Grinding with cubic boron nitride (CBN) superabrasive is a widely used method of machining superalloy in aerospace industries. However, there are some issues, such as poor grinding quality and severe tool wear, in grinding of powder metallurgy superalloy FGH96. In addition, abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels. In this case, the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out. The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation. The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process. It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis. Attrition wear, micro break, and macro fracture had an important impact on material removal characteristics. Besides, compared with the single cutting edge, higher pile-up ratio was obtained by multiple cutting edges, which reduced the removal efficiency of the material. Therefore, weakening multiple cutting edge grinding on abrasive grains in the industrial production, such as applying suitable dressing strategy, is an available method to improve the grinding quality and efficiency.

During assembly process, the miniature part needs to be fixed in its assembly position. In some occasions where adhesive is used, the joining force is not established due to the adhesive curing process, in that case the locking of parts is required. Manual locking is difficult to meet the increasing demand for mass production. To solve this problem and realize fully automatic assembly, a novel gripper module was designed and corresponding locking method was proposed. Thanks to the functional integration, the gripper module is capable of manipulating and locking the part. This module is integrated into the assembly system and plays a crucial role in automatic assembly. The locking method for automatic assembly is based on the integration of the part picking up and the locking unit releasing. After being placed accurately at its desired position, the miniature part can be automatically locked by releasing the locking unit. The innovative structure and mechanism of the gripper module convert the spring force into the locking force of the miniature part, ensuring non-rigid locking and suitable small locking force. Locking principle, flexibility and limitations of the proposed method were clarified in detail. Moreover, an effective compensation strategy was used to achieve accurate and stable pickup of the part, which increased the reliability of the assembly process. During automatic locking, the disturbances to the part due to the eccentric load were analyzed. The effectiveness of the gripper module and proposed method was verified by experiment. Experimental results indicated that the modular system integrated with the gripper module could meet the requirements of fully automatic assembly. Manual locking is replaced by automatic locking, and workers are liberated from tedious manual operations. The improvement of automation level enables assembly equipment to be applied to mass production scenarios.

Abrasive waterjet (AWJ) is widely applied in 2D machining as it offers high machining efficiency and low machining cost. However, machining a 3D surface, especially for a small curvature radius freeform surface (SCRFS), results in over-erosion of the corner, and has been one of the greatest issues of AWJ. To solve this problem, a local smoothing algorithm for SCRFS is developed by the junction of two linear segments at the corner by inserting cubic second-order B-spline to smooth the nozzle path and posture under the setting tolerance error, which is aimed to avoid over-erosion due to the change in dwell time. Analytical solutions of the smooth corner position and orientation of the nozzle path are obtained by evaluating a synchronization algorithm. According to the set tolerance error of the nozzle position and orientation, the interpolation of the smooth path of the corner meets the constraint conditions of the linear feed drive. Path simulation and experimental results show that the proposed method is validated by the experimental results and has been applied to the integral blisk machining of an aero-engine.

In micro electrochemical machining (ECM) processes, stray corrosion causes undesired metal dissolution and the deterioration of shape accuracy. Adopting a sidewall-insulated electrode is an effective approach to suppressing stray corrosion. Most sidewall-insulated electrodes are made of metal substrate and non-metallic thin films. Nevertheless, the thin-film insulating materials attached to a metal substrate are susceptible to damage in an electrolytic environment. This study presents a novel concept of the conductive-material-filled electrode for better sidewall-insulation performance. The micro-scale quartz tube serves as the insulating substrate. Commercially available conductive fillers including metal wire, molten metals, and silver powder are filled inside the working cathode of the quartz tube. Consequently, the metal-wire-filled electrode, molten-metal-filled electrode, and nano-powder-filled electrode are designed and fabricated. From the verification results of electrode toughness, material removal rate, and surface topography, the metal-wire-filled electrode and molten-metal-filled electrode exhibit the same performance as a traditional metal-based electrode and much better durability. By contrast, the nano-powder-filled electrode is unable to withstand long-term ECM processes because of the loss of cured powder particles. In ECM experiments, microstructures with steep sidewalls (taper angle <9.7°) were machined using the metal-wire-filled electrode and molten-metal-filled electrode, which could replace the traditional electrode, achieving a longer service life and superior sidewall-insulation performance.

Zero defection manufacturing (ZDM) is the pursuit of the manufacturing industry. However, there is a lack of the implementation method of ZDM in the multi-stage manufacturing process (MMP). Implementing ZDM and controlling product quality in MMP remains an urgent problem in intelligent manufacturing. A novel predict-prevention quality control method in MMP towards ZDM is proposed, including quality characteristics monitoring, key quality characteristics prediction, and assembly quality optimization. The stability of the quality characteristics is detected by analyzing the distribution of quality characteristics. By considering the correlations between different quality characteristics, a deep supervised long-short term memory (SLSTM) prediction network is built for time series prediction of quality characteristics. A long-short term memory-genetic algorithm (LSTM-GA) network is proposed to optimize the assembly quality. By utilizing the proposed quality control method in MMP, unqualified products can be avoided, and ZDM of MMP is implemented. Extensive empirical evaluations on the MMP of compressors validate the applicability and practicability of the proposed method.

