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Publication Date: 2025
Progress in Additive Manufacturing (23639520)
Extrusion-based additive manufacturing of thermosets and short fiber-reinforced thermoset composites is a challenging task and remains, despite recent advances, unable to fully leverage the entire design freedom offered by state-of-the-art technology due to low viscosity and solidification way of ink. This study introduces an enhanced direct ink writing (DIW) technique for effectively printing thermoset resins and corresponding short glass fiber-reinforced composites, achieved without adding any rheological modifiers and using ultraviolet (UV) curing. The proposed method utilizes time-dependent rheological control to enhance the ink's properties, offering a cost-effective and experimentally simplified approach. Experimental results suggest that the raster angle had no substantial effect on the mechanical properties, or in other words, the printed specimens behave like an isotropic material. To achieve maximum tensile properties, the ink parameters, such as fiber weight fraction, mixing time, and mixing speed, were optimized using the Taguchi design of experiment. The results showed a strong correlation between predicted and observed values, confirming the efficacy of the approach. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Publication Date: 2024
pp. 213-233
Additive manufacturing (AM) technology of thermoset polymer composites has great potential to address the disadvantages of widely used thermoplastic resins in terms of processing, cost, modification of compound formulation, dimensional stability, and stress crack resistance. Whilst there are other AM processes for thermoset polymer composites, the two most common techniques; VAT photopolymerization and extrusion-based methods are discussed. This chapter deals with the basics of these two technologies and attempts to describe the limitations and advantages of each. In particular, the key features and challenges regarding both techniques are presented. Furthermore, common materials available for thermosetting AM systems are described in combination with the 3D printing of fiber-reinforced polymer composites. A description of the important parameters that enhance the performance of printed parts is provided. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.
Publication Date: 2024
International Journal of Advanced Manufacturing Technology (02683768) 132(3-4)pp. 1827-1842
A simple and inactive structure is able to transform into a complex and active one via four-dimensional (4D) printing. Controlling bending deformation, activation time, and temperature is crucial in 4D printing. This study aimed to comprehensively evaluate and analyze the effect of different process parameters on the bending deformation of polylactic acid (PLA) shape-morphing produced by material extrusion additive manufacturing. These parameters included layup, layer thickness, printing speed, nozzle temperature, nozzle diameter, and bed temperature. Since the bending deformation is significantly affected by the specimen wall, this study has focused, for the first time, on the simultaneous influence of process parameters and presence of a wall on the deformation. Furthermore, the study examined the influence of printing parameters on activation time and activation temperature. The results indicated that increasing the pre-strain stored in the parts led to a decrease in activation time and activation temperature. Subsequently, the Taguchi design of experiment method was used to optimize the most influential parameters on the bending deformation. The difference between the optimal predicted and the experimental deformations was less than 2%. Layer thickness, layup, nozzle temperature, and printing speed were recognized as the most effective parameters for controlling deformation, respectively. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.
