Numerical simulation and printability analysis of fused deposition modeling with dual-temperature control

Ideal tissue engineering scaffolds need interconnected pores and high porosity to enable cell survival,migration,proliferation,and differentiation.However,obtaining a high-resolution structure is difficult with traditional one-temperature control fused deposition modeling(FDM).In this study,we propose a dual-temperature control method to improve printability.A numerical model is developed in which the viscosity is a function of temperature and shear rate to study the influence of two different temperature control modes.Quantitative tests are used to assess filament formation and shape fidelity,including one-dimensional filament printing,deposition at corners,fusion,and collapse.By using dual-temperature control,the width of the deposited poly(ε-caprolactone)filament is reduced to 50μm.The comparative results of both the experimental method and numerical simulation suggest that the dual-temperature control FDM can manufacture spatially arranged constructs and presents a promising application in tissue engineering。

Cleated Print Surface for Fused Deposition Modeling

FDM （fused deposition modeling） has become popular among Additive Manufacturing technologies due to its speed, geometric scalability, and low cost; however, the primitive nature of the FDM build surface fundamentally limits the utility of FDM in terms of reliability, autonomy, and material selection. Currently, FDM relies on adhesive forces between the first layer of a print and the build surface; depending on the materials involved, this adhesive bond may or may not be reliable. Thermal contraction between the build plate and build materials can break that bond, which causes warpage and delamination of the part from the build surface and subsequent failure of the part. Furthermore, with each print, the user must use tools or manual maneuvering to separate the printed part from the build surface as well as retexture or replace the used build surface. In this paper, we present a novel build platform that allows for a mechanical bond between the print and build surface by using dovetail-shaped features. The first layer of the print flows into the features and becomes mechanically captivated by the build platform. Once the print is completed, the platform is rolled or flexed open to release the part from the mechanical bond. This design not only lowers the risk of delamination during printing but also eliminates the need for a user to reset or replace the build surface between print jobs. The effectiveness of each geometry was determined by measuring the distance at the pinch point compared to the distance that the extrusion filled below the pinch point. The captivation ratio was measured to compare the different geometries tested and determine which direction of extrusion creates a better ratio.

Design Consideration for Additive Manufacturing: Fused Deposition Modelling

Additive Manufacturing (AM) technologies have progressed in the past few years and many of them are now capable of producing functional parts instead of mere prototypes. AM provides a multitude of benefits, especially in design freedom. However, it still lacks industrial relevance because of the absence of comprehensive design rules for AM. Although AM is usually advertised as being the solution for all traditional manufacturing design limitations, the fact is that AM only replaces these limitations with a different set of restrictions. To fully exploit the advantages of AM, it is necessary to understand these limitations and consider them early during the design process. The establishment of design considerations in AM enables parts and process optimization. This paper discusses the design considerations that will lead to optimize part quality. Specifically, the work discusses the Fused Deposition Modeling (FDM) due to its common use and availability. These considerations are drawn from literature and from experiments done by the authors. The experiments done by the authors include an investigation for the influence of elevated service temperature on the performance of FDM PLA parts, benchmarking the capability of FDM to print overhangs and bridges without supports, studying the influence of processing parameters over dimensional accuracy, and the effect of processing parameters on the final FDM samples modulus of elasticity. The work presents a case study investigating the correct clearances for FDM parts and finally a redesign for AM case study of a support bracket originally manufactured using traditional manufacturing methods taking into consideration the design considerations discussed in this paper.

Complex formulations, simple techniques: Can 3D printing technology be the Midas touch in pharmaceutical industry?

