Thin-walled Workpiece Research Articles

Milling Parameters Optimization of Al-Li Alloy Thin-Wall Workpieces Using Response Surface Methodology and Particle Swarm Optimization

To improve the milling surface quality of the Al-Li alloy thin-wall workpieces and reduce the cutting energy consumption. Experimental research on the milling processing of AA2195 Al-Li alloy thin-wall workpieces based on ... | Find, read and cite all the research you need on Tech Science Press

Finite Element Analysis and Parameter Influence of Non-developable Ruled Surface Impeller Blade in Flank Milling

Through the cutting simulation of titanium alloy impeller blade, the effect of the actual milling processing path on the elastic part deflection to of complicated thin-walled workpiece with low rigidity and high precision is studied. Use the principle of impeller modeling to model the spline of the impeller, and the spline curve of the impeller generated in MABLEB is imported into UG for digital modeling. The spline curve is used to generate the neutral surface, and the suction surface and pressure surface are obtained by the method of non-equidistant offset. The model of the non-stretchable straight surface blade is imported into ABAQUS for static simulation. Using MATLAB to fit the experimental data in the reference literature that fits the milling process range, the side milling experience formula is fitted. Calculate the equivalent milling force corresponding to different axial cutting depths, import into ABAQUS and use Python for secondary development. By simulating the milling process through the life-and-death element method, the local elastic deformation law of the milled thin-walled parts when multi-layer milling the impeller blades is explored. The influence of different machining paths on the deformation of the tool is studied. Simulation results show that the part deflection of workpiece can be reduced by rationally planning the machining path.

Improving Clamping Accuracy of Thin-walled Workpiece in Turning Operation

This study presents theoretical and experimental error analysis and avoidance which results from the fixation of a thin-walled metal disk workpiece on a duplex turning machine. The distance between the rotating workpiece surface and a fixed datum point is measured using a laser displacement sensor (LDS). The measured data are analyzed numerically to get the error in the fixation system in terms of Euler angles. Then the workpiece clamping points are axially adjusted according to the calculated angles. Moreover, the problem formulation and the solution procedures are presented in details. Finally, a case study has been used to verify the proposed approach. The results indicate that the proposed technique can be used to decrease the fixation error to a reasonable range.

Multi-modal method for chatter stability prediction and control in milling of thin-walled workpiece

Chatter stability in milling can be predicted by analytical methods or numerical methods. The system should be considered as multi-modal in milling of thin-walled workpiece. This paper proposes a numerical difference method based on Adams-Bashforth scheme. Moreover, multi-modal scheme of numerical methods is proposed. Analytical methods and numerical methods are verified by performing a series of milling trials. The experimental results are consistent with the predicted critical stability boundaries. Moreover, a new method for analyzing the computational time of analytical methods and numerical methods, which is based on the time complexity modeling, is presented. Computational time can be expressed as exact mathematical expression. By using the expression, the rate of increase of computational time can be derived.

Vibration suppression of complex thin-walled workpiece based on magnetorheological fixture

According to the weak rigidity and complex structure of aerospace thin-walled parts, an auxiliary support method based on magnetorheological fluid, a dynamic model, and a simulation prediction model are proposed. In this paper, the magnetic field distribution in the space of magnetorheological fluid fixture is simulated, analyzed, and measured. Then, the magnetic force is deduced and the empirical formula of milling force is adopted. Based on the Rayleigh damping matrix and the Equivalent force principle, the dynamic model of magnetorheological fluid fixture-complex workpiece is established. In order to find the optimum parameters of magnetorheological fluid (MRF) fixture, the effects of MRF volume, the location, and the magnetic field intensity on vibration suppression are analyzed. Hence, the conclusion is validated by the design of MR fixture experiment and simulation experiment, and the processing quality of thin-walled workpiece has been improved by maching tests.

Asymmetrical nonlinear impedance control for dual robotic machining of thin-walled workpieces

• An asymmetrical nonlinear impedance control (ANIC) is designed for a dual robotic machining system. • A comparison study between asymmetrical nonlinear impedance control and symmetrical linear impedance control is proposed. • The robots under the ANIC act as variable stiffness actuators to adapt the variation in thickness of workpieces. Impedance control is to provide stable tracking by regulating the impedance response of a robot. In this paper, an asymmetrical nonlinear impedance control (ANIC) is proposed for a dual robotic machining system. The symmetrical linear impedance control (SLIC) is also analyzed as a comparison study. We compared two controllers in terms of the stability and the sensitivity property of the grinding force, as well as the trajectory design. The main advantage of the ANIC is that the grinding force is robust to the environmental disturbances and the variation in thickness of workpieces. In contrast to the traditional control concept, which is devoted to compensate the nonlinear effect of the original system, our design philosophy is to increase the system robustness by introducing an artificial nonlinearity to the system. As a result, the dual robotic system acts as variable stiffness actors to adapt the variation in the thickness of workpieces. Grinding experiments are conducted in the dual robotic machining test rig for both workpieces with the uniform and varied thickness. The experimental results show that the dual robotic system with the ANIC can achieve better grinding quality.

