-weight ratio and the modulus of elasticity were evaluated. The experimental results revealed that minimising air gaps and using a triangular infill pattern are beneficial for obtaining a good UTS/weight ratio. Of all the specimens considered, the 20% triangular pattern had the highest UTS/weight ratio. The numerical investigation revealed that the meso-structure approach described in this paper can be used to predict the modulus of elasticity and the breaking point, and does not require input from the unidirectional specimen stress-strain curves. Finally, the meso-structure numerical model and artificial neural network were used to construct a knowledge-based library that can predict the modulus of elasticity of FDM manufactured polylactic acid with three infill patterns and any infill density with an average prediction error of 14.80%.     

Design and experimental validation of self-supporting topologies for additive manufacturing

ABSTRACT

Incorporating additive manufacturing (AM) constraints in topology optimisation can lead to performance optimality while ensuring manufacturability of designs. Numerical techniques have been previously proposed to obtain support-free designs in AM, however, few works have verified the manufacturability of their solutions. Physical verification of manufacturability becomes more critical recalling that the conventional density-based topology optimisation methods will inevitably require post-processing to smooth the boundaries before sending the results to a 3D printer. This paper presents the smooth design of self-supporting topologies using the combination of a new Solid Isotropic Microstructure with Penalisation method (SIMP) developed based on elemental volume fractions and an existing AM filter. Manufacturability of selected simulation results are verified with Fused Deposition Modeling (FDM) technology. It is illustrated that the proposed method is able to generate convergent self-supporting topologies which are printable using FDM.     

A review on composite materials and process parameters optimisation for the fused deposition modelling process

Fused deposition modelling is the most significant technique in additive manufacturing (AM) that refers to the process where successive layers of material are deposited in a computer-controlled environment to create a three-dimensional object. The main limitations of using fused deposition modelling (FDM) process in the industrial applications are the narrow range of available materials and parts fabricated by FDM are used only as demonstration or conceptual parts rather than as functional parts. Recently, researchers have studied many ways in order to increase the range of materials available for the FDM process which resulted in the increase in the scope of FDM in various manufacturing sectors. Most of the research are focussed on the composite materials such as metal matrix composites, ceramic composites, natural fibre-reinforced composites and polymer matrix composites. This article intends to review the research carried out so far in developing samples using different composite materials and optimising their process parameters for FDM in order to improve different mechanical properties and other desired properties of the FDM components.     

Optimization of fused deposition modeling process parameters:a review of current research and future prospects

Fused deposition modeling(FDM) is one of the most popular additive manufacturing technologies for various engineering applications.FDM process has been introduced commercially in early 1990 s by Stratasys Inc.,USA.The quality of FDM processed parts mainly depends on careful selection of process variables.Thus,identification of the FDM process parameters that significantly affect the quality of FDM processed parts is important.In recent years,researchers have explored a number of ways to improve the mechanical properties and part quality using various experimental design techniques and concepts.This article aims to review the research carried out so far in determining and optimizing the process parameters of the FDM process.Several statistical designs of experiments and optimization techniques used for the determination of optimum process parameters have been examined.The trends for future FDM research in this area are described.     

Additive manufacturing of carbon fiber reinforced thermoplastic composites using fused deposition modeling

Additive manufacturing (AM) technologies have been successfully applied in various applications. Fused deposition modeling (FDM), one of the most popular AM techniques, is the most widely used method for fabricating thermoplastic parts those are mainly used as rapid prototypes for functional testing with advantages of low cost, minimal wastage, and ease of material change. Due to the intrinsically limited mechanical properties of pure thermoplastic materials, there is a critical need to improve mechanical properties for FDM-fabricated pure thermoplastic parts. One of the possible methods is adding reinforced materials (such as carbon fibers) into plastic materials to form thermoplastic matrix carbon fiber reinforced plastic (CFRP) composites those could be directly used in the actual application areas, such as aerospace, automotive, and wind energy. This paper is going to present FDM of thermoplastic matrix CFRP composites and test if adding carbon fiber (different content and length) can improve the mechanical properties of FDM-fabricated parts. The CFRP feedstock filaments were fabricated from plastic pellets and carbon fiber powders for FDM process. After FDM fabrication, effects on the tensile properties (including tensile strength, Young's modulus, toughness, yield strength, and ductility) and flexural properties (including flexural stress, flexural modulus, flexural toughness, and flexural yield strength) of specimens were experimentally investigated. In order to explore the parts fracture reasons during tensile and flexural tests, fracture interface of CFRP composite specimens after tensile testing and flexural testing was observed and analyzed using SEM micrograph.     

