فهرست مطالب

مهندسی مکانیک مدرس - سال پانزدهم شماره 13 (اسفند 1394)

نشریه مهندسی مکانیک مدرس
سال پانزدهم شماره 13 (اسفند 1394)

  • ویژه نامه مقالات کنفرانس
  • تاریخ انتشار: 1394/12/13
  • تعداد عناوین: 99
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  • Mohammadreza Zakerian*, Milad Ebrahimi, Yasin Fathalizadeh Pages 1-4
    This study aims to simulate the orthogonal machining process of titanium alloy using finite element method. Simulation with finite element method makes the cutting process easy to understand, increases tool life and reduces the cutting forces. Three-dimensional simulation was performed using the Abaqus software. The effects of machining parameters include the cutting speed and feed rate on the cutting and feed forces, shear stress and tool life were assessed. To validate the results of the application, the experiments were carried out in the field and the results were compared with the values obtained from the tests. The results showedthatthe simulation results are in good agreement with the experimental data.
    Keywords: Abaqus, Finite Element Method, Machining Parameters, 9rthogonal Cutting, Tool Geometry
  • Ali Eskini, Ehsan Zamani* Pages 5-11
    Machining of thin-walled monolithic parts made of aluminum alloys is a key process in industries such as aerospace. In the final machining process, the cutting forces and machining temperature produce deflection for workpiece which results in the dimensional inaccuracies and distortion on the finished component. The purpose of this paper is to study the thermal and mechanical behavior in machining of aluminum alloys (Al)0)5-T0) using P7D (polycrystalline diamond) and 810 (cemented carbide) tools to investigate the correlation between both parameter on distortion. The study was made using a three-dimensional finite element method model in Abaqus software under orthogonal cutting conditions. The results represented the direct effect of the force and temperature on level of distortion in thin-walled workpieces. However, the mechanical loads have more influence on work piece distortion in comparison to the thermal loads. It was concluded that the polycrystalline tool has a superior performance in terms of cutting forces and temperature when compared to the cemented carbide tool. To validate the FEM model, the results were compared with experiments of the other papers. Results showed a good agreement with experiments.
    Keywords: AL)0)5 Alloy, 7utting Forces, Temperatures, Distortion, FEM Analysis Machining, Thin, walled Parts
  • Ali Eskini, Ehsan Zamani* Pages 12-18
    The main problems in the machining of thin walled parts made of aluminum alloys are the distortion and dimensional instability after machining which lead to an increase in the production costs. In general, distortion in machined parts made of aluminum alloy is a function of the residual stresses. In this study, a three-dimensional FEM model in Abaqus under orthogonal cutting conditions is used for investigating the correlation between machining induced residual stresses and the distortion in thin walled cylinder made of AL7075-T6 alloy. Tocompare and validate the FEM model with experimental results of other papers, several simulation are carried out under different conditions using: 10 and P;D tools. Machining force, temperature and distortion were measured.; orrelation between residual stress and distortion was studied by measurement on some workpieces. The results represented the direct effect of stresses on level of distortion. Unlike experimental, there is no limitation in FEM model to compute amount of residual stresses in all directions. Results showed a good agreement with experiment. This indicates that the FEM model can be used to simulate machining process to predict its distortion with no limitation with saving of 600 euros for each test considering the equipments limitation in Iran.
    Keywords: AL7075 Alloy, Distortion, FEM, Machining Thin, walled Parts, Residual Stress
  • Farshid Jafarian*, Hamid Soleimani, Hossein Amirabadi, Hamed Soleimani, Rohallah Soleimani Pages 19-23
    Distribution of thermal loads during the machining process leads to reducing the surface quality and rapid tool wear. Therefore, optimization of thermal loads in machining has always been important. On the other hand depth of the restructured layer can improve mechanical and metallurgical properties and of the workpiece. Since experimental investigation in machining operations is expensive and time-consuming procedure, finite element method is also used as an efficient tool in this regard. Therefore, at the first part of this study, experimental machining tests was carried on Inconel 718 alloy at the different cutting depth, cutting speed and the feed rate to measure machined surface temperature. The results of experiments were used to simulate machining process using commercial software of DEFORM-3D-V10. After calibration and validation of the results of 3D simulation with corresponding experiments, the effect of tool edge radius, tool nose radius, and workpiece hardness was investigated. To improve the accuracy of the simulations, heat transfer coefficient was calibrated by experimental result of temperature and it was defined as function of cutting parameters. Finally, the effect of machining parameters was investigated on the depth of the recrystallized layer using the critical strain criterion.
