Development and Evaluation of Recycled Polypropylene and Bean Pod Powder Composite Biomaterial for Fused Filament Fabrication

Approximately 450 million tons of plastic and agricultural waste are produced each year in the world. Only a small portion of this plastic waste is recycled, and a small portion of this agricultural waste is used as fuel or fertilizer, and the rest of this waste is left in the environment or is burned, resulting in environmental and air pollution. For proper disposal, plastic and agricultural waste can be used in the manufacture of composites as raw materials. In this study, we had evaluated the use of bean pod powder (BPp) was used as natural reinforcing filler in recycled polypropylene (rPP) based composites. BPp/rPP composite filaments were developed using the extrusion method and the samples were printed by Fused Filament Fabrication (FFF). Composites with rPP matrix containing different weight fractions of BPp (5%, 10% and 15%) were fabricated to observe and compare the mechanical properties (tensile, flexural, and compressive strength) of the filament composites. In addition, the filament surface was analyzed for roughness and particle size of bean pod powder. The results established that BPp/rPP composites exhibited better tensile, flexural, and compressive strength than rPP and pure PP. By adding 5 wt% BPp, the tensile strength of rPP increased from 20.4 MPa to 22.8 MPa. The highest flexural strength (15.05 MPa) was obtained at 5 wt% BPp among all composites and the highest compressive strength (24.5 MPa), was obtained at 10 wt% BPp. Therefore, it can be concluded that by carefully selecting the ratio of BPp to bean pod powder, it is therefore possible to positively influence the mechanical properties of the resulting composite.

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

Intense supercontinuum generation in the near-ultraviolet range from a 400-nm femtosecond laser filament array in fused silica

An intense supercontinuum（SC） in the near-ultraviolet range is generated from filamentation by focusing a 400-nm laser into fused silica with a microlens array（MLA）. The spectrum of the SC is shown to be sensitive to the distance between the MLA and fused silica. In our optimal conditions, the near-ultraviolet SC can cover a range of 350-600 nm,where a bandwidth of approximately 55 nm above the 1μJ/nm spectral energy density and 20 nm bandwidth with tens ofμJ/nm are achieved. In addition, the energy conversion efficiency of the 400 nm laser for SC generation is further analyzed.A maximum conversion efficiency of 66% is obtained when the entrance face of fused silica is set around the focus of the MLA.

Recycled, Bio-Based, and Blended Composite Materials for 3D Printing Filament: Pros and Cons—A Review

In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.

熔丝制造3D打印CFRP层内损伤破坏机理与模型研究

为将3D打印技术应用到桥梁工程中,以熔丝制造3D打印碳纤维复合材料锚环为研究对象,开展了材料层内损伤失效机理的基础性研究工作.首先,对锚环进行了张拉锚固破坏试验,明晰材料的损伤失效模式.其次,测试分析了材料的弹性参数及强度参数值,供后续仿真分析使用.最后,通过VUMAT子程序构建了材料的损伤失效本构关系,利用ABAQUS仿真分析软件模拟熔丝制造3D打印碳纤维复合材料锚环的渐进损伤失效全过程,分析其层内损伤失效机理.结果表明:熔丝制造3D打印碳纤维复合材料具有显著的层内损伤现象;选用Hashin损伤起始判据与刚度瞬间退化模型作为熔丝制造3D打印碳纤维复合材料损伤力学模型偏于安全,具有一定的可行性;锚环在高度方向产生纵向裂纹是由纤维拉伸失效导致的.

安全高效钻探用梯度结构金刚石复合片制备技术研究

在油气钻井、深部地层钻探中,聚晶金刚石钻头有着广泛的应用。聚晶金刚石复合片(PDC)由聚晶金刚石层与硬质合金基体所组成。由于聚晶金刚石层与硬质合金基体的热膨胀系数等性质差异,PDC在烧结冷却后内部会存在巨大的残余应力。为降低PDC内部的残余应力,本文提出了一种梯度结构金刚石复合片的制备技术。通过以熔融沉积成型加烧结的工艺方法,确定了梯度结构金刚石复合片的制备技术路线;对制备出的梯度结构金刚石复合片的微观形貌及残余应力的分布情况特征等进行分析;进行室内钻进试验验证了梯度结构金刚石复合片的钻进性能。结果表明,熔丝制造工艺制备的梯度结构金刚石复合片在聚晶金刚石层和梯度层界面处存在1.4 GPa的压应力,显著提高了层间结合能力,相比常规复合片钻进效率提升约36%且使用寿命更长。

