Non-rigid Parts Research Articles

Использование новых видов технологической оснастки при изготовлении нежестких плоскостных алюминиевых деталей методом волновых технологий

It has been suggested that wave technologies in non-rigid plane parts production should be used with the introduction of ultrasonic range vibrations into the shaping zone in combination with technological equipment, i.e. it is- a zero-base system. The traditional technique used in domestic enterprises implies a high probability of out-of-flat conditions and deformations due to the influence of technological residual stresses (TRS) in the process of stock removal or force stresses under plastic deformation of the part when fixing blanks. Using modern universal software systems such as Simulia Abaqus, ANSYS, etc., it was possible to determine the magnitude of deformations, aligment errors caused by residual stresses. The data obtained were used to calculate rational ways for fixing some typical non-rigid plane aluminum blanks on a technological equipment - a zero-based system of German production SCHUNKVERO–SAviation (VSA). The research was aimed at determining the manufacturability for the use of such equipment when making a particular non-rigid blank made of aluminum alloys and finding the most optimal way of its fixing. The estimated values of the TRS were determined by mechanical and X-ray methods. The calculations were performed using real parts of aircraft equipment of the "beam" type and blanks made of aluminum rolled products. The proposed method for determining the maximum amount of deformation of the workpiece under machining is applicable to the most optimal placement of the support and clamping modules of the zero-based system (VSA). In combination with a certain strategy of wave mechanical processing, it makes a practically complete compensation for deformations possible and allows obtaining a suitable product from the first presentation without performing an additional correction operation.

Intelligent control algorithm for industrial robots when performing the assembly operation of cylindrical non-rigid parts

Intelligent control algorithm for industrial robots when performing the assembly operation of cylindrical non-rigid parts

Improving the processing accuracy of the puller shaft of the cotton harvesting machine controlling the dynamic system parameters

The article is dedicated to improving the accuracy of shaft turning by controlling the elastically deformed state of the part during processing. This study is conducted on the example of a puller shaft of a cotton harvesting machine, which belongs to the class of non-rigid parts such as bodies of rotation. To evaluate the possibilities of the method and establish theoretical patterns of the behavior of the part during transverse-longitudinal bending, the equation of the elastic line of a non-rigid shaft is solved. An integral assessment is adopted as a criterion of the accuracy in controlling elastic deformations of a technological system.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ ТОКАРНОЙ ОБРАБОТКИ ЖАРОПРОЧНЫХ СПЛАВОВ ВВЕДЕНИЕМ В ЗОНУ РЕЗАНИЯ ЭНЕРГИИ УЛЬТРАЗВУКОВОГО ПОЛЯ

The use of difficult-to-process heat-resistant alloys is widely used in the design of aircraft engines and gas pumping units. As a rule, thin-walled shell structures are made from them, providing a high density of the layout (for example, blades, electric unicycles). The peculiarity of the manufac-ture of such structures is a small (compared to the occupied volume of the entire product) volume of metal, in which the heat generated during shaping is distributed. Given the low thermal conductivity of such alloys (up to 4-5 times less compared to steels), the shaping of parts from them is associated with the risk of warping in combination with low productivity of blade processing with carbide tools. More effective, but little studied is the processing with tools made of mineral ceramics with the introduction of the energy of the ultrasonic field into the cutting zone. The purpose of the research is to develop a high-performance technology for pre-processing workpieces made of heat-resistant alloys with tools made of mineral ceramics, characterized by a minimum depth of defects in the surface layer.
 Methods. The research was carried out on machine tools in the manufacture of non-rigid parts of aircraft by turning blanks from the heat-resistant alloy HN45MVTYUBR with cutters made of mineral ceramics with the introduction of the energy of the ultrasonic field into the processing zone. 
 It has been established that the use of ultrasonic vibrations during pretreatment with mineral-ceramic tools without coolant can reduce the depth of the defective layer by up to one and a half times and increase productivity by up to 30 times.
 Taking into account the reduction in the depth of the defective layer, it becomes possible to reduce the allowances for final processing, and consequently, to reduce the duration of the technological process and the cost of manufacturing parts.