Optimization of process parameters in fused deposition modelling of thermoplastics: A review

Among the several techniques for additive manufacturing (AM), fused deposition modelling (FDM) is widely used. Fused deposition modelling process uses a thermoplastic material, which is melted and then extruded layer by layer through a nozzle, in order to create a three-dimensional object. As a result of the default setting of process parameters provided by the manufacturers, produced parts normally have a poor surface finish, low mechanical properties, low dimensional accuracy, and increased residual stresses compared to the parts produced using conventional manufacturing processes like molding (casting). Qualities of fused deposition modelled (FDMed) parts are generally affected by process parameters including the layer thickness, extrusion temperature, build orientation, printing speed, raster angle, infill density, raster width, nozzle diameter, and air gap. Increasing infill density, printing temperature, and decreasing print speed and layer thickness lead to increase mechanical strength and improve the surface finish of the printed parts. The optimal process parameters are preferred to achieve superior properties of the parts. This paper reviews the optimal fused deposition modelling process parameters on part qualities for making the stability of used deposition modelled parts for use. Various process parameters are identified in order to obtain desirable qualities in the manufactured parts. Areas for future research are proposed.     

Fused Deposition Modeling for Unmanned Aerial Vehicles (UAVs): A Review

Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.

     

Direct Fused Deposition Modeling 4D Printing and Programming of Thermoresponsive Shape Memory Polymers with Autonomous 2D-to-3D Shape Transformations

Herein, direct 4D printing of thermoresponsive shape memory polymers (SMPs) by the fused deposition modeling (FDM) method that enables programing of 2D objects during printing for autonomous 2D-to-3D shape transformations via simply heating is focused on. The programming process during printing is investigated through designs and experiments. The capability of programming SMPs during printing is illustrated by prestrain and bending capabilities, which are highly related to printing settings, such as nozzle temperature, print speed, layer height, infill patterns, and ratio of active parts in a bilayer structure. A nearly linear relationship for prestrain and bending parameters is experimentally revealed for different printing factors. Quantitative results are presented to be used as a guidance for designing complex 3D structures via 4D printing of 2D structures. Helix structure, twisting structure, DNA-like structures, and functional gripper are designed to demonstrate the potential of direct FDM 4D printing for creating complex 3D structures from simple 2D structures with advantages over traditional manufacturing methods. It is shown that, by removing the need for a layer-by-layer stacking process to achieve a complex 3D shape, FDM can promote sustainability via 4D printing of autonomous 2D-to-3D shape transformer structures with lower materials, time, energy, and longer service life.     

Voigt–Reuss topology optimization for structures with nonlinear material behaviors

This work is directed toward optimizing concept designs of structures featuring inelastic material behaviours by using topology optimization. In the proposed framework, alternative structural designs are described with the aid of spatial distributions of volume fraction design variables throughout a prescribed design domain. Since two or more materials are permitted to simultaneously occupy local regions of the design domain, small-strain integration algorithms for general two-material mixtures of solids are developed for the Voigt (isostrain) and Reuss (isostress) assumptions, and hybrid combinations thereof. Structural topology optimization problems involving non-linear material behaviours are formulated and algorithms for incremental topology design sensitivity analysis (DSA) of energy type functionals are presented. The consistency between the structural topology design formulation and the developed sensitivity analysis algorithms is established on three small structural topology problems separately involving linear elastic materials, elastoplastic materials, and viscoelastic materials. The good performance of the proposed framework is demonstrated by solving two topology optimization problems to maximize the limit strength of elastoplastic structures. It is demonstrated through the second example that structures optimized for maximal strength can be significantly different than those optimized for minimal elastic compliance. © 1997 John Wiley & Sons, Ltd.     

