Effect of printing parameters on properties of 3D printing sand samples

Three-dimensional sand printing(3DSP)is widely applied in sand mold fabrication.In this study,the effects of printing parameters including the resolution of printehead holes,activator content,layer thickness,and recoating speed on the tensile and bending strengths,gas evolution,and loss-on-ignition(LOI)of 3DSP samples were investigated by changing single parameter,and the dimension deviation was also measured.As the resolution increases,the tensile strength,bending strength,gas evolution,LOI,and deviations at X-and Y-axis directions decrease gradually while the deviation at Z-axis direction firstly increases and then deceases.The gas evolution and LOI drops by 13.02%and 8.13%respectively,but the strength only reduces by 2.2% when the resolution increases from 0.08 mm to 0.09 mm.The strengths of samples rise at first and then decline while the gas evolution and LOI rise gradually with the increasing activator content or recoating speed.The activator content is found to have little effect on the gas evolution as the activator increases from 0.14%to 0.34%,the gas evolution is increased by 7.3%which is far less than the LOI increment of 24.1%.As the layer thickness increases,the tensile and bending strengths firstly rise and then drop while gas evolution and LOI descend.Under the optimal printing parameters of 0.09 mm resolution,0.18%activator,-10.28 mm layer thickness and 160 mm·s^(-1) recoating speed,the tensile strengths for X-sample and Y-sample are 1.48 MPa and 1.37 MPa,the bending strengths are 1.84 MPa and 1.75 MPa,the gas evolution and LOI are-19.62 mL·g^(-1) and 1.92%,respectively.

The Effect of Printing Parameters and Wood Surface Preparation on the Adhesion of Directly 3D-Printed PLA on Wood

As additive manufacturing technologies advance,new opportunities are opening up for their application in the furniture industry.Wood remains one of the leading raw materials in the furniture industry;therefore,possible options for combining it with 3D printing have been researched.The bonding of 3D-printed polymer parts with wood or 3D printing with wood-plastic composites is already known,but in our research we attempted to directly 3D print polylactic acid(PLA)on wood surfaces.The effect of printing parameters,as well as the surface preparation of wood on the shear strength of the bond between wood and on-printed material was tested.Microscopic images of cross-sections of samples were analyzed.The results show that with a lower initial layer thickness(0.1 mm),a higher printing temperature(220℃),and with the use of polyvinyl acetate(PVAc)primer on the wood surface before 3D printing,a higher bond strength(5.4 MPa)was achieved,but the values for the bond strength remain low compared to the conventional bonding of wood to wood with PVAc adhesive(around 10 MPa).Microscopy studies revealed barely visible penetration of PLA into the lumens of the wood cells.However,the PVAc adhesive used as primer penetrated more into the cell lumens and served as interface layer between deposited melted PLA and the wood,thus creating stronger joints.

NURBS体参数化模型的无支撑打印算法

处理大角度悬垂结构的打印问题是无支撑打印的主要挑战。针对NURBS(non-uniform rational B-spline)体参数化模型的多自由度无支撑三维打印技术,提出一种锥形切片算法。通过对模型的三维文件进行几何映射,利用水平切片算法对其进行切片,得到模型变形后的连续打印路径G-code;然后对得到的G-code进行逆映射,生成适用于六轴机械臂的多自由度连续打印路径。利用锥形切片算法规划打印路径,可以在无须支撑的情况下,依靠自支撑结构实现对悬空结构部分的打印。最后,通过仿真实验和对比实验,验证了锥形切片算法的准确性、可行性和有效性。锥形切片算法的引入为NURBS体参数化模型的无支撑三维打印提供了一种更加高效、经济和环保的解决方案。