3 D printing is a method of rapid prototyping and manufacturing in which materials are deposited onto one another in layers to produce a three-dimensional object. Although 3 D printing was developed in the 1980 s and the technology has found widespread industrial applications for production from automotive parts to machine tools,its application in pharmaceutical area is still limited. However,the potential of 3 D printing in the pharmaceutical industry is now being recognized. The ability of 3 D printing to produce medications to exact specifications tailored to the needs of individual patients has indicated the possibility of developing personalized medicines. The technology allows dosage forms to be precisely printed in various shapes,sizes and textures that are difficult to produce using traditional techniques. However,there are various challenges associated with the proper application of3 D printing in the pharmaceutical sector which should be overcome to exploit the scope of this technology. In this review,an overview is provided on the various 3 D printing technologies used in fabrication of complex dosage forms along with their feasibility and limitations.

Recipe Development and Mechanical Characterization of Carbon Fibre Reinforced Recycled Polypropylene 3D Printing Filament

Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed specimens were characterized using scanning electron microscopy and standard tensile testing. It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were dispersed throughout the microstructure of the filament. A two-stage filament extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the pores. Recycled polypropylene filaments without reinforcement extruded at high screw speeds above 20 rpm contained a centreline cavity but no spatially distributed pores. However, this cavity is eliminated when extrusion is carried out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than those printed from unreinforced filaments. The values of tensile strength for the filaments were 21.82 MPa and 24.22 MPa, which reduced to 19.72 MPa and 22.70 MPa, respectively, for 3D printed samples using the filaments. Likewise, the young’s modulus of the filaments was 1208.6 MPa and 1412.7 MPa, which reduced to 961.5 MPa and 1352.3 MPa, respectively, for the 3D printed samples. The percentage elongation at failure for the recycled polypropylene filament was 9.83% but reduced to 3.84% for the samples printed with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to failure was 6.58%. The SEM observations on the fractured tensile test samples showed interlayer gaps between the printed and the adjacent raster layers. These gaps accounted for the reduction in the mechanical properties of the printed parts.

人工神经元网络模型预测3D打印部件力学性能的研究

熔融沉积成型(FDM)是一种高效的增材制造技术。将响应面模型与人工神经元网络(ANN)模型相结合,研究了FDM工艺的喷嘴温度、层高和层积角度对尼龙12(PA12)丝材制造部件力学性能的影响。当喷嘴温度、层高和层积角度分别在220~260℃、0.2~0.4 mm、0°~90°之间变化时,部件拉伸强度和缺口冲击强度分别在35.69~60.89 MPa和5.48~19.83 kJ/m^(2)之间。喷嘴温度、层高、层积角度以及层积角度的二阶效应是影响部件拉伸强度的显著因素;喷嘴温度、层积角度以及层积角度的二阶效应是影响缺口冲击强度的显著因素。ANN模型预测拉伸强度和缺口冲击强度的最优结构分别是3-10-5-1和3-25-24-1,预测的拉伸强度和缺口冲击强度均方误差函数(MSE)最低分别为2.54×10^(-4)和2.07×10^(-4),回归系数均在0.97以上。与响应面的二次回归模型相比,ANN模型预测的拉伸强度和缺口冲击强度与实验值的标准偏差分别为0.46和0.32,远低于二次回归模型的2.43和1.58,更适合于优化非线性的FDM工艺。

FDM技术打印参数对成型效率的影响研究

FDM技术可用于工业领域中大型零件模型的打印,提升成型效率成为重要的研究课题。本研究通过响应面分析方法,探究了FDM打印参数对聚乳酸圆柱件成型效率的影响规律,得到了最优打印参数,并经过实际打印验证。结果表明层厚增加,成型效率提高;打印速度增加,成型效率提高;填充率增加,成型效率降低;路径规划和壁厚对成型效率影响不大。影响成型效率的因素按照顺序排列是:层厚>打印速度>填充率,其中层厚和打印速度影响显著。最优打印参数为打印速度85mm·s^(-1)、层厚0.175mm、填充率55%,预测时间为58.8min,实际时间为59min,预测精度达99.7%,为提升成型效率提供了依据。

