Workpiece Dimensions Research Articles

ИССЛЕДОВАНИЕ И ВЫБОР ОПТИМАЛЬНЫХ ПАРАМЕТРОВ ПРОЦЕССА ГОРЯЧЕЙ ОБЪЕМНОЙ ШТАМПОВКИ ПОКОВКИ ТИПА "КРЕСТОВИНА" ПУТЕМ МОДЕЛИРОВАНИЯ В ПРОГРАММНОМ КОМПЛЕКСЕ QFORM

By the method of computer modeling in the QForm program, the technological process of hot die forging for a «crosspiece» type forged-piece has been developed. The influence of technological parameters on the force parameters and the filling of a die cavity was investigated. The stress-strain state and temperature fields of the forged-piece, the optimal shape and dimensions of the initial workpiece providing minimal technological efforts, forging steps, optimal conditions for filling the die cavity and conditions for cooling the forged-piece were determined. The optimal forging scheme was found.

Kinematic Modeling and Error Analysis of Cradle-type WEDM

Due to the structural limitation and the deterioration of the flushing condition caused by wire tilting, it is difficult for the traditional “X-Y-U-V” type wire electrical discharge machining (WEDM) to machine workpieces with a taper larger than 30°. In order to improve the surface quality and dimensional accuracy of the workpieces with a larger taper, a cradle-type WEDM configuration, in which the workpiece swings rather than the wire tilting is proposed. Firstly, a kinematic model for solving the numerical control instructions of the machine tool is established based on this configuration. Then the geometric errors of the machine tool are taken into account for accuracy modeling, and a mapping relationship between these errors and the machined surface is deduced. Finally, wire-EDM experiments are conducted to verify the feasibility of the proposed cradle-type WEDM for machining workpieces with a large taper, and the dimensions of the machined workpiece are measured to verify the plausibility of the error model.

РОЗРОБКА НОВОГО СПОСОБУ ДЕФОРМУВАННЯ ЗЛИТКІВ НА ОСНОВІ КУВАННЯ ПРОФІЛЬОВАНИХ ЗАГОТОВОК

Quantity of massive parts produced from an ingot is increasing today. It is caused by increasing of a massive equipment powerful. However, the quality of produced forging parts does not corresponds to customer`s requirements.Poor quality of the produced forging parts is caused by low quality of forging ingots.Defects of ultrasonic test after forging of the massive forging parts equal to 10%. The defects after ultrasonic test are caused by upsetting operation of the ingots with no equal internal structure. As a result, internal structure is processed unevenly and insufficiently. Increasing of the ingot internal defects occurs during upsetting operation of billets by flat deformationtools.The purpose of this work is establishing the rational geometry of billets with conical faces which guarantee the welding of the axial defects during upsetting operation.Rising diameter of conical face provide decreasing of defect welding degree. The toll conical faces rise the degree of thewelding defects. It was established that decreasing of the diameter and rising of the height the conical faces provide to reduction of convexity of the workpiece. In the initial step of the upsetting operation the “double convexity” is occurred. The convexity is growing at the diameter decrease of the conical faces. The “double convexity” levels out and the external surface of the workpiece obtains the nearly cylindrical shape in the finish upsetting. The relative height and diameter of the conical faceshave to be 0.4...0.6 and 0.5...0.7 respectively concerning the welding defects and equable distribution of the deformations at the upsetting. Obtained data of the upsetting in the manufactured conditions verified the established technological recommendations ofthe workpiece shape and dimensions obtained by theoretical modeling.

Анализ технологичности деталей гибких волноводных секций космического аппарата

Satellite onboard equipment includes waveguide transmission lines. One of the tasks to be solved is the temperature decoupling of the waveguide path and onboard equipment devices. In order to prevent waveguide path deformation during expansion/contraction due to thermal effects, the waveguide is equipped with a flexible waveguide section capable of changing the length without deteriorating radio technical characteristics. The paper considers the issues of fabrication of flexible waveguide parts, concerning the requirements for structure, properties, heat treatment of raw materials, dimensions of workpieces, equipment, and tooling. Within the study, we optimized and tested in practice operations of the technological process of extracting parts from sheet material, rolling, profiling, and shaping, which make it possible to manufacture parts of waveguide paths of the required quality.

