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     

Mechanical characteristics of oil palm fiber reinforced thermoplastics as filament for fused deposition modeling (FDM)

Fibers are increasingly in demand for a wide range of polymer composite materials. This study's purpose was the development of oil palm fiber (OPF) mixed with the thermoplastic material acrylonitrile butadiene styrene (ABS) as a composite filament for fused deposition modeling (FDM). The mechanical properties of this composite filament were then analyzed. OPF is a fiber extracted from empty fruit bunches, which has proved to be an excellent raw material for biocomposites. The cellulose content of OPF is 43%-65%, and the lignin content is 13%-25%. The composite filament consists of OPF (5%, mass fraction) in the ABS matrix. The fabrication procedure included alkalinizing, drying, and crushing the OPF to develop the composite. The OPF/ABS materials were prepared and completely blended to acquire a mix of 250 g of the material for the composition. Next, the FLD25 filament extrusion machine was used to form the OPF/ABS composite into a wire. This composite filament then was used in an FDM-based 3D printer to print the specimens. Finally, the printed specimens were tested for mechanical properties such as tensile and flexural strength. The results show that the presence of OPF had increased the tensile strength and modulus elasticity by approximately 1.9% and 1.05%, respectively. However, the flexural strength of the OPF/ABS composite had decreased by 90.6% compared with the virgin ABS. Lastly, the most significant outcome of the OPF/ABS composite was its suitability for printing using the FDM method.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00287-w.pdf     

Thermal and mechanical properties of 3D printed boron nitride – ABS composites

The current work investigates the thermal conductivity and mechanical properties of Boron Nitride (BN)-Acrylonitrile Butadiene Styrene (ABS) composites prepared using both 3D printing and injection molding. The thermally conductive, yet electrically insulating composite material provides a unique combination of properties that make it desirable for heat dissipation and packaging applications in electronics. Materials were fabricated via melt mixing on a twin-screw compounder, then injection molded or extruded into filament for fused deposition modeling (FDM) 3D printing. Compositions of up to 35 wt.% BN in ABS were prepared, and the infill orientation of the 3D printed composites was varied to investigate the effect on properties. Injection molding produced a maximum in-plane conductivity of 1.45 W/m-K at 35 wt.% BN, whereas 3D printed samples of 35 wt.% BN showed a value of 0.93 W/m-K, over 5 times the conductivity of pure ABS. The resulting thermal conductivity is anisotropic; with the through-plane thermal conductivity lower by a factor of ~3 for injection molding and ~4 for 3D printing. Adding BN flakes caused a modest increase in the flexural modulus, but resulted in a large decrease in the flexural strength and impact toughness. It is shown that although injection molding produces parts with superior thermal and mechanical properties, BN shows much potential as a filler material for rapid prototyping of thermally conductive composites.     

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。     

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.     

Minimizing Warpage for Macro-Size Fused Deposition Modeling Parts

In this study, we investigated warpage and corner lifting minimization for three-dimensional printed parts generated by macro-size fused deposition modeling (FDM). First, the reasons for warpage were theoretically elucidated. This approach revealed that the thermal deformation and differential volumetric shrinkage of the extruded molten plastic resulted in warpage of FDM parts. In addition, low adhesion between the deposited model and the heated or non-heated printing bed may intensify warpage further. As a next step, initial small-size and medium-size models were used to identify parameters to manage and minimize warpage in a way that would reduce material consumption and running time. Finally, a macro-size model was built to experimentally investigate and verify the technical solutions to minimize the warpage of FDM parts. In conclusion, an improved part with reduced warpage was efficiently produced after detailed consideration of thermal effects and adhesion force. Potential exists to widen the application scope of FDM technology in manufacturing for processes like thermoforming that involve mold core fabrication with heating. This technology, which has applications not only in mechanical engineering but also in related engineering fields, is convenient and could readily be applied to practical manufacturing industries.     

Experimental investigations on fused deposition modelling of polymer-layered silicate nanocomposite

Polymer-layered silicate (PLS) nanocomposites exhibit enhanced mechanical and thermal properties when compared with pristine polymers and macrocomposites. Utilizing the benefits of PLS nanocomposite in the fused deposition modelling (FDM) process is of great significance. It could assist to overcome the limitations imposed by availability of materials in the FDM process; the need to widen the range of materials is critical in order to fabricate parts with improved mechanical properties. Experimental investigations were carried out on the development and processing of PLS nanocomposite for the FDM process. Organically modified montmorillonite and polymer pellets were used to develop the nanocomposite. The mechanical properties and mesostructure were investigated experimentally. The nanocomposite was utilised to produce filament and was found to be suitable for use in FDM. Significant improvements in mechanical properties, reduced porosity and better neck formation were observed for the developed nanocomposite which marks the material as a promising candidate for the FDM process. The developed nanocomposite may reduce the gap for availability of materials for FDM in terms of improved mechanical properties. The work will assist to promote low-cost FDM processed parts for direct applications.     

基于混合坐标系的FDM型3D打印机研制

传统FDM（fused deposition molding，熔融沉积成型）型3D打印机在打印倒体件的过程中需设置辅助支撑结构，打印完成后去除支撑结构，这会导致成型件的精度降低。为解决传统FDM型3D打印机存在的问题，设计了一种基于混合坐标系的FDM型3D打印机。将基于笛卡尔坐标系的运动方式转换为基于拟球坐标系的运动方式，由X-Z平面内的旋转运动、X-Y平面内的旋转运动和Z轴方向的直线运动组合成拟球坐标系内的运动，达到无支撑3D打印的目的。介绍了基于混合坐标系的FDM型3D打印机控制系统的硬件和软件设计。用传统FDM型和基于混合坐标系的FDM型3D打印机进行打印实验并作对比，结果表明在同等级精度硬件配置的情况下，基于混合坐标系的FDM型3D打印机可以实现更高的打印精度。基于混合坐标系的FDM型3D打印机创新性强、造价低，拥有自主知识产权，具有广阔的市场前景。     

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.