FDM用ABS复合材料的改性及其应用研究进展

丙烯腈-丁二烯-苯乙烯共聚物(ABS)具有良好的力学性能和可加工性。近年来,随着熔融沉积成型(FDM)三维(3D)打印技术的不断成熟和发展,ABS及其各类改性复合材料也相应被广泛应用于FDM。本文重点基于FDM技术,首先系统整理了金属类填料、无机非金属类填料、有机高分子类填料、回收废旧聚合物类填料等改性ABS基复合材料的现状,并对其相关性能进行了归纳。同时,对相应的各类ABS改性复合材料的FDM打印制品在医学、民用工业、军用电磁与吸波等领域的前沿应用进行了综述。最后,结合FDM打印技术和ABS改性现状,对未来FDM打印方法以及ABS改性技术提出了几点思考。

1+1罗纹3D打印面料的制备

为满足近几年消费者对服装面料可持续创新的需求,丰富3D打印服装面料的结构和外观风格,以柔性聚乳酸为原材料,在3ds Max软件中,采用NURBS曲线建模方法,结合实物测量情况,对1+1罗纹组织进行三维模拟;通过探究分层厚度、打印温度、打印速度、沉积方向对1+1罗纹3D打印面料拉伸性能的影响,确定出最优打印参数;通过FDM工艺,在最优打印参数下,对模拟的组织进行打印,得到1+1罗纹3D打印面料。该面料打印效果与模拟效果相同,线圈平整,无歪斜现象,面料表面无焦黄现象,可形象地表现出纱线的形态及服装的纹理效果,符合后疫情时代消费者对服装面料创新性和多元化的需求。

构建“等效模型”快速验证个性化骨模型的精确度

背景:目前个性化骨模型精确度的验证通常是通过配对t检验或组内相关系数等方法来进行,但这类方法往往需要制作大批量模型,不能满足个性化模型即时使用的需求。目的:探讨构建“等效模型”快速验证个性化骨模型精确度的可行性。方法:随机获取3例成年人骨骼CT影像并进行重建,运用3D打印制作个性化骨模型,再将个性化骨模型进行CT扫描并重建,使用Mimics对比重建模型和骨骼CT影像。运用Geomagic Studio对个性化骨模型CT影像的重建模型与骨骼CT影像的重建模型进行拟合偏差分析。对照骨骼CT影像的重建模型上所标注的测量位置和尺寸,对3D打印的个性化骨模型进行实物测量,并计算误差。结果与结论:①通过对比骨骼CT影像的重建模型与骨骼CT图像,二者在解剖结构和形态上相符,轮廓几乎重合;②通过拟合偏差分析,标准偏差依次为0.176,0.226,0.143 mm,所有结果均<0.25 mm;③通过实物测量并计算,相对误差均数依次为0.44%,0.21%,0.13%,所有结果均在5%的误差范围之内;④通过骨骼CT影像重建的模型符合制作个性化骨模型的基本条件;所构建的等效模型是符合临床需求和设计要求的,使用等效模型方法快速验证个性化骨模型精确度是可行的;⑤此方法可为个性化骨模型精确度的验证提供针对性强、验证迅速的途径,与常规配对t检验或组内相关系数等方法相比可缩短验证时间,能够达到提供临床即时使用的目的。

淀粉基凝胶在食品3D打印中的研究进展

食品3D打印技术是一种在食品领域新兴的、由计算机辅助软件控制的智能化快速成型技术。因其具有高效、便捷、个性化定制的特点,在食品加工领域中有较大的发展潜力。淀粉作为一种可再生的天然高分子,具有无毒害、经济环保、资源丰富的优点,是3D打印优质的食品级油墨。近年来,随着食品3D打印技术的不断发展,如何提高天然食用凝胶的可打印性成为研究热点。为更好地了解淀粉基凝胶3D打印的研究进展,该文从3D打印技术原理、淀粉基原料3D打印特性、影响淀粉基凝胶3D打印效果的因素、淀粉基凝胶3D打印的应用现状以及面临的挑战等方面进行综述,以期为淀粉基凝胶在食品3D打印中的发展和应用提供参考。

