Machine Tool Motion Research Articles

WITHDRAWN: Digital twin-driven machining process for multi-process irregular-shaped parts manufacturing

With the advancement of high-end manufacturing industries, certain critical parts exhibit peculiar shapes and characteristics of multi-process manufacturing, which intensify milling difficulties and give rise to error propagation effects during the machining process. This necessitates machining systems to be adaptive to different working conditions and capable of real-time error analysis and optimization. Digital twin technology can create virtual replicas of physical entities to observe, analyze, and optimize the machining process. Therefore, this paper proposes a framework for digital twin-driven machining of multi-process irregular-shaped parts, consisting of preparation, processing, and optimization stages. In the preparation stage, a mapping relationship between the workpiece and machine tool motion coordinates is established to create a twin simulation environment consistent with actual operational parameters. In the processing stage, the digital thread dynamically updates the digital twin workpiece and machine tool status in real-time, analyzing the machining errors for each process to assess the finished quality. In the optimization stage, a cloud-based machining knowledge graph is constructed to enhance the precision of machining optimization decisions under different error sources and causes in the digital twin system. Finally, a case study of a typical multi-process irregular-shaped part machining task validates the reliability and superiority of the digital twin-driven method. The case study demonstrates that in a total of 260 machining processes, the digital twin-driven method improves machining accuracy by 40%, saves 34.9% of machining time, and alleviates 70% of machining downtime compared to existing machining methods.

Design and Study of Machine Tools for the Fly-Cutting of Ceramic-Copper Substrates.

Ceramic-copper substrates, as high-power, load-bearing components, are widely used in new energy vehicles, electric locomotives, high-energy lasers, integrated circuits, and other fields. The service length will depend on the substrate's copper-coated surface quality, which frequently achieved by utilising an abrasive strip polishing procedure on the substrate's copper-coated surface. Precision diamond fly-cutting processing machine tools were made because of the low processing accuracy and inability to match the production line's efficiency. An analysis of the fly-cutting machining principle and the structural makeup of the ceramic-copper substrate is the first step in creating a roughness prediction model based on a tool tip trajectory. This model demonstrates that a shift in the tool tip trajectory due to spindle runout error directly impacts the machined surface's roughness. The device's structural optimisation design is derived from the above analyses and implemented using finite element software. Modal and harmonic response analysis validated the machine's gantry symmetrical structural layout, a parametric variable optimisation design optimised the machine tool's overall dimensions, and simulation validated the fly-cutterring's constituent parts. Enhancing the machine tool's stability and motion accuracy requires using the LK-G5000 laser sensor to measure the guideway's straightness. The result verified the machine tool's design index, with the Z- and Y-axes' straightness being better than 2.42 μm/800 mm and 2.32 μm/200 mm, respectively. Ultimately, the device's machining accuracy was confirmed. Experiments with flying-cut machining on a 190 × 140 mm ceramic-copper substrate yielded a roughness of Sa9.058 nm. According to the experimental results, the developed machine tool can fulfil the design specifications.

Vision based two-dimensional measurement of machine tool motion trajectory

Vision based two-dimensional measurement of machine tool motion trajectory

Educational design and modelling of electro-hydraulic control system machine tool motion

Purpose. To present the design and modeling technology of real electrohydraulic systems, for use in the educational process of a higher educational institution, and the prospects of the proposed approach in the training of technical specialists. As an example, the model of the motion control system of the hydraulic cylinder of the device for fixing parts on the working table of a milling machine, created on the basis of components of the Festo company, is considered. The methods. The methodological basis of the work is a systematic approach, which consists in the use of modern FluidSim software - comprehensive software for creating, modeling and studying, including electro-hydraulic circuits and educational equipment of the Festo company, which allows students to acquire and develop practical skills and at the same time simulate a real working environment . Additional advantages of computer and physical modeling in the educational process are the interactive component, which facilitates the visualization of educational material and improves the process of problem solving. Findings. Taking into account the pedagogical features inherent in the world trends in technical education, the application of a comprehensive approach using computer and physical modeling in the training of technical specialists in the design of electrohydraulic systems is justified in the educational process. The sequence and results of the students' work on one of the options for the implementation of the educational project – the control system for the motion of the hydraulic cylinder of the device for fixing parts on the work table of the milling machine – have been demonstrated. The result of the proposed approach is also an increase in students' motivation, the achievement of a higher level of practical knowledge and skills compared to the traditional model of education. The originality. A modified algorithm for the formation of an extended model of mastering educational material from electro-hydraulic devices and systems with the use of modern software and equipment has been developed. Which allows students to acquire and develop practical skills and at the same time simulate a real working environment. Practical implementation. The materials of the work can serve as a basis for using the proposed integrated approach, which will improve the process of learning and teaching electrohydraulics, ensuring a higher level of learning outcomes, especially in terms of acquiring practical knowledge and skills.

