فهرست مطالب محمد جواد ناطق

In the production of industrial parts, machining is one of the most important operations in the field of manufacturing parts. The production of an industrial part takes place in three stages: design, process planning and manufacturing, and in all these stages, the computer is used as a powerful tool. In computer-aided process planning, the stage of identifying machining features is a prerequisite and an introduction to the next steps. Extracting information and identifying features from computer-aided design information has been continuously improved due to the increasing complexity of parts, but the research to find an optimal solution is endless. Over the past few decades, several methods have been introduced and applied by researchers to extract and identify machining features from design file information. In all the previous methods, the number and type of features are extracted as independent variables in the machining features identification pattern and from the part design file data. In this research, the charectrestics required to identify the machining features are extracted from the pixel values of the machining feature image by the artificial intelligence system automatically. The artificial intelligence system produced to identify the machining features in this research is able to identify all the information required for machining, including the name, the coordinates of the location of the feature relative to the part, and the dimensions required for the machining, by viewing the image of a part, and the information of the features present in the image the input to the system in a table.

Computer-aided process planning is one of the challenges for researchers to achieve computer-integrated manufacturing, and setup planning is the core of the CAPP system. Based on the literature survey, it has been observed that researchers use different methods for setup planning, and there is a lack of mathematical models in their methods. However, the mathematical model is necessary to implement and develop the setup planning method. Therefore, in this paper, the permutation-based setup planning was selected to determine the setups, and then the setup planning rules were cast into the mathematical model. Finally, the mathematical model is implemented and evaluated in MATLAB software to ensure the accuracy of this model.

Extracting the required information from the design file is one of the main steps in the computer aided process planning. In previous methods of extracting machining features, various methods such as graph-based method, volume analysis method, logic rules method and other methods have been used. In all the previous methods, whether traditional methods or methods based on artificial intelligence, the input data to the machine feature identification system is the output information of a computer-aided design system. Converting the output information of a computer-aided design system to input data of a machining feature identification system is faced with limitations such as the variety of format and type of data arrangement, deleting some data from the design file due to geometric interference of features, slow extraction of features due to extensive information in the design file and the limitation of identifying different types of machining features by a unity feature identification system. In the present study, using artificial intelligence techniques based on deep learning, machining features are extracted directly from the two-dimensional image of a workpiece. The image may be prepared by a computer-aided design file, or it can be taken by a camera.

In this article, the effect of optimal selection of vibration and cutting parameters on cutting forces in the machining process with ultrasonic vibration assistance has been investigated and the results have been compared in two modes of conventional machining and of ultrasonic vibration assisted machining. In the investigation of the effect of ultrasonic vibration assistance on the machining process, analyzes have been carried out in different cutting speeds, and the effect of changing the cutting speed in relation to the tool's oscillation speed has been investigated. Finite element modeling and simulation has been done with DEFORM finite element software. The results show that the application of ultrasonic vibration in the machining process leads to the reduction of tangential and axial cutting and the reduction of heat resulting from the cutting process. By examining the results, it was found that in the machining process with ultrasonic vibration assistance, when the cutting speed is at least 30% lower than the vibration speed of the tool tip, the process has a favorable efficiency, and the favorable effects of applying ultrasonic vibration on the process include reducing shear forces, reducing the heat generated From cutting, reducing the friction coefficient between the tool and the workpiece, helping to improve the chip flow, etc.

Proceedings of 2 nd Iranian National Conference on Advanced  Machining and Machine Tools (CAMMT).

Hard to cut materials such as hardened steel and super alloys are well known and popular in transportation, aerospace, marine and medical industries, due to their strength, high corrosion and fatigue resistance and high working temperature . However, their lowmachinability is one of the major problems in using them. In this article we examine machinability of the hardened CK45 steel in four processes including; conventional turning, hot turning, ultrasonic assisted turning and hot ultrasonic assisted turning as a hybrid machining. The results of these four processes are compared with each other. The heating technique is induction type which has much lower construction cost compared to other techniques such as laser beam and plasma arc. It has been illustrated in the present study that combining the heating technique with ultrasonic vibration has the most effect in improving surface quality and reducing cutting forces compared to other turning process. The chip formation under the heat and ultrasonic vibration and its influence on the surface quality have also shown that hybrid process has the most affection.

In the process of producing a part with the help of computer aided manufacturing, the required information is created for the workpieces whose design model is specified. To prepare machining instructions, the design information is expressed in a pattern called a feature. In this research an advanced artificial intelligence system has been introduced to identify machining features with the help of deep learning method. The proposed method has been prepared with the help of two-dimensional convolutional networks in deep learning. It can identify machining features from the image of a workpiece. The innovations of this research, in addition to introducing a powerful practical and new method for automatic machining features recognition in the field of computer aided process planning, is identifying features that have geometric interference in a workpiece. The previous methods of automatic machining features recognitions have not been able to solve this problem. Furthermore, the lack of need for different CAD output files and the use of an image of a workpiece to identify machining features are the capabilities of the system introduced in this research. Other capabilities of the proposed method are the ability to identify machining features with different image formats such as image with wire frame format, constructive solid geometry format, image of workpiece with different materials and taken with ordinary cameras such as mobile cellphone camera and other imaging devices. The accuracy of detecting machining features in the image of a workpiece is measured %88 and detection error is measured 0.1 using proposed method.

