Milling Of Blades Research Articles

Effect of tool orientation on surface roughness and dimensional accuracy in ball end milling of thin-walled blades

AbstractIn the aerospace industry, high-precision components like impellers and blisks present considerable challenges in machining due to their intricate geometries and the need for reliable performance. Blades, often classified as thin-walled parts with complex, free-form surfaces, are crucial in ensuring the efficiency and safety of aircraft engines. Their geometries and materials require strict control over cutting parameters, such as tool path and orientation, to avoid deformation and maintain surface integrity. This study investigates the impact of tilt angle variation during ball end milling of Ti6Al4V thin-walled parts. Four different tilt angles (15°, 30°, 45°, and 60°) were analysed to evaluate their effect on dimensional accuracy and surface roughness. The results show that tilt angle significantly influences surface quality and dimensional precision. A tilt angle of 30° achieved the best balance between surface finish and dimensional tolerances, with flatness values ranging from 0.038 mm at 30° to 0.101 mm at 60°, representing a 152.5% increase in flatness. The findings provide practical guidelines for optimizing ball end milling of thin-walled components, emphasizing the importance of tool orientation in reducing deformation and enhancing surface quality.

Enhancing Chatter Stability for Milling Thin-Walled Blades by Designing Non-Uniform Allowance

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.

Chatter Avoidance by Spindle Speed and Orientation Planning in Five-Axis Ball-End Milling of Thin-Walled Blades

Abstract Selecting suitable cutting conditions is crucial in maintaining chatter stability and achieving acceptable surface quality. However, the selection of a constant set of cutting parameters is not feasible due to the time-varying dynamics of highly flexible thin-walled blades. This paper presents an optimal selection of tool orientation and spindle speed along the tool path as the metal is removed during the ball-end milling of blades. The effects of tool orientation and speed on the mechanics and dynamics of the ball-end milling process are formulated. Test case simulations are used to demonstrate the impact of tool orientation and speed on chatter stability and forced vibrations. The proposed algorithm identifies the optimal spindle speed and tool orientation by continuously updating the workpiece dynamics as a function of time and tool position to achieve improved stability and surface quality. Stability simulations are conducted to assess the optimization approach's performance, and the results are compared with experiments by machining a series of thin-walled twisted fan blades.

Research into Dynamic Error Optimization Method of Impeller Blade Machining Based on Digital–Twin Technology

A TC4 impeller blade is a typical weak, rigid, thin–walled part. The contact area between a cutting tool and a workpiece has strong time–varying characteristics. This leads to a strong non–linear variation in cutting load. So, in this kind of part, the processing error is difficult to control. To solve this problem, a method of processing error prediction and intelligent controlling which considers the effect of tool wear time variation is proposed by combining digital–twinning technology. Firstly, an iterative model for digital–twin process optimization is constructed. Secondly, an iterative prediction model of the machining position following the milling force and considering the effect of tool wear is proposed. Based on these models, the machining error of the TC4 impeller blade under dynamic load is predicted. Dynamic machining error prediction and intelligent control are realized by combining the digital–twin model and the multi–objective process algorithm. Finally, the machining error optimization effect of the proposed digital–twin model is verified via a comparison experiment of impeller blade milling. In terms of the precision of milling force mapping, the average error after optimization is less than 8%. The maximum error is no more than 14%. In terms of the optimization effect, the average error of the optimized workpiece contour is reduced by about 20%. The peak contour error is reduced by approximately 35%.

Aero-Engine Blade Cryogenic Cooling Milling Deformation Simulation and Process Parameter Optimization.

For the machining of aero-engine blades, factors such as machining residual stress, milling force, and heat deformation can result in poor blade profile accuracy. To address this issue, simulations of blade milling were completed using DEFORM11.0 and ABAQUS2020 software to analyze blade deformation under heat-force fields. Process parameters such as spindle speed, feed per tooth, depth of cut, and jet temperature are used to design both a single-factor control and BBD test scheme to study the influence of jet temperature and multiple changes in process parameters on blade deformation. The multiple quadratic regression method was applied to establish a mathematical model correlating blade deformation with process parameters, and a preferred set of process parameters was obtained through the particle swarm algorithm. Results from the single-factor test indicated that blade deformation rates were reduced by more than 31.36% in low-temperature milling (-190 °C to -10 °C) compared with dry milling (10 °C to 20 °C). However, the margin of the blade profile exceeded the permissible range (±50 µm); therefore, the particle swarm optimization algorithm was used to optimize machining process parameters, resulting in a maximum deformation of 0.0396 mm when the blade temperature was -160 °C~-180 °C, meeting the allowable blade profile deformation error.