Analysis of the configuration characteristics of the chaotic attractor for machine tool dynamic error under the singular spectrum

To explore the chaotic characteristics of the motion error of CNC machine tools, this paper proposes a chaotic attractor feature extraction method for the early motion error of CNC machine tools. Firstly, the chaotic verification of each time series feature of machine tool motion error proves that the change of CNC machine tool motion error is a nonlinear change process with chaotic characteristics. It then establishes the multivariate error phase space and performs a singular spectrum analysis. Because the motion error is strongly disturbed by noise, it is difficult to determine the number of singular values by the traditional singular spectrum analysis method, and this paper proposes to calculate the phase space index of the reconstructed sequence by traversing the number of singular values, to determine the main feature components; Finally, under different noise environments and different signal lengths, three feature extraction methods are introduced for experimental comparison with this paper's method, which shows that the chaotic attractor reconstructed after determining the number of singular values has a more apparent geometric structure. The method proposed in this paper has advantages in machine tool motion error.

A C3 continuous double circumscribed corner rounding method for five-axis linear tool path with improved kinematics performance

Abstract Corner rounding methods have been widely developed to pursue the smooth motions of machine tools. However, most corner rounding methods, which adopt the double inscribed transitions, still remain an inherent issue of retaining large curvatures of transition curves. Even for those double circumscribed transitions-based methods with relatively small curvatures, they also constrain excessively the transition lengths and are limited to a low-order continuity, deteriorating the feedrate and jerk of machine tools. For addressing these problems, a C3 continuous double circumscribed corner rounding (DCCR) method is proposed for five-axis linear tool path. In this method, the C3 continuous double circumscribed B-splines are specially designed to round the corners of tool position and tool orientation, whose transition lengths are analytically determined by jointly constraining the approximation errors, overlaps elimination, and parameter synchronization. Moreover, the excessive constrains of transition lengths imposed by traditional methods are alleviated by fully considering the effects of overlaps and parameter synchronization, and the jerk of rotary axes is also limited with a high-order continuity. Compared to the existing double inscribed corner rounding (DICR) and DCCR methods, experiment results demonstrate that our method can improve further the feedrate while limiting the jerk of machine tools.

Effects of Toolpath Parameters on Engagement Angle and Cutting Force in Ellipse-Based Trochoidal Milling of Titanium Alloy Ti-6Al-4V

Trochoidal milling is an efficient strategy for the rough machining of difficult-to-cut materials. The true trochoidal toolpath has C2 continuity and avoids sharp changes in engagement angle and cutting load, resulting in smooth machine tool movement. However, its total length is too long, and its engagement angle is uneven. These factors limit further improvements in the material removal rate. Based on the true trochoidal toolpath model, this paper develops an ellipse-based trochoidal toolpath generation method by introducing a compression ratio in the trochoidal step direction. The analytical model of engagement angle and the mechanistic model of the cutting force are proposed. A series of simulations and milling experiments were conducted to analyze the effects of toolpath parameters on the engagement angle and the cutting force. The results show that the compression ratio has the most significant effects. A compression ratio of 50% is optimal, using which the total toolpath length is reduced by 34.0%, and the variance of the engagement angle is reduced by 31.2% compared with that of the true trochoidal toolpath. The profile of the total cutting force corresponds to that of the engagement angle.

Rotation-Angle Solution and Singularity Handling of Five-Axis Machine Tools for Dual NURBS Interpolation

Dual NURBS interpolation has been proven an essential technique for high-speed precision machining of complex surfaces. The solution of rotation angles and their derivatives is the basis of kinematic transformation and feedrate optimization in dual NURBS interpolation. The characteristics of the rotation motion of five-axis machine tools with different structures are analyzed. A generic model of dual heads of the vertical five-axis machine tool is established to unify the solution of rotation angles. Then, a generic method for solving the rotation angles and derivatives based on the vector inner product is proposed, and the solution space is analyzed. A singularity handling is given to avoid abrupt rotation angles based on the higher derivatives of the tool orientation vector. The proposed method obtained smooth rotation angles at the singularity points in the cardioid dual NURBS interpolation experiment. It reduced the machining time by 43.3% compared with the simple inverse trigonometric method based on kinematic transformation. Experiment results demonstrate that the proposed method is feasible and effective, and has significant theoretical and practical value for optimizing five-axis CNC machining.

