Shape Of Workpiece Research Articles

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.

Modeling, planning, and control of robotic grinding on free-form surface using a force-controlled belt grinding tool

With the increasing demand for efficiency and intelligence in grinding operations, the research of the automatic robotic processing method for complex surface workpieces becomes necessary. This paper proposes a new approach for robotic grinding on the free-form surface. Particularly, the authors design a novel force-controlled belt grinding tool, on which a contact model of grinding process is further developed. In order to improve the efficiency of grinding, a rapid robot trajectory planning method is proposed based on the workpiece’s computer-aided design model, and the process parameters are identified from simple experiments. Furthermore, a piecewise parameterized force control method based on impendence control for the tool is presented, and the purpose of this method is to compensate for the error caused by the rapid planning method and low consistency workblanks. Finally, the grinding experiments of the plate workpiece and complex shape workpiece are performed. The experiment results demonstrate that the proposed method is effective.

Effect of feed path on the spot continual induction hardening for different curved surfaces of AISI 1045 steel

In order to analyze the effect of feed path on the spot continual induction hardening (SCIH) process for different curved surfaces, a finite element model was built for the SCIH process of AISI 1045 steel. The results show that the eddy current density decreases and its distribution becomes more uniform in the effective coverage area. The appearance position of the maximum value moves away from the center to edge of workpiece with time. The maximum temperature will reach a balance status during the SCIH process and the time and value reaching the balance status are similar in all cases. Both the feed path and workpiece shape have a certain effect on the temperature distribution uniformity. The temperature distribution uniformity decreases with increasing curvature (from concave surface to convex surface) when the feed path of inductor is horizontal but increases when the feed path of inductor is longitudinal. The simulation result of temperature is consistent with the experimental result. The maximum error between simulation and experiment results is about 5%, which indicates that the simulated model is reliable.

Proposal of Contour Line Model for High-Speed End Milling Simulation

A contour line model for end milling simulation, which realizes high-speed arithmetic processing by reducing memory usage, is proposed. In this model, a 3-dimensional shape can be expressed by superimposing the contour lines of the cross-sections obtained by dividing the workpiece along any axial direction. Therefore, the memory usage is reduced compared to a Z-map model or a voxel model as the interior information of the object can be eliminated. The contour line model can also be applied to complicated shapes having overhangs. Furthermore, cutting volume can be calculated from the interference area enclosed by two contour lines of the workpiece and the tool cross-sections. The workpiece shape can be changed by eliminating the interference area. In the contour line model, cutting force can also be predicted with an instantaneous rigid force model using the uncut chip thickness for each cutting edge from the positional relationship between the interference area and the cutting edge. To validate the proposed model, cutting experiments were conducted, which confirmed that the predicted machining shape had good agreement with the actual machined shape. Furthermore, it was confirmed that the cutting force can be predicted accurately.

Improvement of hot forging process of П-shaped forgings from VT14 and VT23 alloys

The effect of temperature deformation parameters and the workpiece shape on the structure and properties of П-shaped die forgings made of the VT14 and VT23 titanium alloys.

Experimental investigations into magnetic abrasive flow finishing process on aluminium 6061-T6

The magnetic abrasive flow finishing (MAFF) process has been developed and investigated as an advanced fine finishing process. It is used for a surface finish (SF) of the straight and complex intricate profile using the ferromagnetic nature of abrasive media. This article presents an experimental investigation on the newly developed MAFF attachment, which was mounted on a shaper machine. A custom design workpiece fixture was used in MAFF attachment for the finishing of a straight hollow cylinder shape workpiece, which can easily modify based on workpiece shapes. A curved workpiece seat was prepared and fasting with two brass plates by nut and bolts arrangement. Taguchi design of experiment approach applied for experimentation on aluminium 6061-T6 workpiece material by MAFF setup. The main process parameters considered for experimentation are magnetic flux density (MFD), number of cycles, abrasive concentration, and piston speed while responses are material removal (MR) and surface finish (SF). The results found after finishing by MAFF were also compared with the AFF. It was identified that remarkable enhancements observed in MAFF responses. The finished surfaces were also observed by scanning electron microscope (SEM) and X-ray diffraction (X-RD).