Exit morphology and mechanical property of FDM printed PLA: influence of hot melt extrusion process

In order to study the hot melt extrusion process in fused deposition modeling (FDM), this study mainly explores the effects of printing temperature, heated block length, feeding speed on the exit morphology and mechanical properties of FDM printed Polylactic acid (PLA) samples. High-speed camera is used to capture the exit morphology of molten PLA just extruded to the nozzle. According to exit morphology, the outlet states of extruded molten material can be divided into four categories, namely, bubbled state, coherent state, expanding state, and unstable state. Tensile test results show that printing temperature, heated block length and printing speed have significant influence on tensile properties and fracture mode of FDM printed samples. When the heated block length is 15 mm and 30 mm, there is a ductile-brittle transition in fracture mode with the increase of printing speed. The printing process window under different heated block lengths and printing temperatures has been figured out and the distribution of printing process window under different printing speeds has been discussed. There is a maximum printing process window under the heated block length of 30 mm. This finding provides a frame work for performance prediction of FDM printed parts and theoretical guidance for expanding the scope of printing process window. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00405-1     

基于塑料微挤出成型的熔融沉积成型技术表面粗糙度研究进展

熔融沉积成型技术(FDM)是一种无模成型技术,易实现复杂模型的个性化定制,使得它在航空、汽车、医疗行业具有广泛、潜在的应用。同时FDM打印也是一种逐层打印技术,但制件表面粗糙,限制了它的应用。文中回顾了近10年来,尤其是近3年来在改进FDM表面粗糙度方面的研究现状和进展,并从制件后处理、软件控制、数学模型预测、优化工艺参数及结合其它成型技术等多方面论述了国内外关于FDM打印件表面粗糙度的改进方法及研究进展。     

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commercial electron beam melting(EBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm~3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.     

Performance analysis of a thick copper-electroplated FDM ABS plastic rapid tool EDM electrode

The importance of rapid tooling (RT) and additive manufacturing (AM) appears to be indispensable for boosting the process of manufacturing and expanding the horizon of production technology worldwide. This concept draws the attention of numerous scholars to arrive at a conclusive theory for the widespread utilization of RT. This study attempts to determine the viability and performance of an RT electrode in the field of electro discharge machining (EDM). The electrode prototype is made using an acrylonitrile butadiene styrene (ABS) plastic by fused deposition modeling (FDM), an AM technique, electroplated with copper of desired thickness, and used in die sinking EDM of D2 steel. The scanning electron microscope analysis of the electroplated samples confirms that it is possible to obtain the desired thickness of the metal by electroplating on any electrically conductive surface. In the present work, an experimental study is performed for examining the electroplated copper thickness of the plastic EDM electrode and its performances. It is found that the electroplated ABS plastic EDM RT electrode successfully performs the machining operation of D2 steel, and the results are comparable with a solid electrode. The study reveals that the RT electrode can be regarded as a viable tool for rough cutting or semi-finishing cut EDM functions. The experimental results are thoroughly discussed, examined, analyzed, and evaluated for the purpose of developing the appropriate form of the concept.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0238-5     

基于熔融沉积法的快速成形柔性丝材技术研究

目的研究柔性材料的熔融沉积(Fused Deposition Modeling,FDM)快速成形工艺。方法通过理论推导和实验研究的方法,针对柔性材料的FDM技术做了初步的探讨。结果柔性材料FDM工艺,相对于硬质材料来说,其进丝量需要更加精准的控制,进丝齿轮旋转角速度和打印速度、打印层厚呈正比关系,其比例系数取决于喷嘴直径、齿轮外径以及所使用丝材直径;同时,打印温度、打印层厚,尤其是首层打印间隙等工艺参数对于柔性打印制件的表观质量有更加重要的影响,这主要是因为熔融态柔性材料粘性较大所导致。结论现有硬质材料的FDM机器,需要作出适当的调整,才能更好地适应柔性材料打印。     

The influence of slicing parameters on the multi-material adhesion mechanisms of FDM printed parts: an exploratory study

ABSTRACT

The potentiality of the Fused Deposition Modeling (FDM) process for multi-material printing has not yet been thoroughly explored in the literature. That is a limitation considering the wide diffusion of dual extruders printers and the possibility of increasing the number of these extruders. An exploratory study, based on tensile tests and performed on double-material butt-joined bars, was thus conceived; the aim was to explore how the adhesion strength between 3 pairs of filaments (TPU-PLA, PLA-CPE, CPE-TPU) is influenced by the material printing order, the type of slicing pattern used for the layers at the interface, and the infill density of the layers below the interface. Results confirm the effectiveness of mechanical interlocking strategies in increasing the adhesion strength even when thermodynamic and diffusion mechanisms of adhesion are not robust enough. Besides, thermal aspects also demonstrated to play a relevant role in influencing the performance of the interface.     

