CIRP Journal of Manufacturing Science and Technology最新文献

With a growing global awareness of the ecological challenges posed by plastic waste, the integration of recycled materials represents a crucial step to sustainable additive manufacturing of plastic products. To assess the applicability of recycled materials in 3D printing, we extruded recycled polylactic acid (PLA) into filament and printed specimens based on the fused filament fabrication (FFF) printing technology. For comparison purposes, we selected the virgin PLA filament as a reference. With the filament extruder, we produced filaments using virgin PLA pellets, a mixture of virgin pellets and recycled PLA, as well as fully recycled PLA. The extrudability and transferability of filaments were comprehensively investigated under various extrusion temperatures and speeds. Subsequently, using extruded filaments, we printed parts of different shapes such as cubes, tensile specimens, and flexural specimens. We measured the surface roughness, dimensional deviations, and mechanical properties of the printed parts. Results demonstrated that filament extruded from virgin pellets exhibited similar quality and mechanical properties as the virgin filament. Recycled PLA required higher extrusion temperature and speed to extrude filament than virgin PLA and mixed virgin PLA and recycled PLA. The tensile and flexural strength of printed parts from fully recycled PLA were more than 15 % lower than that from virgin filament. These findings contribute valuable insights towards the continued development of environmentally conscious practices in the field of additive manufacturing.

The hype around additive manufacturing technologies suggests that any complex shaped structure can be fabricated regardless of the type of material used. Moreover, it is often suggested that additive manufacturing processes will certainly disrupt the supply chain logistics and that everyone will be able to print on the demand at the comfort of their home. In this viewpoint, we describe and demystify some of the common assumptions associated with these set of technologies. We also show that conventional manufacturing processes cannot be fully replaced by additive manufacturing technologies, but rather there is a need for a complementarity between well-consolidated manufacturing technologies and additive manufacturing. While some of the contents presented here are basic for specialists working in the manufacturing field, we expect that this viewpoint can aid researchers working on topics related to additive manufacturing, but with less focus on the manufacturing aspects, helping them understand the actual limitations and advantages associated to these technologies. The four key issues that are addressed in this viewpoint, and their consequences, also intend to shape and mold future entrepreneurial efforts on additive manufacturing, as well as define future impacts (environmental, logistics, commercial and disruptive) associated to additive manufacturing technologies.

Bone drilling mechanism study is the basis for the optimization of cortical bone drilling process and drill geometry. In this paper, a drilling force model for modified drills with thinned chisel edge is established considering the heterogeneous structure of cortical bone. The bone mineral density is embedded into the established model, the model can predict the axial thrust force change along the drilling depth direction, and the model is verified through cortical bone drilling experiments. The thrust force and torque predicted by the model are in good agreement with the drilling experimental results of cortical bone drilling. Then, the drilling performance of the modified drill and the common drill is compared through cortical bone drilling experiments. Compared with common drill bits, the maximum reduction in average thrust force of the modified drill bit during stable drilling is 21.21 % (n = 2500 rpm, V_f=60 mm/min). The maximum reduction in average roughness of the hole wall is 21.87 % (n = 500 rpm, V_f=10 mm/min). The drill chisel edge thinning design reduces the negative impact of the negative normal rake angle on the cutting lip of common drill on drilling force and stability. Therefore, the drill bit chisel edge thinning design can effectively improve the drilling performance.

Counter-rotating electrochemical machining (CRECM) stands out as an efficient and cost-effective method for machining aero-engine casings. To maintain stability in the CRECM process equilibrium state, continuous feeding of the cathode tool is essential. However, this continuous feeding approach with single direction of rotation may result in poor roundness and reduced machining accuracy. This paper aims to analyze the sources and rules of roundness error and asymmetry in CRECM. Based on simulation results, a method involving periodic reverse rotation of electrodes with continuous feeding is proposed for CRECM. This approach aims to mitigate the cumulative machining error, thereby significantly improving machining accuracy. Experimental results validate the efficacy of the proposed method at a rotation speed of 0.2 rpm. The roundness error is markedly reduced from 0.19 mm to 0.04 mm, resulting in a more symmetric convex structure. Additionally, the sidewall taper angle is reduced from 14.5 degrees to 6.4 degrees. This underscores the effectiveness of the proposed method in enhancing machining accuracy.

Recycling of metals is becoming crucial from an economic and environmental point of view. The solid-state recycling process Continuous Friction Stir Extrusion was used to produce wires out of A356-T6 chips. The mechanical properties of the produced wires were explored by varying the main process parameters. Characterization involved Vickers hardness tests, tensile tests, grain size measurements, and fracture surface analysis. It has been found that it is possible to achieve 77 % of the Ultimate Tensile Strength (UTS) and 92 % of Vickers hardness with respect to the as-fabricated A356 alloy. The average grain size increases with the tool rotational with values ranging from about 9 µm to about 11 µm. A 3D dedicated numerical model was used to predict the distributions and histories of primary field variables, and to calculate the Piwnik-Plata parameter, fostering a more in-depth understanding of the process mechanics. This allows for the precise prediction of unacceptable product quality of the bonding when the Plata and Piwnik parameters are low. Predicted temperature close to the rotating tool should reach 400 °C while the cochlea temperature should be below 100 °C for sound wires production thus avoiding early chip bonding and process failure.