Collaborative and Quantitative Prediction for Reinforcement and Penetration Depth of Weld Bead Based on Molten Pool Image and Deep Residual Network

Weld quality is generally determined by reinforcement and penetration depth of weld bead in arc welding. Penetration depth reflects weld strength and reinforcement reflects weld shape. What's more, there is a strong coupling between them, therefore it is necessary to monitor them collaboratively and quantitatively. In this paper, vision sensor system is utilized to collect non-interfering molten pool images during CMT (Cold Metal Transfer) welding process. Meanwhile, according to the locating system and the metallographic diagram, the position of molten pool image on weld bead is measured, as well as the corresponding reinforcement and penetration. A reinforcement-penetration collaborative prediction network model based on deep residual is designed to quantitatively predict reinforcement and penetration depth. Combining the physical_mechanisms of forming process, we optimize the network structure that the backbone network is Resnet34, the input is frequency domain image of the middle and rear areas of molten pool, and the output is dual and synergetic. The correlation characteristics that affect reinforcement and penetration depth in molten pool images are fully studied. The reinforcement prediction error is less than 0.13 mm and penetration depth is less than 0.09 mm for various welding parameters and workpiece shapes.

High Accuracy Control with Lateral Dimension Estimator for Wire EDM

This paper proposes an electrode feed rate controller with a lateral workpiece size estimator which improves the machining accuracy of the skim cutting process for wire electrical discharge machining (EDM). Although EDM demands high accuracy, the residual stresses in the workpiece and the heating effects of EDM decrease the accuracy in the rough cut. Thus, it is important for the skim cut to reduce the machining size error derived from the rough cut. The average working voltage feedback control is often used to adjust the electrode feed rate and attempts to maintain the gap distance between the electrode and workpiece. First, a two dimensional simulation model is proposed and the performances of different kinds of machining controllers are analyzed. The simulation results show that the controller that keeps the average working voltage constant generates a workpiece shape which is the reverse shape of the size relation before machining. Moreover, they show that the workpiece size after the skim cut depends on not only the average working voltage but also the electrode feed rate due to the major discharge point depending on the electrode feed rate even at the same average working voltage. The fast electrode feed rate increases discharge frequency in the feeding direction of the electrode and decreases discharge frequency in the lateral area. Then, the performance of some machining controllers for the skim cut was investigated using a step shaped workpiece which approximates the machining size errors of the rough cut. As a result, the machining size errors become smaller, whereas they remain using a constant electrode feed rate. On the other hand, a feedback controller that maintains an average working voltage reverses the workpiece shape. The relationship between the average working voltage, the electrode feed rate and the workpiece size was also investigated in experiments. Regression analysis of experimental results designed a controller with an estimator of the workpiece size from the average working voltage and electrode feed rate. A proposed controller which maintains the estimated workpiece size is proposed. Furthermore, it also shows the effectiveness of the proposed controller with the state estimator in the experiment.

Geometric simulation of power skiving of internal gear using solid model with triple-dexel representation

Gear manufacturing is a fundamental technology for machine production. Power skiving has rapidly become an efficient method for the manufacturing of internal high-precision gears. To analyze the cutting force during power skiving, a geometric simulation of the power skiving process, particularly a visualization of the resulting machining shape and a prediction of the chip geometry generated during the cutting process, is important. In this study, we propose a novel method for precisely simulating the power skiving process using solid modeling. The resulting shape of power skiving is computed by repeatedly subtracting the swept volume of the cutting edge from a solid model of the workpiece. To realize a robust computation in a subtraction operation, a solid model with triple-dexel representation is used to represent the workpiece shape. To accelerate the operations, the parallel processing function of a graphics processing unit (GPU) is used. An experimental simulation system is implemented, and some computational experiments are conducted.

