Accuracy prediction in fused deposition modeling

Fused deposition modeling (FDM) is a common additive manufacturing (AM) technology able to fabricate physical prototypes directly from virtual model without geometrical complexity limitations. Initially used to create concept models to help product design stage, FDM developed as regard materials, accuracy, and the overall quality of the output improved, becoming suitable for end use. At present, it is employed in process chains to significantly shorten product development times and costs and to produce parts in small and medium batch. A critical drawback which inhibits its diffusion is the obtainable accuracy. Only few indications, relating the dimensional deviations, exist, and they are conflicting each other, not allowing a reliable prediction. In this paper, a geometrical model of the filament, dependent upon the deposition angle and layer thickness, has been developed in order to predict the obtainable part dimensions. The model has been validated by an experimental campaign. The specimens have been investigated by means of profilometer analysis in order to study macrogeometrical and microgeometrical aspects. Finally, a case study highlighted the reliability of the model. The direct implication of this work is the capability, in process planning, to know in advance if the FDM part dimensions will satisfy the specification and the component will fit with others. Moreover, this model can be employed to choose the suitable manufacturing strategy in order to comply with industrial constrains and scopes.     

Sloping wall structure support generation for fused deposition modeling

Support generation is a key technology for some rapid prototype manufacturing processes. A novel support structure with sloping walls, as well as its generation algorithm, based on the STL model, was designed and tested for fused deposition modeling process in this paper. Three different types of support structure are generated according to different overhang geometrical features. Compared to the generally adopted straight wall structure, this support structure significantly reduces the volume of support structure, hence optimizes the fabrication process. Experiments show that it assists the fabrication of parts well and reduces the support material consumption and processing (or fabrication) time by about 30%.     

Planar reinforcement by sheet type stiffeners for fused deposition modeling

Journal of Mechanical Science and Technology - This paper presents a planar reinforcement (PR) method for fused deposition modeling. In the proposed PR method, planar reinforcing parts, such as...     

熔融沉积快速成型工艺过程分析及应用

介绍熔融沉积快速成型技术的基本原理,分析成型工艺过程的技术特点。从机械系统和控制系统等主要组成部分论述了熔融沉积成型设备的整体构造。以一个深沟球轴承为研究案例,详细地论述了成型件的具体加工过程并在MEM320A快速成型机上加工出ABS材料的实物。最后,探讨了熔融沉积快速成型技术在产品设计、功能展示、样品制造和生物医学等领域的应用情况,同时展望了该技术在未来的发展前景。     

Process and material behavior modeling for a new design of micro-additive fused deposition

The aim of this paper is to explore the limits and special requirements for additive manufacturing using polymer extrusion with a nozzle diameter much smaller than the conventional one: 0.050 mm diameter. This work is focused on the nozzle design and analyzes the effect of such a reduced diameter on the extrusion process and on the cooling of material while being deposited on the part. The approach is based on experimental and theoretical studies starting from conventional fused deposition modeling technology where the study tested swelling and cooling of filament material during deposition. Experimental work was used to assess the validity of the theoretical model and the first normal stress equation which estimated a swelling factor (diameter) of 1.249 at 0.087 g/h mass rate. The convection coefficient (h) on the plastic part was estimated as7?W/m²?K on the first deposited layer; considerably lower than some references show.     

Optimization of fused deposition modeling process parameters for dimensional accuracy using I-optimality criterion

Fused deposition modeling (FDM) is one of the widely used additive manufacturing technologies because it has flexibility and ability to build complex parts. The accuracy of parts fabricated by FDM is greatly influenced by various process parameters. FDM process has a complex mechanism in building parts and often poses difficulty in understanding adequately how conflicting FDM parameters will determine part quality and accuracy. Sectors such as medical implant, telecommunication, electronics and aerospace require increasingly higher levels of dimensional accuracy. Thus, traditional methods of ensuring quality do not effectively address global markets and customer’s needs. This study proposes an I-optimality criterion for the optimization of FDM process parameters in order to address the limitations of the commonly used traditional designs. This study also aims to develop mathematical models in order to establish nonlinear relationship between process parameters and dimensional accuracy. The results show that I-optimality criterion is very promising technique in FDM process parameter optimization. Confirmation experiments show that the proposed method has great advantages in the aspect of both accuracy and efficiency compared with traditional methods proposed in previous studies.     