Vibration suppression of thin-walled workpiece milling using a time-space varying PD control method via piezoelectric actuator

The vibration suppression and workpiece surface improvement of thin-walled workpiece milling are highly concerned due to the weak stiffness of the workpiece and the time variant of dynamic characteristics during milling process. In this paper, an active vibration control system is developed to suppress the vibration of thin-walled workpiece milling. The dynamic model of plate-actuator milling system is derived using Hamilton’s principle and solved using FEM method. Acceleration sensor and piezoelectric patch are selected as the sensor and actuator in the control system. Considering the time variant of dynamic characteristics and the position limit of sensor and actuator during milling process, a time-space varying PD (VPD) control method is presented and utilized. The VPD control method applies time varying control parameters. Some simulation and experimental validations are carried out to validate the effectiveness of the control system. The overall results indicate that the proposed control system perform well in suppressing the vibration of thin-walled workpiece milling process.

Real-time width control of molten pool in laser engineered net shaping based on dual-color image

This paper introduces a real time control system for laser engineered net shaping, to improve the machining accuracy of workpiece. A coaxial CCD image system with a dual wavelength narrow-band filter is built to obtain the size information of molten pool. The width of molten pool is extracted by the minimum bounding rectangle method and used as the feedback for molten pool control. The experimental results show that the dimensional accuracy of the workpiece is significantly improved, especially for curved thin-walled workpieces.

Parametric study on the tool inclination angle for side milling thin-walled workpiece edges based on finite element simulation

Side milling thin-walled workpiece edges is an indispensible procedure in the continuous process chains for the high-efficiency machining of thin-walled functional parts, for example, the small- and medium-sized compressor blades. In these operation cases, the workpiece vibration is easy to occur due to the poor stiffness of the thin-walled structures, causing defects to the machined surface finish and even the dimensional accuracy of the thin-walled workpiece edges. To this problem, this study proposes the tool inclination method based on the adaption of the cutting force component in the lowest stiffness direction of the thin-walled workpiece, and it aims, first, to guarantee the machined surface finish which is mostly dominated by the workpiece vibrations mainly induced by the relatively high cutting forces and, second, to guarantee the high machining efficiency. The parametric study on the tool inclination angle for side milling the thin-walled workpiece edges was conducted by using the finite element simulations. First, the finite element models were elaborated and validated by the experimental results in terms of the cutting forces. Then, based on a series of finite element simulations, the effects of the tool inclination angle on the cutting forces adaption and its corresponding mechanism, that is, the chip formation variation, were investigated. Simulation results under the given conditions showed that the optimal tool inclination angle for the minimum absolute value of Fn was 26°. At last, the prediction feasibility for the best machined surface finish when side milling the low-stiffness thin-walled workpiece edges at the optimal tool inclination angle was well validated by the experimental results. The proposed tool inclination method with the solid end mill based on the finite element model to improve the machined surface finish is meaningful and feasible for the high-efficiency manufacturing processes of thin-walled workpieces.

Проблема технологических деформаций при фрезерной обработке тонкостенных заготовок

Проблема технологических деформаций при фрезерной обработке тонкостенных заготовок

Machining Process for a Thin-Walled Workpiece Using On-Machine Measurement of the Workpiece Compliance

Demand for highly productive machining of thin-walled workpieces has been growing in the aerospace industry. Workpiece vibration is a critical issue that could limit the productivity of such machining processes. This study proposes a machining process for thin-walled workpieces that aims to reduce the workpiece vibration during the machining process. The workpiece compliance is measured using an on-machine measurement system to obtain the cutting conditions and utilize the same for suppressing the vibration. The on-machine measurement system consists of a shaker with a force sensor attached on the machine tool spindle, and an excitation control system which is incorporated within the machine tool’s numerical control (NC). A separate sensor to obtain the workpiece displacement is not required for the estimation of the displacement. The system is also capable of automatic measurement at various measurement points because the NC controls the positioning and the preloading of the shaker. The amplitude of the workpiece vibration is simulated using the measured compliance to obtain the cutting conditions for suppressing the vibration. An end milling experiment was conducted to verify the validity of the proposed process. The simulations with the compliance measurement using the developed system were compared to the results of a conventional impact test. The comparison showed that the spindle rotation speed for suppressing the vibration could be successfully determined; but, the axial depth of cut was difficult to be determined because the simulated vibration amplitude was larger than that found in the experimental result. However, this can be achieved if the amplitude is calibrated by one machining trial.