Feasibility of new types of technological equipment in the manufacture of nonrigid flat aluminum parts

In this work, we assess the efficiency of the SCHUNK VERO-S Aviation clamping system in manufacturing nonrigid aluminum parts in comparison with the existing technology of their small-scale production at domestic aircraft plants. The research was conducted using the facilities of mechanical shops that manufacture nonrigid aircraft parts to estimate the time and economic expenditures involved in their production when changing the cutting mode and machining allowances. The proposed technological process was implemented by the HALTEC Russian engineering company at an aircraft manufacturing plant of the Russian Federation. The duration of the technological process amounted to a total of 14 hours, with the existing production technology lasting for 300 hours. The process duration was reduced by eliminating two thermal stabilization operations and shortening the machine-setting time by 50%. The machine-setting time was reduced by increasing the number of cutting mode elements during manufacturing of a non-rigid aluminum part using this tooling, as well as by using a modified machining strategy. The use of the SCHUNK VERO -S Aviation system together with a modified machining strategy for a thin-walled non-rigid workpiece allows for an almost complete compensation of deformations caused by residual stresses of the first kind. The new modern technology of SCHUNK VERO -S Aviation proves to be effective for the small-volume and series production of thin-walled nonrigid components of the required quality without warping, multiple straightening operations, thermal and temporal stabilization.

INVESTIGATION OF CUTTING FORCE DURING BORING OF SCREW NON-RIGID MACHINE PARTS

In the work, the peculiarities of boring of screw workpieces are described. The regularities of the processes of boring screw non-rigid parts have been established. The specifics of the design of the equipment for boring screw non-rigid parts and the expediency and prospects of using screw workpieces are substantiated. It is based on theoretical and experimental studies. A theoretical generalization and a new solution to the scientific and technical problem expressed in the development and creation of technological processes for processing non-rigid screw workpieces, are presented. This will make it possible to ensure the expansion of technological capabilities and the improvement of technical and economic parameters. Calculations were carried out using a package of applied statistical programs for processing and analyzing the results of experimental studies for a PC. According to these results, the dependences of the response surfaces of the optimization parameter and the two-dimensional section of the response surfaces were constructed and analyzed for a visual representation of the results of the experimental studies. The dependences of the change in cutting force on feed and cutting depth were constructed and analyzed. The dependences of the optimization parameter, that is, the dependence of the cutting force on the change of one input factor with a constant value of the other two factors, were also substantiated. After carrying out research using the program «Statistika», a two-dimensional section of the response surface of the dependence of the cutting force on the feed and depth of cut and the response surface of the dependence of the cutting force on the feed and depth of cut were constructed. The obtained experimental broken line was built based on the results of the conducted research. Approximation of it was carried out according to known standard methods, while the amount of deviation (mismatch) was determined by the method of least squares.
 Key words: cutting process, feed, cutting depth, nature of loads, boring process, statistical analysis, lathe and screw-cutting machine.

Bridging the gap between design and manufacturing specifications for non-rigid parts using the influence coefficient method

The manufacturing process may lead non-rigid parts to endure large deformations which could be reduced during assembly. The manufacturing specifications of the single parts should refer to their free state or “as manufactured” state; the functional specifications should instead address the “as assembled” state. Therefore, a functional geometrical inspection requires dedicated fixtures to bring the parts in “as assembled” state. In this paper, through a linearized model that considers fixturing and elastic spring-back, we aim to correlate the functional specification to the manufacturing specifications. The model suggests a hybrid approach called “restricted skin model” that allows to reduce the degrees of freedom considering the form error when relevant. Firstly, the framework is verified in a mono-dimensional test case. Subsequently, it is verified including FEM simulation and actual measurement for two simple assemblies. The results show that the model can correctly interpret the theoretical assembly behaviour for actual applications. The use of the “restricted skin model” approach shows a negligible difference when compared to full FEM simulation with differences of 2.1 · 10−7 mm for traslations and 6.0 · 10−3 deg for rotations. The comparison with actual measurement values showed an error of ±0.2 mm at the assembly features. Furthermore, the linearized model allows a possible real-time application during production that enables to adjust manufacturing specification limits in case of process drifting.

