Advances in Manufacturing最新文献

Ultrasonic-vibration-assisted milling (UVAM) is an advanced method for the efficient and precise machining of difficult-to-machine materials in modern manufacturing. However, the milling efficiency is limited because the ultrasonic vibration toolholder ER16 collet has a critical cutting speed. Thus, a 2D UVAM platform is built to ensure precision machining efficiency and improve the surface quality without changing the milling toolholder. To evaluate this 2D UVAM platform, ultrasonic-vibration-assisted high-speed dry milling (UVAHSDM) is performed to process a titanium alloy (Ti-6Al-4V) on the platform, and the milling temperature, surface roughness, and residual stresses are selected as the important indicators for performance analysis. The results show that the intermittent cutting mechanism of UVAHSDM combined with the specific spindle speed, feed speed, and vibration amplitude can reduce the milling temperature and improve the texture of the machined surface. Compared with conventional milling, UVAHSDM reduces surface roughness and peak-groove surface profile values and extends the range of residual surface compressive stresses from −413.96 MPa to −600.18 MPa. The excellent processing performance demonstrates the feasibility and validity of applying this 2D UVAM platform for investigating surface quality achieved under UVAHSDM.

Reducing the short-circuit rate and increasing the effective discharge rate are important targets for improving the servo control effect of micro-electrical discharge machining (micro-EDM), as these two indicators are closely related to the machining efficiency and quality. In this study, a feed-pulse collaborative control (FPCC) method is proposed for micro-EDM based on two dimensions (space and time). In the spatial dimension, a feed control strategy with a discharge holding process is adopted. Meanwhile, in the time dimension, a forward-looking pulse control strategy is adopted, in which the pulse interval is adjusted based on a sequence analysis of feed commands and discharge states. Process experiments are carried out to determine the key parameters used in this method, including the discharge holding threshold and pulse interval adjustment value ((T_{{text{off}_{{text{adj}}} }})). The feed smoothness and discharge sufficiency analyses of the experimental results show that compared to the traditional double threshold average voltage method, the FPCC method reduces the number of long-distance retreats by 64% and improves the effective discharge time by 40%.

Profile grinding is the most crucial method for the ultra-precision machining of special-shaped surfaces. However, profile grinding produces a unique machining profile, and many random factors in the machining process lead to complex surface characteristics. In this study, the structural and probabilistic characteristics of the profile grinding of a special-shaped surface were analyzed, and a probabilistic algorithm for the forming and 3D characterization of special-shaped surfaces under profile grinding was developed. The forming process of a GH738 blade tenon tooth surface was considered as an example to demonstrate the algorithm. The comparison results showed that the simulation results had similar surface characteristics to the measurement results, and the relative error range of the 3D roughness parameter was 0.21%–19.76%, indicating an accurate prediction and characterization of the complex special-shaped surface under the action of multiple factors.

The problems of severe sawtooth wear, harsh sawing noise, and low surface quality during the processing of circular saw blades need to be solved. To improve the cutting performance of TiC-based cermet saw blades, microtextures parallel to the cutting edge were fabricated on rough and fine sawteeth by laser machining. The cutting tests were performed on a sawing platform under lubricated conditions. Models of the sawing arc length and working sawtooth cutting force variations were developed for sawing steel pipes, and the accuracy of the sawing force model was verified experimentally. The results indicate that the variations in the sawing force are proportional to the sawing arc length. The circular saw blades with microtextures that did not penetrate the sawtooth rake face exhibited the lowest cutting force, sawing noise, and highest machined surface quality. Furthermore, the worn-out distance of the rougher and finisher sawteeth was reduced by approximately 7.4% and 44.1%, respectively, compared with conventional circular saw blades. The main failure modes of sawteeth were tip wear, rake face adhesion, and oxidative wear. In addition, the mechanism by which the textures improve the cutting and wear properties of TiC-based circular saw blades was discussed. This study provided a significant concept for enhancing the cutting performance of circular saw blades and improving the machined surface quality.

The real-time monitoring of the weld pool during deposition is important for automatic control in plasma arc additive manufacturing. To obtain a high deposition accuracy, it is essential to maintain a stable weld pool size. In this study, a novel passive visual method is proposed to measure the weld pool length. Using the proposed method, the image quality was improved by designing a special visual system that employed an endoscope and a camera. It also includes pixel brightness-based and gradient-based algorithms that can adaptively detect feature points at the boundary when the weld pool geometry changes. This algorithm can also be applied to materials with different solidification characteristics. Calibration was performed to measure the real weld pool length in world coordinates, and outlier rejection was performed to increase the accuracy of the algorithm. Additionally, tests were carried out on the intersection component, and the results showed that the proposed method performed well in tracking the changing weld pool length and was applicable to the real-time monitoring of different types of materials.