Influence of Nozzle Jet Flushing on Working Fluid Flow and Wire Electrode in Trim-cut WEDM

In wire electrical discharge machining (WEDM) process, smooth exclusion of debris and bubble generated in the narrow gap is important to keep stable machining performance. Conventionally, the debris exclusion has been carried out by jet flushing of working fluid from upper and lower nozzles. This study aims to clarify the effects of jet flushing on WEDM characteristics by utilizing computational fluid dynamics (CFD) analysis. Then, the fluid flow fields and debris exclusion in the machined kerf during 1st-cut WEDM have been clarified so far. On the other hand, a trim cut is carried out after 1st-cut WEDM. The effects of jet flushing with smaller flow rate have not been investigated, since the geometrical workpiece shape around the wire is quite different from that in 1st-cut. In this study, the flow field of working fluid around the discharging site by jet flushing using nozzles and the influence on wire behavior were analytically investigated by CFD analysis in trim-cut situation. Also, the accuracy of CFD analysis results was verified by comparison with high-speed observation of actual fluid flow in WEDM. Furthermore, the wire deflection in trim-cut situation was simulated by using a structural analysis with considering pressure distribution acting on the wire surface obtained by the CFD analysis. The analytical results showed that the flow field around the wire periodically fluctuated regardless of flow rates with jet flushing when the workpiece thickness is relatively small. The wire deflection shape also changed due to the periodic fluctuation of fluid flow field around the wire. Furthermore, in order to investigate the influence on the trim-cut WEDM performance, the surface roughness of trimmed surface was measured for various workpiece thicknesses. It was found that the surface roughness become larger by the periodic fluctuation when the workpiece thickness is relatively thin.

Modeling and improvement of saddling a stepped hollow workpiece with a profiled tool

A new technological process of forging massive stepped hollow rings has been investigated based on modeling. This process implies the saddling of a hollow blank with a stepped deforming tool. We have devised a procedure of experimental modelling based on the law of geometrical similarity. The procedure makes it possible to establish regularities of change in the shape of a hollow workpiece and in the formation of surface defects while deforming with a stepped tool. The varied parameter was a relative height of the ledge (diameter ratio) of the original workpiece. Based on the research results, we determined the taper of rings, which forms during forging in line with a new technique. The study involved blanks made of lead and steel.Modeling allowed us to determine that the deformation with a stepped tool could lead to the emergence of taper on a ring. These results can be explained by the fact that the process of deformation of the ledge of a hollow workpiece is accompanied by a more intense deformation of the ring in a tangential direction than in the ledge, due to the difference in thicknesses of the stepped hollow workpiece. An increase in the degree of ledge deformation leads to an increase in its diameter. Macrostructural investigation of the wall of a stepped ring has allowed us to establish that the process of forging a stepped hollow workpiece with a ledge die leads to the formation of a fibrous structure that coincides with the profile of the stepped part. Such a location of fiber rules out the possibility of its cutting in the process of machining. Based on the results from experimental modeling, it was determined that it becomes possible to forge stepped hollow rings, which extends the technical possibilities of saddling massive parts for responsible purposes

Prioritization analysis and compensation of geometric errors for ultra-precision lathe based on the random forest methodology

Geometric errors remarkably affect the dimensional accuracy of parts manufactured by ultra-precision machining. It is vital to consider the workpiece shape for the identification of crucial error types. This research investigates the prioritization analysis of geometric errors for arbitrary curved surfaces by using random forest. By utilizing multi-body system (MBS) theory, a volumetric error model is initially established to calculate tool position errors. An error dataset, which contains information of 21 geometric errors, workpiece shape, and dimensional errors, is then constructed by discretizing the workpiece surface along the tool path. The problem of identifying crucial geometric errors is translated into another problem of feature selection by applying random forest on the error dataset. Moreover, the influence extent of each geometric error on the dimensional accuracy of four typical curved surfaces is analyzed through numerical simulation, and crucial geometric errors are identified based on the proposed method. Then, an iterative method of error compensation is proposed to verify the reasonability of the determined crucial geometric errors by specifically compensating them. Finally, under compensated and uncompensated conditions, two sinusoidal grid surfaces are machined on an ultra-precision lathe to validate the prioritization analysis method. Findings show that the machining accuracy of the sinusoidal grid surface with crucial geometric error compensation is better than that without compensation.