Calculation of the deflection of the blade of the disk of an axial gas pumping machine

The mechanism of occurrence of errors leading to failure of parts of compressors and pumps is investigated. A method is proposed for non-destructive control of the accuracy of manufacturing of non-rigid parts with end surfaces of revolution without reducing productivity. Keywords: compressor, non-rigid part, technological system, diagnostics. nga112001@list.ru

Новые технологии изготовления нежестких плоскостных деталей из авиационных материалов

An array of questions related to new technologies for manufacturing non-rigid thin-shell flat parts made of aircraft materials is viewed. To reduce possible deformations and improve the quality, it has been suggested that the energy of a modulated ultrasonic field should be used

Research of the influence of the main parameters of rotary cutting on the surface quality of high-precision non-rigid thin-walled parts

The influence of the main parameters of rotary cutting on the surface roughness, residual stresses and microhardness of the surface layer of the machined part is investigated. It is established that increasing the depth of cutting and feed increase the roughness, residual stresses and hardness of the surface layer. The influence of other cutting parameters on the quality of the surface layer is mainly related to the kinematic and dynamic features of processing. The possibilities of regulating the quality of processing by changing the cutting parameters are revealed. Keywords: rotary cutting, quality, roughness, residual stresses, hardness, regulation, modeling. qafarov@hotmail.com

A Computer-Aided Design-Based Tolerance Analysis of Assemblies With Form Defects and Deformations of Nonrigid Parts

Abstract Product assemblability and functional behavior are affected by geometric deviations. These deviations consist of manufacturing errors and part deformation defects caused by external loads. Taking the sources of deviations into account in tolerance analysis yields not only to more precise and reliable results but also to more complex tasks. In this context, the modeling of assembly parts with defects in a Digital MockUp (DMU) is quite promising. In this article, an integrated decision support tool is proposed to consider the causes of multiple defects, such as tolerances and external mechanical loads, in the tolerancing process. The worst-case concept and the small displacement torsor (SDT) are used to model rigid parts with orientation and positional defects. To model the part with form defects, random positions of each toleranced face points are determined using the Gaussian perturbation method (GPM) and considering the tolerance zone limits. A computer-aided design (CAD) method based on the B-spline interpolation allows the reconstruction of realistic surfaces of parts with form defects. Realistic configurations of nonrigid components subjected to external mechanical loads are determined using the finite element analysis (FEA). The realistic assembly configurations are performed by updating the mating constraints between planar and cylindrical parts. The proposed method considers all tolerance types on CAD models (positional, orientation, and form defects) and part deformations. The tolerance analysis is performed to check the compliance with the functional requirement (FR) and to correct the initial tolerance values. An industrial case study is used to validate the steps of the proposed tolerancing method.

Development of Technology for Producing Holes in Parts with Unpredictable Surface Fluctuations

The article deals with the methods of forming liquid rocket engines parts, in which sheet material is used as a blank. The analysis of the existing methods of processing workpieces with a variable surface profile allows us to conclude that the mechanical method is the most promising type of processing for hole perforation. The drilling holes technology in parts made of sheet blanks is presented. The features of processing non-rigid parts with unpredictable surface fluctuations are considered. The ways of ensuring the stability of the treatment process, increasing the technological indicators, which allowed expanding the area of dimensional machining, are shown. The results of the work contribute to improving the manufacturability of new generations products of equipment, which is important for mechanical engineering.

Экспериментальное исследование жесткости технологической системы на базе промышленного робота KUKA KR 300 R2500 ULTRA

