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Diamond turning of microstructured surfaces based on slow slide servo or fast tool servo technologies suffers from either low machining efficiency or low surface accuracy, due to the highly mixed low-frequency and high-frequency tool trajectory. This work proposes a new parallel tool servo (PTS) turning technology, in which the original tool path is filtered according to an optimal cut-off frequency and then decomposed into independent trajectories separately for a slow slide and a fast stage in parallel. This approach is experimentally validated and compared with existing single-mode servo technologies, with significantly enhanced cutting performance, thus offering a novel perspective for ultra-precision machining. [ABSTRACT FROM AUTHOR]

A barrel cutter has a cutting segment with a large radius on its profile, and this arc segment allows the cutter to tilt away from the part surface, avoiding the collisions of the tool with the part. Therefore, barrel cutters are suitable for five-axis blisk machining. However, the barrel cutters are more challenging for CAM software to generate paths. A method of generating collision-free and large-machining width flank milling paths with smooth axes movements for blisk machining with barrel cutters is proposed. Local gouge between the tool flute surface and the blade to be machined is considered, and the collisions of the blisk with the non-cutting parts of the tool, i.e. tool shank and holder, are also detected. The machined part geometry is the complement of the cutter's swept envelope from the stock. Accordingly, the swept profile of the cutter at each cutter contact point is employed to evaluate the machining width naturally. Thereafter, a multi-criteria tool path generation model is established, and it is converted into a single-objective optimization with the weighted sum method. An algorithm based on the Differential Evolution algorithm is developed to solve this model. The numerical example illustrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A method of generating optimal tool paths for sculptured surface machining with flat-end cutters is presented in this paper. The inclination and tilt angles, as well as the feed directions of the cutter at each cutter contact point on a machining path are optimised as a whole so that the machining width of the tool path can be as large as possible, and concerns such as smooth cutter motion, gouging avoidance, scallop height and machining widths overlap are also considered when calculating a path. A multi-criteria tool path optimisation model is introduced, and it is converted into a single objective optimisation with the weighted sum method. The Differential Evolution (DE) algorithm is suitable for solving this highly non-linear problem. However, the searching process of the DE algorithm may be trapped in local minima due to large number of design variables. Therefore, an algorithm combining the DE algorithm and the sequence linear programming algorithm is developed to solve this optimisation model. The proposed method is applied to two freeform surfaces to illustrate its effectiveness. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel compliant active-force support system (CAFS) to provide force sensing and control capabilities in support of thin-walled parts for precision machining. The CAFS is designed with a dual-feedback parallel mechanism (DFPM) driven by a piezoelectric actuator. Through displacement amplification, the DFPM enables CAFS to provide an active force support for compliant machining. Based on the input and output feedbacks of the DFPM, the contact force between CAFS and workpiece can be derived by the built force-sensing model, and the deformation of workpiece can be measured. Meanwhile, with the obtained force as feedback, the support force can be controlled by adjusting the displacement of piezoelectric actuator in real time. Without needing additional force-sensing components, a fast dynamic response can hence be achieved by the proposed CAFS. The performance of the CAFS is predicted by an established analytical model, and validated by finite-element analysis and experiment. The results show that the developed CAFS prototype with a size of 56 × 56 × 93 mm3 can provide a 220 N support force with a resolution of 0.35 N (0.16%). The first resonant frequency of the developed CAFS prototype can reach 4844 Hz. Closed-loop experiments further demonstrate that the proposed CAFS is capable of regulating the support force in a fast and accurate manner. [ABSTRACT FROM AUTHOR]

Diamond micro milling of high-quality micro lens arrays suffers from low machining efficiency, due to the inevitable milling marks along tangential feed direction and the slow spiral tool path interpolated by multiple linear axes. In this article, an advanced cutting process is proposed, namely dynamic rotating-tool (DRT) turning, in which a U-axis attachment on a rotary stage is developed to enable synchronous cutter rotation and radial feed motions of a diamond turning tool. This method is experimentally verified and compared with milling, with significantly enhanced surface quality and machining efficiency, thus bringing a new perspective into ultra-precision machining. [ABSTRACT FROM AUTHOR]