Laser-assisted turning (LAT) involves locally heating a rotating workpiece using a focused laser beam before the removal of material. A key aspect in optimising productivity with laser-assisted turning is understanding the thermal relationship between laser heating, the improved material removal rate, and machinability. Consequently, in this paper, a thermal heating and laser-assisted turning finite element model and experiments were conducted to assess the machinability of an Al/SiC_p MMC workpiece, considering the circumferential location of the laser beam from the cutting point. The results confirm that laser power and cutting velocity influence the temperature profile from the laser spot to the tool point and the heat-affected depth. Positioning the cutting tool closer to the laser spot effectively reduces the Von Mises stress during cutting at higher cutting temperatures. At the same time, the experiment indicates an increased risk of directly heating the tool, which can affect the integrity of the cutting tool. The work further reveals that at specified cutting velocities, lower specific cutting energy improves the tool condition and surface quality of the machined parts. Based on a range of material removal rates and laser-specific energy density, a new criterion for optimal laser-tool circumferential distance was determined. Establishing this distance can act as a guide for the laser-assisted turning of Al/SiC_p metal matrix composites and potentially other materials.

An important aspect to consider in the evaluation of parts and assemblies by X-ray computed tomography (XCT) is the attenuation coefficient of the different materials involved, which are directly related to their density; depending on this coefficient, the X-ray penetration varies and, therefore, varies the contrast between different materials and with the background. This becomes more critical in those assemblies in which materials are characterized by a high difference in density, where the lighter material could be difficult to be characterised. In this paper, the effect of the presence of metals in the dimensional evaluation of polymeric geometries (having lower density than the metal parts) is studied, to evaluate the errors caused in dimensional measurements of different geometries and surface texture characterization. Based on a common geometry, four scenarios have been experimentally tested with variations of metal amount, in which macro geometries (precision spheres made by different polymers) and micro geometries (inclined ramps manufactured by fused deposition modelling (FDM)) have been characterised. Results show errors in the surface determination of the polymeric features directly related to the presence of metal: a high amount of steel makes significantly difficult to accurately determine the interface between background and material due to the noise and artifacts created, while aluminium has less influence on the irregularities of the features extracted. This effect is more evident for polymers with lower density due to the higher difference. Numerically, most affected parameters are those sensible to variations in surface determination, such as spheres’ form error and ramps’ maximum surface texture (Sz), while more solid features as spheres’ diameters, distances and ramps’ average surface texture (Sa and Sq) remain more stable. In conclusion and to sum up, it has been found that the quantity of metal present in assemblies made of polymeric and metallic materials is correlated with distortions in the dimensional evaluation of polymeric features by XCT.

Nickel-based superalloys exhibit exceptional suitability for operating in environments characterized by corrosive agents and elevated temperatures. Strategic allocation of this expensive material solely to the functional surface areas yields significant economic advantages. The poor tribological property profile of Inconel 718 can be significantly improved through a boriding process. In this study, the possibility of combining a coating process with boriding technology and in situ heat treatment was investigated. Layers of Inconel 718 were deposited to an austenitic stainless steel using wire-based electron beam cladding (EBC) and subsequently subjected to boriding. Based on results from annealing experiments, boriding treatments were performed at various temperature/time regimens with the aim of inducing in situ age hardening during boriding. The focus was on the investigation of the influence of the temperature/time regime during boriding on the microstructure and hardness, as well as examining the wear and corrosion behavior of the resulting borided layers. The results showed that the desired target hardness range was achieved after in situ aging with all boriding variants. Furthermore, it was demonstrated that boriding significantly improved the wear resistance but decreased corrosion resistance.

Visual inspection in remanufacturing, despite technological progress, is still mainly performed by humans. A rough assessment of the product’s general condition and the dedicated inspection of individual product features or defects is necessary to identify the typically unknown product variant and assess the reusability of a used product and its components. Therefore, a system for automated visual inspection must be flexible and runtime-adaptive, as defects to be inspected in detail may occur anywhere on the product. In the present work, this problem is framed as a view planning problem solved by means of supervised learning and reinforcement learning using a specially developed simulation environment. Three variants of neural networks (PointNet, PointNet++, and Point Completion Network) are compared in the supervised learning case, whereas a deep learning SAC algorithm using the Point Completion Network as network structure is evaluated in the reinforcement learning case. Considering the specific boundary conditions prevailing in remanufacturing, the results are obtained from the use case of electric starter motor remanufacturing. The results show that supervised learning and reinforcement learning are suitable for determining the poses of an acquisition system at system runtime to react to an initially unknown inspection task. Our proposed framework is available open source under the following: https://github.com/Jarrypho/View-Planning-Simulation.

Most metal turning processes utilize cutting fluids. Despite extensive experimental and analytical studies, the mechanisms of chip formation under consideration of a cutting fluid are still not entirely understood. Due to fluid-structure interaction, simulating wet cutting processes for an extended duration has not been feasible. The primary objective of this study is to utilize a simulation approach to provide additional information about the wet chip formation process in contrast to measurement methods, with a view to drawing conclusions. As methodology the Finite-Pointset-Method (FPM) is employed to simulate the chip formation process for dry, flood and specifically high-pressure cooling conditions during machining of carbon steel C45 as well as nickel-based alloy Inconel 718. Due to the increased relative velocity between workpiece and cutting fluid with the use of high-pressure cooling compared to flood cooling, numerical stability issues are present. Initially, the modeling approach to handle high-pressure cooling conditions is described and validated by an impact test. Subsequently the cutting simulation model is presented in detail and verified by measurements. The simulation results of stress, temperature and plastic strain rate fields are used to elucidate the observed discrepancies between various cutting fluid strategies in detail. These findings suggest explanations for the high efficiency of high-pressure cooling such as a decline of hydrostatic stresses or activation of ductile damaging.