ANALISA KUALITAS HASIL PRODUK PADA PENGERJAAN POCKETING DENGAN MESIN CNC FRAIS 3 AXIS

The manufacturing industry sector is experiencing increasing development. Especially CNC-based machines and the demands of consumers who want good workpiece quality, precision/accuracy of workpiece dimensions and roughness values are the main elements in the machining process. This study uses an experimental method, namely to determine the quality of the product (dimensions, time, geometry and roughness of the workpiece) in pocket work using a 3 axis CNC Milling Microcontroller Match 3 machine for the manufacture of aluminum ashtray products. For the parameters used, it uses a cutting speed of 150 mm/minute, a cutting depth of 0.5 mm with a Spindle rotation speed of 10,000 RPM. The results of this study can be seen in the aluminum ashtray product, the processing time is 1098 minutes, while the dimensions of the workpiece have an average tolerance of 0.28 mm and for the average roughness value N7 = 2.1 µm and it can be classified that the quality of the products made by the CNC Milling Machine 3 axis Microcontroller Match 3 in standard category for tolerance category and roughness value.

Вычисление радиального съема материала и толщины слоя с текущей шероховатостью при шлифовании хрупких неметаллических материалов

Introduction. The quality parameters of products, which determine its performance and functionality, are finally formed in the finishing operations, which include the internal grinding process. In this case, the removal of material from the rough surface of the workpiece occurs due to the presence of several simultaneously running random processes of shaping, occurring during the contact of the grinding wheel and the workpiece. A probabilistic theoretical approach is used to simulate grinding operations. However, for determination of radial material removal and thickness of layer with current roughness, the known models cannot be used, as it does not allow taking into account specific features of machining products made of brittle non-metallic materials. Purpose of the work. Creation of a new theoretical and probabilistic model allowing to calculate radial material removal and layer thickness, in which current roughness is distributed during grinding of brittle non-metallic materials. The aim is to investigate the regularities of brittle non-metallic material particles removal by radial removal and study the current (for the moment) roughness formed after every radial removal in the contact area. In the work, radial material removal and the layer with current roughness are determined by grinding modes, tool surface condition, workpiece and wheel dimensions, and the initial condition of the machined surface after the previous contact. The research methods are mathematical and physical simulation using basic probability theory, distribution laws of random variables, as well as the theory of cutting and the theory of deformable solids. Results and discussion. The developed mathematical models make it possible to trace the dimensions and shape of the contact zone when grinding holes in billets made of silicon, which are somewhat different from those known when machining billets made of metal. The proposed dependencies show that with an increase in the depth of micro-cutting, the radial material removal and the thickness of the layer with the current surface roughness increase for all values of wheel speed and workpiece speed. From the experimental values obtained, the maximum micro-cutting depth and the thickness of the layer with current surface roughness are calculated. The thickness of the said layer is compared with the experimental values obtained from the ground surface profilographs. A comparison of the calculated and experimental data indicates its compliance with almost all feed values, which confirms the adequacy of the obtained equations, which model the real process of grinding holes made of brittle non-metallic materials quite well.

Accurate estimation of workpiece dimension in plunge grinding without sizing gauge

In the cylindrical grinding process, the residual grinding allowance is left owing to the rubbing of the abrasive grains and the elastic deformation of the grinding system caused by the large normal grinding force. Therefore, a sizing gauge is generally used to monitor the workpiece diameter during the process. However, the sizing gauge disturbs the grinding operations, such as loading and unloading the workpiece. In this study, a new method for estimating the grinding stock of a ground workpiece is proposed. In the proposed method, the grinding stock can be estimated without a sizing gauge. The removed volume of the workpiece can be calculated from the power consumption of the wheel motor, which is easily measured. Before the grinding experiments, the specific grinding energy is determined from several grinding results. During the grinding process, the grinding stock of the ground workpiece was estimated using the determined specific grinding energy. It was confirmed that the grinding stock could be accurately estimated under several grinding conditions.

An online visual measurement method for workpiece dimension based on deep learning

Image preprocessing and edge detection are the two most critical steps when applying machine vision to measure workpiece dimension in industrial field. The surface of the workpiece is usually covered with interference regions, which makes edge detection difficult. Aiming at the problem, the Full Convolutional Network (FCN) model is used to detect interference regions of workpiece images, and then interference regions are processed by the directional texture repair method. To avoid the influence of workpiece surface texture after rough machining, a method based on Holistically-nested Edge Detection (HED) model for rough edge detection of workpiece images is proposed. The edge is obtained by HED, and then it is post-processed based on the non-maximum value suppression and double threshold segmentation methods in the Canny operator to obtain a refined edge image. In order to further improve the accuracy of the dimension measurement, sub-pixel level edge detection accuracy is achieved by cubic spline interpolation. Finally, the method is validated by a shaft workpiece. The measuring accuracy of the outer diameter of the workpiece can reach 0.02 mm, which can effectively meet the requirements of fast semi-finishing inspection. This research provides a common workpiece dimension measurement method in industrial field and methodological guidance for the application of deep learning in industrial inspection.