    Keywords: Depth of the Affected Layer, Finite Element Simulation, Thermal Loads
  • Mohammad Amin Asqari, Javad Akbari* Pages 24-28
    Surface and subsurface cracks in part are induced by mechanical cutting of brittle material specially glass which decrease part's life-cycle. The goal of this research is to present a finite element model for predicting induced median cracks as the most deterministic cracks on the BK7 glass subsurface in micromachining. Bilinear Cohesive Zone Method (CZM) was used for simulation of crack and its specifications. CZM's parameters were obtained and calibrated by micro-Vickers experiment and the results were validated by micro-scratch test. Finite element model demonstrated median cracks dramatically increase from ductile-to-brittle-changing-regime point in micro-scratch. Finally, the validated finite element model facilitated the prediction of the depth of median cracks with respect to tool cutting depth in micromachining.
    Keywords: BK7 glass, Cohesive Zone Method (CZM), Finite Element Model, Median Crack, Micromachining
  • Hojjatollah Ranjbar, Mohammad Hosein Sadeghi*, Amir Rasti, Milad Mohammady Pages 29-33
    In this study, 3D 8inite element simulation of reaming process has been carried out on the hard steel. The cutting parameters in the simulation process were selected based on the optimum experimental results which lead to the smaller cutting forces, lower vibration of the reaming tool and better surface quality. This simulation was used to predict cutting forces as one of the most important reaming output variables. Simulation of material removal process was performed by commercial finite element software SFTC DEFORM-3D and using the explicit Lagrangian code. In addition, some empirical experiments were done on the hardened D2 tool steel workpieces to 8ind the optimum reaming condition and validation of finite element model. Cutting parameters including feed rate and cutting speed were changed and cutting forces were measured, experimentally. The results showed that the numerical results have a good consistency with the experimental one and average difference of 10% was seen. Finally, the effect of input parameters on the cutting force at the simulation and experimental test were investigated. It was seen that the cutting forces error is reduced between two analyses by increasing the feed rate. This indicates that the meshes with higher quality and density are required in lower removal rate.
    Keywords: Finite Element Simulation, Force, Reaming
  • Mohammad Kazemi Nasrabai*, Ali Noori, Seyed Morteza Hosseini Pages 34-38
    Broaching is a specific method of removing metal by tools that have successively increasing cutting edges, the part is made through tool moving in a certain path. The cutting force is high as a result of high removal rate in the broaching process. The process may have too many surface errors since high displacement arose by this cutting force. For this reason, proper attention should be paid in the broaching tool design, geometry analysis and the process conditions. Considering the broach machining table and accessories, the dynamometer installation is complicated. Therefore, the finite element modeling can be used for evaluating the cutting force. In this study, the simulation of broaching process is done using Abaqus Software. After modeling the process, the effect of rake angle and cutting speed parameters on cutting forces are investigated.
    Keywords: Broaching Process, Cutting Forces, Cutting Speed, Rake Angle
  • Behnam Davoodi*, Mohammad Reza Eslami Pages 39-43
    Cutting forces that affects the cutting tool during machining are one of the important parameters must be known to select the economical cutting conditions and mount the workpiece on machine tools, securely. In this paper, the effects of the feed rate in machining of aluminum alloy 5083, used in lightweight structural application in automotive, shipbuilding and aerospace industries, on the cutting tool stresses have been investigated. Cutting forces were measured by a series of experimental measurements while stress distributions on the cutting tool were analyzed using a commercial finite element method (FEM) (ABAQUS). The results showed that the feed rate is the most relevant cutting parameter affecting cutting tool stresses.
    Keywords: AA5083, Cutting Tool Stresses, Feed Rate, Finite Element Method
  • Amir Rasti, Javad Hashemi Khosroshahi, Sina Sabbaghi, Mohammad Hossein Sadeghi* Pages 44-48
    Due to a need for a 3D 7inite element simulation model and having a high solution time, simulation of an oblique cutting process has some limitations and has been studied less. In this study, for solving these limitations, a 2.5D model was developed for analyzing the oblique cutting process and simulation of chip formation in this cutting process was established. Two deformable parts were modeled as tool and workpiece. Johnson-Cook material model and Johnson-Cook damage criteria were used. Then the effect of tool-rake angle, cutting edge inclination angle and cutting depth on aluminum-alloy chip morphologies were analyzed and it was seen that by decreasing the rake-angle, the chips became smaller. The increase in cutting edge inclination angle causes the chips become more conical and more continuous. There were segmented chips by increasing the cutting depth, as a result of increasing the undeformed chip thickness and amount of stress.
