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.     

Experimental and numerical investigation of the thermal behaviour of polylactic acid during the fused deposition process

Fused deposition modelling (FDM) has become the most popular additive manufacturing process worldwide since the early 2000s. However, limited understanding of its deposition process greatly hinders the future growth of the technology. In order to optimise and control the deposition process, modelling and predicting the thermal behaviour change of the material during such a process is required. In this paper, the thermal behaviour of FDM process was studied both experimentally and numerically; effects of nozzle temperature, platform temperature, extrusion speed, and layer thickness on effective diffusion time, maximum vertical distortion, and maximum thermal stress were evaluated. It is shown that the developed simulation model could predict the effective diffusion time with the error of less than 13% in 6 out of 9 experimental conditions, relatively lower than the existing simulation and theoretical prediction models. Both the experimental and numerical results suggested that polylactic acid would have the longest diffusion time at high nozzle temperature, high platform temperature, low printing speed, and high layer thickness. And the numerical model revealed that reducing extrusion temperature, slowing printing speed, decreasing layer thickness are beneficial of reducing the vertical distortion and residual thermal stress.     

Fracture toughness of additively manufactured ULTEM 1010

ABSTRACT

One of the polymer additive manufacturing processes commonly used today is fused deposition modelling (FDM). FDM is the process of manufacturing three-dimensional structure through the use of a layer-by-layer printing of the polymer filament. Due to the anisotropic nature of FDM parts, the orientation of the rasters and the build orientation have an effect on the mechanical properties of a part. This study evaluates the fracture toughness of FDM solid-build specimens manufactured from Ultem 1010. The effects of build orientation and raster orientation were investigated through the use of a full-factorial design of experiments. The fracture toughness was obtained using single-edge notch bend test for a range of build orientations and rasters typically used in the FDM process. The design of experiments uses the results of the single-edge notch bend test to determine the significance the factors, build orientation and raster angle, have on the response variable, conditional critical stress intensity factor. Ultem 1010 parts were also microscopically examined to understand the primary failure mode around the rasters. The primary results of this study include the relationship of the build parameters to each other and to the fracture toughness of Ultem 1010.     

Mechanical properties of bio compatible functional prototypes for joining applications in clinical dentistry

In the presented research, work investigations have been made for mechanical properties of the functional prototypes prepared from biocompatible filament of fused deposition modelling (FDM), comprising of hydroxyapatite (HAp), polypropylene (PP) and polyvinyl chloride (PVC). The functional prototypes will be used in clinical dentistry (mainly for joining application for job-type production activities). The filament has been prepared in house using twin screw extrusion process. For evaluation purpose, standard tensile specimens as per ASTM D-638 have been prepared on FDM. This study highlights the effect of three parameters of FDM (namely: infill percentage, layer thickness and speed of extrusion head) on the mechanical properties (namely: load at peak and load at break). The results of the study suggest that infill density has majorly contributed, 92% on load at peak and 89% for load at break, and deposition speed has very less contribution i.e., 1% towards the mechanical strength of the specimen. Further, the results are supported with thermal analysis using differential scanning calorimeter (DSC), which ensures that the specimen prepared are thermally stable and can be put in for joining applications for job-type production activities in clinical dentistry.     

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。     

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%.     

Parametric appraisal of mechanical property of fused deposition modelling processed parts

Fused deposition modelling (FDM) is a fast growing rapid prototyping (RP) technology due to its ability to build functional parts having complex geometrical shape in reasonable time period. The quality of built parts depends on many process variables. In this study, five important process parameters such as layer thickness, orientation, raster angle, raster width and air gap are considered. Their influence on three responses such as tensile, flexural and impact strength of test specimen is studied. Experiments are conducted based on central composite design (CCD) in order to reduce experimental runs. Empirical models relating response and process parameters are developed. The validity of the models is tested using analysis of variance (ANOVA). Response surface plots for each response is analysed and optimal parameter setting for each response is determined. The major reason for weak strength may be attributed to distortion within or between the layers. Finally, concept of desirability function is used for maximizing all responses simultaneously.     

Effect of support on printed properties in fused deposition modelling processes

ABSTRACT

Additive manufacturing still suffers from redundant support material usage when printing parts with overhanging features. All the supports will be removed after fabrication, resulting in wasted materials. There are many works conducted for reducing support waste by improving support strategies. However, using different support strategies may lead to different printed qualities. In this paper, the effect of support strategy on printed qualities is investigated in fused deposition modelling processes. Three different support strategies are adopted for manufacturing the same 3D part. The finished surface roughness and flexural properties are compared for evaluating different support strategies, as well as the material waste and printing time. The results show that different support strategies may result in different printed surface roughness and flexural properties. To achieve the balance between support consumption and properties of printed parts, it becomes necessary to understand the effect of supports on printed qualities for choosing a best support strategy.     