多材料微流挤出3D打印喷头优化设计

为了满足微流挤出工艺陶瓷3D打印机连续打印多材料以及均匀混合的要求,设计了变内径螺杆挤出式3D打印机挤出混料新结构,不仅可以实现高固含量浆料在喷头内部单向输送,同时通过变内径螺杆旋转搅拌使两种材料混合均匀。通过Ansys响应面优化,在挤出头段以最小压力实现最大面积加权平均速度为目标函数,实现在低功耗高输出的不同需求下匹配不同挤出速度;在螺杆段以优化最大剪切速率为目标函数,实现两种陶瓷浆料的均匀混合。结果表明,通过参数化优化后可以在螺杆低转速与小型化的要求下,实现不同小流率高精度打印及两种材料的均匀混合。

Study of the Mechanical Properties of 3D-printed Onyx Parts: Investigation on Printing Parameters and Effect of Humidity

Recently,an increasing number of parts have been produced using additive manufacturing technology.They are no longer simply prototypes but structural parts whose mechanical characteristics must be known before printing.One of the weaknesses of 3D printing is the significant variability in the dimensions and geometrical and mechanical properties of the printed parts.These properties depend on specific printing parameters and environmental conditions.This study aims to determine the influence of two printing parameters,namely,the orientation and positioning of the parts on the printing platform and the influence of humidity on the mechanical properties of the parts.The studied samples were fabricated with onyx using a Markforged X7 printer.The results showed that onyx could be considered an isotropic material to a certain extent because its mechanical properties do not vary sufficiently according to the orientation angle on the printing platform;a maximum deviation of 10%was observed between the different orientations.In contrast to the orientation,the positioning(flat or XY,on-edge or XZ,and upright or ZX)of the workpieces significantly influenced the mechanical properties.Positioning on the edge allowed the Young’s modulus to be up to 50% greater than that of flat and upright positioning.The study of the sensitivity to humidity revealed that a specimen absorbs approximately 2%of the humidity and loses up to 65%of its Young’s modulus after 165 days of exposure,significantly influencing the mechanical properties of the parts.Consideration should be given to this aging of onyx when using printed parts as structural parts.

Geometric quality evaluation of three-dimensional printable concrete using computational fluid dynamics

The importance of geometrical control of three dimensional(3D)printable concrete without the support of formwork is widely acknowledged.In this study,a numerical model based on computational fluid dynamics was developed to evaluate the geometrical quality of a 3D printed layer.The numerical results were compared,using image analysis,with physical cross-sectional sawn samples.The influence of printing parameters(printing speed,nozzle height,and nozzle diameter)and the rheological behavior of printed materials(yield stress),on the geometrical quality of one printed layer was investigated.In addition,the yield zone of the printed layer was analyzed,giving insights on the critical factors for geometrical control in 3D concrete printing.Results indicated that the developed model can precisely describe the extrusion process,as well as the cross-sectional quality.

非均质NURBS体参数化模型的AMF通用文件生成方法

针对非均质NURBS (Heterogeneous Non-Uniform Rational B-spline,简称HNURBS)体参数化模型的三维打印技术,给出了三维打印通用AMF(Additive Manufacturing File Format)文件生成方法。用灰度值代表材料信息,通过含有灰度信息的控制点构建HNURBS体参数化模型,实现材料信息连续可视化表达;根据NURBS体参数模型细分方法得到等参线网格单元,对等参线网格单元进行三角网格划分和材料插值计算,得到用于AMF文件生成所需的三角形网格单元。结果表明,输出的AMF格式文件可供三维打印软件AMFtools读取和显示。

羊绒织物仿齐针绣数码印花图案参数设计

对传统齐针绣图案进行深入研究,总结肌理特点及适合羊绒织物数码印花的花型和图案。运用Wilcom ES软件对刺绣图案进行基础参数化设计,并在此基础上运用Photoshop软件对刺绣图案的对比度、强化边缘、透明度等各项指标进行参数优化设计,总结出适合于羊绒数码印花仿真齐针绣肌理各项参数的最优取值范围。运用参数优化方案设计的刺绣图案在羊绒织物上进行数码印花实验,验证羊绒数码印花高清仿真齐针绣图案快速、便捷、高效印制的可行性。