    Keywords: Shape sensitivity analysis Shape sensitivity analysis Shape sensitivity analysis Shape sensitivity analysis Shape sensitivity
  • Amin Dadashi*, Naser Bayat, Hasan Amini Pages 49-53
    Meanwhile damages on machine, the created vibrations during the machining process will effect on the significant results of the process, such as surface finishing. Optimized design of the machine tool and high quality of the workpiece would be possible by determining the vibration characteristics of machine structure. In this paper, transient and harmonic dynamic behavior of gantry CNC milling machine (DMC 1000) has been studied. For this reason, rudimentary structure of the machine and its main complex are modeled in the commercial Solidworks software. Then, the natural frequency and dynamic response are evaluated in both transient and harmonic moods using ABAQUS. Finally, the stability condition is investigated for the current machine. Results showed that the system response is more sensitive under frequency of 400 Hz and the largest displacement occurs at >irst locating position of spindle.
    Keywords: Finite Element, Machine Tool CNC, Transient, Harmonic Dynamic Behavior, Vibration
  • Saeed Amini*, Sajjad Abasszadeh Pages 54-58
    Hydraulic valves have very important role in hydraulic industry. Spool is one of the main parts of these valves which defines the valve efficiency and application by determining the fluid flow. The dimensional tolerance and surface quality of spool are the main effective parameters concerning the valve application. Spool requires heat treatment after machining for achieving the desired level of hardness and getting ready for grinding. In this paper, the hydraulic valves spools have first been machined to reach to the desired dimensions. Then, heat treatment has been performed on them to obtain the appropriate hardness. Finally, the spool distortion induced by heat treatment and its surface quality after grinding has been measured has been measured and compared with each other.
    Keywords: Dimensional Tolerance, Distortion, Spool, Surface Quality
  • Saeed Amini*, Sayed Mohsen Asgari, Mohammad Hosein Tavajohi Pages 59-63
    One of the new ways to improve the machining parameters in turning processes methods is the minimum quantity lubrication (MQL) method. In this study, the machining process of Monel K500 super alloy has been investigated using wiper type ceramic tool under dry and minimal lubrication with nano-fluid conditions. First, the necessary equipment was provided to perform the tests in dry and relatively dry (minimal lubrication) conditions. Then, the tests were completed in each of these conditions to determine the shear and feed rates. The utilized tool in experiments is the Wiper Ceramic Insert with the code CNGA 12 04 08 T01020WG-650 that is manufactured by Sandvik. The parameters of machining forces and surface roughness were measured during the tests. The results showed that the machining in the conditions of minimal quantity lubrication using nano-fluid not only reduced the amount of surface roughness, but also reduce shear force at low shear rates.
    Keywords: Cutting Force, Minimum Lubrication, Monel K500, Nano, fluid, Surface Quality
  • Ehsan Mirmohammadsadeghi*, Hosein Amirabadi Pages 64-67
    High pressure hybrid jet assisted machining is an efficient method to improve the machining conditions. The significant advantage of this method is concentration of high pressure fluid on machining zone and reduction in tool-chip interface. In this research, a collection of pumps and water jet pump was used in order to supply a high pressure jet. A specific tool holder was designed and manufactured. Experiments were designed to investigate the process parameters such as jet pressure, cutting speed, feed rate and depth of cut. During the experiments, the cutting forces and surface roughness were measured. Results showed the existence of the optimum conditions of the minimum cutting force and surface roughness in hybrid jet assisted machining. Thus, the optimization of process parameters is necessary in order to use hybrid machining more efficiently. A neural network with suitable topology was utilized which was trained by genetic algorithm to obtain the predictive model. Ultimately, genetic algorithm was applied to optimize process parameters. Results showed the ability of employed algorithm to predict the optimum parameters with considerable accuracy.