In modern machine-building production, there are many parts that have both significant overall dimensions and complex hard-to-reach surfaces for processing. The manufacture of such parts is carried out on specialized equipment, which has the same significant overall dimensions. However, the complexity of the design of a number of parts, such as the body of a rocket engine, large volume tanks, non-separable metal structures, etc., as well as their inaccessibility, level the technological capabilities of this equipment. Currently, industrial robots equipped with tool spindles are used to process such parts. The presence of a large number of degrees of freedom of this equipment, the relatively small overall dimensions and the vastness of the working area allow them to be effectively used in this field of mechanical engineering. However, the insufficiently studied rigidity of this equipment, the lack of specific recommendations for their use significantly limit the scope of their application. Thus, the issues related to the mutual influence of the rigidity of the technological system, cutting forces and cutting conditions in the manufacture of large parts using industrial robots are relevant and require a comprehensive study. In order to study dynamic processes in the manufacture of large-sized parts using an industrial robot, experiments were carried out to determine the amplitude-frequency characteristics of vibrations that occur during processing. An experimental study made it possible to establish that the rigidity of the technological system varies over a wide range. At the same time, the rigidity of the part under an impulse load difIn modern machine-building production, there are many parts that have both significant overall dimensions and complex hard-to-reach surfaces for processing. The manufacture of such parts is carried out on specialized equipment, which has the same significant overall dimensions. However, the complexity of the design of a number of parts, such as the body of a rocket engine, large volume tanks, non-separable metal structures, etc., as well as their inaccessibility, level the technological capabilities of this equipment. Currently, industrial robots equipped with tool spindles are used to process such parts. The presence of a large number of degrees of freedom of this equipment, the relatively small overall dimensions and the vastness of the working area allow them to be effectively used in this field of mechanical engineering. However, the insufficiently studied rigidity of this equipment, the lack of specific recommendations for their use significantly limit the scope of their application. Thus, the issues related to the mutual influence of the rigidity of the technological system, cutting forces and cutting conditions in the manufacture of large parts using industrial robots are relevant and require a comprehensive study. In order to study dynamic processes in the manufacture of large-sized parts using an industrial robot, experiments were carried out to determine the amplitude-frequency characteristics of vibrations that occur during processing. An experimental study made it possible to establish that the rigidity of the technological system varies over a wide range. At the same time, the rigidity of the part under an impulse load differs from the rigidity during milling by at least an order of magnitude, and the rigidity of the spindle during milling differs from the rigidity of the part by at least 2 orders of magnitude. Based on this, in the process of designing the machining of large-sized non-rigid parts using industrial robots, it is necessary to take into account the worst conditions for rigidity. It is advisable to base further recommendations on the appointment of cutting conditions under changing processing conditions on the basis of mathematical modeling of the rigidity of the elements of the technological system. Also, to automate the process of removing the parameters of the rigidity of the technological system, an urgent task is to determine by test determination of vibrations on the spindle of an industrial robot and indirect assessment of microdisplacements on the part

Assembly variation analysis of the non-rigid assembly with a deformation gradient model

PurposeThis paper aims to develop a mathematical method to analyze the assembly variation of the non-rigid assembly, considering the manufacturing variations and the deformation variations of the non-rigid parts during the assembly process.Design/methodology/approachFirst, this paper proposes a deformation gradient model, which represents the deformation variations during the assembly process by considering the forces and the self-weight of the non-rigid parts. Second, the developed deformation gradient models from the assembly process are integrated into the homogenous transformation matrix to model the deformation variations and manufacturing variations of the deformed non-rigid part. Finally, a mathematical model to analyze the assembly variation propagation is developed to predict the dimensional and geometrical variations due to the manufacturing variations and the deformation variations during the assembly process.FindingsThrough the case study with a crosshead non-rigid assembly, the results indicate that during the assembly process, the individual deformation values of the non-rigid parts are small. However, the cumulative deformation variations of all the non-rigid parts and the manufacturing variations present a target value (w) of −0.2837 mm as compared to a target value of −0.3995 mm when the assembly is assumed to be rigid. The difference in the target values indicates that the influence of the non-rigid part deformation variations during the assembly process on the mechanical assembly accuracy cannot be ignored.Originality/valueIn this paper, a deformation gradient model is proposed to obtain the deformation variations of non-rigid parts during the assembly process. The small deformation variation, which is often modeled using a finite-element method in the existing works, is modeled using the proposed deformation gradient model and integrated into the nominal dimensions. Using the deformation gradient models, the non-rigid part deformation variations can be computed and the accumulated deformation variation can be easily obtained. The assembly variation propagation model is developed to predict the accuracy of the non-rigid assembly by integrating the deformation gradient models into the homogeneous transformation matrix.

