Advances in Manufacturing最新文献

High-pressure die casting (HPDC) is one of the most popular mass production processes in the automotive industry owing to its capability for part consolidation. However, the nonuniform distribution of mechanical properties in large-sized HPDC products adds complexity to part property evaluation. Therefore, a methodology for property prediction must be developed. Material characterization, simulation technologies, and artificial intelligence (AI) algorithms were employed. Firstly, an image recognition technique was employed to construct a temperature-microstructure characteristic model for a typical HPDC Al7Si0.2Mg alloy. Moreover, a porosity/microstructure-mechanical property model was established using a machine learning method based on the finite element method and representative volume element model results. Additionally, the computational results of the casting simulation software were mapped with the porosity/microstructure-mechanical property model, allowing accurate prediction of the property distribution of the HPDC Al-Si alloy. The AI-enabled property distribution model developed in this study is expected to serve as a foundation for intelligent HPDC part design platforms in the automotive industry.

Smart structures realize sequential motion and self-assembly through external stimuli. With the advancement of four-dimensional (4D) printing, the programming of sequential motions of smart structures is endowed with more design and manufacturing possibilities. In this research, we present a method for physically programming the timescale of shape change in 4D-printed bilayer actuators to enable the sequential motion and self-assembly of smart structures. The effects of the geometric and printing parameters on the time-dependent behavior of 4D-printed bilayer actuators are investigated. The results show that the thickness of the active layer directly affects the timescale of motion, and increasing the thickness leads to faster motion until the thickness ratio is close to 4:6. Similarly, a higher printing speed results in faster motion. Conversely, a higher printing temperature and a greater layer height result in a slower shape change. The effects of the length-width ratio, line width, and filling ratio on the timescale of motion are not as straightforward. Finally, we demonstrate several smart structures that exhibit sequential motion, including a labyrinth-like self-folding structure that is choreographed to achieve multi-step self-shaping and a flower-shaped structure where each part completes its movement sequentially to avoid collisions. The presented method extends the programmability and functional capabilities of 4D printing.

This paper presents the design and fabrication of an aluminium oxide cutting insert with an internal cooling channel formed through an additive manufacturing method. The formed insert is subjected to a controlled densification process and analysed through a series of characterisation investigations. The purpose of the study is to develop the design concept and analyse the forming and sintering parameters used in the lithographic ceramic manufacturing process. The results validated the feasibility of the geometrical design, providing the required structural conformity with the integrated internal feature using conditional specifications. It is confirmed that the forming parameters would affect the material properties of the green body. Furthermore, the results indicate that the heating rate and temperature variance of the de-binding and thermal treatment regime influences the microstructural growth kinetics and the quality of the densified insert. Using a novel application of liquid gallium as an internal coolant, experimental results showed a decrease in tool wear difference of 36% at (V_{{text{c}}}) = 250 m/min, and 31% in tool wear difference at (V_{{text{c}}}) = 900 m/min between cooling and non-cooling conditions. When external cooling was applied, the results showed at (V_{{text{c}}}) = 250 m/min, the difference between the tool wear rates with the internal coolant relative to the external coolant was 29%. Increasing to (V_{{text{c}}}) = 900 m/min, the results revealed a 16% tool wear difference. The results clearly indicate the potential of liquid gallium as a heat transfer agent in internal cooling applications for cutting inserts, and by extension demonstrable reduction in tool wear.

Metallization, which is coating metals on the surface of objects, has opened up new possibilities for lightweight structures while integrating polymer and metal features. Electroless plating is a potential method for metalizing plastic 3D-printed parts; however, conventional approaches rely on pre-surface activation and catalyzation with expensive metal catalysts and hazardous acids. To address these issues, the current study represents a novel eco-friendly and low-cost approach for direct metallization of non-conductive 3D-printed parts, without using hazardous, toxic, and expensive conventional pre-treatments. Using the developed methodology, we electrolessly copper plated polymer-copper infused 3D-printed part as well as plastic components for the first time, directly. We initiated and implemented the idea of exposing the copper particles embedded in the polymer to the surface of copper-polymer parts by applying a sustainable mechanical or chemical method to make the surface conductive and ready for direct plating. A formaldehyde-free (green) electroless copper solution was developed in-house in addition to skipping conventional etching pre-treatment using harmful chemicals, making this a real step forward in the sustainable metallization of 3D-printed parts. In this study, the mechanical properties of copper-polylactic acid (PLA) 3D-printed parts revealed a 65% reduction in tensile strength and 63% increase in tensile modulus, compared to virgin PLA. Furthermore, the morphological characterization of the copper coated 3D-printed parts showed a homogeneous copper coating on the surface after direct electroless plating, with a plating rate of 7.5 μm/h. Allowing complex and functional devices printed in this manner to be quickly metalized without modification using toxic and costly solutions is a significant advancement in lowering the cost and manufacturing complexity of 3D-printed parts, increasing efficiencies, and lowering weight, and thus is a game changer in the technology’s adoption.