Corner smoothing for CNC machining of linear tool path: A review

Computer numerical control (CNC) machine tools are widely used in various industrial fields ranging from aerospace, automotive, ship building, and the die/mould to manufacture products. However, tool paths of most CNC machine tools are composed of a series of linear motion commands (G01), which will inevitably cause the discontinuity in curvature and feedrate at the junctions between adjacent linear tool path segments, deteriorating the surface quality with unfavorable marks and decreasing the machining efficiency. To solve this problem for obtaining the steady and continuous motions of machine tools, the local corners have to be smoothed. Generally, the existing corner smoothing methods can be classified as the global smoothing and the local corner smoothing, where the specially designed transition curves or the directly planned motion of machine tools are adopted to generate the geometrically corner-free tool path. Moreover, some new methods that focus on developing different transition or rounding strategies are also developed for further improving the kinematics performance of machine tools. In this paper, the recent advances and researches on corner smoothing methods are reviewed from different categories, and the conclusions, remaining challenges and future directions in corner smoothing are also presented.

Design of Micro Five-axis CNC Machine Tool and Research on Virtual Simulation Machining

By studying the structure and functional characteristics of five-axis linkage CNC machine tool, design five-axis CNC machine tool with X, Y, Z linear motion axes, B and C rotation axes. The virtual simulation system of miniature five-axis machine tool is built based on the VERICT, and an impeller part was simulated and processed as an example. Check whether the state of each moving axis in the machine tool movement is correct, and judge the rationality of the structure design of the machine tool based on the error information such as interference and collision in the processing. It is proved by simulation that the machine can realize five-axis linkage machining within the design range and meet the design requirements.

Piecewise Decoupling Tool Orientation Re-Scheduling for Four-Axis Reciprocal Toolpaths of Blades Based on S-θ Plane with Monotonicity Constraint

Reciprocal toolpaths with four-axis simultaneous motion of five-axis or four-axis machine tools are commonly used in the machining of blades which are widely applied in high-end equipment such as the aero-engine and the marine steam turbine. Due to the complex geometry of the blades, the tool orientation always suffers from frequent swing for this kind of toolpaths, which induces unnecessary acceleration/deceleration of the feed axes, thus degrading processing efficiency and quality. Although there are tool orientation optimization methods aiming at solving the above problem, they are mainly proposed for universal processing of the toolpaths for complex surfaces. Different from them, this paper proposes a piecewise decoupling tool orientation re-scheduling method for this kind of toolpath specifically, which takes full use of the characteristic of the reciprocal toolpaths of the blades, and takes the monotonous variation of rotation axes as an additional constraint. The re-scheduling process is realized based on the construction of a S-θ plane, where the scheduling problem is converted to the adjustment of a S-θ curve inside a feasible channel. Through two procedures, namely linearization scheduling and control-point assigning-based smoothing, the tool orientation path expressed by the S-θ curve can be effectively scheduled in a piecewise manner, and the smoothness between two adjacent pieces of the toolpaths can be ensured directly. The whole algorithm is lightweight and does not involve complex iterative operations or functional optimization solutions. Simulation and experimental tests verify the feasibility and superiority of this method. The results show that the machining efficiency of the blade is improved by 24.5%, due to the reduction of the requirement on highest feed-axis kinematics parameters after rescheduling. In addition, compared with the existing methods, the proposed method not only can improve the dynamics of feed axes in multi-axis machining, but also has advantages in computational complexity and monotonic variation property of the tool orientation.

Five-axis toolpath planning for aero-integral blisk cavities

Integral blisks generally made of high-temperature alloys (such as titanium alloys) are important components in aero-engines. During machining, the tool load is large and the tool wear is serious. Because trochoidal milling can maintain a small contact angle between the tool and the workpiece during the cutting process, it is widely used in the processing of complex aviation blisks. However, when the traditional U-shaped trochoidal toolpath or the maximum inscribed trochoidal toolpath is applied, there are high cutting vibration and low efficiency. Therefore, this paper proposes a new five-axis trochoidal side milling strategy, which is suitable for machining more complex three-dimensional cavities by adjusting the shape of the inscribed arc. Different from the traditional trochoidal pattern, the proposed method can generate a spatial UV parameter line-based tool path from a given complex 3D cavity and map it to the machining surface. In addition, a scheme to optimize the tool orientation of the boundary tool is proposed, so that the machine tool motion axis can run smoothly, thus the blisk can be roughened efficiently. Finally, the proposed schemes are verified by computer simulation and physical cutting experiments, and results show the validity and effectiveness.