基于骨架提取的弯管类结构无支撑3D打印混合切片方法

弯管类结构存在丰富的悬空部位,采用传统熔融沉积3D打印技术制造需要消耗大量支撑,影响成本与成型表面质量。基于此,提出一种用于弯管类模型的骨架提取方法及相应的混合切片算法。与现有的简单沿骨架法面切片或分区多向切片技术不同,该方法充分利用弯管STL模型点云特点提取骨架和模型分层信息,引入干涉检查与切片路径检查,采用沿骨架法面切片与圆弧切片结合的混合切片方式,完成模型无支撑打印切片。最后,算法在4类模型上进行了切片仿真实验,验证其有效性和可行性。

聚丙烯基3D打印材料的设计及制备研究进展

综述了3D打印用聚丙烯(PP)专利技术最新进展。通过多种改性途径,可以将PP改性为3D打印用免喷涂材料、低收缩材料、防翘曲材料、高韧性材料、荧光材料、交联材料、超低密度材料、增韧材料、耐辐照材料、可低温打印材料、中子屏蔽材料、纳米材料、丙烯酸树脂改性材料、超高相对分子质量聚乙烯改性材料及溶剂法材料,进而得到具有不同性能、满足不同行业需求的3D打印材料。

熨烫处理对3D打印成型件表面特性的影响

为了有效提高3D打印成型件的表面质量和美观度,通过熔融沉积成型(FDM)3D打印机挤出头对成型件表面进行熨烫处理,采用表面粗糙度测试、光泽度测试、颜色属性测试评价了熨烫处理对FDM成型件表面特性的影响。粗糙度测试结果表明,熨烫处理后FDM成型件的轮廓算术平均偏差Ra和轮廓最大高度Rz平均值分别降低了46.18%和37.36%;光泽度测试结果表明,熨烫处理后FDM成型件在20°,60°,85°入射角下的光泽度平均值分别提高了45.65%,31.63%,20.34%;颜色属性测试结果表明,熨烫处理后FDM成型件的色相H平均值基本保持不变,明度L*、彩度C*平均值分别增大了7.25%和6.14%。对比工业显微镜拍摄的细节放大图可见,与熨烫处理前较粗的表面纹理相比,熨烫处理后FDM成型件的表面纹理更加细密,质感更显光滑,其表面的凸起物得到有效去除,“缺陷”基本消失,光泽度有所提升,颜色显得更加明亮、鲜艳。因此,熨烫处理可以有效改善FDM成型件的表面特性,具有较高的应用推广价值。

复合喷头-多材料FDM 3D打印机研究进展

当前传统熔融沉积成型(FDM)型3D打印机基本采用单喷头结构,这导致了打印速度相对较低和打印材料单一的问题,进而限制了其进一步应用。复合喷头-多材料FDM 3D打印机可以实现多材料复杂模型的3D打印,有效弥补了传统单喷头FDM型3D打印机在打印材料和打印速度方面的不足。首先,本文结合3D打印成型理论和3D打印机喷头结构设计,对比并简要分析了复合喷头-多材料FDM 3D打印机相对于传统单喷头3D打印机的创新之处。第二,总结了复合喷头-多材料FDM 3D打印机的基本结构分类。第三,深入探讨了不同结构下复合喷头-多材料FDM 3D打印机的研究进展,并针对具体应用场景详细阐述了其各自的优缺点。最后,对复合喷头-多材料FDM 3D打印机的未来发展趋势进行了总结与展望。复合喷头-多材料FDM 3D打印机在多材料应用、高效率打印及定制化服务方面展现了显著优势,并在新材料与新工艺的研发、机械稳定性和精度的提升,以及与人工智能技术的融合等方面仍具备广阔的发展空间,可极大促进3D打印技术的普及与应用。

