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

This research investigates tool wear, elemental analysis (EDAX) on the machined surface, surface roughness, microhardness and microstructural changes in the cross-section of milled 304L stainless steel samples under dry and Minimum quantity lubrication (MQL) methods. The MQL process was able to improve the surface roughness for all milling parameters from 17% to 41% compared to the corresponding dry conditions. In dry machining, defects such as built up edge, severe flank wear and tool chipping were created. In MQL mode, these defects were significantly reduced and tool chipping was almost eliminated. By increase of cutting speed and depth, the surface hardness has increased. Compared to the dry method, the MQL reduces the hardness values and hardened depth below the machined surface. According to EDAX analysis on dry and MQL machined surfaces, applying the roughest cutting parameters, it was determined that no change of chemical elements occurred on machined surfaces. Increasing cutting parameters or dry machining causes the plastic deformation to intensify, the microstructure is flattened and the microstructure grains are compressed in the vicinity of the machined surface. The maximum reduction in thickness of deformed layer in MQL compared to dry method is 39%. For each milling sample, there is a direct relationship between the hardened depth and thickness of the corresponding microstructurally deformed layer.

Today, the machining and milling of composites is of great importance; Because composites are used in various sectors and have found great efficiency in various industries. Considering this, in this article, in order to save the cost of milling composites, the effectiveness of various parameters that affect the cutting force and tool wear, including spindle speed (rpm), feed rate (mm/rev), cutting depth (mm) and percentage of sic, has been discussed; To minimize tool wear and cutting force by creating optimal conditions. Performing a sensitivity analysis according to the regression equations of cutting force and tool wear has shown that spindle speed with 63% and the percentage of composite silicon carbide with 22% have the greatest effect on tool wear and depth of cut with 47% and advance with 23% have the greatest effect on cutting force.

Achieving the required dimensional and geometrical accuracy as well as the appearance and performance quality in the production of industrial parts and the availability of interchangeability in the assembly and supply of spare parts for products has been one of the important challenges of the industry. In this research, the effect of adding axial ultrasonic vibration to the tool on the geometric accuracy of the Al6061-T6 work piece in the milling process was investigated. By analyzing the results, it was found that the presence of axial ultrasonic vibration improves the parallelism and flatness of the wall and the smoothness of the bottom surface as well as the perpendicularity of the wall with the bottom. It was also observed that a higher feed speed increases geometric deviations and surface roughness, while a higher cutting speed reduces them. By comparing the graphs, it was found that the positive effect of ultrasonic vibrations on the quality of the surface and the geometric accuracy of the work piece is more noticeable in the conditions of lower cutting speed and higher feed; That is, the condition in which we face the worst surface quality and the lowest geometric accuracy in conventional milling.

Advances in many engineering fields depend on materials with appropriate properties. The use of metal-matrix composites is rapidly growing as a suitable alternative to conventional materials due to their strength-to-weight ratio, resistance to wear and creep, etc. Machining of metal-based composites is a difficult task due to the presence of very abrasive reinforcing particles in its based metal. Therefore, it is necessary to investigate the factors affecting these materials. In this research, a methodical study has been conducted to investigate the effect of the parameters of spindle  speed, feed rate, depth of cut and the percentage of reinforcing particles on the behavior of cutting force and tool wear using experimental design methods, modeling and statistical sensitivity analysis methods. . Detailed analysis of behaviors has been done by providing statistical regression equations and optimization by Deringer's method and E-Fast-Sensitivity Analysis. According to the obtained results, the cutting depth had the greatest effect on the machining force. Also, cutting speed with 77%, advance rate with 9% percent and cutting depth and weight percent of reinforcing particles with 7% percent are other parameters affecting tool wear in the milling process of this composite.

Today, various military, aerospace, automotive, etc. industries need materials with a high strength-to-weight ratio. The use of metal-based composite materials, especially aluminum-based composites, has increased greatly. Machining is needed to achieve high dimensional accuracy in products made with aluminum-based composites. Due to the presence of reinforcing material such as silicon carbide, machining of this type of material is difficult. Therefore, it is important to study the parameters affecting the machining of aluminum-based composites. In this study, the effect of spindle speed, feed rate, depth of cut and percentage of reinforcing particles were discussed using experimental and statistical test methods. The responses of surface roughness and material removal rate were investigated. The behavior of the input parameters on the responses of the process has been carefully investigated quantitatively and qualitatively. Answers have also been optimized. According to the obtained results, the spindle speed has the greatest effect on the surface roughness. Also, feed rate 33%, spindle speed 28%, depth of cut 26% and the percentage of reinforcing particles 13% have an effect on the chipping rate.