During the last two decades, industrial applications of augmented reality (AR) have been incorporated in sectors such as automotive or aeronautics in tasks including manufacturing, maintenance, and assembly. However, AR’s potential has yet to be demonstrated in the railway sector due to its complexity and difficulties in automating tasks. This work aims to present an AR system based on HoloLens 2 to assist the assembly process of insulation panels in the railway sector significantly decreasing the time required to perform the assembly. Along with the technical description of the system, an exhaustive validation process is provided where the assembly using the developed system is compared to the traditional assembly method as used by a company that has facilitated a case study. The results obtained show that the system presented outperforms the traditional solution by 78% in the time spent in the localization subtask, which means a 47% decrease in the global assembly time. Additionally, it decreases the number of errors in 88% of the cases, obtaining a more precise and almost error-free assembly process. Finally, it is also proven that using AR removes the dependence on users’ prior knowledge of the system to facilitate assembly.

High quality micro mould tools are critical for ensuring defect-free production of micro injection moulded products. The demoulding stage of the micro injection moulding can adversely affect the surface integrity due to friction, adhesion and thermal stresses between the metallic mould and polymeric replicated part. In the present work, we propose the use of precision electropolishing (EP) as a shaping and polishing process to control the draft angle and fillet radius of micro features in order to ease demoulding. Typical defects that occur in replicated polymer parts include cracks, burrs and distorted features. A nickel mould having multiple linear ridges and star shape patterns was designed for the present investigation to have characteristic dimensions ranging from 10 μm to 150 μm and with various aspect ratios to study the effect of electropolishing on modifying the shape of micro features and surface morphology. A transient 2D computational analysis has been conducted to anticipate the effect of shaping on the Ni mould after electrochemical polishing with non-uniform material removal rates, based on the distribution of current density. The experimental results indicate that after shaping using EP, the draft angle of star-patterns and linear patterns can be effectively increased by approximately (3.6^circ), while the fillet radius increases by up to 5.0 μm. By controlling the electropolishing process, the surface roughness can be maintained under 50 nm. This work uses a green and environmental friendly nickel sulfamate electrolyte which can be effective for shaping of nickel micro features without causing any surface deposition.

Recently, low-cost desktop three-dimensional (3D) printers, employing the fused deposition modeling (FDM) technique, have gained widespread popularity. However, most users cannot test the strength of printed parts, and little information is available about the mechanical properties of printed high-impact polystyrene (HIPS) parts using desktop 3D printers. In this study, the user-adjustable parameters of desktop 3D printers, such as crisscross raster orientation, layer thickness, and infill density, were tested. The experimental plans were designed using the Box-Behnken method, and tensile, 3-point bending, and compression tests were carried out to determine the mechanical responses of the printed HIPS. The prediction models of the process parameters were regressed to produce the optimal combination of process parameters. The experimental results showcase that the crisscross raster orientation has significant effects on the flexural and compression strengths, but not on the tensile strength. With an increase in the layer thickness, the tensile, flexural, and compression strengths first decreased and then increased, reaching their minimum values at approximately 0.16 mm layer thickness. In addition, they all increased with an increase of infill density. It was demonstrated that when the raster orientation, layer thickness, and infill density were 13.08°/–76.92°, 0.09 mm, and 80%, respectively, the comprehensive mechanical properties of the printed HIPS were optimal. Our results can help end-users of desktop 3D printers understand the effects of process parameters on the mechanical properties, and offer practical suggestions for setting proper printing parameters for fabricating HIPS parts.

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process windows. Thus, the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld interface. Current formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld material. However, collision welding fundamentally depends on the impacts that generate shockwaves in weld members, which can dominate the stress propagation velocities in thin weld sections. Therefore, this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D Rankine-Hugoniot relations. The shock upper limit is validated against the experimental and simulation data in the collision welding literature, and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.