The exploration of component states for optimizing maintenance schedules in complex systems has garnered significant interest from researchers. However, current literature usually overlooks the critical aspects of system flexibility and reconfigurability. Judicious implementation of system reconfiguration can effectively mitigate system downtime and enhance production continuity. This study proposes a dynamic condition-based maintenance policy considering reconfiguration for reconfigurable systems. A double-layer decision rule was constructed for the devices and systems. To achieve the best overall maintenance effect of the system, the remaining useful life probability distribution and recommended maintenance time of each device were used to optimize the concurrent maintenance time window of the devices and determine whether to reconfigure them. A comprehensive maintenance efficiency index was introduced that simultaneously considered the maintenance cost rate, reliability, and availability of the system to characterize the overall maintenance effect. The reconfiguration cost was included in the maintenance cost. The proposed policy was tested through numerical experiments and compared with different-level policies. The results show that the proposed policy can significantly reduce the downtime and maintenance costs and improve the overall system reliability and availability.

An axial wrinkle defect was observed in the inner wall of the sinking zone of a thick-wall steel tube processed by cold radial forging. Wrinkles can evolve into fissures. The present study focuses on the evolution of wrinkles and the effects of process parameters on them using a three-dimensional radial forging process finite element model, radial forging experiments, and surface morphology observations. The results indicated that the vertical section angle of the hammer die and the size of the tube blank significantly affect the evolution of wrinkles. The height-to-width ratio λ was introduced to describe the morphology of wrinkles. It had an approximately linear relationship with the radius reduction in the sinking zone. There was a linear correlation between the growth slope of λ and the axial to circumferential strain ratio |ε_r/ε_θ|, which can predict the λ under few process parameters. For the 30SiMn2MoVA steel, at the junction of the forging and sinking zones, the threshold of λ of the wrinkle that can evolve into a fissure is approximately 1.123.

Model design and slicing contour generation in additive manufacturing (AM) data processing face challenges in terms of efficiency and scalability when stereolithography files generated by complex functionally graded structures have millions of faces. This paper proposes a hybrid modeling and direct slicing method for AM to efficiently construct and handle complex three-dimensional (3D) models. All 3D solids, including conformal multigradient structures, were uniformly described using a small amount of data via signed distance fields. The hybrid representations were quickly discretized into numerous disordered directed lines using an improved marching squares algorithm. By establishing a directional HashMap to construct the topological relationship between lines, a connecting algorithm with linear time complexity is proposed to generate slicing contours for manufacturing. This method replaces the mesh reconstruction and Boolean operation stages and can efficiently construct complex conformal gradient models of arbitrary topologies through hybrid modeling. Moreover, the time and memory consumption of direct slicing are much lower than those of previous methods when handling hybrid models with hundreds of millions of faces after mesh reconstruction.

Currently, simultaneous buffer and service rate allocation is a topic of interest in the optimization of manufacturing systems. Simultaneous allocation problems have been solved previously to satisfy economic requirements; however, owing to the progress of green manufacturing, energy conservation and environmental protection have become increasingly crucial. Therefore, an energy-efficient approach is developed to maximize the throughput and minimize the energy consumption of manufacturing systems, subject to the total buffer capacity, total service rate, and predefined energy efficiency. The energy-efficient approach integrates the simulated annealing-non-dominated sorting genetic algorithm-II with the honey badger algorithm-histogram-based gradient boosting regression tree. The former algorithm searches for Pareto-optimal solutions of sufficient quality. The latter algorithm builds prediction models to rapidly calculate the throughput, energy consumption, and energy efficiency. Numerical examples show that the proposed hybrid approach can achieve a better solution quality compared with previously reported approaches. Furthermore, the prediction models can rapidly evaluate manufacturing systems with sufficient accuracy. This study benefits the multi-objective optimization of green manufacturing systems.

The vibration disturbance from an external environment affects the machining accuracy of ultra-precision machining equipment. Most active vibration-isolation systems (AVIS) have been developed based on static loads. When a vibration-isolation load changes dynamically during ultra-precision turning lathe machining, the system parameters change, and the efficiency of the active vibration-isolation system based on the traditional control strategy deteriorates. To solve this problem, this paper proposes a vibration-isolation control strategy based on a genetic algorithm-back propagation neural network-PID control (GA-BP-PID), which can automatically adjust the control parameters according to the machining conditions. Vibration-isolation simulations and experiments based on passive vibration isolation, a PID algorithm, and the GA-BP-PID algorithm under dynamic load machining conditions were conducted. The experimental results demonstrated that the active vibration-isolation control strategy designed in this study could effectively attenuate vibration disturbances in the external environment under dynamic load conditions. This design is reasonable and feasible.