    Keywords: Jet of Fluid, Genetic Algorithm, Hybrid Machining, Neural Network, Predictive Model
  • Farshid Jafarian*, Alireza Barghak Pages 68-72
    Having unique properties such as high melting point and hardness, Inconel 718 superalloy has been found a widespread application in turbines and aerospace industries. Due to these properties, Inconel 718 superalloy cutting with traditional methods is dif Keywords: Arti<icial Neural Network, Inconel 718, Laser, Cutting Process
  • Mohammad Mahdi Abootorabi* Pages 73-77
    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.
    Keywords: Artificial Neural Network, Imperialist Competitive Algorithm, Milling, Surface Roughness
  • Hamed Hassanpour, Amir Rasti, Mohammad Hossein Sadeghi*, Javad Hashemi Pages 78-81
    Micromilling is a suitable method for fabrication of miniature parts with 3D complex geometries. This method has wide applications in fabricating of medical micro tools. Titanium alloys were used in medical applications extensively due to their high strength-to-weight ratio, corrosion resistance and biocompatibility. Owing to the fabricating of micro parts in implants and medical tools, studying the micromilling of titanium alloys becomes more important. In this study, the surface roughness produced by micromilling of Ti6Al4V alloy is investigated. Spindle speed, feed rate and axial depth of cut have been considered as cutting parameters. Micromilling has been done with three lubricating and cooling conditions: dry, wet and minimum quantity lubrication (MQL). TiAlN coated carbide micro-end mill tool with the diameter of 0.5mm were used. Taguchi method has been used to design and analyze the experiments. The results showed that the surface roughness is minimized by the use of the minimum quantity of lubricant. Surface roughness decreased with the increase in cutting speed and feed, regardless of the lubrication and cooling condition. The minimum surface roughness was 118 nm in the condition of spindle speed= 30000 rpm, feed rate= 0.8 µm/tooth and depth of cut= 60 µm.
    Keywords: Lubrication, Cooling, Micromilling, Surface Roughness, Ti6Al4V Titanium Alloy
  • Amir Rasti, Hamed Hassanpour, Mohammad Hossein Sadeghi*, Sina Sabbaghi Pages 82-85
    Ultimate surface quality in machining process has a great effect on the workpiece performance and is the most important characteristic of machined surface. Using cutting fluid, as an effective factor on surface integrity improvement, has environmental problems and is harmful for operator’s health. As a result, using minimum quantity lubrication (MQL) is considered as an alternative method. In this study, surface roughness of Ti-6Al-4V alloy workpieces were investigated in high speed milling process and using MQL method. Full factorial experiments including 5 levels of cutting speed and 2 levels of feed rate were implemented. Results revealed that a surface roughness of 0.2 µm could be achieved in high speed milling of Ti-6Al-4V alloy in proper cutting conditions and in presence of MQL method. Furthermore, minimum surface roughness was reported in cutting conditions of Vc=450 m/min and fz=0.08 mm/tooth.
    Keywords: High Speed Milling, MQL, Surface Roughness, Ti, 6Al, 4V Alloy
  • Majid Yousefitabar*, Mohammad Khaled Matapouri Pages 86-89
    High speed machining has many advantages such as increasing productivity, reducing production cost and improving final workpiece properties. On the other hand, final surface roughness is one of the most important of machined workpiece. In present study, relationship between high speed milling parameters and workpiece surface quality made of 1.7765 steel alloy and hardness of 50 HRC in presence of minimum quantity lubrication method was investigated. Cutting speed, feed rate and axial and radial cutting depth were studied and totally 30 experiments were done. Results showed that among main cutting parameters, feed rate and cutting speed had the most effect on surface roughness and surface roughness reduced with increasing cutting speed. In addition, using minimum quantity lubrication had a good performance in high cutting speed and cutting depth.
    Keywords: High speed milling, response surface method, surface roughness
  • Reza Ahadi, Ali Rabbani, Mohammad Javad Nategh* Pages 90-94
    In the last years hexapod machine tool with six degrees of freedom has got the attention of experts for achieving high dexterity and high speed machining. Free form surfaces are widely used in today industries. These surfaces are much encountered in aerospace, auto and other industries. Therefore machining of these surfaces is very important. For interpolation of free form surfaces, NURBS curves are commonly used. For investigating the quality of machined surface, final surface roughness is very important and is the most important feature of machined surface. In this study the effect of machining parameters such as cutting depth, feed rate and cutting speed on surface roughness were investigated. Design of experiments was done using Taguchi method. Then with using of neural network and genetic algorithm the best case for surface roughness was achieved. The cutting tool used in this study was ball end-mill and the work piece was aluminum of three thousand series. The results showed that cutting speed and depth of cut had the most effect on the surface roughness.
