Advances in Manufacturing

Anisotropy in tensile properties and fracture behaviour of 316L stainless steel parts manufactured by fused deposition modelling and sintering

Lin-Ju Wen, Xiao-Gang Hu, Zhong Li, Zhan-Hua Wang, Ji-Kai Wu, Qiang Zhu

2022, 10(3): 345-355. doi:10.1007/s40436-022-00402-4

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Fused deposition modelling and sintering (FDMS) is a potential metal additive manufacturing technology due to its low cost and high efficiency. The mixture of metal powder and binder goes through heating, extrusion, debinding and sintering processes to produce the compact finished part. However, it is generally believed that parts produced by FDMS possess poor and anisotropic tensile properties, which always attributes to the weak interlayer combination. The current work aimed to enhance tensile properties and better understand the anisotropic fracture behavior of the 316L stainless steel prepared by FDMS. By process optimization, the yield strength and ultimate tensile strength obtained in this work are increased by 26.1% and 15.2%, based on the highest performance reported in previous studies. According to the ultimate tensile strength, the performance difference between the horizontal and vertical directions has been reduced to 27%. Furthermore, the experimental results indicated that the clustered irregular shape holes evolved from primitive voids prefer to distribute in the build direction, resulting in anisotropic tensile performance. It is suggested that the mechanical properties could be improved by applying a smaller extrusion diameter and rolling-assisted printing. In addition, the current FDMS parts show qualified performance for producing the customized and small batch components.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00402-4

Molecular dynamics study on surface formation and phase transformation in nanometric cutting of β-Sn

Zhi-Fu Xue, Min Lai, Fei-Fei Xu, Feng-Zhou Fang

2022, 10(3): 356-367. doi:10.1007/s40436-022-00399-w

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Atomic motion and surface formation in the nanometric cutting process of β-Sn are investigated using molecular dynamics (MD). A stagnation region is observed that changes the shape of the tool edge involved in nanometric cutting, resulting in a fluctuation in the cutting forces. It is found that single-crystal tin releases the high compressive stress generated under the tool pressure through slip and phase transformation. The tin transformation proceeds from a β-Sn structure to a bct-Sn structure. The effects of the cutting speed, undeformed chip thickness (UCT) and tool edge radius on material removal are also explored. A better surface is obtained through material embrittlement caused by a higher speed. In addition, a smaller UCT and sharper tool edge help reduce subsurface damage.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00399-w

On-machine measurement of tool nose radius and wear during precision/ultra-precision machining

Jiang Guo, Xing-Yu Wang, Yong Zhao, Chen-Yi Hou, Xu Zhu, Yin-Di Cai, Zhu-Ji Jin, Ren-Ke Kang

2022, 10(3): 368-381. doi:10.1007/s40436-022-00397-y

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The tool state exerts a strong influence on surface quality and profile accuracy during precision/ultraprecision machining. However, current on-machine measurement methods cannot precisely obtain the tool nose radius and wear. This study therefore investigated the onmachine measurement of tool nose radius on the order of hundreds of microns and wear on the order of a few microns to tens of microns during precision/ultra-precision machining using the edge reversal method. To provide the necessary replication, pure aluminum and pure copper soft metal substrates were evaluated, with pure copper exhibiting superior performance. The feasibility of the measurement method was then demonstrated by evaluating the replication accuracy using a 3D surface topography instrument; the measurement error was only 0.1%. The wear of the cutting tool was measured using the proposed method to obtain the maximum values for tool arc wear, flank wear, and wear depth of 3.4 lm, 73.5 lm and 3.7 lm, respectively.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00397-y

Research on the underlying mechanism behind abrasive flow machining on micro-slit structures and simulation of viscoelastic media

