Milling Of Blades Research Articles

A combined approach to tool path generation for flank milling of impeller blades with non-developable ruled surfaces

Impeller blades are often constructed by non–developable ruled surfaces. Due to their twisted feature, the application of flank milling to these blades would inevitably cause significant interference between the cutter edge and the machined surfaces. In view of the advantages of flank milling operations, this paper proposes a combined approach to flank milling these blade surfaces with acceptable precision and fairly high efficiency. Centring on the minimisation of the interference, the non–developable blade surface is divided into a number of strips, the cutter profile is modified accordingly, and then the tool paths are calculated strip by strip. Along with the basic idea, related issues are investigated in detail focusing on the strip width determination, cutter profile modification, and cutter location calculation. For practical use of the proposed approach, necessary algorithms are also provided. Finally, a case study is presented, together with numerical simulation of the cutting process. The results show that the proposed approach is not only feasible but also much more efficient than the conventional point milling method. [Received 6 November 2013; Revised 16 June 2014; Accepted 2 October 2014]

The Research of Cutter-Location Optimization for Flank Milling Blades of Undevelopable Ruled Surfaces with Toroidal-End Cutter

To improve the efficiency and precision of five-axis numerical control machining for undevelopable ruled surfaces,a cutter-location optimization algorithm was proposed for flank milling of blades with a toroidal-end cutter. Firstly, it is established initial cutter-location of toroidal-end cutter by optimizing algorithm of three-point offset based on geometry features of toroidal-end cutter, and optimized cutter vector by introducing scaling factors. A new method which was based on dynamic sliding index calculating optimal cutter orientation vector was proposed. The method which applied deviation measurement algorithm computed overcut or undercut values of programming error in different scaling factors state. Finally, through the instance of machining verified the rationality of the method, and effectively reduces programming error.

Particulate characterization of bovine bone granules pulverized with a high-speed blade mill

A bovine bone block was pulverized by an automatic high-speed blade mill together with ice blocks made of normal saline. The bone granules obtained were classified with standard sieves of 500, 710, 1000 and 2000μm in mesh size. Micrographs taken under an optical microscope were binarized to measure the major and minor axes of each granule with image analysis software. To obtain the particle size distribution by combining the results from sieving and image analysis, a new approach was proposed. When the Heywood diameter was used as a characteristic diameter, the existence of granules larger than the mesh size was recognized. This result can be attributed to the prolonged shape of the bone granules as explained by using the Feret diameter. A tendency that a larger aspect ratio was observed for smaller granules was found. This result can also be explained to be due to the anisotropy in shape, attributed to the intrinsic property of bone.

Error prediction and compensation based on interference-free tool paths in blade milling

We propose a method which uses interference-free tool paths to predict and compensate for deformation error during the spiral milling of blades. Firstly, a finite element simulation of the blisk blade milling process was conducted using an interference-free spiral milling NC machining tool path based on the curvature attribute of the blade twisted surface, observing the variation in blade milling error under different processing parameters and yielding a surface quality variation law. Next, the model was corrected by combining this error prediction data with precision design requirements, and a blade deformation error compensation scheme was suggested. Finally, an interference-free processing program containing the error compensation information was applied to carry out another blade milling simulation and a blisk milling experiment. The results showed that both the blade deformation error and the surface quality satisfied design requirements, while the accuracy of the simulation was verified.

A Study of Chatter Stability Domain in Different Phases of Milling Process of Thin-Wall Component

Aeronautical thin-wall components are widely used in Aero-Engine, and the machining stability of the thin-wall components is a difficulty issue. In this paper, a single freedom dynamic model is set up to describe the dynamics of thin-wall milling process, and the stability of the dynamic model is analyzed with the discretization method. Then the modal parameters are gained in the different milling phases and the resonance region of spindle speed is proposed. Optimize the milling parameters with the chatter stability domain at different milling phases. The result shows that the cutting chatter can be restrained if getting the spindle speedcutting depth parameters considering the superposition area of chatter stability domains and avoiding the resonance region in the different milling phases. At last, the method is applied in Aero-Engine thin-wall blade milling, the metal remove rate increases greatly and the machining accuracy is improved greatly.

Turbine Blade Distortion Analysis during Spiral NC Milling Based on FEM

Turbine blade plays an important role in aero engine and power generation equipment. As thin-walled and free-form surface component, deflection in spiral milling of turbine blade is common, which result in bad dimensional precision. In this paper, a five-axis milling experiment was firstly conducted to get the cutting force components. Then, deflections were studied at different positions. The results show that compensation can be made based on the FEM analysis.