A tolerance analysis model of CAD assemblies considering thermo-mechanical deformations of non-rigid parts

A tolerance analysis model of CAD assemblies considering thermo-mechanical deformations of non-rigid parts

Decomposing deviations of scanned surfaces of sheet metal assemblies

We present a finite-element-based approach to support quality assurance for assembly processes of non-rigid sheet metal parts in the automotive and aerospace industries. These parts have adjustable mechanical boundaries, making it possible to compensate geometrical deviations caused by the production process of components. Every part produced must be adjusted individually. Determining what boundaries to adjust to and in what direction is challenging and requires experience. Our goal was to identify sources of measured surface deviations after part assembly and provide valuable information to the quality assurance engineer. We solve the corresponding parameter estimation problem via a least-squares approach. From the estimated parameter states that led to measured deviations, additional visualizations are calculated to support the inspection engineer when deriving countermeasures.

Influence of Factors Involved in the Elastic Rolling Process on Residual Stresses in the Surface Layer of Equipment Parts

The article presents the results of studies into the influence of various factors involved in a new elastic rolling process on residual stresses in the surface layer of high-precision non-rigid thin-walled parts. Modeling and optimization of the process are carried out to ensure maximum compressive residual stresses in the surface layers of equipment parts.

Computer-Aided Design/Tolerancing Integration: A Novel Tolerance Analysis Model of Assemblies With Composite Positional Defects and Deformations of Nonrigid Parts

Abstract Nowadays, the tolerancing integration in computer-aided design (CAD) tools remains among the major goals of mechanical manufacturers. In the virtual product development, ideal and rigid models are used in the digital mockup (DMU). Hence, research works developed integrated CAD models for tolerance analysis, while considering manufacturing defects. However, the tolerance analysis in the case of composite positional tolerance for feature patterns, commonly used in the industry, becomes a difficult activity with the consideration of parts deformations. Thus, this paper presents a novel CAD model for the tolerance analysis considering composite positional defect of features set and nonrigid component deformations due to external mechanical loads. The modeling of rigid components with dimensional defects is established based on the numerical perturbation method. Indeed, the relationships between driving and driven dimensions are determined to obtain the configurations in maximum and least material of the CAD model. Thereafter, the geometrical deviations are modeled by face displacements. The modeling of composite positional errors is performed while respecting the feature relating position tolerance zone framework and the pattern-location tolerance zone framework constraints, as well as the maximum or least material condition. The deviations caused by nonrigid part deformations are considered by the integration of finite element results into the CAD model. The realistic configurations of the assembly are obtained after the updating of mating constraints between rigid and nonrigid parts with defects. The composite positional tolerance is analyzed with the simulation of relative motion between parts. A case study is proposed to evaluate the developed tolerancing method.

Calculating the gravity-free shape of sheet metal parts

This paper presents an iterative finite element (FE)–based method to calculate the gravity-free shape of nonrigid parts from an optical measurement performed on a non-over-constrained fixture. Measuring these kinds of parts in a stress-free state is almost impossible because deflections caused by their weight occur. To solve this problem, a simulation model of the measurement is created using available methods of reverse engineering. Then, an iterative algorithm calculates the gravity-free shape. The approach does not require a CAD model of the measured part, implying the whole part can be fully scanned. The application of this method mainly addresses thin, unstable sheet metal parts, like those commonly used in the automotive or aerospace industry. To show the performance of the proposed method, validations with simulation and experimental data are presented. The shown results meet the predefined quality goal to predict shapes within a tolerance of ± 0.05 mm measured in surface normal direction.

Application of the Modern Stationary Workholding Systems for Increase Capacity and Quality of Non-Rigid Aircraft Parts

Review of results experimental, production tests and features of machining forging workpiece of part type «chassis beam» from aluminum alloy V93pchT3 with significant deformations during milling process on SCHUNK VERO-S AVIATION system. Increase of production capacity on 2.9 times and significant better quality, geometrical properties if compare with conventional fixation by clamps.