An Increase in the Energy Efficiency of Axial Turbines by Ensuring Vibration Reliability of Blade Milling

Ensuring the vibration reliability of power equipment is one of the fundamental problems in modern power machinery. This problem has become more critical due to a permanent increase in the machining performance of high-speed milling of axial turbine blades. This article aims to identify reliable vibration parameters for high-speed milling of turbine blades to increase the energy efficiency of gas and steam turbines. For this purpose, mathematical models of free and forced oscillations of turbine blades during machining were developed. As a result of considering experimental and finite element analysis data, critical frequencies and corresponding mode shapes of free oscillations were identified using regression procedures by the best fit of analytical and empirical approaches. Additionally, after considering the forced oscillations of blades during high-speed machining, the magnitude of the specific cutting force and external damping ratio in the system ‘axial turbine blade and milling head’ were evaluated. The resulting magnitude of forced oscillations during machining was calculated. Finally, the amplitude–frequency response was also assessed, considering the machining parameters. Overall, the proposed methodology increases energy efficiency due to a decrease in the obtained machining quality of turbine blades.

A Deformation Control Method in Thin-Walled Parts Machining Based on Force and Stiffness Matching Via Cutter Orientation Optimization

Abstract In the milling process, significant machining errors may occur due to the low stiffness of thin-walled parts. To reduce the cutting force-induced deformation in milling thin-walled parts such as blades, a cutter orientation optimization algorithm based on stiffness matching is proposed. The concept of maximum stiffness direction is put forward according to the phenomenon that different deformations are produced when applying forces with the same magnitude but in different directions. The stiffness of the in-process workpiece is obtained using the stiffness updating method. The cutter orientation optimization algorithm is presented to match the force with the maximum stiffness direction. The best cutter orientation is obtained by adopting the quantum particle swarms optimization algorithm at the key cutter location points, and then the cutter orientations of all cutter location points are obtained by the quaternion interpolation algorithm. The proposed deformation control method is verified on thin-walled blade milling experiments, and the experimental results show that the machining deformation of the blade with the optimized cutter orientation is reduced by about 36.51%, indicating that the proposed method can effectively reduce the machining deformation of the thin-walled parts.

Arabinoxylans Release from Brewers' Spent Grain Using Extrusion and Solid-State Fermentation with Fusarium oxysporum and the Antioxidant Capacity of the Extracts.

Brewers’ spent grain (BSG) is the most abundant byproduct generated from the beer-brewing process. BSG is a material rich in hemicellulose, composed of arabinoxylans (AX). However, the high crosslinking of this material causes low availability of AX, for which it is necessary to apply different treatments. The objective of this research is to increase the release of arabinoxylans through solid-state fermentation with Fusarium oxysporum f. sp. lycopersici using extruded brewery spent grain. First, the BSG is subjected to two types of physical treatments: extrusion at 20% moisture, 200 rpm and 50 °C (BSGe), and blade milling (BSGm). The chemical composition is determined for each sample (BSG, BSGe and BSGm). Subsequently, the solid-state fermentation process (SSF) is carried out on each sample. The fermentation kinetics at 30 °C are monitored for 7 days. Once the SSF concludes, AX are extracted, and the purity of AX is determined by the phloroglucinol colorimetric assay. Finally, the total phenolic compounds, phenolic acids and antioxidant capacity by DPPH are quantified. No significant differences (p ≥ 0.05) in the protein, lipid, ash or total dietary fiber contents are found among the samples. No significant difference (p ≥ 0.05) in the content of soluble fiber is found, although BSGe and BSGm have higher values than BSG. On the other hand, the yields of soluble AX exhibit significant differences (p ≤ 0.05) among nonfermented samples (BSG, 0.03%; BSGm, 0.53%; BSGe, 0.70%) and with SSF (BSG, 2.95%; BSGm, 6.24%; and BSGe, 9.58%). In addition, the contents of free phenolic compounds and free phenolic acids and the percent inhibition of free extracts by 2,2-diphenyl-1-picrylhydrazyl (DPPH) differ significantly (p ≤ 0.05) between samples subjected to SSF and nonfermented samples. Therefore, extrusion and SSF treatment increase AX release from BSG as well as the antioxidant capacity of the extracts.