Bao-Cai Zhang, Shi-Fei Chen, Nasim Khiabani, Yu Qiao, Xin-Chang Wang

2022, 10(3): 382-396. doi:10.1007/s40436-022-00395-0

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In this study, the machining mechanism of abrasive flow machining (AFM) microstructures was analyzed in depth according to the transmission morphology and rheological behaviors of the abrasive media. The transmission morphology demonstrated the excellent combination of the polymer melt with abrasive grains at the interface, indicating that the polymer melt, combined with the uniform distribution of the polymer chains, could exert a harmonious axial force on the abrasive grains. Based on the rheological behavior analysis of the abrasive media, for example, the stress relaxation and moduli of storage and loss, a machining mechanism model was established incorporating the effect of microplastic deformation and continuous viscous flow, which was further verified by the grooves along the flow direction. In addition, the PhanThien-Tanner (PTT) model combined with a wall slipping model was employed to simulate the machining process for the first time here. The value of the simulated pressure (1.3 MPa) was similar to the measured pressure (1.45 MPa), as well as the simulated volumetric rate (0.011 4 mL/s) to the measured volumetric rate (0.067 mL/s), which further proved the validity of the simulation results. The flow duration (21 s) derived from a velocity of 1.2 mm/s further confirmed the residual stretched state of the polymer chains, which favored the elasticity of the abrasive media on the grains. Meanwhile, the roughly uniform distribution of the shear rate at the main machining region exhibited the advantages of evenly spread storage and loss moduli, contributing to the even extension of indentation caused by the grains on the target surface, which agreed with the mechanism model and machined surface morphology.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00395-0

Precision measurement and compensation of kinematic errors for industrial robots using artifact and machine learning

Ling-Bao Kong, Yi Yu

2022, 10(3): 397-410. doi:10.1007/s40436-022-00400-6

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Industrial robots are widely used in various areas owing to their greater degrees of freedom (DOFs) and larger operation space compared with traditional frame movement systems involving sliding and rotational stages. However, the geometrical transfer of joint kinematic errors and the relatively weak rigidity of industrial robots compared with frame movement systems decrease their absolute kinematic accuracy, thereby limiting their further application in ultraprecision manufacturing. This imposes a stringent requirement for improving the absolute kinematic accuracy of industrial robots in terms of the position and orientation of the robot arm end. Current measurement and compensation methods for industrial robots either require expensive measuring systems, producing positioning or orientation errors, or offer low measurement accuracy. Herein, a kinematic calibration method for an industrial robot using an artifact with a hybrid spherical and ellipsoid surface is proposed. A system with submicrometric precision for measuring the position and orientation of the robot arm end is developed using laser displacement sensors. Subsequently, a novel kinematic error compensating method involving both a residual learning algorithm and a neural network is proposed to compensate for nonlinear errors. A six-layer recurrent neural network (RNN) is designed to compensate for the kinematic nonlinear errors of a six-DOF industrial robot. The results validate the feasibility of the proposed method for measuring the kinematic errors of industrial robots, and the compensation method based on the RNN improves the accuracy via parameter fitting. Experimental studies show that the measuring system and compensation method can reduce motion errors by more than 30%. The present study provides a feasible and economic approach for measuring and improving the motion accuracy of an industrial robot at the submicrometric measurement level.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00400-6

Effects of process parameters on periodic impact force exerting on cutting tool in ultrasonic vibration-assisted oblique turning

Long-Xu Yao, Zhan-Qiang Liu, Qing-Hua Song, Bing Wang, Yu-Kui Cai

2022, 10(3): 411-427. doi:10.1007/s40436-022-00398-x

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During ultrasonic vibration-assisted machining, the large impact force induced by tool-workpiece reengagement (TWR) is an important factor that affects tool chipping. However, mechanical analysis into process factors that affect the impact force and their influencing mechanisms are insufficient. Herein, a prediction model for the instantaneous cutting force during both TWR and the stable turning process, which depends on the process parameters and material properties, is firstly proposed based on the kinematic and dynamic analysis of ultrasonic vibration-assisted oblique turning (UVAOT). The results calculated using the developed cutting force model agree well with the experimental results presented in the literature. Next, the linear change law of the instantaneous cutting force with cutting time during the actual TWR is clarified using the proposed model. The effect of the UVAOT process parameters on the average impact force during the periodic TWR process is discussed, and the influence mechanism is analyzed from the perspective of mechanics. A positive linear correlation is discovered between the feed speed and average impact force. The ultrasonic amplitude and cutting speed do not significantly affect the average impact force of the new sharp cutting tools. These findings are consistent with the experimental observations of tool chipping and are applicable to select process parameters for reducing tool chipping during UVAOT.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00398-x

Relationship between dynamic characteristics of air film of aerostatic spindle and mid-frequency of surface topography