    Keywords: Machining, Surface Roughness, Hexapod, NURBS Surfaces, Genetic Algorithm, Regression
  • Mohammad Kazemi Nasrabai*, Ali Noori, Ali Jafari Pages 95-99
    High-speed milling is widely used in the manufacturing industry. This method is faster and more precise than the traditional milling. The feature of precision and speed in the method of manufacturing has made it suitable for manufacturing of bigger and high precision milling parts. This research studies the effect of tool length on stable materials removal rate in high speed milling processes. It is shown that the tools length is highly affected the natural frequency of the most flexible mode and the high material removal rate is obtained when the tools length in the stable region is accessible with the fastest speed. Furthermore, sometimes longer tools provide higher material removal rate than the short ones.
    Keywords: High Speed Milling, Material Removal Rate, Stability Lobes, Tool Length Effect
  • Mohammad Orouji, Mahdi Sadeqi Bajestani, Behnam Moetakef Imani* Pages 100-106
    As a single-pass machining operation, broaching is extensively used to produce simple and complicated profiles with finished surface quality. Broaching is often used for mass production. Since, it is a special manufacturing process, few researches has been reported in this area. In this research, the dynamic effects of cutting forces for different cutting speeds on Aluminum 7075 have been theoretically and experimentally analyzed using MATLAB. Moreover, to make sure of the results, experimental setup has also been designed to investigate the effect of cutting speed on surface quality and cutting force. For this purpose, a servo hydraulic system based on position control has been designed. With the increase of cutting speed from 2 m/min to 8 m/min, an undeniable decrease in cutting force is observable, while the surface quality experiences an interesting increase. It can be concluded that the higher cutting speeds are to be preferred for processing this material. In practice, it is applicable for especially car manufacturing industry to shorten the time and lower the cost of production.
    Keywords: Aluminum 7075, Broaching, Cutting Speed, Dynamic Cutting Forces, Surface Quality
  • Pouyan Ghabezi, Mohammad Reza Farahani*, Mohammad Kazem Besharati Givi Pages 107-112
    The objective of this work is to investigate the influence of cutting speed (rpm), feed rate (mm/min) and tool diameter (mm) on the uncut fiber and delamination damage of a type of composite sandwich structures including PVC foam, Trapezoidal corrugated sheets and faces made of E-Glass/polyester. VARTM method has been used for manufacturing of samples. A design of experiments (full factorial) was used to assess the importance of the drilling parameters. The drilling operation was assessed based on two introduced factors including the delamination factor (DF) and uncut fiber factor (UCFF). Minitab software has been used for obtaining the role of each parameter on output factor. Analysis of the experimental results for DF indicated that the feed rate and drill diameter were the most significant and insignificant parameters, respectively. But, experimental results for UCFF showed that the tool diameter has greatest influence where UCFF increased with increasing diameter, too. Also, the results revealed that the both factors increase with the increase of feed rate. There is an optimum point for cutting speed and tool diameter in evaluation of UCFF. Whereas, increasing tool diameter leads to decrease of DF and generally there is a maximum point in variation of cutting speed for UCFF.
    Keywords: Cutting Speed, Delamination, Drilling, Feed Rate, Sandwich Panel
  • Vahid Tahmasbi*, Majid Ghoreishi, Mojtaba Zolfaghari Pages 113-119
    3one drilling is one of the common processes in orthopedic operations for therapy and maintaining different parts of a broken bone with together. The most important possible problem during operation is the unwanted increase in drilling process temperature (higher than 67o C) which causes thermal necrosis or cell death and local burnt in bone tissue.Applyinghigher forces to the bone may lead to break or crack and consequently serious damage in the bone. In this paper, a second order linear regression model is introduced to predict process temperature during bone drilling as a function of drilling speed, feed rate and effective interactions. This model can specify the maximum speed of the surgery to stay within the acceptable range. Applying design of experiments, modeling and optimization of effective parameters using response surface method in bone drilling, optimized drilling speed and feed rate were obtained to minimize force and surface roughness. Using multi objective optimization, this was done within the acceptable temperature range without tissue damage which can remarkably reduce the regeneration of the bone cells and less therapy period. Drilling speed and feed rate variations were considered in wide ranges of 500 to 2500 rpm and 60 to; 0 mm Keywords: 3one, Drilling, Machining, 2ptimization, =esponse Surface Methodology
  • Mohammad Reza Vaziri Sereshk*, Abbas Khwakram Pages 120-123
    Delamination is the main defect caused by drilling of composite laminates. This phenomenon endangers integrity and strength of structure as well as assembly procedure. This defect is the reason of 306 of re7ections during the uality control process. Several approaches are presented to decrease delamination, however the geometry of drill bit is still under consideration. In this paper, the effect of cutting edge geometry of twist drill bit is investigated, experimentally. The result demonstrated that the grinding of drill bit point can improve the performance, considerably.