Impact of sorghum grain processing on morphological characteristics of particles of wholegrain sorghum flour

This work studies the physical characteristics of sorghum whole flour particles produced with grains reduced in tannins by hydrothermal treatment. Flours ground with two types of mills: a roll mill and a blade mill were used; grains were hydrated with a moisture content of 25%. For this moisture the maximum yield was obtained. The effect of the grain moisture during the grinding was evaluated regarding the morphological characteristics, the granulometry and fractal dimension (Df) of particles. In all the analysed samples, bimodal size distribution curves were obtained. The treated samples showed medium size particles bigger than the samples without treatment. The samples without hydrothermal treatment presented particles with lower damage than the treated samples for both mills. The difference in Df between samples indicated more roughness for the samples with treatment. The proposed treatment could contribute to the development of sorghum whole flour with different properties for the development of gluten-free food.

Vol4 num3-3 Manufacturing of carbon fiber reinforced PET from wastes of CFRP and PET bottles

This work is focused on two current and important issues. On one hand, 12 millions of tons of PET are thrown into the sea each year. In fact, in spite of being a recyclable polymer, less than 50 % of processed PET is recycled in Europe. On the other hand, thermoset matrix composites are widely used in the industry and the end-of-life products and scraps need to be recycled. Compared to thermoplastics, thermosets present a problem for being recycled or remolded due to their irreversible curing. Many researches are focused on the recycling of carbon fiber reinforced epoxy, presenting three different paths: mechanical, thermal and chemical recycling. Thermal recycling is the most promising because it allows to recover clean fiber. However, it is an energetically expensive and non-environmentally friendly process. Chemical recycling, for its part, needs hazardous products, such as nitric acid, to dissolve the matrix. Finally, both, fibers and matrix, are recovered with mechanical recycling which consists on milling the composite to obtain finer parts. In this work, unidirectional carbon fiber reinforced epoxy is blade-milled and it is used as reinforcement of a new composite. As matrix, PET coming from recycled bottles is used. First of all, pellets of PET are produced from the bottles with a blade mill. Recycled composite and PET are mixed and a sheet is manufactured with a hot plates press. The resulting material is chemically and mechanically tested.

EVALUATION OF THREE LIGNOCELLULOSE BIOMASS MATERIALS (BARLEY HUSK, CORN COBS, AGAVE LEAVES) AS PRECURSORS OF ACTIVATED CARBON

Lignocellulosic biomass is a promising alternative and renewable energy source that can be transformed into other value-added products such as activated carbon. The objective was to evaluate the barley husk (Hordeum vulgare L.), the corn cobs (Zea Mays L.) and the agave leaves (Agave salmiana) as potential precursors of activated carbon. These precursors were obtained from Almoloya and Apan in the State of Hidalgo, Mexico. The raw materials were washed with distilled water, dried at 105 ºC for 72 h in an oven, ground in a blade mill to obtain a particle size of 0.3-1.0 mm and finally sieved through mesh sieves of 18 and 45. Humidity was determined according to ASTM D3173 (ASTM, 1996), ash according to ASTM D3174 (ASTM, 2000), volatile matter according to ASTM D3175 (ASTM, 1997), fixed carbon according to ASTM D3172 (ASTM, 1997), total sugars and fats according to TAPPI T204 (TAPPI, 1997), Klason Lignin according to TAPPI T222 (TAPPI, 1998), holocellulose according to the method described by (Wise et al., 1946), and (, ( and ( cellulose according to TAPPI T203 (TAPPI 1999). The results show that contents from 82 to 83% for holocellulose, from 52 to 79% for cellulose, and from 15 to 26% for lignin, were determined. Elemental analysis showed high carbon contents with values of 42-45%. Particle sizes between 390.9 mm and 610.7 mm were found. Thermogravimetric analysis showed similar profiles of thermal decomposition, being cellulose the main stage, with peaks around 300 °C. Regarding the surface morphology, the lignocellulosic residues showed fibrous and porous structure. From these findings, it is established that the precursors analyzed can be considered as potential precursors of activated carbons. The results presented here may facilitate improvements in the pyrolysis and activation areas of this lignocellulosic residues. The conditions for an acceptable yield of biochar were tested, these were: carbonization temperature of 400 °C, carbonization time of 30 min, precursor mass of 2-10 g and N2 flow rate of 150 cc/min. The biocarbons produced under these conditions were physically and chemically characterized. Biochar yields of 19.75% were obtained for corn cob (CCB), 32.88% for barley husk (BHB) and 31.14% for Agave salmiana leaves (ALB). Biocarbons with a predominantly macroporous structure, amorphous structure, numerous oxygen functional groups, anionic surface and moderate ash content were obtained. The results of this investigation show that barley husk, corn cob, and agave leaves are likely precursors for biochar production with good dye adsorption capacities.