The two additional rotational motions of five-axis machining make the determination of the optimal feed direction and tool orientation a challenging task. A new model to find the optimal feed direction and tool orientation maximising the machining width and avoiding local gouging at a cutter contact (CC) point with a flat-end cutter considering the tool path smoothness requirement is developed in this paper. The machining error is characterised by a signed distance function defined from a point on the bottom tool circle of the cutter to the design surface. With the help of the differential evolution approach, the optimisation model can be resolved to determine the optimal tool orientation and feed direction at a given CC point, and generate the smooth tool paths following the optimal feed direction. Simulation examples demonstrate the developed techniques can improve the tool orientation and feed direction at a CC point to increase the machining width, improving the efficiency of freeform surface machining. [ABSTRACT FROM PUBLISHER]

Coordinate measuring machines are widely used in the precision measurement of manufacturing workpieces. However, the nature of a point-by-point probing characteristic limits their efficiency in the measurement of complex parts, which normally requires dense sampling points for fully evaluating machining errors with high fidelity. To address this problem, this article proposes a generative model-driven sampling strategy to reduce the number of sampling points while preserving the measurement accuracy. Specifically, the reconstruction of surface errors with sparse sampling is transformed as a point cloud super-resolution task, which constructs a generative model to estimate accurate dense results from sparse sampled data. A multiscale neural network architecture is designed to achieve reconstruction, and the fractional Brownian motion is applied to simulate machining errors and synthesize a large-scale dataset for model training. The generalized neural model can then utilize sparse measurements to reconstruct global machining errors, which dramatically reduces the sampling time and increases measurement efficiency. Both computer simulations and actual measurements are carried out to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to planning cylindrical cutter location for flank (or side) milling of ruled surfaces. It contains two steps: tool positioning and re-positioning. In the former step, first an adaptive mesh is constructed on the designed ruled surface with the existing algorithm, and then a sequence of initial cutter locations (CLs) is determined using the offset points of the grid sampled points via semidefinite programming (SDP). In the latter step, a smooth tool axis surface is generated by interpolating the initial CLs using the dual mapping theory; afterwards, the tool is re-positioned by adjusting the offset value of each sampled point on the designed surface according to the predicted cutting errors. The cutter positioning methods for rough and finish milling are both developed in this framework. Example and numerical simulation illustrate the efficiency of the novel strategy. [ABSTRACT FROM AUTHOR]

Large skin parts play an important role in the aerospace industry. The wall thickness of the machined pocket in the skin part needs to be strictly controlled to ensure the transport capacity and structural strength. The wall-thickness accuracy is generally decreased by various factors, such as the shaping error of the workpiece blank, fixing error, machine tool error, and deformation caused by cutting force or internal stress. These factors are usually inevitable and stochastic due to the extremely weak rigidity and easy-to-deflect characteristics of the large skin parts. To ensure the wall-thickness accuracy, a fuzzy v-support vector machine (Fv-SVM)-based wall-thickness error decomposition method is proposed. The wall-thickness errors, which are monitored in the cutting process, are decomposed into spatial-related errors and time-related errors. The Fv-SVM-based decomposition method with the principle of spatial statistical analysis is a data-driven approach for intelligent manufacturing. The data-driven method can consider all factors that affect the wall-thickness accuracy, while the model-driven method usually only considers one factor, such as the workpiece deformation or fixing error. After decomposition, the spatial-related wall-thickness error is offline compensated, and the time-related wall-thickness error is compensated by using a real-time strategy. The novel method can be applied to complex tool paths. The cutting experiment of rectangular pockets in a large skin panel was conducted to verify the effectiveness of the proposed method. The wall-thickness accuracy can be improved to 0.05 mm for the workpiece with only 2 mm thickness. [ABSTRACT FROM AUTHOR]

Five-axis NC machining provides a valid and efficient way to manufacture the mechanical parts with complex shapes, which are widely used in aerospace, energy and national defense industries. Its technology innovations have attracted much attention in recent years. In this paper, the state-of-the-art techniques for five-axis machining process planning are summarized and the challenging problems are analyzed from the perspectives of tool path generation, integrated geometric/mechanistic simulation and machining stability analysis. The recent progresses in accessibility-based tool orientation optimization, cutter location (CL) planning for line contact and three-order point contact machining, shape control of cutter envelope surface and milling stability prediction are introduced in detail. Finally, the emerging trends and future challenges are briefly discussed. [ABSTRACT FROM AUTHOR]

