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Abstract For thin-walled parts, uniform allowance to each machining surface is allocated by the traditional machining method. Considering the sequence of the adjacent machining features, it may cause poor stiffness for some side walls due to a minor wall thickness, which may cause the deformation of the final formed parts to be large, or deduce mac...
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... structure is widely used in aircraft structural parts, as shown in Fig. 1. For this kind of parts, the structure is complex and the machining accuracy re- quirement is high. In order to ensure that the final de- formation of thin-walled parts is within machining tolerance, it is necessary to meet the specific require- ment of the part stiffness in the process of machining, especially in the finishing stage ...
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... is easy to know that the first side wall is the worst in stiffness by the proposed method. If the maximum value of its deformation is within the required range, the amount of deformation of the remaining three side walls is also within the required range. As shown in Fig. 10, select the 21 reference points along the horizontal direc- tion to draw the deformation trend map of different po- sitions of the first side wall. In the same way, we use the same load and constraint to simulate the deformation of the first side wall under the non-uniform allowance method. We can easily find that the maximum deform- ...
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... allowance method. We can easily find that the maximum deform- ation is located at the middle point on the top surface of the side wall. It is obvious that the deformation at each reference point of the non-uniform allowance method is smaller than that of the uniform allowance method when compared the deformation of these two methods (shown as Fig. 11), and the maximum deformation de- creases from the original 1.443 mm to 0.944 mm, which means a reduction by ...
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... order to fully compare the deformation of these two methods, the maximum deformation of the four walls of the pocket is given in Fig. 12. It can be seen from the diagram that the maximum deformation of the four walls is more uniform under the non-uniform allowance allocation method. Meanwhile, it is obviously that the maximum deformation of the four walls under the non-uniform allowance allocation method is much Fig. 12 Maximum deformation of four walls smaller than the ...
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... deformation of the four walls of the pocket is given in Fig. 12. It can be seen from the diagram that the maximum deformation of the four walls is more uniform under the non-uniform allowance allocation method. Meanwhile, it is obviously that the maximum deformation of the four walls under the non-uniform allowance allocation method is much Fig. 12 Maximum deformation of four walls smaller than the maximum deformation of the first side wall under the uniform allowance allocation ...
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Citations
... Zhao et al. [18], based on this, used on-machine positioning measurements combined with in-machine measurements, alignment, and isometric measurements to iteratively solve the constrained optimization algorithm for machining allowances. Jiang et al. [19] proposed a method of non-uniform distribution of finishing allowances for thin-walled structural components based on the stiffness of the transition state of machining characteristics, which can effectively improve the stiffness of the parts. Han et al. [20] established an interpolated mathematical model of the machining process based on the theoretical foundation of the deformation technique, designed the process parameters by analyzing the process constraints, and finally constructed a margin model. ...
Aiming at the chattering problem generated in the machining process of thin-walled parts with complex curved surfaces, a process optimization strategy based on the non-uniform allowance of ɛ influence factor is proposed from the finishing margin with the goal of simplicity and practicality. Firstly, the machining allowance is planned using the ɛ influence factor, and then the theoretical evaluation of the chattering stability of milling operations for uniform allowance blades and nonuniform allowance blades based on the ɛ influence factor by semi-discrete time-domain analysis is carried out and compared, and the results show that the stabilizing region of the optional spindle speed and depth of cut is increased by about 50%, thus effectively improving the productivity. Finally, through the test machining of the whole impeller and the surface contour inspection of the whole impeller, it is verified that the process optimization strategy based on the non-uniform allowance of ɛ influence factor has an obvious effect on the suppression of chattering, which is instructive for the machining and manufacturing of thin-walled parts with complex curved surfaces.
... This contributes to maintaining high stability, high rigidity, and long lifespan in its operational environment. To achieve these objectives, Jiang et al. [1] proposed a method for non-uniform allocation of finishing allowances in thin-walled structural component precision machining based on the transitional state stiffness of machining features. This method effectively enhances the component's stiffness and reduces deformation. ...
In addressing the phenomenon of chatter during the machining of thin-walled components, a machining strategy involving the implementation of a continuous non-uniform toolpath has been proposed as a remedy for chatter suppression. The methodology commences with a meticulous determination of machining allowances, accomplished by utilizing fitting functions. Subsequently, the stiffness coefficients and natural frequencies inherent to the workpiece-tool system are extracted through modal analysis. A stability lobes diagram is formulated, employing the principles of regenerative chatter analysis. This diagram encompasses both uniform toolpath scenarios and non-uniform continuous toolpath scenarios, with the latter established via the least squares method. The resultant stability lobes diagram effectively delineates the boundaries within which chatter remains stable, under varying depths of cut. The stability lobes diagrams substantiate the effectiveness of the non-uniform continuous toolpath constructed via the least squares method in significantly augmenting the inherent stiffness coefficient of the workpiece-tool system, thereby mitigating chatter. This approach serves as a valuable guide for the manufacturing of intricate curved thin-walled components.
