Advances in Manufacturing

Flat-end tool orientation based on rotation-minimizing frame

Xiang Zou, Hon-Yuen Tam, Hai-Yin Xu, Ke Shi

2019, 7(3): 257-269. doi:10.1007/s40436-019-00271-4

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Well-designed tool orientation is crucial for the quality execution of five-axis machining with flat-end tools. Tool orientation can be specified in terms of tool inclination and tool tilt angles. For a given surface path, these aspects need to be specified for each cutter contact point along the path, because poor tool orientation choice can cause large axial acceleration of the machine tool, leading to inferior quality of the machined surface. The rotation-minimizing frame aims to reduce unnecessary frame rotation during movement. This concept has been adopted to develop tool orientation methods that allow variation in the inclination angle, the tilt angle, and both the inclination and tilt angles. The intention is to reduce unnecessary rotation of the tool frame as the tool follows a specified path. Evaluation was conducted in the context of five-axis flat-end tool machining. Based on these methods, tool orientation was planned along surface paths of a torus, sphere, and dome. Changes in tool orientation were always smooth. From the perspective of reducing tool orientation changes and axial acceleration, it was demonstrated that simultaneous variation of the inclination and tilt angles based on rotation minimization provided the best results.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00271-4.pdf

Understanding the formation mechanism of subsurface damage in potassium dihydrogen phosphate crystals during ultraprecision fly cutting

Yong Zhang, Ning Hou, Liang-Chi Zhang

2019, 7(3): 270-277. doi:10.1007/s40436-019-00265-2

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Potassium dihydrogen phosphate (KDP) crystals play an important role in high-energy laser systems, but the laser damage threshold (LDT) of KDP components is lower than expected. The LDT is significantly influenced by subsurface damage produced in KDP crystals. However, it is very challenging to detect the subsurface damage caused by processing because a KDP is soft, brittle, and sensitive to the external environment (e.g., humidity, temperature and applied stress). Conventional characterization methods such as transmission electron microscopy are ineffective for this purpose. This paper proposes a nondestructive detection method called grazing incidence X-ray diffraction (GIXD) to investigate the formation of subsurface damage during ultra-precision fly cutting of KDP crystals. Some crystal planes, namely (200), (112), (312), (211), (220), (202), (301), (213), (310) and (303), were detected in the processed subsurface with the aid of GIXD, which provided very different results for KDP crystal bulk. These results mean that single KDP crystals change into a lattice misalignment structure (LMS) due to mechanical stress in the subsurface. These crystal planes match the slip systems of the KDP crystals, implying that dislocations nucleate and propagate along slip systems to result in the formation of the LMS under shear and compression stresses. The discovery of the LMS in the subsurface provides a new insight into the nature of the laser-induced damage of KDP crystals.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00265-2.pdf

Accelerating sample preparation of graded thermoelectric materials using an automatic powder feeding system

Hua-Yan Pu, Rong-Qing Xie, Yan Peng, Yang Yang, Shi-Yang He, Jun Luo, Yi Sun, Shao-Rong Xie, Jun Luo

2019, 7(3): 278-287. doi:10.1007/s40436-019-00269-y

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In recent years, the development of techniques for the controlled preparation of functional graded materials (FGMs) has become a vigorous research field. In this study, to improve the efficiency and accuracy of sample preparations, an automated feeding system based on gravimetric principles for dry powder with three dosing feeders is designed and realized. The feeding rate and accuracy can be regulated by coordinating the protruded length L (mm) and rotational speed V (r/min) of the feeder stirrer. To demonstrate this automatic sample preparation system, the well-known thermoelectric material Bi_xSb_2-xTe₃ (x=0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) is selected and prepared by the developed system, and the composition distribution of the functional graded material is characterized. Experimental results show that the Bi_xSb_2-xTe₃ (x=0.3-0.8) functionally graded material crystalizes in the rhombohedral phase after hot-pressing sintering and annealing and the prepared sample has a good gradient composition distribution. This verifies the reliability and accuracy of the feeding system. The concept of samples with a gradient component and application of the automatic powder feeding system could considerably accelerate the research and development of new materials.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00269-y.pdf

Variation characteristic of drilling force and influence of cutting parameter of SiCp/Al composite thin-walled workpiece

Shu-Tao Huang, Chao Li, Li-Fu Xu, Lin Guo, Xiao-Lin Yu

2019, 7(3): 288-302. doi:10.1007/s40436-019-00264-3

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In this paper, the variation characteristic of the drilling force, and the influences of cutting speed, feed rate, and workpiece thickness on the drilling force, were evaluated when drilling a silicon carbide particle reinforced aluminum matrix (SiCp/Al) composite thin-walled workpiece with a high volume fraction. Under the condition that the workpiece thickness was less than the drill tip height, three characteristic stages of drilling force variation were proposed. The results indicate that there is a significant difference between the variations in the drilling force when drilling a thin-walled workpiece compared to thick-walled workpiece. When the chisel edge drills out the lower surface of the workpiece, there is an abrupt decrease in the thrust forces of the thin-walled and thick-walled workpieces. In addition, there is an abrupt decrease in the torque of the thick-walled workpiece, whereas that of the thinwalled workpiece increases. According to the thickness of the thin-walled workpiece, the instant of the abrupt decrease in the thrust force may lead or lag behind the theoretical instant at which the chisel edge reaches the lower surface of the workpiece without deformation. When drilling a thin-walled hole, the cutting speed has a slight influence on the thrust force, and there is a slight increase in the torque in accordance with an increase in the cutting speed. The thrust force and torque increase in accordance with an increase in the feed rate. When drilling a thinwalled workpiece with a thickness of 1 mm, the critical thickness of workpiece cracking decreases in accordance with an increase in the cutting speed, and increases in accordance with an increase in the feed rate. When drilling a thin-walled workpiece with a thickness of 0.5 mm, the concave deformation of the workpiece and the critical thickness of the workpiece cracking increase in accordance with an increase in the feed rate. However, the increment in the critical thickness of the workpiece cracking is less than that in the concave deformation of the workpiece.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00264-3.pdf