工艺参数对FFF制造碳纤维增强尼龙零件力学性能的影响与预测

以熔丝制造(FFF)技术加工了碳纤维增强尼龙零件,采用田口试验设计研究了填充图案类型、填充密度、层高和打印方向对零件拉伸强度的影响,利用径向基网络(RBF)预测了不同工艺条件下零件拉伸强度。基于信噪比分析发现,在研究的4个试验因素中,填充密度对零件拉伸强度的影响最显著,其他因素的影响有如下顺序:打印方向>层高>填充图案类型。熔丝制造最优参数水平组合为:填充密度100%,打印方向0°,层高0.1 mm,填充图案类型六边形,在最优参数组合下,零件拉伸强度试验值为114.09 MPa,高于方差分析的回归方程预测值(108.18 MPa)。当径向基网络中隐含层神经元个数为56时,预测零件拉伸强度的均方误差(MSE)最低,为0.003 2,预测最优参数组合下零件拉伸强度为113.24 MPa。径向基网络预测值与试验值的MSE为0.46,回归方程预测值与试验值的MSE则达到20.01,表明径向基网络预测熔丝制造技术加工的零件拉伸强度更准确。

工艺参数对聚乳酸线材熔融沉积尺寸的影响

熔融沉积(FDM)成型中线材直径的变化对打印精度有重要影响。文中利用实验和数值模拟方法研究了单根聚乳酸线材FDM过程中从喷嘴挤出到沉积固化各阶段的直径变化。根据FDM工艺特点及材料性能,量化分析了工艺参数(喷嘴温度、挤出速度、打印速度、层高)对线材喷嘴附近、挤出胀大阶段、拉伸阶段、沉积阶段直径的影响,并推导了打印过程中线材沉积固化时直径的估算公式。研究表明,提高喷嘴温度、增大挤出速度、减少层高可有效改善打印过程中线材的尺寸稳定性,提高打印件的精度。最后,利用沉积固化时的直径公式,完成了线材直径补偿“精度实验”,补偿后打印制品尺寸精度提高了74.1%。

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.

利用不同波形振动加工的熔丝成型制品表面质量研究

熔丝成型(fused filament fabrication,简称FFF)是目前应用最广泛的增材制造技术之一,能够制造几乎任意几何形状的实体模型。然而,逐层累加的制造工艺使得FFF制品的表面质量存在明显的局限性,为此提出利用不同波形振动改善FFF制品表面质量的方法。完成了振动式FFF设备的改装,并制备了利用不同形式的振动(正弦波、方形波和三角波)加工的制品样件。利用激光显微镜完成了FFF样件表面粗糙度的实验研究,确定了不同振动波形对表面粗糙度的影响规律。基于结合颈成型过程,建立了利用不同波形振动加工的FFF制品表面粗糙度理论模型。通过对比分析理论与实验结果,验证了所建模型的正确性,阐明了利用不同波形振动改善FFF制品表面质量的机理。

面向喷头空行程长度最小化的多零件优化布局方法

多零件在打印腔室中的布局往往直接影响熔融沉积批量制造的效率和能力。同时,喷头空行程长度对上述效率和能力具有显著的影响。为此,提出了一种面向空行程最小化的多零件优化布局方法,通过优化地减少零件之间喷头的空行程长度来提升熔融沉积批量制造的效率以及打印腔室可容空间。首先,为兼顾空行程长度计算的效率(如加速几何干涉检测)和计算的准确度,以层厚为基准,构建每个零件相应的、逐层堆叠的体素代理模型。然后,基于贪心策略和粒子群优化算法,以逐对累积的方式确定每个体素代理模型的放置顺序和放置位置。最后,将体素代理模型置换为对应的零件,获得输入零件集紧凑的布局。在一组形状复杂的零件集上开展实验。结果表明:在相同的衡量标准下,该方法相比于Magics空行程总量约减少了31.17%。与现有的商业化软件中的布局功能相比,该方法在实施批量制造形状复杂零件集时具有可显著减少喷头空行程长度总量的巨大潜力。

基于CCD传感器的3D打印进给误差补偿系统

熔融沉积(FDM)3D打印机通过将丝状耗材融化堆积成型,当打印耗材直径发生波动时,机器本身并不能动态调整,而是继续工作直到打印结束。针对FDM打印过程中耗材误差进行研究,提出一种基于CCD传感器的进给检测系统。使用CCD传感器模块对打印过程中的耗材直径进行测量,然后将测量值和理论值对比,实现动态调整进给量,提升打印质量。为验证检测系统的可行性,搭建了实际的测试平台,选择PLA耗材(标准直径1.75 mm)进行实验。结果表明,该检测系统对打印质量有明显的提升效果,且整体成本较低。

基于支持向量回归的熔丝制造3D打印能效优化模型

基于响应面法和支持向量回归模型对熔丝制造3D打印能效进行预测与优化。首先,利用田口方法设计六因素三水平正交试验,通过响应面法分析得出对加工能效影响较为显著的3个因素即层高、打印速度和热床温度;然后,通过支持向量回归方法建立加工能效预测模型,并与BP神经网络方法进行对比,结果表明支持向量回归方法建模预测性能更优;最后,建立以加工时间和能效为目标的优化模型,利用NSGA-Ⅱ、MOEA/D、SPEA2和MOPSO 4种算法分别对模型进行求解,分析比较4种算法的Pareto前沿,结果表明NSGA-Ⅱ算法在求解此问题时综合表现最佳,对比NGSA-Ⅱ算法求得的优化结果与试验结果可知,NSGA-Ⅱ算法具有有效性和合理性。

