1,721,234 research outputs found
Stainless steel deep drawing with polymer punches produced with fused filament fabrication technology: effect of tool orientation on the printing plate
No full textIn this research the potential of using polymer punches in a deep drawing process to realize stainless steel cups having diameter equal to 40 mm and drawing depth equal to 18 mm was investigated. Punches have been Additive Manufacturing printed following two different orientations (horizontal and vertical) and two different wire orientations with respect to the drawing direction (45° and 90°). Cups and punches radii, heights, roundness tolerances and linear profiles have been acquired to compare process performances. Results highlight benefits and problems of all tested punches
Deep drawing punches produced using fused filament fabrication technology: Performance evaluation
No full textCurrently, manufacturing industries require parts-production characterized by low volume and high customization, making conventional processes such as sheet stamping expensive due to the initial investment required for tooling production. Additive manufacturing, thanks to its flexibility for customized production and low cost, is becoming a valid alternative for rapid tooling fabrication. In this study, we investigated the benefits of using fused filament fabrication (FFF) to produce punches for the deep drawing process. Different process parameters were analyzed, such as the punch fillet radius, blank material, drawing ratio, and drawing depth. The best results were achieved by drawing aluminum blanks with a drawing ratio of 1.8
Stress-induced stabilization of pyrolyzed polyacrylonitrile and carbon nanotubes electrospun fibers
Full text linkThe unique properties of graphitic carbons have gained widespread attention towards their development and application. Carbon materials can be synthesized by thermal decomposition and, more specifically, carbon pyrolysis from polymer precursors. The paper shows the pyrolysis process of polyacrylonitrile (PAN) in the presence of multi-walled carbon nanotubes (MWCNTs) according to different manufacturing process conditions. The electrospinning process of the PAN-MWCNTs solution on multi-plates collectors was firstly analyzed. The morphology and the particles arrangement of the electrospun fibers was studied under scanning and transmission electron microscopes. Moreover, the composite fibrous mats were characterized by RAMAN spectroscopy to identify the effects of a mechanical tension application during the thermal stabilization phase performed before the pyrolysis treatment to obtain carbon fibers from the precursor polymer. The results show that the graphitization of the pyrolyzed fibers is enhanced by the combination of MWCNTs and a mechanical stress applied during the thermal treatment
Production of carbonized micro-patterns by photolithography and pyrolysis
Full text linkThe preparation of carbon micro-patterns is reported in this paper. Different carbon micro-patterns were created using photolithography of the epoxy-based negative photoresist SU-8. Photoresist patterns were optimized in terms of resolution and aspect ratio and subsequently subjected to pyrolysis to obtain carbonized and conductive 3D structures. The latter step requires the optimization of the resist cross-linking time as well as the temperature and time of the resist post-bake. This step is crucial in order to avoid any severe modification of the geometry of the patterns produced during the actual pyrolysis. By observing optical and scanning electron microscope images, the morphology of the structures before and after pyrolysis was studied and the same patterns were also characterized by a laser probe profilometer. Finally, the thus obtained carbon patterns on Si wafers were used to carry out cell culture tests with Neural Stem Cells (NSC). The adhesion and the arrangement of the stem cells were analyzed to verify the ability of the patterned substrates to guide the orientation and, therefore, the differentiation of the cells
Advances in Material Modeling for Manufacturing Analysis and Simulation (Deformation and Cutting Processes)
No full textThere are many different reasons to use a model in the cutting and forming operations fields, such as the following: processes design, processes optimization, processes control, processes simulation, and equipment design. This chapter describes how the features to build a good simulative and analytical model. In order to realize a reliable simulative and/or analytical model for cutting and forming environments, it is important to know some parameters since they strongly influence the final results. The most significant parameters are material characterization (known also as flow stress law); friction model and value; and failure criteria of the material. In manufacturing processes, the knowledge of the friction conditions between a workpiece and a tool or die is very important for determining the material flow and the part feasibility. In order to quantitatively express the interface friction, it is normal to refer to two models: the Coulomb model and the Schley model
Design and fabrication of customized tracheal stents by additive manufacturing
No full textAdditive Manufacturing (AM) is already becoming part of our life from a technological, economic and social point of view. Nowadays, it is applied in several manufacturing sectors. In particular, AM shows huge opportunities in the medical field and for healthcare applications. Due to its capability to produce complex geometries directly working on medical 3D images and thanks to the possibility to 3D-print biocompatible materials, AM is a key technology for the fabrication both of external and internal medical devices. In particular, the use of AM for medical applications is typically articulated in three steps: 3D-scanning of the patient anatomy, segmentation the medical scan and elaboration through CAD software for the preparation of a STL file suitable for the AM process. One of the main research topic in this field is the definition and optimization of procedures that, taking precise data from an individual patient, could be applied to the design and fabrication of customized components for medical applications. Therefore, this paper presents a project aimed at the fabrication of customized tracheal stents starting from the actual patient anatomy. In particular, it follows an approach based on molds FDM fabrication followed by biocompatible silicone casting. Molds were designed to obtain a tracheal stent based the patient anatomical tracheal lumen and were fabricated using FDM technology. Moreover, since the surface roughness is one of the most critical aspects related to the FDM, the produced molds were finished with a chemical surface post-treatment based on the use of acetone vapours. Overall, the whole developed procedure results in an effective custom-made medical devices realization
