جستجوی مقالات مرتبط با کلیدواژه « وایرکات » در نشریات گروه « مکانیک »

Cutting with high accuracy is possible using wire electrical discharge machining or WEDM. Nonetheless, while machining parts, amplitude of vibration causes inaccuracy of cutting. The main topic of this research is investigating the factors affecting amplitude of vibration of the wire-tool in WEDM using mathematical governing equation of motion of wire electrode. Hence, machining and finding ways to reduce the amplitude of vibration is the main purpose of this research. The consequence of reducing amplitude of wire vibration is cutting with higher accuracy and having smoother finished surface. In this research, the governing equations of motion of the wire-tool vibration are obtained using the Euler-Bernoulli beam model, fixed at both ends and moving in axial direction. The wire undergoes different forces including the body force produced by electrical discharge, damping force caused by the dielectric fluid, thermal force produced in the machining area and the axial force. Thereafter, the partial differential equation of motion of the wire-tool is converted to an ODE equation using Galerkin's method and then it will be solved using fourth order Runge-Kutta method. The results of this research show that the amplitude of vibration can be decreased by increasing the axial force and the decreasing of electrical discharge frequency, wire length, temperature differences and reduction of the workpiece width. Also, the results show that increasing the temperature by 70 degrees in the axial force of 17.5N can lead to a 60% increase in the vibration amplitude of the wire. Also, the results show that increasing the temperature by 70 degrees in the axial force of 17.5N can lead to a 60% increase in the vibration amplitude of the wire.

One of the industrial parts that requires very high manufacturing accuracy is industrial molds and especially cutting molds. In these molds, the clearance of the dies is equal to 0.1 of the thickness of the sheet, so the accuracy of making these molds is very important. Today, the wirecut process is widely used in making these molds. In the process, due to the lack of contact between the tool and the work piece, there is no mechanical tension and the produced parts have high precision. Nevertheless, in order to achieve the high precision required in the production of cutting molds, various methods are used. In this research, using the response surface method, the dimensional accuracy value has been investigated based on three parameters of wire speed, wire tension and generator power for Mo40 steel workpiece. Based on this method, at first, the importance of each parameter on dimensional accuracy was determined. Then, by deriving the equation according to the conducted tests, the optimal value of dimensional accuracy was extracted based on the mentioned parameters. The results showed that for tension values of 1.3485 kg, wire speed of 10 cm/s and power of 46.7677%, the accuracy value reaches its maximum value. Finally, these values were experimentally tested and a 0.2% error was recorded. Therefore, by using the method of the response procedure, the amount of dimensional accuracy can be used in the wirecut process of industrial steel molds.

Pressing molds are widely used in the industry due to the high speed of parts production. Due to the very low clearance between the mandrel and the matrix and having complex shapes, the production of these molds is very expensive and costly.  The hardness of the mold and subsequently their fatigue life should be high. One of the processes that has the ability to create surfaces with high dimensional accuracy and complex shapes is the wirecut process. In this research, in order to improve the performance and increase the life of cutting dies, the hardness of Mo40 steel is optimized. For this purpose, based on the method of the response procedure, the design of the experiment has been designed for the three parameters of wire feed speed, wire tension and generator power. Next, the obtained data are clustered and then fuzzy rules with three inputs (wire speed, tension and power) and output (hardness) are extracted. The obtained rules were entered in the toolbox of fuzzy inference systems of MATLAB software. Based on the defined fuzzy inference system, it is possible to predict the hardness based on the parameters of wire speed, wire tension and generator power. In the next phase, based on this system and within the range of available variables, the optimal value of hardness and corresponding variables were extracted. In the final phase, these values ​​were experimentally tested and their agreement with the obtained value was observed.

Wire electrical discharge machining (WEDM) is one of the methods of producing tungsten carbide parts, which due to its poor machinability; optimal cutting with traditional methods is not possible. Material removal rate and surface roughness are the most important output indicators of the wire cut process. In this research, the Wire cut electrical discharge cutting process on tungsten carbide alloy has modeled and optimized. Mathematical modeling has used to establish an accurate relationship between input parameters and process outputs. In this regard, first, the necessary data collected by conducting an experiment, designed by the Design of experiments (DOE) by Taguchi method. Then the types of regression functions including linear and second order fitted for this data. In the next step, the validity of these models has been assessed using statistical hypothesis tests and analysis of variance. With the help of the proposed model, the parameters that have the greatest impact on the two outputs of material removal rate and surface roughness can be determined. After determining the appropriate models, the process optimization is performed using the genetic algorithm based on non-dominated sorting (NSGA-II) and the optimal combination of input parameters table is presented. Finally, a validation experiment performed with one of the compositions of the optimal table and the results of this experiment compared with the results obtained through optimization. Obtained results show good confirmation.

Wire Electrical Discharge Machining (WEDM) is known as an advanced manufacturing process, especially for producing delicate and intricate shapes and cutting difficult-to-cut materials. Machining error on is an important problem associated with this process. The current paper investigates experimentally the machining errors of three-stage WEDM on the small straight and arced paths. To reveal the reason behind these errors and to compensate them, residual materials of each cutting stage on the straight and arced corner paths were separately measured and analyzed. Machining errors of each WEDM stage in both paths were accurately considered and the causes of these errors in the straight and small arced paths were experimentally and theoretically determined and discussed. Experiments showed that the roughing stage has such a serious deteriorating influence the machining errors on the arced paths that it cannot be compensated in the following finishing stages. The spark angle domains of the roughing stage on the arced paths were calculated and the effects of these domains on the machining errors due to wire diversion from the programmed path were analyzed. In addition, this research proposes a novel guide in multi-stage WEDM by defining some machining concepts and developing equations for error calculation of WEDM finishing stages on these paths. The machining errors estimated by equations have consistency with the related experimental ones. of this study can be employed in the accurate WEDM cuttings.

In this study, as for the re-casting, surface alloying and re-solidification layer of this alloys at the work piece level machining with Wire Electro discharge machining (WEDM), changes of surface micro hardness with changes of operational parameters has been studied. Therefore, study shows using surface alloying phenomena with the diffusion of wire material into the machined surface and selection of operational parameters and suitable materials for wire cutting, surface mechanical properties can be modified simultaneously with the workpiece machining process. Also Shown in this study, by changing operating parameters such as peak power and open circuit voltage, the diffusion of wire material into the workpiece surface layer is increased, whereas with increasing pulse off time and dielectric flushing pressure, the diffusion of wire material into the workpiece surface layer is decreased. At last with increasing these parameters also change of micro hardness surface layer accompanied by a change alloy surface layer formed on the surface.