基于熔融沉积成型的一种近无支撑分体打印方法的研究

研究一种模型分解方法,以解决熔融沉积成型(Fused Deposition Modeling,FDM)过程中由于需要生成额外的支撑结构,从而导致打印物体表面质量不佳、材料浪费和打印时间长等问题.利用三自由度单喷头FDM打印机对选定的3种模型(人头、六面锥体和树袋熊)进行分体打印,验证了该模型分解方法的可行性.通过与传统整体打印工艺进行对比,基于该模型分解方法的分体打印工艺实现了近无支撑彩色打印,并且打印材料大幅减少,表面质量较传统整体打印工艺有很大改善.分体打印工艺对FDM技术真正实现高质量无支撑打印多悬垂结构物体具有极强的指导意义和参考价值.     

Process parameter optimization for fused deposition modeling using response surface methodology combined with fuzzy inference system

Fused deposition modeling (FDM) is gaining distinct advantages because of its ability to fabricate the 3D physical prototypes without the restrictions of geometric complexities, while when it comes to accuracy and efficiency, the advantages of FDM is not distinct, and so how to improve them is worthy of study. Focusing on process parameter optimization, such parameters as line width compensation, extrusion velocity, filling velocity, and layer thickness are selected as control factors, input variables, and dimensional error, warp deformation, and built time are selected as output responses, evaluation indexes. Experiment design is assigned according to uniform experiment design, and then the three output responses are converted with fuzzy inference system to a single comprehensive response. The relation between the comprehensive response and the four input variables is derived with second-order response surface methodology, the correctness of which is further validated with artificial neural network. Fitness function is created using penalty function and is solved with genetic algorithm toolbox in Matlab software. With confirmation test, the results are obtained preferring to the results of the experiment 1 with the best comprehensive response among the 17 experiment runs, which confirms that the proposed approach in this study can effectively improve accuracy and efficiency in the FDM process.     

Parametric optimization of fused deposition modeling and vapour smoothing processes for surface finishing of biomedical implant replicas

This study focuses on formulation of robust design for vapour smoothing, an advanced surface finishing technique for finishing ABS replicas where hot vapours tend to level the uneven surface asperities. The process parameters of combined Fused Deposition Modeling (FDM) and Vapour smoothing (VS) process are optimized for sustainability of ABS replicas for biomedical applications. Six input parameters have been investigated, two of FDM and four of VS processes while surface roughness and hardness of ABS part is taken as response. The vapour smoothing process ensue ultra smooth finish with negligible deterioration of upper surface deducing maximum contribution of smoothing time (51.07%) and number of cycles (40.08%) on surface roughness. Hardness of replica has been slightly increased by maximum impact of orientation angle (34.69%) and postcooling time (44.46%) of ABS replicas which endorsed the use of FDM replicas for investment casting of biomedical implants.     

Studies on profile error and extruding aperture for the RP parts using the fused deposition modeling process

Fused deposition modeling (FDM) is one of the leading rapid prototyping processes for producing acrylonitrile butadiene styrene prototypes. However, the extruding accuracy in part fabrication is subject to transmission machinery and filament diameter. The parts cannot be filled up completely. Therefore, profile error and extruding apertures are two substantial quality characteristics to be considered. This study proposed an original image measurement method for examining profile error through a series of standard cylinders laid on the contour of the part. Also, images captured can be used to identify non-filled regions on part appearance to calculate aperture area on the surface layer. Besides, this study investigated the effects of extruding parameters, including contour width, contour depth, part raster width, and raster angle, on quality characteristics by Taguchi??s method. A thin solid model based on a 2-D spiral was designed to demonstrate the proposed approach. Results of ANOVA and confirmation experiments showed that the parametric criteria concluded in this study could obtain satisfactory performances on profile error and extruding apertures in the FDM process.     

FDM快速成型技术中原理性误差分析

在全面分析FDM快速成型制件误差产生原因的基础上,着重分析了三角化过程及切片过程误差产生的原因.在三角化过程中,利用pro/E软件求出了不同弦差(ε)对应三角形数目.在切片过程中,分析了台阶效应产生的原因,并以四分之一的球体为例求出了阶梯误差(δ)的计算公式.最后提出了减小阶梯误差的方法,即斜切法、自适应切片法、直接切片法等.     

Electrical contact resistance for a conductive Velcro system

Conductive Velcro fasteners are employed as a joining material for various types of connections due to their detachable properties, especially when an electrical connection is established. Due to microscopic actual contact spots between the fibers and hooks in the Velcro joints, a large electrical contact resistance is established that could cause heat and potentially short-circuit. In this study, the electrical contact resistance behaviors in the conductive Velcro are estimated according to the electrical load, frequency and load amplitude. The wear behavior due to these effects is investigated after long exposure to dynamic loading under a specific frequency at a low load amplitude.     

Experimental validation of theoretical models for hypercube models made by fused deposition modelling technology

Journal of Mechanical Science and Technology - This paper aims to define theoretical model for sandwich core models such as core-fill and core-space models. These models are made of a polymer with...     