    Keywords: Cutting Edge Geometry, Composite Laminates, Delamination, Drilling
  • Hadi Parvaz, Mohammad Javad Nategh * Pages 124-128
    In this study, the mathematical modeling of jamming occurrence in fixtures is presented using minimum norm principle. The incorporation of this principle eliminates the indeterminacy in equations and results in a non-linear quadratic optimization problem. 2y solving the optimization problem, the contact modes are determined and the jamming occurrence is predicted. The presented model provides a dexterous tool for fixture designer to avoid jamming in their locating plans. This method benefits from less computations, more accurate results (in comparison to the previous studies) and eliminates the pre-known initial contact modes requirements. This method can be integrated in the CAFD applications due to the straight forward systematic approach. Also, it assists the fixture designer in the early stages of fixture design practice when there is no sufficient information about contact modes and behavior. The model capabilities in jamming prediction are evaluated by two case studies: peg in hole and block & palm. The verification procedure is performed by comparing the results to the previous studies.
    Keywords: Fixture design, Jamming, Locating system, Minimum norm principle, Rigid body dynamics
  • Hadi Parvaz, Mohammad Javad Nategh* Pages 129-133
    In this study, an analytical model for designing the locating system for non-polyhedral parts is presented. The model is based on constraining maximum (possible) workpiece D0Fs using accurately posed locators. The model consists of three main rules: parallelism between locators, maximum (available) distance between locators and maximum reciprocity (in screw theory) between base, side and stop locators. The model states that the simultaneous consideration of the mentioned three rules is necessary for obtaining a robust locating system. The modeling of the rules is implemented using the innovative base, side and stop locating matrices. The scoring method is employed for selecting the base, side and stop surfaces between locating candidates. A turbine blade model is incorporated to evaluate the suggested model’s capabilities in presenting robust and stable locating system.
    Keywords: Degree of freedom, Fixture design, Free, form surfaces, Locating rules, Locating system
  • Vahid Sanjabi, Mohammad Javad Nategh* Pages 134-138
    Appropriate fixture design for manufacturing a product with quality and in accordance with the requirements is important task and depends on the designer’s experience and skills. In fixture design, the appropriate locating and clamping surfaces automatic selection is the most important of design step. Computer aided fixture design softwares ease the fixture design. In this paper, a new method is presented for automatic selection of appropriate clamping and locating surfaces based on the normal vector graph and linear algebra. At first, locating and clamping surfaces are classified with normal vector graph. Then, the best surfaces among the classified locating and clamping surfaces has been selected with the use of linear algebra method. The results for several sample parts have been tested. The obtained results of this study are applied in computer aided fixture design automation.
    Keywords: Clamping, Computer Aided Fixture DesignFixture, Linear Algebra, Locating, Normal Vector Graph
  • Davood Manafi, Mohammad Javad Nategh* Pages 139-143
    Setup planning is an important function in CAPP systems which is a bridge for integration of CAD and CAPP systems. All features in a specific setup must have the same TAD and satisfy the technical and geometrical rules. Also, these features must be machined in one machine tool. Setup planning must be regenerated if features in a specific setup need different equipment and machine tools. So, it is important for machine tools to be considered during the setup planning to avoid the setup replanning. In this paper, the effect of machine tools on the setup planning was studied and the mathematical formulas were introduced for this purpose. Finally, setup planning method was developed based on these mathematical formulas. The algorithm was programmed and verified in Python,CC.