In this paper, the error of tool deflection in perpendicular to a milling process feed direction is investigated and novel compensation method to this error is proposed. While the end mill tool is machining, due to the existence of perpendicular disturbing force on the feed path while the endmill tool is machining, a deflection which reduces machining accuracy. If a compensation force is exerted to the middle of tool, the deflection can be reduced. By using a hydraulic actuator, the compensation force would be proportional to the disturbing machining force, in the opposite direction so that this error can be reduced. It is necessary to estimate disturbing forces and tool deflection magnitude in lateral side of machining precisely before applying the proportional force to the endmill. The first step endmill is modeled on SolidWorks and in the next step The machining operation is simulated to calculate the error causing force in which both the milling tool and the workpiece are 3D flexible. By obtaining the force results of the tool under different machining modes from Abaqus, a semi -analytical model is established on Simscape Multibody module of matlab software. By comparing Abaqus results the parameters of the lumped model are adjusted. The output force is extracted from Abaqus and put in tabular form the tool deflection is extracted from MATLAB SimScape which calculation speed is faster than the numerical model in this method. To find the compensating force, the beam theory obtains a factor of 3.2 times the machining force applied to the middle of the tool. This force is applied in open loop to the MATLAB model and the result indicates almost 70 percent reduction in the tool tip lateral deflection.

Today, Carbon fiber-reinforced polymer composites (CFRP) have extensive use in different fields such as aerospace, automotive, oil, gas, and defense industries compared to metals, due to the high ratio of strength to weight. Machining of these materials regard to their non-homogeneity structure is complicated. Due to the different thermal expansion coefficients between the fibers and resin polymer composite milling materials difficult to create one of the final parts. Achieve optimal machining conditions, with high efficiency, which need proper analysis and careful investigation. Minimizing the machining time became important Due to developments in CNC technology. One of the time minimizing methods is high-speed machining technology. In this study, composite plates made of carbon/epoxy to a thickness of 10 millimeters, which are often used in the body of Aerospace structures and missiles, have been manufactured by hand layup. The cutting parameters used during the milling operation of the CFRP panel ranged from 1000 rpm to 7000 rpm for the spindle speed, feed rate from 1000 mm/min to 3000 mm/min, and lastly 1.0 mm to 3.0 mm range for depth of cut. the combination of spindle speed, feed rate, and depth of cut are studied at five different levels. 20 runs of experiments are performed based on Response Surface Methodology (RSM). the milling process with two-flute tungsten carbide - coated diamond insert with a 20 mm diameter was performed. their surface quality after milling process is measured. So after roughness, material removal rate and required analysis were performed. Spindle speed has a greatest effect on surface roughness. In conclusion, the influence of the cutting parameters is higher spindle speed, lower feed rate, and lower depth of cut resulting in low surface roughness. The optimized cutting parameters were spindle speed, feed rate, and depth of cut of 7000 rpm, 1000 mm/min and 1 mm respectively with the surface roughness of 1.9 um.

Determination of machining forces in order to calculate the required power and torque for cutting and select the right tools, equipment, and cutting parameters (feed rate, cutting depth, cutting speed) for machining the desired geometry and material prior to the process is significant. The analysis of machining forces is necessary to determine the forces to reduce the cost of performing multiple empirical experiments. In this study, the components of, , and  milling forces with two cutting edges with main adjustment angle were predicted by the mechanistic modeling method by calculating cutting and edge force coefficients. Also, for the first time, the cutting section of the workpiece was designed in order to eliminate the calculating error of the round corner of inserts.To avoid the interaction of the parameters, simultaneous change of cutting speed with feed rate was avoided and 8 experiments with different feed rates but with the same cutting speed were performed. A comparison of the modeled forces curve with the results obtained from the dynamometer shows acceptable agreement.As the feed rate increases, the difference between the predictive and experimental force decreases relative to the increase of force.