熔融沉积技术增材制造先进陶瓷材料研究现状和发展趋势

熔融沉积技术增材制造先进陶瓷材料具有高效、低成本和粉体适应性广等突出优势。通过分析先进陶瓷材料增材制造代表性技术的适用范围及其局限性,然后基于线材和螺杆挤出两种熔融沉积技术的原理和特点,综述了熔融沉积方法在结构陶瓷、功能陶瓷、生物陶瓷和陶瓷基复合材料领域的研究进展。从机械臂辅助3D打印、打印过程的监控与缺陷控制和增材制造过程的计算模拟三个方面对熔融沉积技术的发展趋势和研究重点进行了展望。

FDM多工艺参数对PLA制件尺寸误差的影响

为探索熔融沉积快速成型技术(FDM)的工艺参数对聚乳酸(PLA)制件成型尺寸误差的影响规律,通过逆向数据采集方法对制件的长度误差、宽度误差、厚度误差进行测量对比,在4个单一工艺参数(外墙打印速度、外墙线宽、打印温度、打印层高)变化对尺寸误差影响分析的基础上,采用响应面法对筛选出的3个主要因素进行交互实验与分析。结果表明,长度误差受工艺参数的影响最大,其次是厚度误差,工艺参数对长度误差、宽度误差以及厚度误差的影响程度的排序均为:打印层高>打印温度>外墙线宽。

气体辅助对PLA/TPU/GF复合材料3D打印性能的影响

熔融沉积成型(FDM)是一种应用比较广泛的快速成型工艺,但生产出的热塑性产品存在力学性能差的问题。将气体辅助挤出与FDM技术相结合,利用高温高压气体对打印件表层进行瞬间加热促进层间黏结,从而提高制件的机械强度。制备了热塑性聚氨酯(TPU)和玻璃纤维(GF)共混改性聚乳酸(PLA)3D打印材料,对比了PLA改性前后流变性能的变化。分别研究了不同气体辅助参数,如气体温度、气体流量及气体压力对FDM制件拉伸性能和冲击性能影响。结果表明:GF和TPU改性的PLA相对于纯PLA非牛顿性更强,流变性能有所提升,有助于3D打印成型。在气体辅助条件下,FDM 3D打印成型的制件强度较无气体辅助时均有所提升,最高可提升116.1%。不同气体参数对FDM制件力学性能影响规律不同,其中气体流量对制件性能影响最大。综合考虑,当气体温度、体积流量及压力分别为250℃、0.8 L/min、0.4 MPa时,制件成型性能最佳。

熔融沉积型3D打印的翘曲现象研究

为研究聚乳酸(PLA)材料在熔融沉积型3D打印机中打印后的翘曲变形现象,通过单因素实验,研究了打印过程中打印底面面积与翘曲面积、高度与深度的影响规律,得出如下结论:打印底面面积较小时,由于受热均匀,无翘曲现象或现象不明显;打印底面面积较大时,翘曲面积、高度与深度也随之增大,但翘曲面积占比变化不大。

Indirect 3D printed ceramic:A literature review

Additive manufacturing(AM),also known as 3D-printing(3DP)technology,is an advanced manufacturing technology that has developed rapidly in the past 40 years.However,the ceramic material printing is still challenging because of the issue of cracking.Indirect 3D printing has been designed and drawn attention because of its high manufacturing speed and low cost.Indirect 3D printing separates the one-step forming process of direct 3D printing into binding and material sintering,avoiding the internal stress caused by rapid cooling,making it possible to realize the highquality ceramic component with complex shape.This paper presents the research progress of leading indirect 3D printing technologies,including binder jetting(BJ),stereolithography(SLA),and fused deposition modeling(FDM).At present,the additive manufacturing of ceramic materials is mainly achieved through indirect 3D printing technology,and these materials include silicon nitride,hydroxyapatite functional ceramics,silicon carbide structural ceramics.