Topology optimization of multiscale elastoviscoplastic structures

This paper extends current concepts of topology optimization to the design of structures made of nonlinear microheterogeneous materials. The objective is to maximize the macroscopic structural stiffness for a prescribed material volume usage while accounting for the nonlinearity and the microstructure of the material. The resulting design problem considers two scales: the macroscopic scale at which the optimization is performed and the microscopic scale at which the material heterogeneities and the nonlinearities are observed. The topology optimization at the macroscopic scale is performed by means of the bi‐directional evolutionary structural optimization method. The solution of the macroscopic boundary value problem requires as inputs the effective constitutive response with full consideration of the microstructure. While computational homogenization methods such as the FE² method could be used to solve the nonlinear multiscale problem, the associated numerical expense (CPU time and memory) is highly unacceptable. In order to regain the computational feasibility of the computational scale transition, a recent model reduction technique of the authors is employed: the potential‐based reduced basis model order reduction with graphics processing unit acceleration. Numerical examples show the efficiency of the resulting nonlinear two‐scale designs. The impact of different load amplitudes on the design is examined. Copyright © 2015 John Wiley & Sons, Ltd.     

Toward qualification of additively manufactured metal parts:Tensile and fatigue properties of selective laser melted Inconel 718 evaluated using miniature specimens

Combined with the topology optimization,additive manufacturing can be used to fabricate metal parts with complex shapes.However,due to the geometrical variation...     

Sensitivity analyses of FORM‐based and DRM‐based performance measure approach (PMA) for reliability‐based design optimization (RBDO)

In gradient‐based design optimization, the sensitivities of the constraint with respect to the design variables are required. In reliability‐based design optimization (RBDO), the probabilistic constraint is evaluated at the most probable point (MPP), and thus the sensitivities of the probabilistic constraints at MPP are required. This paper presents the rigorous analytic derivation of the sensitivities of the probabilistic constraint at MPP for both first‐order reliability method (FORM)‐based performance measure approach (PMA) and dimension reduction method (DRM)‐based PMA. Numerical examples are used to demonstrate that the analytic sensitivities agree very well with the sensitivities obtained from the finite difference method (FDM). However, as the sensitivity calculation at the true DRM‐based MPP requires the second‐order derivatives and additional MPP search, the sensitivity derivation at the approximated DRM‐based MPP, which does not require the second‐order derivatives and additional MPP search to find the DRM‐based MPP, is proposed in this paper. A convergence study illustrates that the sensitivity at the approximated DRM‐based MPP converges to the sensitivity at the true DRM‐based MPP as the design approaches the optimum design. Hence, the sensitivity at the approximated DRM‐based MPP is proposed to be used for the DRM‐based RBDO to enhance the efficiency of the optimization. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermometric investigations for the characterization of fatigue crack initiation and propagation in Wire and Arc Additively Manufactured parts with as-built surfaces

Metal Additive Manufacturing (AM) allows for the fabrication of complex shapes with high added value at low costs. Indeed, as-built structures are near net shape: they require few to no finishing operations. However, as-built AM parts present significant roughness caused by the layer discretization. In the case of the Wire and Arc Additive Manufacturing (WAAM) process, used for large-scale structures, the as-built roughness is estimated to several hundreds of micrometers. For complex geometries, a complete machining of the surfaces is not necessarily possible. In this study, an experimental method is proposed, relying on thermoelastic stress analysis, to characterize the effect of as-built WAAM surface roughness on high-cycle fatigue properties. Using an infrared camera, multiple cracks can be detected and monitored over a large surface on rough WAAM samples under cyclic bending. The collected data constitutes valuable information for the identification of a fatigue model dedicated to as-built WAAM structures.