On-machine measurement method for dynamic stiffness of thin-walled workpieces

This paper proposes a novel measurement method for the dynamic stiffness of thin-walled workpieces. The proposed method is called the displacement sensorless piezoexcitation (DSPE) method. The DSPE method uses a piezoelectric shaker attached to a machine tool spindle. Sensor setup on workpieces is not required because workpiece displacement is estimated from the excitation force and input voltage to the shaker. A measurement instrument based on the DSPE method was developed. The measurement accuracy of the DSPE method was verified by comparing its measurement results to those of a conventional piezoexcitation method and impact tests. The experimental results demonstrate that the DSPE method is almost comparable to the conventional methods. Cutting experiments were conducted to analyze the workpiece compliance measured by the DSPE method and the vibration amplitude during cutting. The results demonstrate that the DSPE method can accurately evaluate the dynamic stiffness affecting vibration during the cutting process.

Investigation on milling force of thin-walled workpiece considering dynamic characteristics of workpiece

The idea of integral calculus is used in traditional milling force prediction methods. In the traditional method, the milling cutter is divided into many micro-elements, the force of each micro-element is calculated, and then the integral summation process is applied to all the micro-elements. In traditional milling force prediction methods, both the workpiece and the tool are assumed to be rigid bodies. In this paper, the method is improved; the Fourier series expansion is used to approximate the periodic milling force and the workpiece is considered as a single degree of freedom spring-damping-vibration system. Through the forced vibration model of periodic force, the vibration displacement of the workpiece is obtained. Then, the radial cutting depth is corrected by the vibration displacement of the workpiece. Finally, the original milling force is corrected with the corrected radial cutting depth. The milling force prediction model based on thin-walled workpiece is obtained through the above process. The model is named as variable-radial-cutting-depth-algorithm (VRCDA). Finally, the accuracy of this model was verified through modal test and milling force acquisition experiments.

Investigation of flow fields during the electrochemical machining of variable-section pit arrays

Variable-section pit arrays play an important role on the linear cutter staplers, which are used for surgical suturing. Although numerous methods can be employed to generate pits on the surface of a workpiece, it remains a challenge to form variable-section pit arrays on the surfaces of thin-walled workpieces with high precision and efficiency. Thus, this paper proposes a method for the electrochemical machining of variable-section pit arrays using a radial internal fluid supply. By using simulations and experiments to investigate the flow fields of the electrolyte, it was found that electrolyte supplied by internal electrodes enhanced the accuracy and consistency of the pit profiles. The influence of the electrolyte pressure, pulse current, and feeding speed on the pit profiles of machined variable-section pit arrays was analyzed. To fabricate the designed pit (length = 1750 ± 20 μm, width = 1000 ± 20 μm, and depth = 400 ± 10 μm), the machining parameters were optimized. Using these optimized parameters (electrolyte pressure = 0.5 MPa, pulse current = 35 A, feeding speed = 0.42 mm min−1), ten rows of variable-section pit arrays were generated on a 17-4PH stainless steel plate with a thickness of 1 mm. The resulting length, width, and depth (mean ± SD) were 1750.56 ± 0.55 μm, 999.62 ± 0.63 μm, and 396.71 ± 0.53 μm, respectively, demonstrating the high precision and efficiency of the proposed method.

A tunable passive damper for suppressing chatters in thin-wall milling by considering the varying modal parameters of the workpiece

Removal of the materials during thin-wall milling leads to obvious change of the modal parameters of the thin-walled workpiece. This article proposes a new method for designing a passive damper to suppress the chatters in thin-wall milling by considering the workpiece’s in-process varying modal parameters. The modal parameters of the workpiece during cutting process is theoretically derived by including the influence of material removal, and the design principle of equal peaks is used to calculate the optimal parameters of the passive damper. Based on the derivation, the passive damper is then designed and manufactured. A series of milling experiments are conducted for the cases with and without the designed passive damper. Experimental observations show that the passive damper has good performance in suppressing chatters and improving the stability of the cutting system.