Investigation of Trochoidal Milling Nickel-Based Superalloy

Nickel-based superalloy is a relatively new class of materials that exhibit high mechanical strength, ductility, creep resistance at high operating temperatures and stress levels. It is widely used in aero engine parts such as blade and blisk. Due to its high hardness and high strength at high temperature, it’s difficult to machine nickel-based alloy. In order to reduce tool wear, trochoidal milling strategy is studied in this paper. With trochoidal tool path strategy, tool load can be reduced and the tool has enough time to be cooled under high cutting temperature. Tool immersion angle in trochoidal milling is smaller than slot milling, thus the tool load can be reduced. Experiment results show that tool flank wear with normal slot milling is about four times larger than that with trochoidal milling. Trochoidal tool path strategy can be further developed for rough milling of compressor blades or rough milling hub of blisks.

Numerical robust optimization of spindle speed for milling process with uncertainties

This work is motivated by the fact that the conventional cutting parameters optimization in milling process has been widely investigated based on the assumption that the dynamics of the milling system is deterministic. Since there are many uncertain factors in a practical milling process, nominal cutting parameters derived from the deterministic cutting parameters optimization formulation cannot guarantee the stability of milling process and cannot lead to actual maximization of material removal rate and minimization of surface location error at the shop floor level. We develop a robust spindle speed optimization formulation, in which the upper bound of surface location error and lower bound of Lobe diagram are adopted as the optimization object and the constraint condition, respectively. For a comparison, we also give a deterministic spindle speed optimization formulation, without uncertainties. Time finite element approach is employed as the conventional deterministic model to obtain the Lobe diagram and surface location error. The upper and lower bounds of Lobe diagram and surface location error due to the model parameters uncertainties are calculated using the sensitivity analysis. The optimization problems are solved by an augmented Lagrangian function method. Experiments of milling of blades with spindle speeds derived from the deterministic and robust optimization results are implemented. The robust optimization result leads to stable milling process, while the deterministic one does not. The experimental results validate the proposed method. The robust optimization formulation given in this paper is helpful to the decision making in a practical milling process.

Deformation Control and Chatter Suppression in 5-Axis Milling of Thin-Walled Blade

This paper deals with deformation control and chatter suppression in the milling of thin-walled blade. The purpose is to generate tool paths that can control machining deformation and suppress chatter during milling. To achieve this object, symmetrical spiral milling approach is proposed to release residual stress on both sides of the blade in the same machining circle to control machining deformation. Besides, in order to suppress chatter during milling of thin-walled blade, nonuniform-allowance is left on both sides of the blade during machining, this can effectively increase the rigidity, thereby chatter cannot easily occur during machining. Machining experiments showed that the proposed approaches can dramatically improve the machining quality, decrease deformation and suppress chatter in the milling of thin-walled blade.

Production Efficiency and Product Quality Improvement through Factory Mechanization and Computerization

Our mission is to manufacture optimum products using provided design data. Thanks to analysis tools brought in recently, the design of more efficient propellers have become possible. To manufacture propellers with maximum design efficiency, a high level manufacturing technology is essential. The Tamashima Works, is a specialized facility for manufacturing large-sized fixed pitch propellers. Manufacturing size ranges from 5 meters up to a maximum of 12 meters in diameter, and a maximum weight of 150 tons. Here, we succeeded in developing special facilities, the only one of its kind in the world, such as the blade milling machine which can control 5 axis at the same time, the balancing machine, and the propeller overturning facility. These special facilities resulted in higher machining accuracy.

Optimisation of spiral tool path for five-axis milling of freeform surface blade

This paper deals with optimisation of five-axis tool paths in the context of milling of turbine blade. The purpose is to generate tool paths that respecting kinematical performance of machine tool while ensuring the geometrical conformity of the machined part. To achieve this object, outer transverse curves are created at the leading edge and trailing edge of the blade while generating spiral tool path, it allows the machine tool to maintain the programmed feed rate while respecting the kinematical limits of the machine tool. As for the leading and trailing edges of the blade, they are machined along height direction of the blade. Machining experiments showed that machine tool moved smoothly and no overcut or dot marks would occur with the proposed method, thereby demonstrating the feasibility of the presented approach.

A general approach to simulating workpiece vibrations during five-axis milling of turbine blades

Workpiece vibrations have a significant influence on the machining process and on the quality of the resulting workpiece surface, particularly when milling thin-walled components. In this paper a simulation system, consisting of an FE model of the workpiece coupled with a geometric milling simulation for computing regenerative workpiece vibrations during the five-axis milling process, is presented. Additionally, a modeling method for visualizing the resulting surface is described. In order to validate the simulation model, turbine blades were machined and the experimental results were compared to the simulation results.