     

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.     

聚乳酸/聚乙二醇/羟基磷灰石多孔骨支架的3D打印制备及其生物相容性

聚乳酸(PLA)是一种应用广泛的生物高分子材料,但在应用过程中存在韧性、亲水性、生物活性差等缺点。用聚乙二醇(PEG)和羟基磷灰石(HA)对PLA进行改性。通过熔融共混制备不同质量比的PLA/PEG/HA复合3D打印线材,并通过分析PLA/PEG/HA线材的力学性能、结晶性能、热性能、流变性能等,筛选更适合熔融沉积成型(FDM)的3D打印成型线材,进而利用3D打印制备精度高的力学性能试样及生物相容性好、细胞可增殖和分化的生物多孔支架。结果表明:PEG的添加提高了PLA的韧性,降低了PLA的熔点。HA的添加则提高PLA/PEG/HA复合材料的弹性模量和冷结晶温度,同时HA也可以改善复合材料的加工性能。SEM与荧光标记结果表明多孔支架与细胞具有良好的生物相容性。生物支架对体外细胞的成功培养,为进一步发掘生物多孔支架在动物体内、生物医学及定制化应用方面提供了潜在可能。     

Investigation on the effect of surface modification of 3D printed parts by nanoclay and dimethyl ketone

Fused deposition modeling (FDM) has emerged as one of the most utilized 3D printing technique. However, the surface properties of the FDM built parts lacks integrity due to layer by layer manufacturing technique. Therefore, post treatment is done on FDM printed parts. In the present research work, an effort has been made to improve the surface properties of the 3D printed parts by surface modification via chemical/nanoparticles. Nanoclay and dimethyl ketone were utilized for the surface modification of acrylonitrile butadiene styrene specimens. Parameters namely nanoclay content, immersion time, heat treatment and layer thickness were investigated to study their effect on surface roughness, surface hardness and dimensions. Also, the effect of nanoclay on UV absorbance of 3D printed parts was observed. Structural and morphological analysis was performed to characterize the surface of the 3D printed specimens after surface modification process. The results show that the surface roughness was reduced by 94.9%, surface hardness was increased by 9.7% while maintaining minimum dimensional deviation of ?0.03 and +0.07?mm. Also, UV absorbance was increased in 350–380?nm range. The results of the present study highlight the capability of the surface modification process for improving the surface properties of FDM parts.     

Additive manufacturing of mechanical testing samples based on virgin poly (lactic acid) (PLA) and PLA/wood fibre composites

3D printing in additive manufacturing is considered as one of key technologies to the future high-precision manufacturing in order to benefit diverse industries in building construction, product development, biomedical innovation, etc. The increasing applications of 3D printed components depend primarily on their significant merits of reduced weight, minimum used materials, high precision and shorter production time. Furthermore, it is very crucial that such 3D printed components can maintain the same or even better material performance and product quality as those achieved by conventional manufacturing methods. This study successfully fabricated 3D printed mechanical testing samples of PLA and PLA/wood fibre composites. 3D printing parameters including infill density, layer height and the number of shells were investigated via design of experiments (DoE), among which the number of shells was determined as the most significant factor for maximising tensile strengths of PLA samples. Further, DoE work evaluated the effect of material type (i.e., neat PLA and PLA/wood fibres) and the number of shells on tensile, flexural and impact strengths of material samples. It is suggested that material type is the only predominant factor for maximising all mechanical strengths, which however are consistently lower for PLA/wood fibre composites when compared with those of neat PLA. Increasing the number of shells, on the other hand, has been found to improve almost all strength levels and decrease infill cavities. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0211-3     

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.     

高分子基功能复合材料的熔融沉积成型研究进展

3D打印又称增材制造技术,是基于材料、机械控制、计算机软件等多学科交叉的先进制造技术,可得到传统加工不能制备的形状复杂制件.熔融沉积成型(FDM)是目前最通用的3D打印技术之一,具有设备简单、成本低、操作便捷等特点,广泛应用于航空航天、医疗、汽车工业等领域.本文介绍了国内外3D打印技术的整体布局、发展和规划,总结了常见...     

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.     

适于快速成型制造工艺的短纤维增强复合材料研究

对短切玻璃纤维增强ABS 复合材料进行了一系列的改性研究。短切玻纤的加入, 能提高纯ABS 的强度、硬度且显著降低ABS 的收缩率, 减小制品的形变, 但同时使材料变脆。本实验通过适量加入增韧剂和增容剂, 较大提高了挤出的复合材料丝的韧性及力学性能, 从而使制备出的短切玻璃纤维增强复合材料适用于熔融沉积制造(FDM ) 工艺。并用改性了的短切玻璃纤维增强ABS 作为原料, 在快速成型机上制备试样, 测定其力学性能, 从宏观及微观上对改性效果进行了分析与评定。     

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.     

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.     

聚合物管载胶熔融沉积3D打印增强层间结合强度

目的 熔融沉积3D打印的聚合物产品由于不同层的熔丝间作用力弱,其层间结合强度显著降低,难以满足工业应用的需求,已成为FDM工艺的瓶颈难题.方法 提出管载胶FDM新方法 ,以聚合物管材为胶水的载体,通过打印后胶水的化学反应使熔丝间形成化学键粘接,从而显著提升层间结合强度.结果 与传统无胶产品相比,打印产品的拉伸强度提高9...