    Keywords: CAPP, Machine Tools, Mathematical modeling, Permutation, Setup Planning
  • Saeed Khodaygan*, Amir Ghasemali, Hamed Afrasiab Pages 144-149
    In sheet metal structures, due to high flexibility of the sheets, the dimensional and geometrical errors do considerably influence the assembly tolerances. 4n one hand, various stages of design, manufacturing and assembly of mechanical sets are involved in various factors such as dimensional, geometrical and material uncertainties. As a result, presenting a comprehensive model based on which propagation of the changes resulted from the uncertainties of the manufacturing processes and their relations with assembly tolerances could be approximated with a high accuracy seems necessary. In normal influence coefficients method, neglecting the contact effects between the components not only causes the diffusion of contact surfaces, but also leads to errors in predicting assembly tolerances. In this paper, an applicative method for tolerance analysis of flexible sheet structures and precise prediction of abundant errors in assembly characteristics is presented by modifying the influence coefficients method and by considering the effects of components’ contacts using finite element method (FEM). To do so, a proper strategy based on modeling and the analysis of effective uncertainties in the process of the assembly of the sets with flexible components has been proposed. At the end, the capabilities of the proposed method are investigated by presenting an example and the accuracy of the obtained results has been compared with Monte Carlo and experimental results.
    Keywords: Contact Analysis, Flexible Sheet Metal Structure, Finite Element Method, Method of Influence Coefficients
  • Hamid Ramazani Sales, Hossein Amirabadi * Pages 150-157
    Enhance in efficiency and accuracy of the parts production with complex surface by CNC machines is a necessity in nowadays industrial world. Selecting the type of tool-path strategy in CAM software has a significant role in determining the length of tool movement, the material removal rate and the number of axes required in each stage of machining operation. ptimal choice of the tool-path and its peripheral configuration can improve machining precision and efficiency. This research aim is to identify and evaluate the different tool-path strategies in multi-axes machining in order to choose the best strategy for each models of concave spherical, convex spherical, freeform surfaces, revolve surfaces, steep slope surfaces and extruded surfaces. In this regard, Powermill and Vericut softwares were used for simulation of machining operation and NC program optimization. Then, with experimental testing of three-axes machining and three-axes and five-axes machining simulation, different tool-path strategies were compared with each other in terms of machining time and the average of residual of machining on surface unit. Finally, the optimal strategy for each model was selected. Results demonstrated that incorporation of varying and optimal feed rates in different strategies of tool-paths causes their machining times to be close together.
    Keywords: CAD7CAM, Complex Surfaces, Multi, axes Milling, Simulation of Machining peration, Tool, path Strategy
  • Saeid Alimohammadi*, Behnam Motakef Imani Pages 158-162
    CNC machine tools incorporate the interpolators to generate reference points due to physical movement. In this study, initially the! URBS curve has "een generated and sent to interpolator. By consideration of NURBS curve properties and other dynamic conditions like ma imum velocity, the ma imum acceleration and the ma imum jerk of the reference points have "een generated for each sample time. The current interpolators generally work "ased on 2nd degree Taylor series, "ut the numerical errors which are produced "ecause of the nature of numerical truncations are not considerate. In this report, the real time interpolation of feed rates has "een investigated in order to precisely control position on  a is ! ta"le with Milne-Simpson predictor corrector. In this approach, the numerical errors have "een reduced with correction of the main calculating core of the interpolation unit that has "een led to the higher accuracy. This claim has "een proved "y e perimental tests on 2 a is ! ta"le with "ID controller.
    Keywords: CNC, Interpolator, Milne, Simpson, NURBS
  • Mohammad Zadshakoyan*, Vahid Pourmostaghimi, Hasan Heidary Pages 163-170
    In traditional machining systems, cutting parameters are usually selected prior to machining according to handbooks or user’s experience and variations during the machining process such as tool wear and dimensional changes are not considered in selecting cutting parameters. This practice will have a negative effect on the performance of machining. Adaptive control systems have been proposed and developed to find optimal cutting parameters by considering ongoing variations during machining process. Optimization of machining process can be done by off-line or on-line methods. The majority of researches in this field have been conducted in off-line mode. In other words, selection of optimal cutting parameters has been done without considering progressive tool wear. In order to investigate the effect of tool wear in selection of optimal cutting parameters, on-line methods for optimization of machining process should be used. In this paper, the gradient method has been proposed to find optimal cutting parameters during hard turning operation. The results of performed simulations showed that by using adaptive control optimization techniques, the performance of machining process improved and material removal rate increased remarkably.