Experimental Research on Cutting Forces of 5-Axis Milling of Al-Alloy Blade

The cutting force in manufacture process was observed with Kistler dynamometer. A special clamp was designed to simulate the real condition of blade cutting. Series of experiments were done. Cutting force reflected structure of the blade and movement of machine. Cutting force was changed with feed speed varied and the rotation of axis B & C. Resultant cutting force was uniform in back and basin of blade and increased with cutting speed went up. Resultant force was waved in edge of blade. Back and basin forces were lager than edge force in X direction. Force X invoked vibration.

Ordering and Magnetoelastic Properties of Fe-Ga Alloy

In this paper the investigations of the ordering, microstructure and magnetomechanical properties of the Fe80Ga20 alloy and its composites are presented. The composites consisted of the Fe-Ga particles with a size distribution in the range between 20 to 50 μm. These particles were produced by blade milling of arc-melted alloy. After milling the powders were annealed at 723K for 2.5, 7.5 and 12.5 hours. The epoxy-bonded composites in rectangular shape were made from the as-cast as well as from the annealed powders. Mossbauer spectroscopy studies revealed that the as-cast alloy is completely disordered. After annealing at 723 K the long range atomic order appeared. It was stated that the best magnetoelastic properties were exhibited by composites made from ferromagnetic particles obtained from the as-cast alloy. The measured saturation magnetostriction was λs= 70 x 10-6 for the bulk alloy and λs=100 x 10-6 for composite.

A novel spiral machining approach for blades modeled with four patches

This paper aims at developing a novel spiral machining technique for four- or five-axis milling of blades. The main contributions are twofold. First, detailed algorithms are presented to model the blade surface with the idea that it can be separated into four patches, i.e., the pressure surface, the suction surface, the leading edge surface, and the trailing edge surface. The G1 continuity across the boundary of each patch is considered. Second, based on the four patches modeled, the key routine of a new spiral machining method is further addressed in detail. It is carried out by machining the pressure and suction surfaces actually whereas passing by the leading and trailing edges in air cut. Experimental results show that the proposed methods can improve the machining quality and avoid overcut near the leading and trailing edges.

Evaluation of cutter orientations in 5-axis high speed milling of turbine blade

Recently, the development of aerospace and automobile industries has brought new technological challenges, related to the growing complexity of products and the new geometry of the models. High speed milling with a 5-axis milling machine has been widely used for 3D sculptured surface parts. When turbine blades are machined by a 5-axis milling, their thin and cantilever shape causes vibrations, deflections and twists. Therefore, the surface roughness and the waviness of the workpiece are not good. In this paper, the effects of cutter orientation and the lead/tilt angle used to machine turbine blades with a 5-axis high speed ball end-milling were investigated to improve geometric accuracy and surface integrity. The experiments were performed using a lead/tilt angle of 15° to the workpiece with four cutter directions such as horizontal outward, horizontal inward, vertical outward, and vertical inward directions. Workpiece deflection, surface roughness and the machined surface were all measured with various cutter orientations such as cutting directions, and lead/tilt angle. The results show that the best cutting strategy for machining turbine blades with a 5-axis milling is horizontal inward direction with a tilt angle.

Arbitrary Surface Flank Milling of Fan, Compressor, and Impeller Blades

It is generally conceived that a blade surface is flank millable if it can be closely approximated by a ruled surface; otherwise the slow machining process of point milling has to be employed. However, we have now demonstrated that the ruled surface criterion for flank milling is neither necessary nor sufficient. Furthermore, many complex arbitrary surfaces typical of our blades in fans, axial compressors, and centrifugal impellers in aviation gas turbines are actually closely flank millable and can be rendered exactly flank millable with one or more passes per surface often without sacrificing, indeed usually with gain, in performance.

Maternal anger and the behavior of two-year-old children

This work aimed at developing pasta with different types of flour to evaluate how different raw materials and particle size affect pasta quality. Triticum aestivum flour was obtained from two cultivars: Klein Guerrero and Baguette Premium 11. Grains were milled into white flour, whole-grain flour A (obtained by a cyclonic mill) and whole-grain flour B (obtained by a blade mill) to make white flour (FP), whole-grain A (WFAP) and whole-grain B (WFBP) extruded pasta. Particle size distribution and flour composition were determined in all flour samples, as were pasta cooking and nutritional properties. All types of flour showed different particle size distribution depending on composition and milling method. Both whole-grain flour pasta showed shorter optimal cooking time than FP samples due to disruptions in the gluten matrix by bran-germ particles. Cooked WFAP and WFBP samples were harder than FP samples. The highest antioxidant properties were obtained for whole-grain pasta although flour particle size did not influence protein and antioxidant contents. Even though whole-grain pasta did not show the same technological quality as that in FP, they offered a better nutritional profile due to higher protein and antioxidant levels and other healthy compounds, like fiber, found in the whole grain.

Blade milling machine: Engineers' Digest, Vol. 5, No. 7

Blade milling machine: Engineers' Digest, Vol. 5, No. 7