Publication Date: 2023
Composites Part A: Applied Science and Manufacturing (1359-835X) 171
Additive manufacturing (AM) has a great potential to create complex parts and systems lighter and stronger compared to traditional manufacturing operations. So far, several polymeric materials including different types of thermoset polymers and recently fiber reinforced thermosetting composites have been used in different additive manufacturing processes. Printed parts have shown an enhanced performance compared to their counterparts made by conventional techniques. This review article presents the state-of-the-art in the field of polymer-based additive manufacturing processes employed for thermoset resins, their corresponding fiber reinforced composites, main process parameters, build strategies, and their effects on the mechanical behavior of printed parts. This paper enlightens the basics of material extrusion, vat photopolymerization, and hybrid AM processes. In particular, these techniques involve Direct Ink Writing (DIW), Frontal Polymerization (FP), Reactive Extrusion (RE), In-bath print and cure (IBPC) that fall under extrusion-based AM system, and Stereolithography (SLA), Digital Light Processing (DLP) falling under vat photopolymerization AM. © 2023 Elsevier Ltd
Publication Date: 2022
International Journal of Adhesion and Adhesives (01437496) 118
Various geometric and material parameters such as adhesive thickness, adhesive overlap, adherend thickness, and composite layup may affect the strength of the joint under quasi-static loading and failure mode of bonded composite-to-composite single-lap joints (SLJs) and are investigated by previous studies. The study herein broadens these findings by looking into the effect of lamina fiber angle adjacent to the adhesive layer on the damage initiation and evolution in detail. In this regard, a composite-to-composite adhesively bonded SLJ with adherends made of E-glass/epoxy composites and [04//θ/03] (where//shows the adhesive location) layups are manufactured and tested under quasi-static tensile loading. The adhesive type is semi-flexible Araldite 2015. Experimental results show that by increasing the fiber angle from 0° to 90°, the shear stress in the adhesive layer is decreased while the peel stress is increased. In examining typical fracture interfaces for each layup configuration, a full description of failure mode assessment is obtained. In particular, the SLJ is modeled in Abaqus using cohesive elements with bilinear traction-separation law. Numerical results indicate that the bilinear cohesive law cannot model the exact load-displacement curve due to semi-flexible behavior of the epoxy adhesive, but it can predict maximum strength precisely. The failure of composite joints is significantly influenced by shear stress. © 2022
Publication Date: 2021
Journal of Manufacturing Processes (15266125) 67pp. 12-22
Precision injection molding of high performance components requires primary error sources affected the molded component to be identified and isolated such that these errors can be reduced if needed. To systematically isolate and quantify the contribution of misalignment, thermal variation and component warpage to the accumulated error observed on the component, a methodology is presented and tested around an existing mold which produced parts with high dimensional variability. The mold featured two concentric guide pillars on opposite sides of the parting plane and rectangular centering block elements at three locations. Mold displacements at the parting plane were measured through the incorporation of three eddy-current linear displacement sensors. Thermal error sensitivity was investigated using FEM simulations such that the induced variability from thermal expansion and filling phase was identified and quantified. Finally, molded component warpage was isolated and quantified, again by the means of FEM simulation. The results were confirmed by using the mold on two injection molding machines to produce an array of parts whose key dimensions were measured. © 2021 The Society of Manufacturing Engineers
Publication Date: 2019
Applied Sciences (Switzerland) (20763417) 9(19)
This paper introduces two new deposition-strategies for five degrees of freedom (5DOF) and 6DOF extrusion-based additive manufacturing (AM), called the tool path projection- and parent-child-approach, respectively. The tool path projection method can be automated, and allows for the generation of concentric shells layers, which remedy geometrical deviations (known as the stair-case effect) that are typically seen in 3DOF AM processes that potentially require secondary post treatment by machining or grinding of the final part. In the parent-child approach, the designer specifies the manufacturing direction for each distinct feature, thereby helping to remove the need for support material, as well as enabling new features to be dynamically added to the part. © 2019 by the authors.
Publication Date: 2018
Precision Engineering (01416359) 52pp. 201-210
Tolerance analysis provides valuable information regarding performance of manufacturing process. It allows determining the maximum possible variation of a quality feature in production. Previous researches have focused on application of tolerance analysis to the design of mechanical assemblies. In this paper, a new statistical analysis was applied to manufactured products to assess achieved tolerances when the process is known while using capability ratio and expanded uncertainty. The analysis has benefits for process planning, determining actual precision limits, process optimization, troubleshoot malfunctioning existing part. The capability measure is based on a number of measurements performed on part's quality variable. Since the ratio relies on measurements, elimination of any possible error has notable negative impact on results. Therefore, measurement uncertainty was used in combination with process capability ratio to determine conformity and nonconformity to requirements for quality characteristic of a population of workpieces. A case study of sheared billets was described where proposed technique was implemented. The use of ratio was addressed to draw conclusions about non-conforming billet's weight expressed in parts per million (ppm) associated with measurement uncertainty and tolerance limits. The results showed significant reduction of conformance zone due to the measurement uncertainty. © 2017 Elsevier Inc.