台式扫描电子显微镜钨灯丝的熔断分析及维护

对近两年来已熔断的不同使用寿命的钨灯丝进行对比总结,发现在有效长度基本一致的情况下,使用寿命长的钨灯丝发叉处的夹角比使用寿命短的大;而且相比未使用的钨灯丝的微观形貌,使用后的钨灯丝的表面产生了很多褶皱。结合多年来的管理和维护实践,提出了台式扫描电子显微镜延长钨灯丝使用寿命的方法,对提高扫描电子显微镜的开放共享具有借鉴意义。

FDM工艺过程中丝材的粘结机理与热学分析

分析了熔融堆积成形(FDM)工艺中挤出丝材的温度随时间、路径的变化规律,通过对丝材物理模型的合理假设,建立了挤出丝材温度场的数学模型,并根据Stratasys商用机FDM2000所使用的ABS-P400丝材的热学参数,结合聚合物的粘结机理,验证了模型的合理性.

FDM工艺出丝过程影响因素分析

介绍了FDM工艺的送丝出丝过程以及与此有关的脉冲发生器和步进电动机驱动器 ,阐述了送丝速度、螺杆转速和挤出速度三者之间的关系 ,通过实验给出了挤出速度的实测值。最后着重分析出丝过程的影响因素 ,说明各因素间的合理组合对正常出丝的重要性。

熔丝成型制品三维表面粗糙度的理论与实验研究

熔丝成型(fused filament fabrication,FFF)是通过挤出材料丝相互堆积、累加形成三维实体的一种增材制造技术,而逐层累加的制造工艺使得FFF制品的表面质量存在明显缺陷.为提出有效的改进措施,需明确FFF制品表面粗糙度的产生机理.基于结合颈成型过程,以材料丝表面轮廓为研究对象,创建了基于横、纵两向结合颈垂直/平行于纤维方向的表面粗糙度数学模型.制备FFF样件,利用激光显微镜获取样件表面粗糙度.理论与实验结果验证了模型的正确性,为FFF制品表面质量的改进与提高提供了理论依据和技术支持.

3D打印PC/ABS合金的性能

以马来酸酐接枝ABS树脂(ABS-g-MAH)为增容剂,制备聚碳酸酯(PC)/丙烯腈–丁二烯–苯乙烯塑料(ABS)合金,对其力学性能、热性能及熔体流动性等进行了研究,结果表明,当该合金质量比PC∶ABS∶ABS-gMAH=70∶30∶6时,PC/ABS合金的缺口冲击强度为33.92kJ/m^2,远高于纯PC与其它配方合金的缺口冲击强度,且其它性能较好。采用3D打印耗材挤出机将纯PC及PC/ABS合金制成丝材,PC丝材直径为(1.75±0.27)mm,PC/ABS合金丝材直径为(1.75±0.05)mm,PC/ABS合金的尺寸稳定性得到很好地改善。研究两种丝材的熔融沉积成型(FDM)性能以及打印方向对试样力学性能的影响。结果表明,当采用FDM工艺水平向和侧向打印时,试样的力学性能超过注塑工艺成型试样,但是竖向打印试样力学性能较差。与纯PC打印试样相比,PC/ABS合金试样的缺口冲击强度得到大幅提高,侧向打印PC/ABS合金的缺口冲击强度为40.13kJ/m^2,而侧向打印纯PC的缺口冲击强度仅5.73kJ/m^2。

振动场下FFF热熔喷头内熔体表观黏度的理论研究

热熔喷头内部熔体的表观黏度是影响熔丝制造成型(FFF)产品机械性能的关键因素之一.本文首先提出利用振动改善FFF热熔喷头内部熔体表观黏度的方法,即对喷头施加纵向的正弦振动力场;然后针对施加振动后热熔喷头内部熔体的表观黏度进行了理论建模,并利用已有文献中的实验结果验证了理论模型的正确性;最后,利用所建模型探讨了施加不同频率振动后熔体表观黏度的变化规律,阐明了相应机理.研究表明:熔体表观黏度的理论与实验结果吻合度较好,理论模型正确;对热熔喷头施加振动场后,熔体表观黏度有效值随着振动频率的增大而逐渐降低.

熔丝成型薄板表面粗糙度理论模型与实验验证

针对熔丝成型(fused filament fabrication,FFF)产品的表面质量缺陷问题,提出了一种FFF产品表面粗糙度的理论建模方法.以材料丝表面轮廓为研究对象,考虑样件表面的实际情况,分别建立了FFF产品垂直和平行于纤维方向的表面粗糙度理论模型;与此同时,利用激光显微镜完成了相关样件表面粗糙度的实验研究;通过对比理论分析与实验结果,验证了所建模型的正确性;理论模型的敏感性分析研究表明,增大挤出宽度或打印层厚度会增大FFF产品的表面粗糙度,而增大重叠区域宽度则会降低表面粗糙度.