Relationship between Processing Parameters, Product Dimensions, and Wave Strain Hardening

Abstract This article considers the influence of the size of processed workpieces during their strain hardening based on the impact of deformation waves on the processed surface. For the first time, the specificity of the hardened layer formation by wave strain hardening (WSH) makes it possible to draw attention to the fact that, with equal volumes of hardened samples and processing modes, different diagrams of microhardness distribution in the surface layer are observed. The aim of this work is to establish the relationship between processing parameters, workpiece dimensions, and the WSH nature for the first time. The experiments are carried out on a specially designed bench. It is established that WSH occurs not only from the front side (along which the processing was performed), but also from the back side, while leaving the original material hardness in the middle of the sample. The results obtained form a basis for the further development of WSH technology.

An Improved Tool Wear Monitoring Method Using Local Image and Fractal Dimension of Workpiece

Tool wear is a key factor that dominates the surface quality and distinctly influences the generated workpiece surface texture. In order to realize accurate evaluation of the tool wear from the generated workpiece surface after machining process, a new tool wear monitoring method is developed by fractal dimension of the acquired workpiece surface digital image. A self-made simple apparatus is employed to capture the local digital images around the region of interest. In addition, a skew correction method based on local fast Fourier transformation energy is also proposed for the surface texture direction adjustment. Furthermore, the tool wear quantitative evaluation was derived based on fractal dimension utilizing its high reliability for inherent irregularity description. The proposed tool wear monitoring method has verified its feasibility as well as its effectiveness in actual milling experiments using the material of AISI 1045 in a vertical machining center. Testing results demonstrate that the proposed method was capable of tool wear condition evaluation.

Three dimensional prediction of stability lobes in end milling of thin-walled structures based on tool and workpiece dimensions

Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled structures during the machining process due to their broad application in aerospace, automotive industries and etc. One of the main problems in machining of thin-walled structures is unstable chatter vibrations, which causes the poor machined surface quality and decreases the system life span. In this regard, the main aim of this paper is to propose a practical method to solve the chatter instability problem during the milling process of thin-walled components. To this end, first the effects of geometrical parameters like workpiece height, thickness, and tool overhang, diameter and their ratios on the chatter stability are investigated. Then three dimensional stability lobe diagrams (SLDs) base on the mentioned parameters are presented for the first time. In which one can implement the mentioned diagrams to switch the unstable machining process to stable one by changing the value of the system parameters. Finally, the results obtained by the experimental test show that the presented three dimensional diagrams can be utilized to avoid chatter instability in the milling process.

Constant Speed Control of Slider-Crank Mechanisms: A Joint-Task Space Hybrid Control Approach

In this paper, a constant speed control of slider-crank mechanisms for machine tools is proposed. A joint-task space hybrid controller based on a second-order sliding mode control and time-base generator was used to guarantee a constant speed trajectory tracking and a complete turn of the mechanism crank. A switching criterion was implemented in order to avoid the singularities located at the two extreme positions of the slider stroke. A trapezoidal speed profile with parabolic blends was designed directly over task space slider trajectory considering a constant cutting speed, the workpiece dimensions and the slider stroke length. Stability of the second-order sliding mode control was validated with the Lyapunov stability theory. Simulations were carried out to verify this approach.

Вплив схеми базування на похибку базування як складову мінімального проміжного припуску для механічної обробки

An important stage in the design of technological processes for machining workpieces of machine parts is to determine the values of the minimum intermediate allowances, on the basis of which the technological dimensions and dimensions of the original workpiece are determined during the subsequent stages. An effective means of determining intermediate allowances is the computational and analytical method proposed by Professor V. M. Kovan. According to this method, one of the components of the minimum intermediate allowance is the installation error, an important component of which is the positioning error. For the conditions of processing a batch of blanks on a tuned machine, the positioning error, as a component of the minimum allowance, should be determined as the distance between the limiting positions (scattering field) of the surface from which the allowance will be cut, relative to the tool set for the size. With this in mind, we considered and analyzed some common variants of basing schemes for workpieces in machine tools, regarding the presence of a positioning error, as a component of the minimum intermediate allowance for machining main holes in a workpiece of a “Lever” type part, since during the design of technological processes for the manufacture of just this type of parts due to the multivariance of possible basing schemes, certain difficulties arise in determining the basing error as a component of the minimum intermediate allowance. For the considered variants of basing schemes, dependencies were obtained for calculating the magnitude of the basing error. The results of the work can be used in the design of technological processes of mechanical processing, as well as in the educational process of training specialists in mechanical engineering specialties.