The heat generated and accumulated on the machined surface of an Inconel 718 workpiece causes thermal damage during the cutting process. Surface-active media with high thermal conductivity coated on the workpiece to be machined may have the potential to reduce the generation of cutting heat. In this study, a theoretical model for predicting the instantaneous machined surface temperature field is proposed for surface-active thermal conductive medium (SACM)-assisted cutting based on the finite element and Fourier heat transfer theories. Orthogonal cutting experiments were performed to verify the results predicted using the proposed surface-temperature field model. Three SACMs with various thermal conductivities were used to coat Inconel 718 surface to be machined. Thermocouples embedded into the workpiece were used to measure the cutting temperature at different points on the machined workpiece surface during the cutting process. The experimental results were in agreement with the predicted temperatures, and the maximum error between the experimental results and predicted temperatures was approximately 9.5%. The cutting temperature on the machined surface decreased with an increase in the thermal conductivity of the SACM. The graphene SACM with high thermal conductivity can effectively reduce the temperature from 542 °C to 402 °C, which corresponds to a reduction of approximately 26%. The temperature reduction due to SACM decreases with an increase in the distance between the temperature prediction point and machined workpiece surface. In conclusion, the cutting temperatures on the machined workpiece surface can be reduced by coating with SACM.

Fast drilling electrical discharge machining (EDM) is widely used in the manufacture of film cooling holes of turbine blades. However, due to the various hole orientations and severe electrode wear, it is relatively intricate to accurately and timely identify the critical moments such as breakout, hole completion in the drilling process, and adjust the machining strategy properly. Existing breakout detection and hole completion determination methods are not suitable for the high-efficiency and fully automatic production of film cooling holes, for they almost all depend on preset thresholds or training data and become less appropriate when machining condition changes. As the breakout and hole completion detection problems can be abstracted to an online stage identification problem, in this paper, a kurtosis-based stage identification (KBSI) method, which uses a novel normalized kurtosis to denote the recent changing trends of gap voltage signals, is developed for online stage identification. The identification accuracy and generalization ability of the KBSI method have been verified in various machining conditions. To improve the overall machining efficiency, the influence of servo control parameters on machining efficiency of each machining stage was analyzed experimentally, and a new stage-wise adaptive control strategy was then proposed to dynamically adjust the servo control parameters according to the online identification results. The performance of the new strategy is evaluated by drilling film cooling holes at different hole orientations. Experimental results show that with the new control strategy, machining efficiency and the machining quality can be significantly improved.

Wire electrochemical machining (WECM) is a potential method for manufacturing macrostructures from difficult-to-cut materials, such as turbine slots, with good surface integrity and low costs. In this study, a novel tube electrode with array holes in the front and insulation in the back was applied using WECM to improve the machining precision and efficiency. Additionally, assisted by an immersion electrolyte and axial flushing, the electrolyte-deficient gap was supplemented to achieve the cutting of a very thick workpiece. The simulation results indicated that this method could effectively reduce the machining gap and improve the uniformity of the electric- and flow-field distributions. Experiments verified that when the uninsulated range (machining angle) was reduced from 360° to 90°, the side machining gap was reduced from 462.5 µm to 175 µm. Finally, using optimized machining parameters, array slits with gaps as small as (175±10) μm were machined on a powder superalloy René 88DT sample with a thickness of 10 mm at a feed rate of 16 µm/s. The feasibility of fabricating complex profiles using this method was verified using a self-designed servo device.

Impact hydroforming (IHF), as a novel sheet metal forming technology with the advantages of high strain rate forming and flexible liquid loading, is highly suitable for efficiently manufacturing aluminum complex-shaped sheet parts. In this paper, deformation characteristics of complex sheet parts under IHF are systematically investigated. The mechanical properties of 2024 aluminum alloy under a wide range of strain rates (10−3 s−1–3.3×103 s−1) were studied. It indicated that the elongation of 2024 aluminum alloy was improved by 116.01% under strain rates of 3.306 × 103 s−1, referring to 10−3 s−1. Further, a complex-shaped part with symmetrical and asymmetrical structures was selected. The deformation characteristics of sheet and role of inertial effect under IHF were investigated with well-developed solid–liquid coupling finite element (SLC-FE) model with high accuracy. Differentiating deformation tendency is found for symmetrical structure with notably prior deformation at central zone, showing a “bulging” profile at initial forming stage. Whereas, synchronous deformation is presented for asymmetrical structure with a “flat” profile. Additionally, distinctive inertial effect was observed at different positions change for both symmetrical and asymmetrical structures, in which lower values were resulted at their central regions. Meanwhile, the inertial effect evolved with the impacting speed. Specially, larger difference of inertial effect was observed with increasing impacting speed.

As one of the indispensable actuating components in micro-systems, the shafted microgear is in great production demand. Microforming is a manufacturing process to produce microgears to meet the needs. Due to the small geometrical size, there are uncertain process performance and product quality issues in this production process. In this study, the shafted microgears were fabricated in two different scaling factors with four grain sizes using a progressively extrusion-blanking method. To explore the unknown of the process, grain-based modeling was proposed and employed to simulate the entire forming process. The results show that when the grains are large, the anisotropy of single grains has an obvious size effect on the forming behavior and process performance; and the produced geometries and surface quality are worsened; and the deformation load is decreased. Five deformation zones were identified in the microstructures with different hardness and distributions of stress and strain. The simulation by using the proposed model successfully predicted the formation of zones and revealed the inhomogeneous deformation in the forming process. The undesirable geometries of microgears including material unfilling, burr and inclination were observed on the shaft and teeth of gear, and the inclination size is increased obviously with grain size. To avoid the formation of inclination and material unfilling, the punch was redesigned, and a die insert was added to constraint the bottom surface of the gear teeth. The new products had then the better forming quality.