    Keywords: Adaptive Control, Hard Turning, Optimization
  • Mohammad Zadshakoyan, Vahid Pourmostaghimi* Pages 171-175
    In metal cutting, it has been acknowledged that the tool-chip contact length significantly affects many aspects of machining such as chip formation, cutting forces, cutting temperatures, tool wear and tool life. Significant decrease in the tool-chip contact length decreases the thickness of the secondary shear zone which leads to a decrease in the cutting temperature and cutting force. As a result, it has a great effect on the finished surface and tool life. Several ways have been proposed in different works to find its value which have given discordant results for the same set of cutting conditions. In this paper, the genetic equation for the tool chip contact length is developed with the use of the experimentally measured contact length values and genetic programming. The suggested equation has shown to correspond well with experimental data in various machining conditions with associated cutting parameters. This model predicts tool-chip contact length better than other known solutions.
    Keywords: Cutting Parameters, Genetic Programming, Machining, Tool, chip Contact Length
  • Iraj Lirabi, Hossein Amirabadi* Pages 176-181
    Developments in face milling inserted cutters have considerably contributed to the efficiency of the process. In this article, a geometrical model for face milling of surfaces with parabolic cross-sections has been considered. These surfaces are produced by welding techniques for purposes such as retrieving lost geometry, improving wear and fatigue properties and implementation of rapid manufacturing concept. So as to obtain an integral flat surface, the produced layer has to be truncated. 0n the other hand, machining depth is not constant due to special cross-section of the weld beads. A precise model for definition of depth of cut in face milling of surfaces with parabolic cross-sections is presented owing to have the most important effect on machining forces. First, the parabolic cross-sections and rectangular inserted disc with 10 degree a8ial immersion were de9ined using mathematical relations. Ne8t, intersection curves were e8tracted and the related depths of cut were calculated. Finally, the depth of cut model was verified and the method to incorporate the results in the mechanistic force model was discussed. It is shown that the proposed method is very effective in finding the proper instantaneous depths of cut for use in the unified machining model.
    Keywords: Face Milling, Intersection Curve, Mechanistic Force Model, Parabolic Cross section, Variable Depth of Cut Model
  • Mohammad Reza Karimi Nejad, Saeid Amini*, Mohsen Aghaei, Mohammad Hosein Karimi Pages 182-186
    In this research, a reliable method for estimating the amount of tool wear is presented using image processing in MATLA5 software. Program code that can display wear of the blade milling numerically in the chart is designed to showcase all stages of wear. Preparation of experiments is done. The preparation process includes milling operations, tool, workpiece, vision measuring machine (VMM) and camera were provided for testing. First, the initial configuration for milling machine process (such as: spindle rotational speed, feed rate, depth removal) on the AISI10+0 steel workpiece with covered plating tool was done and picture was taken from all stages of cutting condition. In addition for verifying the performance of the designed code in MATLA5, after each time the edge of tool observed by VMM and wear rate was recorded and data of experiments were stored. As a result, the possibility of determining tool life was carried out with the help of image processing in the milling process. The output data from image processing can specify the tool life and trend of tool life completion.
    Keywords: AISI10+0 Steel Milling, Image Processing, Tool Life, Tool =ear
  • Saeed Amini*, Alireza Salehi, Ahmad Hoseinpoor Pages 521-524
  • Davoud Karimi*, Mohammad Mehdi Malekian Pages 525-529
    Strain and strain rate are two of the most important parameters of machining. They directly affect the material behavior during chip formation. The study of chip formation, consideration of material behavior in different shear zones during machining, developing analytical models and understanding the process is highly dependent on the measurement of strain and strainrate. Flow stress, as an instance of material behavior, is the function of strain and strainrate. Flow stress is measure dusing Split Hopkinson bar test. It is shown that the data obtained using this test can not beaccuratelyemployedformachiningsimulationsasthestrainandstrainraterangesarefardifferentduring machining. This factindicatesthenecessityofdevelopingƒtestset-upbywhichdirectmeasurementofstrainandstrainrateduring machiningispossible.Inthispaper,ƒnon-contactmethodbasedonimagecorrelationanalysisisemployedtodirectlymeasurethestrain andstrainrateduringthemachiningprocess,bymeansofwhichthematerialbehaviorcouldbemoreaccuratelystudied.
    Keywords: ImageCorrelation, Machining, Strain, StrainRate