模切机传纸机构驱动凸轮参数化设计

运用MATLAB强大的可视化编程功能,针对模切机传纸机构中的关键零件—凸轮进行了参数化设计计算,得到了驱动递纸牙按照规定的轨迹运动的2个凸轮轮廓轨迹曲线,并检验了凸轮压力角,以验证传纸机构的合理性。当需要进行机构的某方面调整时,可以利用修改凸轮个别参数从而非常方便的进行更新,大大提高了机构设计的调整适应性,提高了快速设计产品的进程。

Effects of FDM-3D printing parameters on mechanical properties and microstructure of CF/PEEK and GF/PEEK

Fused deposition modeling(FDM)has unique advantages in the rapid prototyping of thermoplastics which have been developed in diverse fields.However,although great efforts have been made to optimize FDM process,the mechanical properties of printed parts are limited by the weak interlamination bonding as well as the poor performance of raw filaments used,such as acrylonitrile butadiene styrene(ABS),polylactic acid(PLA).Adding fibers into thermoplastic matrix and preparing high-performance filaments have been indicated to enhance the properties of fabricated parts.Recently,heat-resistant polyetheretherketone(PEEK)and its fiber reinforced composites were proposed for FDM process due to overcoming the limitation of equipment and process.However,few researches have been reported on the effects of FDM-3 D printing parameters on the mechanical properties of fiber reinforced PEEK composites.Therefore,5 wt%carbon fiber(CF)and glass fiber(GF)reinforced PEEK composite filaments were prepared respectively in this study.The effects of various printing parameters including nozzle temperature,platform temperature,printing speed and layer thickness on the mechanical properties(including tensile strength,flexural strength and impact strength)were surveyed.To analyze the microstructure and failure reasons of printed CF/PEEK and GF/PEEK samples,the tensile fractured surfaces were investigated via scanning electron microscope(SEM).

基于3D打印技术的服饰品造型创意设计研究

3D打印技术作为服装行业的新兴科技,在服饰品造型、结构、材料设计等方面都有广阔的发挥空间。本研究以3D打印技术为依托,进行服饰品造型创意设计,通过分析3D打印技术在服饰品应用中的可行性,结合参数化设计方法,进行服饰品造型创意设计。运用SLS选择性激光烧结技术和尼龙粉末进行3D打印实验,通过成品分析服饰品造型创意设计的方法和效果。研究表明,在参数化设计方法的辅助下,运用SLS成型技术和尼龙粉末能够制造出繁复立体的空间结构,适合于创意、未来风格的服饰品设计。3D打印技术的应用为设计者提供了较大的创作空间,缩短了服饰品设计研发的流程,提高了创新设计的效率。

用于印字模切机的控制式差动无级变速器的结构研究及虚拟装配

印字模切机需要印字辊和模切棍能适用于多种模板的印制,这就需要很灵活的调速和变速范围,因此将控制式差动无级变速装置结合到印字模切机中,利用控制式差动无级变速装置的调速优点来达到所需效果。在无级变速装置的结构分析与设计过程中,利用Pro/E软件建立虚拟装配,来检验各主要参数的准确性及合理性,实现参数化设计,提高工作效率。

基于参数化与3D打印的智能陪护机器人设计

为了帮助医护人员减轻工作量和给予患者优质服务,采用参数化设计方法与3D打印技术进行智能陪护机器人设计。根据用户需求提出智能陪护机器人设计方案,规划机器人的组成与具体功能;利用“Rhino+Grasshopper”组成的参数化设计平台进行参数化逻辑建立与优化;对比分析熔融沉积成型、选择性激光烧结、光固化成型技术适用的产品类型并对比各项工艺的优势与劣势,选用熔融沉积成型技术打印出实体模型进行验证,为智能陪护机器人设计提供参考。