Milling process of the thin-walled structures has broad applications in aerospace, automotive industries and etc. One of the main problems in their machining is unstable chatter vibrations, which causes not only the poor machined surface quality but also decreases the system life span and machining efficiency. So, lots of researchers are interested in investigating the dynamic behavior of the thin-walled structures during the machining processes and restrain its pernicious effects. In this regard, the main purpose of this paper is to l the effects of geometrical parameters of machining system including workpiece height, thickness, and tool overhang and its diameter on the chatter stability. To this end, first by utilizing relative transfer function concept, dynamic models of tool and workpiece were derived. Then experimental tests conducted to extract cutting force coefficients. Finally, stability lobe diagrams were constructed under impression of tool and workpiece dimensions. Results proved that by increasing tool overhang length, chatter stability decreases.

Nowadays, with the advancement of materials science and the production of materials with special properties such as super alloys, composites and ceramics used in advanced industries, the use of traditional machining methods for the production of these parts is not possible. Therefore, the use of modern methods has been considered. One of these methods, which has the ability to add to traditional cutting processes, is the use of ultrasonic vibrations during the machining process. In this paper, analytical relations have been derived to calculate machining forces associated with ultrasonic vibration based on the undeformed chip thickness. Then numerical simulation of ultrasonic assisted milling process is performed by applying the vibrations to the workpiece in the feed direction by using the ABAQUS finite element software and the machining forces are determined. The results obtained by analytical and numerical data show that the use of ultrasonic vibrations can change the direction of movement of the tool and change the thickness of the undeformed chip and thus reduce the machining forces in the milling process. Also, based on the results, it was found that there is a good agreement between the results obtained from analytical analysis and 3D FEM modeling in macro scale.

Reducing energy consumption in production is an urgent need. In manufacturing processes, especially machining, more than 90% of the environmental impacts are due to energy consumption in machine tools. The purpose of the present study is to estimate and compare the energy consumption of AISI 316 steel milling process in conventional (wet) and minimum quantity lubrication (MQL) modes as well as the experimental measurement of energy consumption in each of these two modes. Studies have suggested different types of energy consumption modeling in machining but few studies have been conducted on the use of these modeling techniques and the minimum quantity lubrication method has been rarely compared with the wet state in terms of energy consumption. Empirical experiments were used to confirm the modeling performed to predict energy consumption in the milling process. The results show that the proposed method is efficient and practical for predicting energy consumption with 5% error. After confirming the modeling, using two levels for feed rate and spindle speed and applying full factorial design of experiments, energy and power consumption in MQL and wet cutting modes using the power meter connected to the input 3-phase power cable of the milling machine were experimentally measured. Energy consumption in the minimum quantity lubrication method was decreased by 16% compared to the wet state. The average power consumption in MQL milling is 33% lower than in wet milling.

In the milling of sculptured surfaces, cutting forces and the final part accuracy can be affected by surfaces curvatures. In this paper, an analytical formulation containing the explicit form of the principal curvatures of the surface is developed for extracting the engagement boundaries between a ball-end mill and a sculptured surface, and the effect of surface curvatures on the milling forces is investigated. To this end, first, a mechanistic cutting force model is presented for calculating the milling forces acting on a ball-end tool. Orthogonal to oblique cutting technique is used to calculate the cutting force coefficients, and the model is verified by comparing the predicted milling forces with the existing ones in the literature. Then, parametric studies are performed to investigate the effects of cutting depth and surface curvatures on the milling forces. The results show that at a constant cutting depth, the milling forces are more influenced by the surface curvatures at the concave and saddle regions of the surface in comparison with the convex regions. Furthermore, for constant values of curvatures, the effect of surface curvatures on the milling forces increases as the cutting depth decreases. In other words, as the cutting depth decreases, neglecting the effect of surface curvatures results in more relative error in the calculated milling forces. Furthermore, the obtained results show that the surface curvature perpendicular to the feed direction has more influence on the milling forces than the curvature in the feed direction.