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.     

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.     

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     

316L不锈钢电弧增材制造工艺研究

目的 研究电弧增材制造过程中焊接速度和层间冷却时间对成形件精度和力学性能的影响。方法 使用316L不锈钢焊丝在钢板上进行20层往复式堆积试验,设置了不同的焊枪运行速度和层间冷却时间,完成了4个金属薄壁墙体的制备,对沉积样品的形貌外观、显微组织、硬度和拉伸性能进行了研究。结果 4组试样的制备过程都比较稳定,表面成形良好,层与层结合较为平滑,层间分明,无裂纹、塌陷等缺陷出现。当层间冷却时间达到一定值时,熔池凝固,样品的成形精度和高度较为稳定。单位时间内加入熔池的金属质量和热输入均随着焊接速度的增大而减小,不同焊接速度下沉积样品的层高和层宽不同。由于焊接速度增大、热输入减小,试样的硬度略微增大,拉伸性能增强。沿薄壁件的构建方向,4组试样的维氏硬度曲线呈波浪形,从每个熔合层的底部到顶部逐渐降低。结论 增材制造工艺参数对产品的成形质量、显微组织和力学性能都有影响,在保证成形过程稳定的前提下,提高焊枪堆积速度能提高产品的力学性能。     

Experimental investigation on shore hardness of barrel-finished FDM patterns

Barrel finishing (BF) process is widely used to improve the surface finish and dimensional features of metallic and non-metallic parts using different types of media. As a matter of fact the change in shore hardness (SH) features of fused deposition modelling (FDM)-based master pattern is one of the important considerations from its service point of view. The main objective of present research work is to investigate the effect of BF process on SH of acrylonitrile–butadiene–styrene (ABS)-based master patterns prepared by FDM. Six controllable parameters of FDM and BF, namely, geometry of prototype, layer density, part orientation, types of BF media, weight of media and finish cycle time, were studied using Taguchi’s L18 orthogonal array in order to find their effect on SH of master pattern. Results indicated that process parameters significantly affect the SH of master patterns. It has been found that FDM part layer density contributed the maximum (about 67.52%) for SH of master patterns.     

纤维增强聚合物基复合材料熔融堆积成型技术的研究进展及产品的力学性能

增材制造(Additive manufacturing,AM)技术,又称3D打印技术,是一种新兴的顺序叠层制造工艺。近几年来,大量关于引入连续碳纤维增强相以改善打印结构力学性能的研究为打印高性能聚合物基复合材料开辟了新的途径。本文首先简要介绍聚合物材料增材制造工艺发展史,阐述技术革新和材料革新(引入增强相)对打印聚合物基材料产品性能优化的积极作用。随后着重描述了熔融堆积成型(Fused deposition modelling,FDM)技术制造连续纤维增强聚合物复合材料的工艺原理,并介绍了打印连续纤维增强聚合物基复合材料的力学性能优势及存在的问题。最后,从材料、工艺参数及复合材料细观/微观结构等方面分析了影响打印纤维增强聚合物基复合材料力学性能的主要因素,为读者了解分析FDM技术的优势和存在的问题提供参考。      

3D打印主要成形工艺及其应用进展

3D打印是以计算机图形数据为基础,通过逐层堆积的方式构建实体,具有高柔性制造以及对复杂零件自由快速成形的特点.从文献研究入手,重点介绍了光固化成形、熔融沉积制造、选区激光烧结、选区激光熔化、三维印刷成形、分层实体制造等典型3D打印工艺的成形原理以及研究进展,在此基础上着重概述了3D打印在生物医学、航空航天、建筑工程领域的应用.简要分析了当前3D打印技术发展中存在的一些问题并提出了一系列解决方案.3D打印技术的出现,给传统制造技术带来了革命性改变,其应用范围广泛,未来一定会融入到人们生活的方方面面.     