Publication Date: 2017
pp. 297-298
Injection moulding is characterized by high precision requirements. In particular, the demands regarding the mould plates alignment are in order of few micro meters. This research introduces a methodology to measure the misalignment in injection moulding. Eddy current sensors are used in the system to perform measurements for a whole cycle. In a long run of the mould, a comparison of mould deviation between the first and the last cycles is obtained.
Publication Date: 2016
Materials and Design (0264-1275) 104pp. 276-283
Additive manufacturing is rapidly developing and gaining popularity for direct metal fabrication systems like selective laser melting (SLM). The technology has shown significant improvement for high-quality fabrication of lightweight design-efficient structures such as conformal cooling channels in injection molding tools and lattice structures. This research examines the effect of cellular lattice structures on the strength of workpieces additively manufactured from ultra high-strength steel powder. Two commercial SLM machines are used to fabricate cellular samples based on four architectures— solid, hollow, lattice structure and rotated lattice structure. Compression test is applied to the specimens while they are deformed. The analytical approach includes finite element (FE), geometrical and mathematical models for prediction of collapse strength. The results from the the models are verified with experimental data and it is shown that they agree well. The results from this research show that using lattice structures significantly reduces the strength of material with respect to solid samples while indicating no serious increase of strength compared to hollow structures. In combination with an analysis of microstructures, a description of strength analysis is obtained with respect to process parameters. © 2016 Elsevier Ltd
Additive manufacturing has shown significant improvement in material and machines for high-quality solid freeform fabrication processes such as selective laser melting (SLM). In particular, manufacturing lattice structures using the SLM procedure is of interest. This research examines the effect of cellular materials on compression strength. The specimens are manufactured additively using industrial 3D printing systems from high-strength alloy. The material has the right mechanical properties for manufacturing tool components. This includes samples with solid and lattice structures. The Compression tests are applied to the both samples while they are deformed. The flow stress curves from this research show that using cellular material significantly reduces the yield stress of the samples. This reduction compromises the efficiency of the new structure with respect to the material save.
Publication Date: 2015
pp. 325-334
Previous studies have described a high performance transfer press for the application in micro forming. This research extends this finding by conducting a two-stage forming process for the machine tool in order to examine the efficiency of the machine in a real multi-stage process. In particular the analysis focuses on quantifying the effect the forming force has on the elastic deflection of the machine and the tools by examining the displacement of the moving plate under loaded and unloaded conditions. The results of the measurements were used to describe the tilting effect due to the off-center loading applied to the upper tool plate.
Publication Date: 2015
Microelectronic Engineering (01679317) 133pp. 104-109
A process has been developed to fabricate discrete three-dimensional microcontainers for oral drug delivery application in Poly-l-Lactic Acid (PLLA) polymer. The method combines hot embossing for the definition of holes in a PLLA film and mechanical punching to penetrate the polymer layer around the holes, after filling them with drug. Here, we demonstrate the fabrication of microcontainers with a diameter of 340 μm and a height of 50 μm. The process is temperature benign so that the compositional integrity of the drug is preserved. It also provides a good flexibility for creating different sizes and shapes of microcontainers. Finally, the process is compatible with roll-to-roll processing that could lead to low cost high volume production. © 2014 Elsevier B.V. All rights reserved.
Publication Date: 2015
pp. 53-54
The purpose of this research is to fabricate billets for an automated transfer press for micro forming. High performance transfer presses are wellknown in conventional metal forming and distinguished from their automation and mass production. The press used in this research is a vertical mechanical press. When using a vertical mechanical press, the material is fed as billets into the forming zone. Therefore, a large number of highly uniform billets are required to run mass production in such a setup. Shearing technique was used for manufacturing the billets. The efficiency of the shearing tool is examined in terms of volume control, circularity, dimension and sheared surface quality. The shearing tool is based on holders for both bar and cutoff. The tool is fixed in dimensions, since the dimensions of billets are fixed throughout experiments of this research. The paper presents the experimental analysis of the precision of the billets prepared by the tool.