Minimization of surface roughness in 5-axis milling of turbine blades

The Reynolds number of turbine blades can be reduced by decreasing the surface roughness of the blades, which decreases energy loss in energy production systems. Due to the challenges of the polishing process in reducing roughness of machined blades, the application of optimized machining parameters to decrease surface roughness is a practical solution. Virtual machining system is explored in this research to improve the efficiency of machined parts. The aim of this research is to provide a virtual machining system that can predict and effectively reduce roughness in gas turbine blade 5-axis machining operations. The machining parameters were optimized using Genetic algorithm to reduce surface roughness. The turbine blades were machined using a 5-axis CNC machine tool, and the surface roughness of the machined parts was measured using a CMM machine to validate the developed methodology in the study. The optimized machining parameters result in a 26.2% reduction in observed surface roughness and a 27.3% reduction in expected surface roughness in the machined blades. The developed virtual machining system can be used to improve the surface quality of machined turbine blades and hence improve the efficiency of gas turbines during the power production in gas turbines.

Use of additive technologies in the manufacture of central impactors

Purpose. Analysis of methods of manufacturing centrifugal blades by 3D printing methods on the example of a modernized cooling system of the AI-450M engine of the Mi-2MSB helicopter.
 Research methods: calculation method of finite elements, analytical.
 Results. Studies have shown that the use of layer-by-layer printing technology of the centrifugal wheel of the cooling system provides the following opportunities and improvements:
 - reduce the percentage of rejection of finished products by 8–9 times;
 - reduce material consumption by 300–400 %;
 - increase the speed of production, experiments and testing the manufacture of working elements through the development of new technologies for rapid production (rapid fabrication);
 - easy printing of previously “impossible” geometry.
 The analysis of possible types of manufacturing of working centrifugal wheel and the calculated estimation of thermodynamic parameters in the course of step-by-step drawing of layers of metal is carried out. The problem of a large percentage of defects in the process of classical-mechanical milling of blades was solved by changing the type of production to additive one.
 Scientific novelty. In today's world, the spread of CAD / CAM / CAE / PLM technologies and the accumulation of a wide library of materials open up a large number of new and more efficient, in terms of economy and quality, methods of manufacturing components and units. Following the example of such giants in the production of aircraft engines as Rolls-Royce Motor, General Electric and Pratt & Whitney, it is clear that the use and development of the latest methods of three-dimensional printing is appropriate.
 Practical value. The obtained results are important in the further process of production and modernization ofMi-2 helicopter of all modifications with the latest engines, as well as for projects for the development of helicopter construction in Ukraine - МСБ-2 “Hope”, МСБ -6 “Otaman”, МСБ-8 and others. The ability to increase the efficiency of manufacturing the main working elements - blades allows you to reduce the cost of components, their further repair, operation. The most important factor is to increase reliability, as in the manufacture reduces the likelihood of defects, which will not be detected at the stages of intermediate and final control.

Investigating the influence of work piece geometry on the specific energy use in size reduction with a multi-blade shaft mill

This study investigated the specific milling energy of rectangular pine ( Pinus sylvestris L.) boards using a new size reduction technology, which can produce fine wood powders in a single-step operation. Multilinear regression (MLR) analysis was used to model the milling energy of a multi-blade shaft mill through a designed series of experiments having three input parameters: the moisture content of the board, milling blade speed and board feeding speed. The observed specific milling energy ranged from 60 to 172 kWh t −1 [DM] and the MLR model showed it was proportional to the blade speed and the moisture content. The results suggest that multi-blade shaft milling is a two-dimension extension of singular circular blade milling with regard to work piece shape and sawblade teeth engagement effects. The findings were compared with the specific milling energy of pine logs obtained in a previous study. • Modelled specific milling energy is proportional to moisture content and blade speed. • Wood shape and shaft teeth engagement in two dimensions influence milling energy. • Multi-blade shaft milling is a two-dimension extension of singular circular blade milling. • MBSM milling is analogous to sawing wood and opposite to impact-based milling.

Comparison on Milling Force Model Prediction of New Cold Saw Blade Milling Cutter Based on Deep Neural Network and Regression Analysis

A four factors and three levels orthogonal milling force (MF) test is designed, which qualitatively obtains the influence of four factors, namely workpiece material, workpiece diameter, milling speed and feed per tooth, on MF of the new cold saw blade milling cutter (NCSBMC), then further verifies the reliability of test data with simulation analysis of MF. The multiple linear regression analysis and deep neural network (DNN) are used to accurately fit and predict the magnitude of MF in three directions of NCSBMC, taking into account the influence of workpiece material factors on MF. Compared with the results of empirical formula, DNN has higher prediction accuracy. The research results provide theoretical guidance for the optimization of milling parameters in actual machining process.