... The findings demonstrate that the technique expertly suppresses the chattering of thin-walled workpieces and attains a high stability limit [35]. Ultimately, the procedure for adjusting the process stiffness of thin-walled components is achieved by applying the method with non-uniform allowances [36][37][38][39]. Built upon the above studies, this thesis centers around how the traditional design of thin-walled parts can produce a certain inhibitory effect. ...
... However, due to the influence of deformation prediction accuracy, and secondly, the topological structure characteristics of the part structure have not been taken into account, there are still certain limitations in the application of thinwalled complex structural components. Reference [38] proposes to measure the static deformation of parts on the machine, then calculate the allowance compensation value, and achieve stable milling of thin-walled parts by adaptively adjusting the cutting depth during precision machining. This method is intuitive, simple, and effective, but it is limited by in-machine measurement and first part trial cutting and is currently only suitable for conventional thin-walled components such as partition frames and wall panels. ...
During the milling of thin-walled blades, the removal of material exhibits strong time-varying dynamics, leading to chatter and a decrease in surface quality. To address the issue of milling vibrations in the machining of complex thin-walled blades used in aerospace applications, this work proposes a process optimization approach involving non-uniform allowances. The objective is to enhance of he stiffness of the thin-walled parts during the milling process by establishing a non-uniform allowance distribution for the finishing process of thin-walled blades. By applying the theory of sensitive process stiffness and conducting finite element simulations, two processing strategies, namely uniform allowances and non-uniform allowances, are evaluated through cutting experiments. The experimental results demonstrate that the non-uniform allowance processing strategy leads to a more evenly distributed acceleration spectrum and a 50% reduction in amplitude. Moreover, the surface exhibits no discernible vibration pattern, resulting in a 35% decrease in roughness. The non-uniform allowance-processing strategy proves to be effective in significantly improving the rigidity of the thin-walled blade processing system, thereby enhancing the stability of the cutting process. These findings hold significant relevance in guiding the machining of typical complex thin-walled aerospace components.
... Assembly stress analysis [16][17][18] is the basis for evaluating and optimizing structural assembly performance. Utilizing the experimental method of reflected photoelasticity, the effects of assembly stress on the stresses around circular holes under uniaxial tension was investigated by Younis [19]. ...
... For the machining allowance analysis, Zhang et al. [25] proposed a force-measuring-based approach for feed rate optimization considering the machining allowance. Jiang et al. [26] proposed a non-uniform allowance allocation method for NC programming of structural parts. ...
... Rotation speed 100 r/min ≤ ≤ 6000 rpm The value ranges of each sub-objective functions are listed in Table 15, and those can be used to calculate the normalized values by using Equation (26), and backwards as equal. Like the cylindrical turning, the number of the operation repeating time was set to be 100, namely = 100. ...
... The priorities of each phase can all be met by doing so. (2) This research further enhances the recommendation of relative larger setting of machining allowance of rough machining, and small setting of finishing machining, like [4,26]. ...
Machining allowance distribution and related parameter optimization of machining processes have been well-discussed. However, for energy saving purposes, the optimization priorities of different machining phases should be different. There are often significant incoherencies between the existing research and real applications. This paper presents an improved method to optimize machining allowance distribution and parameters comprehensively, considering energy-saving strategy and other multi-objectives of different phases. The empirical parametric models of different machining phases were established, with the allowance distribution problem properly addressed. Based on previous analysis work of algorithm performance, non-dominated sorting genetic algorithm Ⅱ and multi-objective evolutionary algorithm based on decomposition were chosen to obtain Pareto solutions. Algorithm performances were compared based on the efficiency of finding the Pareto fronts. Two case studies of a cylindrical turning and a face milling were carried out. Results demonstrate that the proposed method is effective in trading-off and finding precise application scopes of machining allowances and parameters used in real production. Cutting tool life and surface roughness can be greatly improved for turning. Energy consumption of rough milling can be greatly reduced to around 20% of traditional methods. The optimum algorithm of each case is also recognized. The proposed method can be easily extended to other machining scenarios and can be used as guidance of process planning for meeting various engineering demands.