Hybrid multi-layered scaffolds produced via grain extrusion and electrospinning for 3D cell culture tests
Full text linkPurpose: The purpose of this paper is to focus on the production of scaffolds with specific morphology and mechanical behavior to satisfy specific requirements regarding their stiffness, biological interactions and surface structure that can promote cell-cell and cell-matrix interactions though proper porosity, pore size and interconnectivity. Design/methodology/approach: This case study was focused on the production of multi-layered hybrid scaffolds made of polycaprolactone and consisting in supporting grids obtained by Material Extrusion (ME) alternated with electrospun layers. An open source 3D printer was utilized, with a grain extrusion head that allows the production and distribution of strands on the plate according to the designed geometry. Square grid samples were observed under optical microscope showing a good interconnectivity and spatial distribution of the pores, while scanning electron microscope analysis was used to study the electrospun mats morphology. Findings: A good adhesion between the ME and electrospinning layers was achieved by compression under specific thermomechanical conditions obtaining a hybrid three-dimensional scaffold. The mechanical performances of the scaffolds have been analyzed by compression tests, and the biological characterization was carried out by seeding two different cells phenotypes on each side of the substrates. Originality/value: The structure of the multi-layered scaffolds demonstrated to play an important role in promoting cell attachment and proliferation in a 3D culture formation. It is expected that this design will improve the performances of osteochondral scaffolds with a strong influence on the required formation of an interface tissue and structure that need to be rebuilt
Characterization of the Chemical Finishing Process with a Cold Acetone Bath of ABS Parts Fabricated by FFF
No full textAdditive Manufacturing (AM) is going through an impressive growth from 15 years to today. Its main strength is the capability to fabricate complex parts for a wide range of applications. In contrast, its typical layer-by-layer building method can cause a low surface finishing of the parts. Post-processes as chemical treatments can be used to enhance the finishing but few studies are published on the topic. This work focuses on the surface prost-treating of ABS parts made by FFF. During the treatment, the part is immersed in a cold acetone bath to chemically dissolve and smooth its surface. The process is characterized by varying the duration of treatment, the orientation of the surface with respect to gravity and using samples covering the full range of initial roughness. The results are statistically analyzed showing the robustness of the process. Moreover, the effectiveness of the treatment is proven by an overall reduction of the roughness which is 97% on average within 1 min of treatment
Characterization and optimization of the hydroforming process of AISI 316L steel hydraulic tubes
No full textHydroforming is a metal forming technology that enables the fabrication of complex parts in a low cycle time. The process is based on the plastic deformation of a blank sheet using a pressurized fluid. This paper focuses on the design of a tube hydroforming (THF) process to replace the current cut-and-weld practice for components produced by a company. Specifically, the study focuses on the characterization and optimization of the THF process for stainless steel T-joint parts produced in two sizes: small and large. The new production must improve the final components’ quality and maintain the technical requirements of the previous one, especially in terms of the parts’ geometry (in particular, the third branch minimum height and thickness) and material (AISI 316L), with competitive production costs. Accordingly, the process optimization is performed in three sequential steps. Initially, the process is characterized by the material flow stress and the friction between a tube and die. Subsequently, this information is used to develop a finite element method (FEM) model, which is validated based on experimental data. The FEM is used to optimize the process parameters (pressure, stroke, and trust force of the counterpunch) to improve the final component quality and guarantee the specific dimensional requirements. Finally, further improvements of the process are implemented (initial precrash of the tube, optimal length of the blank tube, and calibration pressure to avoid wrinkles in the final component). After the THF process optimization, emphasis is placed on the punch geometry. A study is conducted to avoid stress concentrations that may cause punch breakage. The results of this study allow the minimization of tube thinning during the hydroforming process, and guarantee the target value for the third branch height with minimal material consumption. Moreover, the evaluation of different geometrical alternatives allows the stresses acting on the punches to be reduced by 45%
Milling tool optimization by topology optimization technique
Full text linkIn milling operations, the weight of the milling tool greatly affects the motion speed of the mandrel, especially when a complex tool path must be performed. Thus, it is essential to realize more lightweight tools, without a significant decrease in the mechanical and production performance. Traditionally, due to the limitation of the conventional manufacturing processes, the design of a new milling tool cannot be too much complex and thus cannot fully satisfy the mentioned goals. Nowadays, thanks to the topology optimization technique and the additive manufacturing (AM) technologies, such as the selective laser melting (SLM), it is possible to realize more complex part geometries to obtain more lightweight and high-performance tools. In this paper, a new design of a milling tool with a weight reduced by 30% is presented; SLM process has been selected to realize the milling tool. In order to minimize the use of support structures, required by the SLM process to correctly realize the desired part, the new geometry has been little modified. A more lightweight milling tool has been produced and every support structure has been successfully removed from the component
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