Quasi-Homogenous Model of Electrochemical Machining of Turbine Engine Parts

Abstract In order to increase the efficiency of jet engines hard to machine nickel-based and titanium-based alloys are in common use for aero engine components such as blades and blade integrated disks (BLISK). Electrochemical Machining (ECM) provides an economical and effective method for machining high strength and heat-resistant materials into complex shapes with high material removal rate without tool wear and without inducing residual stress. This article presents the physical and mathematical models of electrochemical shaping used in the manufacture of turbine engine parts. The modelling is based on the assumption that the multi-phase mixture filling the gap is treated as two-phase quasi-homogenous medium. The model describes the workpiece shape evolution in time, distribution the local gap size, flow parameters such as the static pressure and the velocity, temperature and void fraction as result of gas generation. The major features of the numerical computer program are briefly described with a selected example of machining a typical turbine blade. The results of computer simulation of effects of setting parameters ECM on accuracy-machined profile are discussed. The improvement of accuracy has been reached by using described sequence of ECM and Pulse ECM processes.

Three-Dimensional Tolerance Analysis Modelling of Variation Propagation in Multi-stage Machining Processes for General Shape Workpieces

The quality control of general shape workpieces has become one of research hotspots because of the increasing diversity of products. The theory of stream of variation (SoV) for machining processes is a successful method in researching variation propagation rule. However, with the consideration of all key elements in manufacturing system, there is no unified and integrated model for workpieces in different kinds of shapes. In this paper, a new variation propagation model in multi-stage machining processes for general shape workpieces is established. It visually demonstrates the variation propagation chain and expands the universality of current SoV models. The connection of all key elements in manufacturing system is defined as an assembly chain, in which the variations are defined and propagated by modified three-dimensional tolerance analysis method. The equivalent conversion of the connection between workpiece and fixture realizes the modelling of general shape workpiece regardless of its machining method and locating scheme. Real experiments validate the effectiveness and accuracy of the new SoV model for different shape workpieces. This model has great potential to be applied toward multi-scale variation modelling, process control, and fault diagnosis for general shape workpieces.

Flexible circulated-cooling liquid metal coil for induction heating

Induction heating is well-established as a technique to provide fast, contactless and efficient heating of conductive materials, where the induction coil is of key importance for inductive power transfer. This paper reports on a novel flexible liquid metal coil (LMC) for induction heating system through adopting liquid metal as current-carrying conductor and circulated-cooling fluid, respectively, which could be dynamically remodeled as needed to a variety of coil geometries for adapting to the workpiece shape. A novel LMC structure, composing of two connected silicone tubes filled with circulated-cooling liquid metal, was designed to prevent the alternating current flow into cooling system. The experiment and simulation results demonstrated that the circulated-cooling liquid metal could effectively inhibit the temperature rise of LMC induced by eddy-current losses, which only lead to a small temperature raise of 0.39 °C for flow rate of 1 ml/s and coil losses of 1 W. In addition, impacts of the LMC size, flow speed and the loaded current on the LMC temperature were investigated in detail. A liquid metal multiple-channel structure was also developed to significantly reduce the coil losses of LMC to its 32.6%. The present study opens the way for further development of LMC applications in inductive power transfer.

Milling stability analysis with considering process damping and mode shapes of in-process thin-walled workpiece

As an unfavorable factor of machining process, chatter threatens the machined quality of workpiece, which determines the assembly and fatigue performance of the workpiece. During the interaction between machine tool and thin-walled workpiece, the process damping effect, multiple modes response and dynamic changes caused by the material removal of the in-process workpiece (IPW) will make the machining process more complicated and introduce great difficulties to dynamic modeling and performance prediction. In this paper, we considered the process damping determined by the indentation volume between flank face of milling tool and machined surface, and used multi-mode model to describe this behavior. In order to establish the assembled material removal model of the IPW dynamics with multiple modes, the structure dynamic modification (SDM) and finite element method (FEM) were combined together. The updated third-order full discretization method was applied to solve the dynamic equation in modal space. Then, the three-dimensional stability lobe diagrams (SLDs) with and without material removal along the tool path were obtained respectively by enveloping multiple modes of the IPW and milling tool together. Finally, the cutting tests were carried out. The experiments showed that the assembled model could predict the dynamics of IPW accurately, and the proposed stability analysis model was relatively close to experimental results. Besides, the modes of thin-walled workpiece with weak rigidity do not always play a dominant role in the process of machining. Although the material removal rate is limited by considering the multiple modes of the system, the processing quality can be ensured.