Large scale additive manufacturing of eco-composites

The evolution of additive manufacturing processes is enabling the production of parts with improved dimensional accuracy, mechanical, physical and chemical properties [1]. New materials also contribute to this trend, and in this scope, eco-composites, materials with environmental and ecological advantages, which include natural polymers, have been acquiring increased relevance [2]. The purpose of this study is to develop composite material parts manufactured from recycled thermoplastics and natural fibres, in this case, wood residues. Additive manufacturing (fused deposition modelling) will be accomplished using a robot combined with extrusion unit. The objective is to access the influence of the main manufacturing parameters, such as temperature, distance between layers or deposition speed, on the final part characteristics, especially dimensional accuracy. Reverse engineering and several material analysis techniques will be employed to achieve this goal.     

Investigating the shape memory properties of 4D printed polylactic acid (PLA) and the concept of 4D printing onto nylon fabrics for the creation of smart textiles

3D printing is an ever growing industry that provides many benefits to the advanced manufacturing and design industry. However, parts tend to be static, rigid, and lack multi-purpose use. Recently, a new technology has emerged that uses 3D printing to print parts with the ability to change shape over time when exposed to different external stimuli. This new technology has been called 4D printing. Creation of a new material that is capable of changing shape when exposed to different stimuli and possess the ability to be 3D printed can be a difficult and a long process. Due to this strenuous process, the potential of a common fused deposition modelling material, poly(lactic) acid (PLA), for use in 4D printing is investigated and the concept of combining PLA with nylon fabric for the creation of smart textiles is explored. PLA possesses thermal shape memory behaviour and maintains these abilities when combined with nylon fabric that can be thermomechanically trained into temporary shapes and return to their permanent shapes when heated.     

Optimisation of FDM process parameters by Taguchi method for imparting customised properties to components

Customisation of material properties by route of controlling the process parameters is a landmark ability of the additive manufacturing (AM) processes. Parametric optimisation of fused deposition modelling process using Fortus 250mc modeller is accomplished for conical primitives of constructive solid geometry in the present research. Experiments were designed according to the Taguchi technique for four factors at three levels each – slice height (SH), contour width (CW), raster width and air gap (AG). Analysis of signal-to-noise ratios is utilised for establishing the optimal process parameters and the relative percentage contribution of factors is estimated using ANOVA. Optimal levels of process parameters are found to vary with the variation in the type of basic shape of primitive. It has been established that AG has a maximum impact over the part build volume followed by CW and SH. Also, it can be safely concluded that the interaction effect of parameters is relatively less important.     

Effect of chemical treatment on tensile strength and surface roughness of 3D-printed ABS using the FDM process

Fused deposition modelling (FDM) is one of the most commonly used additive manufacturing processes because of its environment-friendly nature and cost-effectiveness. However, it suffers badly from low surface quality due to a larger layer resolution. The surface finish of FDM parts can be enhanced by post chemical treatment using various solvents. The chemical treatment reduces the surface roughness by dissolving the external surfaces of 3D-printed samples. Chemical treatment is an easy, fast and economical technique. In the present investigation, the effect of chemical treatment on surface roughness and tensile strength of acrylonitrile butadiene styrene (ABS) parts made using the FDM process is investigated using two chemicals, namely acetone and 1, 2 dichloroethane. The post chemical treatment dramatically improves the surface finish and dimensional accuracy of ABS specimens. But chemical treatment results in the reduction of the tensile strength. Better tensile strength is obtained while using acetone solvent and a better surface finish is obtained using dichloroethane.     

Additive Manufacturing of Porous Structures for Unmanned Aerial Vehicles Applications

Unmanned aerial vehicles (UAVs) have shown promising benefits in many applications. This has been enabled by the emergence of additive manufacturing (AM), which give the designers a large amount of geometrical freedom. In this paper, a novel design process of fused deposition modeling (FDM) combining both topology and infill optimization is introduced for AM of high performance porous structures. Tensile testing of FDM printed samples is first carried out to study the effect of the build orientation on the mechanical properties of acrylonitrile butadiene styrene (ABS) samples. It is found that samples built perpendicular to the load axis are the weakest with a tensile strength of 29 MPa and Young's modulus of 1960 MPa. The materials properties are fed to the finite elements analysis (FEA) for geometrical topology optimization, aiming to maximize stiffness and reduce weight of those parts. Afterwards, an infill optimization is carried out on the topology optimized parts using different mesostructures such as honeycomb, triangular, and rectangular to achieve high structural performance. The results showed that triangular pattern with 50% infill density had the lowest developed stresses, less mass, and strain energy when compared to other structures. Optimum UAVs parts of a quadcopter are successfully manufactured, assembled, and tested.