... Wang et al. 32 discovered the basic principle of threedimensional digital matching and alignment of geometric components combined with the finishing allowance modeling and analysis framework of large thin-walled components. Jiang et al. 33 found that reasonable allowance allocation to the related machining surface can improve the stiffness of the designed part. Zhang et al. 34 studied the optimization model of finishing allowance by means of the capability maturity model. ...
Owing to reliability and high strength-to-weight ratio, large thin-walled components are widely used in the aviation and aerospace industry. Due to the complex features and sequence involved in the machining process of large thin-walled components, machining deformation of component is easy to exceed the specification. In order to address the problem, it is important to retain the appropriate finishing allowance. To find the overall machining deformation, finishing allowance-induced deformation (web finishing allowance, sidewall finishing allowance) and initial residual stress-induced deformation were considered as major factors. Meanwhile, machined surface residual stress-induced deformation, clamping stress-induced deformation, thermal deformation, gravity-induced deformation and inertial force-induced deformation were neglected in the optimization model. Six-peak Gaussian function was introduced to fit the initial residual stress. Based upon the obtained function of initial residual stress, a deformation prediction model between initial residual stress and finishing allowance was established to attain the finishing allowance-induced deformation. In addition, linear programming optimization model based on the simplex algorithm was developed to optimize the overall machining deformation. Results have concluded that the overall machining deformation reached the minimum value when sidewall finishing allowance and web finishing allowance varied between 1 and 2 mm. Additionally, web finishing allowance-induced deformation and sidewall finishing allowance-induced deformation were 1.05 mm and 0.7 mm. Furthermore, the machining deformation decreased to 0.3–0.38 mm with the application of optimized finishing allowance allocation strategy, which made 39–56% reduction of the overall machining deformation compared to that in conventional method.
Precise control of machining deformation is crucial for improving the manufacturing quality of structural aerospace components. In the machining process, different batches of blanks have different residual stress distributions, which pose a significant challenge to machining deformation control. In this study, a reinforcement learning method for machining deformation control based on a meta-invariant feature space was developed. The proposed method uses a reinforcement-learning model to dynamically control the machining process by monitoring the deformation force. Moreover, combined with a meta-invariant feature space, the proposed method learns the internal relationship of the deformation control approaches under different stress distributions to achieve the machining deformation control of different batches of blanks. Finally, the experimental results show that the proposed method achieves better deformation control than the two existing benchmarking methods.
Existing studies on analyzing the chatter problem in the milling process of the thin floors only included the dynamic responses of the cutter and the thin floors, however, the static lateral bending defections of the cutter also have actual effect on the stability of the process. This article develops a dynamic model to study the stability of the thin floor milling process by comprehensively considering the multi-flexibilities from both the static bending defections and the dynamic responses. The instantaneous dynamic chip thickness, which is required in the dynamic model, is analytically derived in the three-dimensional space by fully considering the following two factors. One is the bending effect induced by the static and dynamic deflections of the cutter in the X- and Y-directions, and the other is the tensing-compressing effect originated from the dynamic defections of the cutter and the workpiece in the Z-direction. At the same time, based on the substructure and sensitivity analysis theories, the in-situ dynamic parameters of the in-process floor, i.e. the natural frequency and the modal shape, are theoretically formulated by well combining the change of the cutter position with the removal of material. Based on the above derivations, the dynamic cutting forces together with the dynamic governing equation of the milling system are mathematically formulated, and then, the stability of the thin floor milling process is analyzed through solving the critical stability boundary. Finally, a series of milling tests are conducted on a typical thin floor structure to experimentally validate the accuracy and reliability of the proposed model.
This article presents a theoretical method to analyze the dynamic behavior of the milling process of the pocket-shaped thin-walled workpieces, which are filled with viscous fluid to suppress the chatter vibrations. Dynamic models of both the spindle-tool system and the pocket-shaped thin-walled workpiece with the viscous fluid are derived by extending the principles of the fluid-structure interaction dynamics theory and structural mechanics. The in-process dynamical parameters of the tool and the workpiece, i.e. natural frequency and modal shape, are solved by comprehensively integrating the effects of the viscous fluid, material removals, and tool position changes. Based on the built models, a method for analyzing the machining stability of this kind of workpieces after using the viscous fluid in the milling process is carried out and the avoidance principle of chatter vibrations is established by reasonably selecting the cutting parameters. A series of simulation and experimental tests are conducted on a typical pocket-shaped thin-walled workpiece to verify the reliability and effectiveness of the proposed methods for the suppression of chatter during the whole milling process.