Cooling/lubricant fluids are typically used in machining processes to reduce the tool-workpiece friction, decrease machining heat and improve surface quality. In recent years, however, several laws have been used in place to protect human health and environment, requiring industry to reduce coolants consumption and expand the use of low-risk and renewable ones. For this reason, a recent new lubrication technique called minimum quantity lubrication (MQL) has been developed for the machining processes. Vegetable oils are kinds of bio-based lubricants and have a significant capacity to be used in MQL due to their environmentally friendly and renewable properties. Stainless steels are considered to be difficult to machining materials and hence their machinability improvement has always been the subject of research. In this investigation, the effects of MQL and type of lubricant in the milling process of martensitic stainless steel EN 1.4903 have been studied. For this purpose, one type of vegetable oil derived from sesame seeds in two conditions including non-additive (pure) and with antioxidant additives, as well as one type of mineral oil have been applied in the experiments. Then, milling force, surface roughness and surface texture have been evaluated. Also, in order to compare the results with other lubrication methods, the tests have been performed under dry and wet conditions. The results show that the MQL compared to the conventional lubrication methods increases the machinability of stainless steel by reducing forces and improving surface quality. Moreover, the type of oil applied has a great influence on the process outputs.

The surface roughness is a widely used index of surface quality which depends entirely on the input parameters and cutting conditions. This paper presents an approach for determining the optimum cutting speed, feed rate, radial depth of cut and milling type leading to minimum surface roughness in milling process of AISI 420 stainless steel by integrating Arti9icial Neural Network (ANN) and Imperialist Competitive Algorithm (ICA). The combination of these two methods to optimize the cutting process is provided for the 9irst time in this article. 54 different cases were tested and surface roughness was measured in each experiment. The predicted results using ANN indicated good agreement between the predicted values and the experimental values. ICA was used to determine the optimal machining parameters leading to minimum surface roughness. The obtained results proved that the ANN-ICA approach is capable of predicting the optimum machining parameters to minimum surface roughness in milling process.

Presence of porosity and gas layers around the Al2O3 particles are one of the most important reasons of decreasing in mechanical properties of aluminum metal matrix composites. In this research, for decreasing of porosity, increasing of wettability and uniformly distribution of particles in matrix three method were used; using inert gas for injection powder with 5 liter/ min flow rate, particles heat treatment in 1100 ̊C for 20 min and mill Al2O3 particles with Al particles in ratio of Al / Al2O3= 1. The effect of these parameters on microstructure and mechanical properties of composite were investigated. The results showed that amount of porosity and agglomeration of particles were high in metal matrix composite with handy injection of particles. While injection with inert gas, using heat treatment and Al / Al2O3 milled Cause improve wettability and uniformly distribution of particles in molten Al. the results showed the maximum value of hardness, compression strength and impact energy have obtained in metal matrix composite reinforced with Al / Al2O3 milled with value of 78.7 BHN, 539.1 MPa and 8.2 Joule, respectively.

AISI4340 hardened steel have a vast functionality in industries. Hard machining of this steel have several benefits such as, higher productivity, lower production cost and improved workpiece properties. In machining operation, ultimate surface roughness is the most important characteristic of machined surface and plays an important role in workpiece life. One of the effective factors on surface integrity is cutting fluid used in machining operation, which have health and environmental problems is spite of positive effects. As a result, using minimum quantity lubrication is considered as an alternative method. In present study, relations between milling parameters and final surface quality in milling of AISI4340 hardened steel, in the presence of lubrication systems including; dry, wet and minimum quantity lubrication have been investigated. Cutting speed, feed rate, axial and radial depth of cut have been considered as main parameters of milling operation. Totally, 90 experiments have been done using response surface method to analyze the effects of process parameters on surface roughness. Results revealed that feed rate and cutting speed have the most Influences on surface roughness. Also higher values of cutting speed and lower values of feed rate are necessary to reduce surface roughness. In addition, compared to other lubrication methods, minimum quantity lubrication have the best performance in surface quality, especially in high cutting speed and depth of cut.

In this paper, in order to avoid the problems induced by cutting liquids like higher cost, environmental pollution and dangerous for operator health in milling process and also using the benefits of them such as increasing tool life and machined surface quality, machining by minimum quantity of lubrication (MQL) or near dry lubrication was introduced and that’s effects on main outputs (consumed power and surface roughness) was compared with other lubrication methods such as lubrication by cutting fluids and by air. In order to perform a series of experiments and investigate the effects of different process parameters such as tools rotational speed, feed rate, gas pressure and liquid flow rate on main outputs, the Taguchi method of design of experiments was employed and then the analysis of variance (ANOVA) was used to find the most important factors effecting main outputs. The results obtained by experiments showed that employing near dry lubrication leads to lower electrical power and comparable surface roughness as compared with other lubrication methods. The analysis of variance showed that feed rate is the most important factor affecting consumed power and liquid flow rate is the most important factor influencing surface roughness.