熔融沉积快速成形机的螺旋挤压机构设计

首次将螺旋挤压原理真正用于熔融沉积快速成形机，并借助流体动力学原理、实验数据和设计经验对螺旋挤压机构进行设计。对于螺旋挤压熔融沉积制造，在设计螺旋挤压机构时，必需要综合考虑最高压力、压力敏捷性、压力一致性、温度适应性、机构可靠性和成本等因素。在实际使用中验证了所设计的螺旋挤压机构完全达到设计预定目标。     

色母粒影响聚乳酸成型质量的实验研究

针对不同添加剂(色母粒等)的聚乳酸(PLA)材料,在熔融沉积式(FDM)打印机成型质量不同的问题上,对FDM打印机成型过程涉及的工艺参数进行归纳研究,提出了一种根据PLA添加剂(色母粒等)不同而进行调整FDM成型工艺参数的方法。基于材料力学的理论知识,建立了PLA材料成型过程的数学模型,选取了某厂家同批次的6种PLA材料,用正交试验方法验证了不同添加剂(色母粒等)的PLA材料对成型质量的影响。实验结果表明,添加剂色母粒对聚乳酸成型质量有较大影响,使用不同色母粒添加剂的聚乳酸时,必须适当调整成型工艺参数,以保证成型质量,并能够有效指导PLA材料在桌面版3D打印机的应用。     

Multi-index optimization design for electrical resistance tomography sensor

A multiple index optimization method for ERT sensors is put forward which combines an orthogonal design and fuzzy analysis. This method first establishes a scientific and proper fuzzy evaluation method using fuzzy mathematics to define ERT index satisfaction (ERTIS) and overall ERT index satisfaction (OERTIS) and to construct their satisfaction functions. It unifies all of ERT sensor indices into a single comparable satisfaction value. Then, the OERTIS analysis is developed which allows a set of multiple index orthogonal experiments to be transferred into a single index orthogonal experiment. Where, the uniformity index and the correlation coefficient index of the ERT sensor are set as the optimization objectives. The experiments are set up based on multi-index orthogonal design. The experimental results indicate that the method can derive an evenly distributed sensitivity field and a better image with the optimized sensors, and improve the OERTIS of the ERT sensors by 13.75%.     

面向机电产品方案设计的绿色特征建模

针对产品方案设计阶段缺少有效绿色设计理论方法和技术支持的问题,建立了基于绿色特征的机电产品方案设计阶段环境影响信息表达模型。提出了绿色特征的概念,对产品方案设计阶段的各种环境影响信息进行描述。提出基于绿色特征的方案设计阶段信息表达方法。通过绿色特征对绿色信息进行识别、筛选、提取和聚合,最终建立以绿色特征为基础的方案设计环境信息表达模型。以小型通用电机为例,验证了绿色特征的提取过程,并建立了该电机的环境信息表达模型。通过电机具体实例验证了该模型的正确性。     

基于PSpice的热式空气流量计发热电阻模型

简要介绍了热式空气质量流量计的原理,运用King热耗散方程对发热电阻的工作状况进行分析,得到流量计的基本方程.采用PSpice软件中的受控电源模型,建立了一个发热电阻的仿真模型.结合具体电路结构,从流量计基本方程中得出发热电阻的PSpice等效电路模型参数.针对仿真电路的启动特性进行了仿真,仿真结果与测试结果基本吻合.所建立的模型,适用于对电路参数进行修改测试,加快流量计电路设计进程.     

The compressive behaviour of ABS gyroid lattice structures manufactured by fused deposition modelling

Additive manufactured (AM) cellular structures have received much research attention due to their specific strength and energy absorption capabilities, and     

Image reconstruction algorithm for capacitively coupled electrical resistance tomography

Capacitively Coupled Electrical Resistance Tomography (CCERT), which is on the basis of Capacitively Coupled Contactless Conductivity Detection (C⁴D), is a novel electrical tomography technique. As a developing technique, more research work should be undertaken. This work focuses on the study of image reconstruction algorithm of CCERT. Combining Tikhonov regularization principle and Simultaneous Iterative Reconstruction Technique (SIRT), a new hybrid image reconstruction algorithm is proposed. Tikhonov regularization is introduced to obtain the initial reconstructed image. SIRT is used to obtain the final reconstructed image. With a 12-electrode CCERT prototype, image reconstruction experiments are carried out. Experimental results show that the images reconstructed by the proposed image reconstruction algorithm are satisfactory and are in accord with the actual distributions of two-phase flows. The research work also indicates that the proposed image reconstruction algorithm is more suitable for image reconstruction of CCERT, comparing with the conventional image reconstruction algorithms of Electrical Capacitance Tomography (ECT) and Electrical Resistance Tomography (ERT).