Abstract: Based on the tangency condition in envelope theory and the body velocity representation in spatial kinematics, a closed-form solution of the swept envelope of a general rotary cutter moving along a general tool path defined in the NC programs is derived. No additional moving frames or local frames are required, and the computational formulas are independent of the types of the machines. The results can be applied to NC machining simulation, tool path optimization, and CAD/CAM of spatial cams. [Copyright &y& Elsevier]

Excessive static deformations often occur during the end-milling of large thin-walled parts, which play an important role in the aerospace industry. The real-time adjustment of axial cutting depth (ACD) is often adopted to compensate deformation errors. Owing to the coupling effect between the ACD and the force induced deformation, the iterative adjustment of ACD is needed. However, it may not converge with the limited adjustment times especially in high-speed machining with large ACD. We hereby propose an approach to speed up the convergence of the ACD iterative adjustment. Firstly, the real-time full compensation process, which is commonly used in the existing real-time compensation methods, is mathematically analyzed and proved to be only first-order convergent. Then, an approach based on the secant method, which provides a higher order of convergence, is developed and introduced into the real-time compensation process for large thin-walled plate machining. Finally, the superiority and effectiveness of the proposed approach are demonstrated through an ACD iterative adjustment simulation and an experiment of cutting square pockets. • The iterative adjustment of axial cutting depth for real-time deformation error compensation in large thin-walled parts machining is modeled as a root-finding problem. • It is proved that the conventional full compensation method only has the convergence rate of one. • An approach with a convergence rate of 1.618 is developed. • The proposed accelerated convergence approach has been successfully implemented in the mirror milling machine tools. [ABSTRACT FROM AUTHOR]

Functional microstructure surfaces with sub-micrometric form accuracy and nanometric surface roughness are gaining wider applications due to their excellent innate properties. However, for the three-axis machine tool equipped with the X , Z , and C -axes, it is difficult to machine complex micro structures due to the interference between the tool flank and the workpiece, caused by the relative rotation of the cutting tool. In this work, an additional high-precision air-bearing rotating stage is introduced to adjust the tool posture relative to the workpiece in real time. The integrated machining system and the tool path generation considering the tool setting error in the Y direction are introduced first. Then, to achieve the high-precision tracking performance, a double closed-loop controller is designed to control the stage. The observer-based sliding mode control method is used in the speed-loop first to suppress the influence of disturbances, while the proportional–integral–derivative control method is used in the position-loop to achieve high-precision tracking. The effectiveness of the proposed control scheme is verified by trajectory tracking experiments. Finally, the experiments of cutting various straight-groove-type micro structure arrays are performed on a three-axis ultra-precision lathe equipped with the air-bearing rotating stage, and the machined workpieces are inspected with a white light interferometer. The experimental results show that the proposed method can avoid the tool–workpiece interference and improve the machining quality effectively. [Display omitted] • A novel method for machining complex micro structures with the three-axis ultra-precision lathe is presented. • An additional high-precision air-bearing rotating stage is used to adjust the tool posture in real time. • The tool path generation considering the tool setting error in the Y direction are introduced. • A double closed-loop controller is designed to achieve the high-precision tracking performance. • The integrated machining system and the proposed method are validated by cutting experiments. [ABSTRACT FROM AUTHOR]

A novel analytical five-axis path-smoothing algorithm is developed for the high speed machining of a linear five-axis tool path. Segment junctions of the linear tool path in the machine tool coordinate system, which are tangent-discontinuous points, are all blended by two transition cubic Bézier curves. One cubic Bézier curve is used to smooth the segment junction of the translational path, and the other Bézier curve is used to smooth the segment junction of the rotational path. The tangency and curvature continuities are both guaranteed in the new path. The dual-Bézier transition algorithm has three advantages: (1) Compared with the path-smoothing method in the workpiece coordinate system, the new dual-Bézier transition method directly and simultaneously smooths the machine tool axis trajectories of both translational path and rotational path. The feed speed and stability will both be improved because the tool path discontinuities are the most important source of feed fluctuation. (2) The constraints of approximation error and the synchronization of parametrization of two smoothed curves, which are the most challenging problems in the smoothing of 5-axis tool path, are both considered. (3) The transition cubic Bézier curve pair has an analytical solution and can be easily integrated in the real-time interpolator. Computational examples and the cutting experiment of an impeller blade show that the novel path-smoothing method has obvious advantages in both feed smoothness and cutting efficiency over the original linear interpolator. [ABSTRACT FROM AUTHOR]