Publication Date: 2014
CIRP Annals (00078506) 63(1)pp. 497-500
Multi-step micro bulk forming is characterized by complex processes and high precision requirements. In particular the demands regarding handling accuracy between different forming steps are of the order of a few μm. The paper introduces a methodology for the analysis and characterization of this transfer system on component level and system level. Laser interferometry is used in combination with analytical models to predict the positioning ability of the actuator in a static as well as dynamic mode. In combination with an analysis of the grippers, a full description of the transfer precision inside the forming press is obtained. © 2014 CIRP.
Publication Date: 2014
Procedia Engineering (18777058) 81pp. 1445-1450
Multi-step micro bulk forming is characterized by complex processes and high precision requirements. Several process parameters influence on accuracy of micro forged parts where small tolerances in the order of few μm are in demand. The paper introduces a high performance transfer press for micro cold bulk forming. A methodology for selection of linear motors on the bases of the process parameters was obtained. In order to examine the effectiveness of the machine, specific geometry was investigated for production. Kinematic parameters were found for a production rate of 200 strokes per minute. A forged part with three different diameters in height was produced in a two-stage forming process using the introduced transfer press. © 2014 The Authors. Published by Elsevier Ltd.
In the earlier studies, it was shown that a whole multi stage former can be divided into three major sub-sections, the positioning unit, the gripping unit and the forming unit. The two first units were investigated and related parameters and features of each were discussed. This research herein deals with the forming unit. For this research, the positioning unit and the gripping unit are applied to the forming unit including a micro press equipped with a die system. The analysis focuses on verifying the results already extracted from previous researches by implementing all mentioned units together. A motion study of the system gives an overview of different steps and movements inside the multi stage former. Significantly, increasing the production rate increases the acceleration and also causes the time frame tight. The time limitations put overlaps on the moving parts in terms of milliseconds. A high speed camera was used in the experiments with high resolution to show the details of the motion while enabling to detect any unwanted movement within milliseconds. Importantly, increasing the frequency of image capturing within the movement is another beneficial feature in the high speed camera in order to give sufficient information on critical movements where they may need sensors and enough time to ensure getting at the right position as programmed. In this research the production rate raised to 169 strokes per minute. The results show that the concept introduced for the manipulator works very well at a real process implementation. This significantly approves the techniques already were given to evaluate the precision in the positioning unit and the gripping unit. Copyright © 2013 by ASME.
Publication Date: 2013
Key Engineering Materials (10139826) 554pp. 900-907
Many fasteners used in electromechanical systems are micro metal parts which should be manufactured with high accuracy and reliability and in large quantities. Micro forming is promising to fulfill these demands. This research focuses on investigating a gripping unit in a multi stage former, as the positioning unit was discussed earlier. The parameters which play important roles in the gripping unit will be discussed and the precision and reproducibility evaluated to show the performance of the unit. This includes two different tests. The first test will show how accurately the unit can locate the parts and the second one is intended to depict how the unit transfers the parts with different diameters with respect to the front profile of the fingers. The experiments showed that the manipulator can handle the parts with 7 μm accuracy, 2 μm reproducibility and 9μm uncertainty for a 20mm distance between two adjacent stations. Copyright © 2013 Trans Tech Publications Ltd.
Publication Date: 2006
Journal of Materials Processing Technology (0924-0136) 177(1-3)pp. 179-182
Large diameter pipes that are made by the U-O bending process, before an expanding operation, should have sufficient material and the required profile. Therefore an analysis of condition in each forming operation is necessary in order to obtain an optimum condition under the low O-shape forming load. In this paper, a forming analysis algorithm for the pipe profile from U-formed blank to circular pipe is presented. In order to obtain the realistic behaviour in the deformation process, a theoretical analysis is made for the elastic, linear work-hardening material. In this analysis the U-shaped blank is divided into some elements and the deformation of each element is analysed by considering the history of deformation. The result obtained from forming of a blank profile has been presented and then compared to the present data reported by other researchers. Good agreements between them show the validity of the program developed. © 2006 Elsevier B.V. All rights reserved.
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