Key machining characteristics in ultrasonic vibration cutting of single crystal silicon for micro grooves

Jun-Yun Chen, Tian-Ye Jin, Xi-Chun Luo

2019, 7(3): 303-314. doi:10.1007/s40436-019-00263-4

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Structured complex silicon components have been widely used in solar cells, biomedical engineering and other industrial applications. As silicon is a typical brittle material, ultrasonic vibration cutting (UVC) is a promising method to achieve better cutting performance than conventional techniques. High-frequency 1D UVC possesses higher nominal cutting speed and material removal rate than many 2D/3D UVC systems, and thus, it has great development potential in industrial applications of structured silicon components. However, few researchers have applied 1D UVC to the cutting of structured silicon surfaces, since its main drawback is tool marks imprinted by the vibration on machined surface. In this study, to uncover the key machining characteristics under the condition of 1D UVC, a series of tests involving diamond cutting grooves were first performed on the silicon surface. The machined surface and chips were subsequently measured and analyzed to evaluate the critical undeformed chip thickness, surface characteristics, and chip formation. Regarding the main drawback of 1D UVC, a novel theoretical model was developed for predicting the length of tool marks and evaluating the impact of tool marks on the surface finish. The results demonstrated that the critical undeformed chip thickness of silicon reached 1 030 nm under a certain vibration amplitude and that an array of micro grooves was generated at the plastic region with a surface roughness (Ra) as low as 1.11 nm. Moreover, the micro topography of the continuous chips exhibited discontinuous clusters of lines with diameters of dozens of nanometers, only composed of polysilicon. The novel theoretical model was able to predict the length of tool marks with low error. Thus, the impact of tool marks on the surface finish can be reduced and even eliminated with help of the model.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00263-4.pdf

Bio-inspired motion planning for reaching movement of a manipulator based on intrinsic tau jerk guidance

Zhen Zhang, Xu Yang

2019, 7(3): 315-325. doi:10.1007/s40436-019-00268-z

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This study proposed a bio-inspired motion planning approach for the reaching movement of a robot manipulator based on a novel intrinsic tau jerk guidance strategy, which was established by some cognitive science researchers when they studied motion patterns through biology. In accordance with the rules of human reaching movement, the intrinsic tau jerk guidance strategy ensures continuity of the acceleration; further, it also ensures that its value is zero at the start and end of the movement. The approach has been implemented on a three-degrees-offreedom 3R planar manipulator. The results show that, within a defined time, both the position gap and attitude gap can be reposefully closed, and the curves of joint velocity, acceleration, and driving torque are continuous and smooth. According to the dynamic analysis, the proposed approach tends to consume less energy. The bioinspired method has the potential to be applied in particular scenarios in the future, such as a mobile robot with a manipulator exploring an unknown environment.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00268-z.pdf

Research on temperature field of non-uniform heat source model in surface grinding by cup wheel

Shi-Jie Dai, Xiao-Qiang Li, Hui-Bo Zhang

2019, 7(3): 326-342. doi:10.1007/s40436-019-00272-3

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To address the problems of thermal damage to a workpiece surface caused by the instantaneous high temperature during grinding and the difficulty in monitoring temperature in real time, the temperature field in the case of composite surface grinding by a cup wheel is studied. In order to predict the grinding temperature, considering material removal and grinding force distribution, a nonuniform heat source model with different function distributions in the circumferential and radial directions in the cylindrical coordinate system is first proposed; then, the analytical model is deduced and the numerical model of the temperature field is established based on the heat source model. The validation experiments for grinding temperature field are carried out using a high-definition infrared thermal imager and an artificial thermocouple. Compared to the temperature field based on the uniform heat source model, the results based on the non-uniform heat source model are in better agreement with the actual temperature field, and the temperature prediction error is reduced from approximately 23% to 6%. Thus, the present study provides a more accurate theoretical basis for preventing burns in cup wheel surface grinding.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00272-3.pdf

Surface reconstruction from unorganized point clouds based on edge growing

Xu-Jia Qin, Zhong-Tian Hu, Hong-Bo Zheng, Mei-Yu Zhang

2019, 7(3): 343-352. doi:10.1007/s40436-019-00262-5

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Owing to unorganized point cloud data, unexpected triangles, such as holes and slits, may be generated during mesh surface reconstruction. To solve this problem, a mesh surface reconstruction method based on edge growing from unorganized point clouds is proposed. The method first constructs an octree structure for unorganized point cloud data, and determines the k-nearest neighbor for each point. Subsequently, the method searches for flat areas in the point clouds to be used as the initial mesh edge growth regions, to avoid incorrect reconstruction of the mesh surface owing to the growth of initial sharp areas. Finally, the optimal mesh surface is obtained by controlling the mesh edge growing based on compulsive restriction and comprehensive optimization criteria. The experimental results of mesh surface reconstruction show that the method is feasible and shows high reconstruction performance without introducing holes or slits in the reconstructed mesh surface.

The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00262-5.pdf

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