Search

In order to improve the machining quality and efficiency and optimize NC machining programming, based on the existing cutting force models for ball-end, a cutting force prediction model of free-form surface for ball-end was established. By analyzing the force of the system during the cutting process, we obtained the expression equation of the instantaneous undeformed chip thickness during the milling process and then determined the rule of the influence of the lead angle and the tilt angle on the instantaneous undeformed chip thickness. It was judged whether the cutter edge microelement is involved in cutting, and the algorithm flow chart is given. After that, the cutting force prediction model of free-form surface for ball-end and pseudocodes for cutting force prediction were given. MATLAB was used to simulate the prediction force model. Finally, through the comparative analysis experiment of the measured cutting force and the simulated cutting force, the experimental results are basically consistent with the theoretical prediction results, which proves that the model established in this paper can accurately predict the change of the cutting force of the ball-end cutter in the process of milling free-form surface, and the error of the cutting force prediction model established in this paper is reduced by 15% compared with the traditional cutting force prediction model.

Surface integrity has a significant impact on the performance and life cycle of the blisk blade. Residual stress, as one of the important characterization parameters of surface integrity, is closely related to the performance of the aeroengine blisk blade. A certain interval of residual compressive stress can significantly inhibit the generation of microcracks. This paper proposes an optimization method of polishing process parameter interval based on sensitivity analysis. This research studied the effect of polishing parameters of the alumina ACW (abrasive cloth wheel) on the surface residual stress of the GH4169 superalloy blisk blade. Firstly, the experiment was designed by four factors and three levels response surface method, the multiple regression of the experimental data based on Minitab software was used to get a prediction model of polished surface residual stress. And an analysis of variance was performed on the model. Subsequently, the model of relative sensitivity was got based on this model. The sensitivity order of polishing surface residual stress to each polishing parameter was obtained. And the judging method of stable interval and instable interval was put forward. Then, a parameter interval optimization method was proposed, and the optimal interval of process parameters was obtained. Finally, a polishing verification experiment was performed. The results show that: for the polishing of GH4169 superalloy blades, the surface residual stress is most sensitive to the feed rate vf of the ACW, followed by the granularity p and the rotation rate ω, and the compression depth ap is the least sensitive. The optimal interval of polishing process parameters is: the rotation rate ω is [11000 r/min, 11500 r/min], the feed rate vf is [100 mm/min, 200 mm/min], the compression depth ap is [0.6 mm, 1.0 mm], and the granularity p is [400 #, 600 #]. The optimized polishing process parameters can obtain a large and stable surface residual compressive stress, which is helpful to increase fatigue strength of the blisk blade.

Uniform material removal depth has an important influence on the profile accuracy and surface quality of the blisk blades in polishing. In order to guarantee the consistence of the polishing removal depth, a preferred method of polishing process parameter range based on sensitivity analysis is proposed. Firstly, the sensitive process parameters of polishing material removal depth were determined by four-factor three-level orthogonal experiments. Then, the three-factor central composite sequential (CCD) design experiment in the response surface method is used to obtain the quadratic regression empirical prediction model of polishing depth by multilinear regression through Minitab software, and the polishing material removal depth prediction model is analyzed significantly. Secondly, a mathematical model of relative sensitivity is established to determine the method of dividing the stable and unsteady domains of the process parameters, and the stable domain of each polishing process parameter and the sensitivity to the polishing removal depth were obtained. Finally, the comparative experiment verification was carried out by blisk polishing. Abrasive cloth wheel which is 12 mm in diameter and P600# in abrasive size and has abrasive of Green Sic is used to the polishing of TC4 titanium alloy blade. The results show that the optimal stability ranges of significant parameters through sensitivity analysis are as follows: compression amount within [0.6 mm, 0.8 mm], rotation speed within [5000 r/min, 6000 r/min] and feed speed within [200 mm/min, 400 mm/min]. The depth of polishing in the stable domain is the most sensitive to the compression amount, followed by the speed, and the feed speed sensitivity is the lowest. The optimized polishing process parameters effectively reduce the fluctuation of the removal depth, and the surface quality has greatly improved by using the optimized polishing parameters.

The blisk is a typical cantilever beam structure, which is prone to vibration during the polishing process. This vibration will cause the polishing tool to wear seriously and reduce the surface quality of the blade.In order to control the vibration of polishing process, a method of predicting the RMS (root mean square) value of polishing vibration signal was proposed. Firstly, an empirical model of process parameters for polishing vibration was established by an orthogonal experiment. Then, based on the response surface and sensitivity analysis method, the stability range of the process parameters and the influence on the polishing vibration are obtained. Finally, through the polishing experiment, it is determined that the stable range of each process parameter is reliable. There is no significant vibration during the polishing process. By analyzing the surface texture and surface topography of the blade, the surface quality of the blade meets the requirements. The results showed that the optimal stability ranges of significant parameters through sensitivity analysis are compression depth within [0.6 mm, 0.9 mm], spindle speed within [6000 r/min, 7500 r/min], feed rate within [0.4 mm/min, 0.6 mm/min], and granularity within [400#, 600#]. This study provides a basis for the theoretical research of polishing vibration in the flexible polishing process and the relationship between process parameters and polishing vibration.