Design and research of digital twin machine tool simulation and monitoring system

The numerical control machine tool is an important part of manufacturing. The speed and accuracy of the machine tool simulation and the monitoring of machine physical model movement, model collision, and operation health are the most common bottlenecks. The previous studies on these problems are discrete and poor in real time. In this paper, combined with the digital twin (DT) technology, a perception-monitor-feedback system architecture is constructed. Based on the improved Gilbert–Johnson–Keerthi (GJK) distance algorithm, the collision information of tool and machine tool can be better detected during the simulation and monitoring of machine tool movement, and the more real workpiece shape can be displayed. Based on the model synchronous motion driven by the production perception data and its potential information extraction, the tool wear online monitoring is carried out. The tool wear online monitoring is performed based on the production perception data–driven model synchronous movement and extraction of its potential information. Finally, the usability and efficiency of the system are verified by an example of a typical shaft part processed by a numerical control machine tool.

Design and Sensitive Analysis of Incremental Linear Actuator

Abstract:This paper presents a novel single-sided linear actuator design and sensitivity analysis of different geometric parameters on the performances of the actuator. A numerical model based on the finite element method is developed for that purpose. Thus, the electromagnetic behavior of the actuator is analyzed with 2D magneto-static analysis, and the electromagnetic characteristics were presented with the study of the effect of different geometric parameters on the thrust force. Indeed, the magnetic flux distribution and the force profile are presented and discussed. The analysis of different parameters on the actuator's performance allows the selection of the appropriate values of these parameters to obtain optimal performance of the actuator. The analysis shows the air gap and stack length has a powerful influence on the actuator's performance. Furthermore, the increase of supply current has a significant effect, but a high level of Ampere turns to bring the magnetic circuit to the saturation zone. It is important to determine the optimal geometrical dimensions to reduce the mass of the motor. It is critical to choose the optimum power values for the actuator to obtain optimum performance and avoid exceeding operating limits.Background:The linear switched reluctance motor is used in many industrial applications such as the linear motion of machine tools, sliding door applications, and conveyors.Objective:A new design approach for a linear switched reluctance motor is developed in order to determine the geometric parameters of the structure.Methods:Finite element method is used to predict the characteristics of the motor and the analysis its performances.Results:The simulation results obtained by finite element analysis make it possible to study the electromagnetic behavior of the motor and to validate the established geometric model.Conclusion:The study was carried out to choose the optimal parameters in order to obtain optimal performance and avoid exceeding the operating limits of the motor.

Non-isometric dual-spline interpolation for five-axis machine tools by FIR filtering-based feedrate scheduling using pseudo curvature under axial drive constraint

Due to the nonlinear relationship between workpiece-space and joint-space motions of five-axis machine tools, feedrate scheduling for dual-spline interpolation is acknowledged as a challenging task. Existing methods mainly employ iterative computation, repetitive toolpath discretization, or large feedrate margin, to solve the nonlinear problem. To avoid them, this paper presents a FIR (finite-impulse-response) filtering-based dual-spline interpolation algorithm using pseudo curves. A 3D translational-axis pseudo curve and a 2D rotary-axis pseudo curve are proposed as intermediaries to reduce the dimension of five-axis feedrate-scheduling problem thus figuring out partial nonlinear matters. The FIR filtering is employed to smooth the low-order continuous or even discontinuous axis velocities, to the jerk bounded ones, which further tackles the rest of the nonlinear matters. Although above methods solve the nonlinear issue, they induce new problems which are defined as the filtering-induced-tooltip-contour-error (FITCE) and the filtering-induced-tool-orientation-contour-error (FIOCE) here. To deal with these new problems, two extra constraints, namely the FITCE/FIOCE limitation and a frequency limitation, are added into the interpolation process beyond routine axis drive limitations. Additionally, the presented method does not require constant distance between two splines of the toolpath, which indicates that it is suitable for non-isometric dual-spline toolpath as well. Illustration and experimental tests demonstrate that the presented method merely conducts one-step toolpath discretization without iteration, and performs well in both motion efficiency and smoothness, as well as in real-time capability.