Three-dimensional modeling and reconstructive change of residual stress during machining process of milling, polishing, heat treatment, vibratory finishing, and shot peening of fan blade

Three-dimensional modeling and reconstructive change of residual stress during machining process of milling, polishing, heat treatment, vibratory finishing, and shot peening of fan blade

Virtual Minimization of Residual Stress and Deflection Error in Five-Axis Milling of Turbine Blades

Virtual Minimization of Residual Stress and Deflection Error in Five-Axis Milling of Turbine Blades

Virtual Minimization of Residual Stress and Deflection Error in the Five-Axis Milling of Turbine Blades

To simulate and analyse the real machined parts in virtual environments, virtual machining systems are applied to the production processes. Due to friction, chip forming, and the heat produced in the cutting zone, parts produced using machining operation have residual stress effects. The machining force and machining temperature can cause the deflection error in the machined turbine blades, which should be minimized to increase the accuracy of machined blades. To minimize the residual stress and deflection error of machined parts, optimized machining parameters can be obtained. In the present research work, the application of a virtual machining system is presented to predict and minimize the residual stress and deflection error in a five-axis milling operations of turbine blades. In order to predict the residual stress and deflection error in machined turbine blades, finite element analysis is implemented. Moreover, to minimize the residual stress and deflection error in machined turbine blades, optimized parameters of machining operations are obtained by using a genetic algorithm. To validate the research work, experimentally determining residual stress by using a X-ray diffraction method from the machined turbine blades is compared with the finite element results obtained from the virtual machining system. Also, in order to obtain the deflection error, the machined blades are measured by using the CMM machines. Thus, the accuracy and reliability of machined turbine blades can be increased by analysing and minimizing the residual stress and deflection error in virtual environments.

Layout optimization of auxiliary support for deflection errors suppression in end milling of flexible blade

The service performance and life of the aero-engine are directly affected by the blade machining accuracy. In the end milling of the flexible blade, the profile tolerance would usually be violated by the deflection errors induced by excessive static deformations under the action of milling force. In order to predict the blade deflection errors, this paper presents an iterative algorithm considering the coupling relationship between milling force and elastic deformation based on the milling finite element simulation model. Then a novel multipoint rod-shaped auxiliary support technology is proposed to suppress the blade deflection errors. Taking the influence of layout parameters on blade deflection errors into account, the layout of auxiliary support is optimized by a genetic algorithm. To verify the effectiveness of the proposed method, an auxiliary support mechanism is designed and manufactured, and the deflection errors suppression experiment is implemented. The measured results show that the prediction error of blade maximum deflection is 17.6%. Furthermore, the blade average deflection error on two measured curves reduces from 45.88 μm to 24.39 μm with the support of the designed mechanism. Thus, this auxiliary support mechanism and layout optimization method can achieve higher accuracy in blade milling.

Influence of the particle size distribution on dust explosion: How to choose the right metrics?

It is well established that the a diameter' of a powder and its explosivity are strongly correlated. But, in fact, what diameter should be considered? The mass median diameter d50 is often used as an indicator of the particle size distribution (PSD) of a powder, but this choice is not always consistent with the mechanisms involved in a dust explosion. Moreover, authors mainly refer to the initial diameter of the powder, whereas it is more relevant to consider its characteristics at the exact time of the ignition. Many other metrics can be of interest concerning dust explosion: Sauter diameter, d10, solid surface concentration. To highlight these points, tests were performed on raw starch powders of 24 microm d50 and 0.49 m2.g-1 specific surface area. They were mechanically agglomerated with an Instron press and then coarsely ground by a blade mill. Different size classes up to 283 microm d50 and 0.16 m2.g-1 specific surface area were selected by sieving. The PSD of the samples were compared before and during their injection in the explosion vessels. The influence of the actual PSD on their explosion severity and minimum ignition energy (MIE) was determined. It has been demonstrated that the evolution of the MIE with regard to PSD is subject to a threshold phenomenon. Moreover, if the mass median diameter can be interesting for kinetics controlled by homogeneous chemical reaction and directly related to the fuel equivalent ratio, the reactive surface is more relevant when the combustion is controlled by surface reaction or diffusion to the surface as it is the case for the various starch samples. Chromatography measurements of the combustion gases confirm these results. Finally, when the agglomerates are partially fragmented by the injection, both the agglomerate and primary diameters must be considered.