Dong-Ju Chen, Shu-Pei Li, Xuan Zhang, Jin-Wei Fan

2022, 10(3): 428-442. doi:10.1007/s40436-022-00391-4

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The dynamic characteristics of the gas film of an aerostatic spindle primary affect workpiece waviness in ultra-precision machining. To improve the machining accuracy of the machine tool and provide a firm theoretical basis for the design of an aerostatic spindle, a simulation model combining transient computational fluid dynamics (CFD) analysis and transient dynamic analysis is established in this study to investigate the dynamic characteristics of the spindle under unstable operating conditions. Based on a large eddy simulation, a three-dimensional flow model of an air film in an aerostatic spindle is established. The simulation results show that the gas flow in the throttle chamber is turbulent, and that complex vortices are formed. Using dynamic grid modeling technology, a CFD numerical model for the unsteady calculation of the spindle is established, and the dynamic characteristics of the gas film are obtained. A transient dynamic simulation model of an aerostatic spindle is established, and the effect of the nonlinear dynamic characteristics of the gas film on the spindle displacement response is investigated. Subsequently, a surface morphology prediction model is established. Results show that film fluctuation significantly affects the dynamic characteristics of the spindle and subsequently affects the generation of surface ripples on the workpiece.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00391-4

An integrated machine-process-controller model to predict milling surface topography considering vibration suppression

Miao-Xian Guo, Jin Liu, Li-Mei Pan, Chong-Jun Wu, Xiao-Hui Jiang, Wei-Cheng Guo

2022, 10(3): 443-458. doi:10.1007/s40436-021-00386-7

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Surface topography is an important factor in evaluating the surface integrity and service performance of milling parts. The dynamic characteristics of the manufacturing system and machining process parameters significantly influence the machining precision and surface quality of the parts, and the vibration control method is applied in high-precision milling to improve the machine quality. In this study, a novel surface topography model based on the dynamic characteristics of the process system, properties of the cutting process, and active vibration control system is theoretically developed and experimentally verified. The dynamic characteristics of the process system consist of the vibration of the machine tool and piezoelectric ceramic clamping system. The dynamic path trajectory influenced by the processing parameters and workpiece-tool parameters belongs to the property of the cutting process, while different algorithms of active vibration control are considered as controller factors. The milling surface topography can be predicted by considering all these factors. A series of experiments were conducted to verify the effectiveness and accuracy of the prediction model, and the results showed a good correlation between the theoretical analysis and the actual milled surfaces.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00386-7

Continuous generating grinding method for beveloid gears and analysis of grinding characteristics

Bing Cao, Guo-Long Li, Alessandro Fortunato, Heng-Xin Ni

2022, 10(3): 459-478. doi:10.1007/s40436-022-00388-z

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Continuous generating grinding has become an important gear processing method owing to its high efficiency and precision. In this study, an adaptive design model is proposed for the continuous generation of beveloid gears in common gear grinding machines. Based on this model, a method for determining the installation position and grinding kinematics is developed alongside an analytical meshing model for grinding contact trace and derivation of key grinding parameters. By combining these aspects, a general mathematical model for the continuous generation of beveloid gears is presented, comprising the entire grinding process from worm wheel dressing to the evaluation of grinding deviation. The effects of the worm and dressing wheel parameters on the grinding deviation were analysed, facilitating the development of an approach to improve the grinding accuracy. The presented procedure represents a novel design method for the continuous generation of beveloid gears in common gear grinding machines, facilitating the appropriate selection of worm and dressing wheel parameters.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00388-z

Model reconstruction for worn blades based on hybrid surface registrations

Kang Cui, Rui-Song Jiang, Lin Jing

2022, 10(3): 479-494. doi:10.1007/s40436-022-00390-5

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Model reconstruction is crucial in blade repair because it directly determines the shape precision and finish of a repaired surface. However, owing to insufficient surface data pertaining to defective regions and the unique deformation caused by harsh environments, modeling a worn blade remains difficult. Hence, a model reconstruction method for worn blades is developed in this study. Unlike conventional methods of constructing and interpolating sectional curves, the proposed method focuses on modifying a nominal computer aided design (CAD) model to reconstruct the worn blade. Through weighted rigid registration and constraint-based non-rigid registration, the design surface extracted from the nominal CAD model can be deformed to align with the surface data of the worn blade without a significant loss of its initial shape. Verification results show that the deformed design surface exhibits sufficient smoothness and accuracy for guiding tool path generation in the subsequent blade repair.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00390-5

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