Research on procedure optimisation for composite grinding based on Digital Twin technology

The complexity of composite grinding movement, the variety of machining features and available grinding wheels, and the changing working conditions pose a challenge to the rapid programming of safe and efficient composite grinding procedure. The procedure optimisation plays an important role in solving this difficult problem. Therefore, a procedure optimisation method is proposed for composite grinding based on a Digital Twin (DT) system, which takes procedure time as optimisation objective to achieve high efficiency and ensures process rationality and safety by constructing corresponding constraint conditions. Moreover, the actual working conditions mapped into the DT system, such as workpiece parameters, machining requirements, grinding wheel parameters and status, machine tool motion position, and so on, are obtained to update the parameters involved in the optimisation model. And thus, the proposed method has the ability to timely find the optimal procedure under changing working conditions. In addition, a combination algorithm based on genetic algorithm (GA) and dynamic programming is proposed, which greatly reduces the search space of GA and realises the two-class co-optimisation of grinding wheel selection and procedure. Finally, the case study verifies the effectiveness of the proposed method to reduce procedure time and the dynamic response ability to changing working conditions.

Solution of numerical control motion and experiment for machining split equal-base circle bevel gear

The purpose of this study is to realise numerical control (NC) gear cutting on the split wheel blank of equal-base bevel gears, based on the instantaneous cutter position information in tooth surface forming and NC machining theory, the coordinate system of split equal-base bevel gears is established. According to the movement of tool centre coordinate and its transformation, the linear motion of machine tool is solved. By the rotation and translation of the tool axis vector, the solution of the rotary motion of the machine tool is obtained. According to the different rotation direction and concave-convex property of tooth surface, the calculating model of the starting point of processing of each tooth surface is deduced. The complete machining trajectory is formed by analysis and extension of the tool starting point and terminal point of machining, and the automatic generation of the NC machining program is realised. Finally, the simulation of gear cutting on the split wheel blank is carried out using VERICUT software. The experimental and tooth surface measurement results show that the mathematical model of motion trajectory is correct and the machining method is feasible.

Prediction of Machine Tool's Motion Accuracy Deterioration Based on Chaotic Evolution of Thermal Error

Prediction of Machine Tool's Motion Accuracy Deterioration Based on Chaotic Evolution of Thermal Error

Kinematic Analysis and Parameter Measurement for Multi-Axis Laser Engraving Machine Tools

Multi-axis Laser Engraving Machine Tools (LEMT) are widely used in precision processing of parts with complex surface. The accuracy of kinematic model and parameter measurement are the key factors determining the processing quality of LEMT. In this paper, a kinematic model of multi-axis LEMT was established based on Homogeneous Transformation Matrix (HTM). Two types of unknown parameters, linkage parameters and positioning parameters, were measured in the presented model. Taking advantage of the characteristics of laser processing, this paper proposed a rapid measurement method of linkage parameters by combining the machine tool motion with the laser marking action. For positioning parameters, this study proposed a non-contact measurement method based on structured light scanner, which can obtain the translation values and the rotation values from the Workpiece Coordinate System (WCS) to the Basic Coordinate System (BCS) simultaneously. After the measurement of two kinds of parameters of a multi-axis LEMT was completed, the processing of a spatial curve was performed and the average contour error was controlled at 15.1 μm, which is sufficient to meet the project requirements.

Machining process analysis of multi-tasking machine tools based on form-shaping motions

With the increase in machine tool types, it becomes difficult to select an appropriate machine tool to achieve high-efficiency and high-quality machining. This study aims to automate the selection of machine tools by evaluating and comparing machining processes for the machining of targeted parts. A fundamental method for analyzing machining processes is proposed by introducing the functional description of machine tools in the previous study. However, a simple machine tool structure is supposed as a first step in the proposed method. Therefore, in this study, the machining process analysis method is reconstructed to handle complex machine tool structure such as that of a multi-tasking machine tool. The functional description of machine tools is expanded to represent form-shaping motions of a multi-tasking machine tool by adding new suffixes that indicate the orientation of plural spindles and the posture of non-rotational specific functions. Additionally, evaluation indexes of rationality and similarity of machining operations to exclude unsuitable machining operation candidates are proposed. Case studies are conducted and confirmed that the system developed based on the novel proposed method can derive accountable machining processes according to a multi-tasking machine tool. The results of the machining process analysis may thus support the machine tool selections.