Prediction and compensation of countersinking depth error in drilling of thin-walled workpiece

The countersink depth accuracy is a remarkable quality index in modern aerospace industry, and it needs to be controlled quite accurately due to the extremely tight tolerances. However, the wide use of the thin-walled workpiece with low stiffness makes it difficult to achieve the required tolerance because of the complex deformation in the countersinking process. Focusing on the accurate control of countersink depth in the drilling of thin-walled workpiece, this paper provides a novel insight into the study on predicting of the feasible workpiece deformation and compensating for the countersink depth error through both theoretical and experimental analyses. An analytical model of workpiece deformation is first presented with the Fourier series approach in this study, and the finite element simulation is carried out to verify the model precision. Then a flexible cutting force model is developed to help to analyze the effect of deformation on the thrust force in the countersinking process. A novel approach of integrated iterative algorithm, that considers both the deformation and the cutting force, is established to calculate the final feasible deformation and make decision for the countersink depth error compensation, and the generalized convergence and adaptability of this iterative algorithm are investigated based on the calculus theory. Finally, the proposed integrated methodology is verified by multivariate simulations and experiments, and the results show that the countersink depth accuracy could be effectively guaranteed by countersinking with compensation based on this integrated methodology. The work in this paper enables us to understand the causes of poor countersink depth accuracy in the drilling of thin-walled workpiece and develop new countersinking techniques to satisfy the tight tolerance.

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

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 thin-walled 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 thin-walled 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.

Vibration analysis of milling process with helix-angle cutter based on Euler method

The chatter vibration is the major limiting factor in increasing the metal removal rates of the machine tools. In this paper, a program for dynamic analysis of thin-walled milling process with helical milling cutter is developed, based on Euler iteration. The program can take into account the characteristics of thin-walled workpiece, the contact separation between workpiece and cutter, the helical angle of cutter teeth and other actual cutting process characteristics. Based on the stability lobe diagram obtained by semi-discrete method, the stability simulation in different cutting parameters around the stable island was carried out. The unstable form of the cutting process was determined by spectrum analysis and Poincare mapping method. The results show that the method is in good agreement with the results of stability Lobe diagram and can capture the stability island in small radial cutting process. This method can well grasp the cutting force and vibration evolution process in cutting process, and provide an effective means for stability analysis of cutting process.

An Active Control Method for Chatter Suppression in Thin Plate Turning

This paper presents an active control method, consisting of an adaptive sliding-mode controller (ASMC) and a displacement field reconstruction (DFR) method, for chatter suppression in turning of thin-walled workpieces (such as compressor disks and casings in aircraft engines) where low workpiece stiffness renders machining with potential regenerative chatter. Due to the presence of multi-modal dynamics, variant modal parameters, and measurement difficulties, active chatter control of thin plate turning has been challenging. Unlike existing controls based on a lumped-parameter single degree-of-freedom cutting model, a distributed-parameter dynamic model of a rotating thin plate with multiple vibration modes is used to analyze the machining stability with the designed controller. Moreover, model parameters of the plate are not needed to construct the controller. The DFR is employed to capture the plate dynamic behavior for feedback to the ASMC during turning, overcoming the long existing difficulties to measure plate vibration at the cutting point. A fast tool servo is utilized in the control implementation. Theoretical analyses, numerical simulations, and experimental evaluation on a lathe demonstrate that chatter in thin plate turning can be effectively attenuated with the proposed active control method.

Stability Research Considering Non-Linear Change in the Machining of Titanium Thin-Walled Parts.

Aiming to solve the problem whereby the damping process effect is significant and difficult to measure during low-speed machining of titanium alloy thin-walled parts, the ploughing coefficient of the flank face is obtained based on the frequency-domain decomposition (FDD) of the measured vibration signal and the energy balance principle, and then the process-damping prediction model is obtained. Aiming to solve the problem of non-linear change of dynamic characteristics of a workpiece caused by the material removal effect in the machining of titanium alloy thin-walled parts, a prediction model of dynamic characteristics of a workpiece is established based on the structural dynamic modification method. Meanwhile, the effect of material removal on the process-damping coefficient is studied, and the internal relationship between the process-damping coefficient and the dynamic characteristics of the workpiece is revealed. The stability lobe diagram is obtained by the full discretization in the titanium alloy milling process. The correctness of the model and stability prediction is verified by experiments under different working conditions. It is found that the coupling characteristics of process-damping and workpiece dynamic characteristics control the stability of the milling process. The research results can provide theoretical support for accurate characterization and process optimization of titanium alloy thin-walled workpiece milling.