Calculation of the size of a hollow workpiece with a thin wall with interchangeabe thickness and determination of the parameters of its crimping in a matrix with a cone-cylindrical deforming surface

The article is devoted to the production of conical hollow products with a cylindrical part and a thin wall with different thickness in height from low-carbon steel. The finite element method was used to determine the shape and dimensions of the original hollow workpiece, as well as the parameters of cold crimping of such a workpiece. The shape and dimensions of the original workpiece are determined by a two-stage simulation of the alignment of the product wall in height with the achievement of the cylindrical outer surface. At the first stage, the straightening is simulated by expansion with the help of a punch of the cylindrical part of the wall and the place of transition of the cylindrical part to the conical one. At the second stage, the cylindrical outer surface of the wall is reached by punching. Upon receipt of the original workpiece, the wall becomes thinner and its height increases. Such an original crimp blank can be obtained in two passes using extrusion and thinning stretching operations. In the analysis of crimping in a matrix with a conical and cylindrical deforming surface, an elastic-plastic metal model was used. The dependences of the crimping force and the force of pushing the product out of the matrix on the movement of the deforming tool are determined. The stress-strain state of the deformed workpiece at the end of crimping is determined. the final shape and dimensions of the product are determined. The results of crimping simulation, in which the wall thickening occurs, confirmed the possibility of calculating the shape and size of the workpiece. Prediction of the yield stress of the deformed metal along the height of the wall of the product was carried out from the distribution of the intensity of deformations.

Study of phenomena responsible for part distortions when turning thin Inconel 718 workpieces

• A thorough in-situ experimental procedure to measure geometrical errors is presented. • Geometrical errors due to cutting forces and machining induced residual stresses are separated. • In the studied case, the impact of subsurface residual stresses on the total geometrical error is not negligible. • Tool wear dramatically increases the distortions linked to cutting forces and subsurface residual stresses. • The proportion of total errors linked to machining induced residual stresses increase with tool wear. Machining thin workpieces is a challenging task as geometrical errors may result from the combination of several phenomena. Among these, elastic workpiece deformation and machining induced residual stresses may be predominant sources due to low part stiffness. There is a lack of studies trying to quantify the influence of machining induced residual stresses on the total geometrical errors. A thorough experimental methodology is developed to quantify the influence of both phenomena separately by comparing the workpiece shape and dimensions, in-situ , before and after machining, using laser sensors. The proposed methodology can also be used to quantify the geometrical errors linked to clamping or stress rebalancing following material removal. The case study is the finish turning of thin Inconel 718 workpieces using carbide tools. In the studied case, machining induced residual stresses are responsible for 3–32 % of the total geometrical errors depending on tool wear and cutting parameters.

Study of the properties of large-sized blanks of turbine blades made of 15Kh11MF-Sh steel depending on the method of obtaining the initial metal

We consider the manufacturing process of forgings for turbine blades of extra-large dimensions (length >2 m) from electroslag remelting steel 15H11MF-Sh. With an increase of the workpiece dimensions (weight >450 kg), we face the problem of choosing the technology for obtaining the original billet. The production technology is known to affect the structure of the material and, as a consequence, the final properties of the product. We present the results of studying the influence of the method of obtaining the original metal blanks (hot-rolled steel bars and forged billets) on the properties of large-sized forgings of turbine blades. The mechanical characteristics, microstructure properties, chemical composition and content of δ -ferrite were determined by examining the initial samples of long products and forged rods. It is shown that billet in the forged state exhibit higher strength characteristics. However, after the stamping process, the properties of the blades equalize, i.e., after stamping and heat treatment, the same structure is formed, regardless of the method of obtaining the original workpiece. The results obtained can be used in the serial production of large-sized turbine blades of a new profile.