Modeling the techological process of pipe forging without a mandrel

A broaching technique for thick-walled pipes has been investigated. The proposed technique implies the deformation of a hollow workpiece without a mandrel. The procedure has been devised to conduct theoretical studies using FEM. The procedure is aimed at determining the thermal, stressed state and a shape change in the workpiece while forging pipes without the use of a mandrel. The variables applied were the internal diameter of a hollow workpiece, which ranged in the interval of 0.30; 0.55; 0.80. Based on the finite-element modeling, the following was established: the distribution of temperatures and intensity of logarithmic deformations within the volume of a pipe after broaching without the use of a mandrel. The diameter of a pipe’s hole has been determined, which is formed at broaching when applying a given technique. The dependences of intensity of lengthening and thickening of the wall of a pipe have been established. A special indicator was devised to estimate the elongation rate of a pipe. It was determined that increasing the inner diameter increases the lengthening of a pipe and decreases the intensity of the hole forging. The common dependence for the simulated broaching schemes is that the magnitude of elongation of a hollow workpiece changes insignificantly for different degrees of reductions at constant relative sizes of a pipe. It has made it possible to establish a recommended feed in order to increase the elongation of a hollow forging and to decrease the degree of closing a hole. The rational feed shall be (0.05...0.15)D. The results from the finite element modeling were verified by experimental study using lead samples. An experimental modeling procedure has been devised. It was established that at an inside diameter of the workpiece of (0.5...0.6)D one observes a maximum of the wall thickening. It was established that the results for a workpiece shape change, obtained from a theoretical study using FEM, exceeded those acquired experimentally by 9.14 %. The validity of results from theoretical modelling is confirmed by data from experiments on decreasing the internal diameter of the pipe. Difference between the theoretical and experimental results amounts to 9...12 %. The established patterns make it possible to determine the resulting diameter of a pipe’s hole. It was found based on the results from modeling that it is impossible to broach pipe workpieces without a mandrel. This technique extends the possibilities of technological processes aimed at manufacturing pipe workpieces.

Intensification of the process of the cold envelope of humidified semi-fabricates for the receiving products with a changing window installation

The finite element method has been used to determine the drawing of the details of the shape of the initial blank for compression and to establish the parameters of cold warping of such a high-carbon steel blade to obtain a hollow product with a variable wall thickness. By calculation, the shape and size of the initial workpiece have been determined. It has been shown that the use of a cold form of compression of the matrix of the traditional form does not allow the product of the desired form to be obtained due to the great strain and thickening of the walls in the bottom part of the deformed workpiece. Application of a matrix of a special profile, in which the deformation surface is formed by intersecting troughs with the same diameter of the cross section and consistently arranged with the same step, has reduced the effect of frictional forces, reduce the force of compression and the formation of a hollow product with a wall of variable thickness. Efforts and deformation work, distribution of specific forces on contact surfaces are established. The stressed-deformed state of the metal, the final form and the size of the product are determined. By the distribution of the intensity of deformations, the prediction of mechanical properties of deformed metal is carried out.

Proposal of a Decision Method of Workpiece Shapes During a Machining Operation Considering Dynamic Stiffness

Proposal of a Decision Method of Workpiece Shapes During a Machining Operation Considering Dynamic Stiffness

Haptic metal spinning

Sheet metal spinning is an incremental forming technique practiced for a long time only by experienced, skilled craftsmen. Over the last sixty years, attempts have been made to automate the process, but today the industrial practice still relies heavily on the skill of experienced operators. Complete analytical solutions to predict workpiece failure based on the path of the tool are not available, and finite element simulations of the process are too time-intensive to be of practical use for online toolpath correction. Therefore, today the design of toolpaths to avoid failure in spinning remains an art acquired by practice. In this paper, we approach the issue by designing an enhanced teach-in/playback system. We connect a haptic device to a CNC spinning machine; this device allows a human operator to control the working roller manually while feeling the force applied to the workpiece. Position, force and workpiece shape sensors allow collecting information on the toolpath followed by the operator and on its influence over the mechanics of the process. The opportunities offered by this system to derive rules for toolpath design are explored in two case studies on force control and wrinkling recovery, with new insights on the relationship between toolpaths and failure. A research agenda is outlined to exploit the full potential of haptic metal spinning.