Desgaste da ferramenta de corte de metal duro – uma abordagem estatística

A usinagem é considerada um processo de fabricação onde tem-se remoção de material na forma de cavaco, conferindo à peça de trabalho forma, dimensões e acabamento. Pode-se dizer, que o torneamento é o processo de usinagem mais executado na indústria, por ser fácil de operar e economicamente viável, apresentando uma grande participação na fabricação de peças usinadas. Este trabalho tem como objetivo principal avaliar o desgaste de uma ferramenta de corte de metal duro após operação de torneamento, bem como, avaliar a efetividade do método utilizado por análise estatística. O material escolhido para os testes de usinagem foi o aço AISI 1020. Para os ensaios de usinagem, foram realizadas operações de desbaste em torno CNC, onde avaliou-se alguns parâmetros como rugosidade, temperatura e o diâmetro da peça a cada passe. Foram realizados ensaios de dureza Rockwell B e análise metalográfica no aço 1020. Para avaliar o desgaste do inserto, mediu-se as suas dimensões antes e após os testes de usinagem, confrontando as medidas via projetor de perfil com as medidas realizadas utilizando micrômetro. Após os testes de usinagem, a ferramenta de metal duro apresentou predominantemente desgaste de cratera e de flanco. Os testes estatísticos realizados (coeficiente de Pearson, teste t e distribuição normal), indicaram que este método de determinação de desgaste da ferramenta de corte, pode ser um método alternativo de avaliação.

Correlation of Barreling Effect with Boundary Friction Coefficient during Upsetting of Various Materials Workpieces under Processing Conditions

The necessity of taking into account the barreling effect at the design of die cavities, and open die and closed die forging processes on the basis of pre-forming of billets by upsetting is shown. The division of ideas about the indices of “bulk” and “linear” barreling (barrel shape), which is determined by the ratio of the bulk and linear dimensions of the workpiece after upsetting by flat dies, was made. The functional relation (correlation) between these indices and the friction coefficient on the boundary surface between flat dies and the upsetted workpiece has been determined. The qualitative and quantitative effect of workpiece dimensions (diameter-to-height ratio), strain range, temperature (conditions of cold and hot processing) and type of forming material (structural carbon steel, some of Cu-grades and Al-grades) on the barreling effect and friction coefficient during upsetting was found. The developed method makes it possible to predict a change in the friction coefficient during the upsetting of various material workpiece under given conditions of forming and to monitor their effect to the final shape.

Analysis on Rotational Speed and Material of Twist Drill to Its Worn and Burr Formation in Drilling Ti-6Al-4V

Ti-6Al-4V is a material that is mostly used in aerospace. In this industry, especially on stabilizer horizontal structure, minimizing burrs height is important, These structures are assembled and drilled. To be economically viable, it is preferred to minimized or even removed burr during drilling process. Aerospace industry needs to drill component in an operation without reprocessing (disassembled, deburred, and fastened). Burr will lead to distortion of work piece dimension, damage to subsurface, and make difficult to handling and assembling of part. Burr occurs during machining because of inoptimum choice of material, tool, and cutting speed. This research uses experimental method by variating rotational speed and material and type of twist drill to find the optimum choice of the parameter and tool for drilling process of Ti-6Al-4V. The quality of drilling process was measured by the height of burr and wear on the tool. The result shows that the lowest burr is 0,085 mm by using HSS-Co twist drill in 500 rpm of speed. The use of HSS-Ti and HSS-Co in high speed will cause chipping worn. Therefore, it is unsuitable to minimize the burr height.

Analytical modeling of material removal mechanism in dry whirling milling process considering geometry, kinematics and mechanics

Whirling milling is a promising machining process that couples the tools and workpiece motions while both conventional turning and milling are carried out, which is widely used for machining precision screw parts made of hard materials, such as titanium alloy, quenched steel, etc. The challenge is due to the complex kinematics can lead to the varying tool-workpiece engagement and undeformed chip geometries which affect significantly the mechanics, quality and productivity. The existing studies are mainly based on the simplification of process mechanism to study the mechanics and quality however, the material removal mechanism and influences of cutting parameters are still not well understood. This paper presents an analytical approach to investigate the material removal mechanism in whirling milling, thus to predict the undeformed chip geometry, material removal rate (MRR), cutting forces and form errors. The varying tool-workpiece engagement geometry along the cutting trajectory is identified to model the varying undeformed chip geometry including instantaneous chip thickness, cross-section area and tool-workpiece contact length. The form errors including circularity error, scallop height and surface roughness are defined and predicted as a function of tools and workpiece motion, position and dimension parameters. The whirling milling experiments were conducted to validate the analytical modeling approach with the largest error 11.3% and average error 13.0% for force and surface roughness prediction, respectively. The influences of cutting parameters on surface roughness and MRR are finally analyzed to explore the potential of productive cutting conditions for whirling milling.