The contact stiffness between workpiece and fixture locating system is one of the decisive factors for maintenance of the stability of workpiece during the machining process. In order to estimate the contact stiffness, it is needed to determine the locator reaction forces. These forces are created by the clamping forces, cutting forces, workpiece weight and friction effects of the contact between the workpiece and fixture locating system. Some analytical approaches have already been presented for calculating the location reaction forces. However, there are six equations for a (3-2-1) locating system, but 18 unknown parameters. Therefore, an optimization solution is proposed in the literature to obtain the reaction forces which involves several simplifying assumptions which result in considerable errors in the solution. In this study, in addition to presenting the mathematical model of the total system, an experimental approach has been proposed in order to determine the locator reaction forces. This can provide a suitable means for evaluating the optimization solutions and analytical models for determining the locator reaction forces and contact stiffness and diminishing the errors. an experimental approach has been proposed in order to determine the locator reaction forces. This can provide a suitable means for evaluating the optimization solutions and analytical models for determining the locator reaction forces and contact stiffness and diminishing the errors.

The Arabic translation of Heron's treatise on crane by Qusta ibn Luqa, in the absence of its Greek original, is among the most important texts on mechanics remained from the Islamic civilization. It was thought hitherto the extant manuscripts of this translation were limited to those available in Leiden, Britania and Manchester libraries. The authors of the present paper have found some manuscripts of the Arabic translation of Heron's treatise in Iran's libraries, in addition to several Persian treatises. These Arabic manuscripts are important for completing the works already undertaken by some orientalists such as Carra de Vaux, Nix and Schmidt. The Persian manuscripts were inspired by Qusta's translation. It is tried in the present paper to present a brief but comprehensive introduction of all of Qusta's manuscripts, in order to provide the necessary background for the future studies. The life of Heron has also been shortly investigated, especially to make the date of the original treatise of crane clear as it has been in a veil of obscurity.

Chattering, being the focus of this study is a kind of self-excited vibration that is encountered in different machining processes such as milling and turning. This type of self-excited vibration rapidly develops after commencement and destabilizes the whole process. This phenomenon leads to, among others, increased noise, wavy surface finishes, discontinuous chips, and failure in the tool or machine parts. The depth of cut is the main parameter in the occurrence of chattering in machining processes. Avoiding the critical depth of cut ensures the stability of the process. Process modeling is a way to obtain the critical depth of cut. The vibration assisted turning process, having many advantages, is of a different nature than the conventional machining. In this paper, the vibration assisted turning process is modeled and numerically solved and the critical depth of cut is obtained. Validation of the results is performed using experimental data and comparison with conventional machining. In the vibration assisted turning process, higher stability is obtained with lower ratios of cutting duration to the total vibration period. This ratio is directly proportional to vibration frequency and amplitude and is inversely proportional to the cutting speed.

Jig and fixture design for workpieces with freeform geometry has more complexity in comparison with the polyhedral parts. The locating and clamping system design construct the basis of the jig and fixture design activities. In this study, a theoretical analysis is suggested for automatic design of clamping points for freeform workpieces. The clamping design is performed in three main stages which the clamping application points are determined through the first two principles and being verified through the last stage. The mentioned principles consist of: (1) the minimum quantity of clamps, (2) the maximum clamping force components on the locating directions and (3) the workpiece static stability under the external wrenches. After mathematical modeling, the suggested analysis was implemented into the already designed CAFD framework by the authors. Three machining models were chosen as case studies to evaluate the capabilities of the implemented system in robust design of clamping layout. The minimum quantity of clamps (single clamp for two case studies and double clamp for the third one) was designed by the developed method that verified the robustness and reliability of the suggested and implemented clamping system design model. The automatic design of clamping scheme for workpieces (regardless of the geometry) beside its capability in integration with the other modules of fixture design activities provides the opportunity for the system to be used in industrial applications.

A hexapod machine tool with a parallel structure has six degrees of freedom. This machine has a high dexterity unlike traditional machine tools. The hexapod can be used in machining free form surfaces. Free form surfaces are widely used in today industries. These surfaces are much encountered in auto, aerospace and mold design industries. Therefore machining of these surfaces has attracted the attention of researchers. In this field much research has been done in five axis machine tools. In this paper machining free form surfaces with hexapod machine tool has been investigated. The main topic of this paper is the feasibility of using hexapod as a machine tool table and machining with it. First, the interpolation of free form surfaces for parallel structure machines is explained. Then NURBS curves and surfaces are described and its formulation in matrix form is explained. Then extracting information of free form surfaces with NURBS formulation is explained. Subsequently, some explanation about preparation of machining is given. Finally two free form surfaces designed in Catia and have been machined with the developed hexapod machine tool.

This paper is seeking to add a CNC G-code to hexapod CNC system. The mentioned G-code is five axis tool radius compensation. Once the tool radius is changed, especially in the case of tool size changing with tool wear in machining, a new NC program has to be recreated. Five axis tool radius compensation correct cutter path automatically. This G-code contains all the main parts of a standard code such as: interpreter, interpolator and inverse kinematics unit. The interpreter unit extracts the position and orientation from the received code and sends it to the interpolation and kinematics units to correct the errors and achieve the desired six pods lengths. In the tool radius compensation algorithm, the unique vector of the movement direction of the tool tip and the normal vector of the machining surface have been used to calculate the direction of the tool radius compensation. The offset path is calculated by offsetting the tool path along the direction of the offset vector. Accuracy of the proposed method tested with a number of experiments. The experimental results confirmed the accuracy of the proposed methods.

Rotary forging is a forming method in which, the forces exerted on the workpiece can be reduced by using an inclined forming tool. The final shape of workpiece is formed gradually. The conventional machines used in this process, typically have separate rotational and linear (feeding) motions. The rotational motion is applied by an eccentric mechanism; the feeding motion is exerted with a linear actuator. These machines follow forward kinematics which does not consider the geometry of the workpiece to create motion profiles. Hence, having a special profile to be fully compatible with the piece is not possible. Such compatibility is beneficial to applying a more precise control on the material flow and achieving sound forgings. In this study, the feasibility of performing the rotary forging process on a hexapod table has been investigated. A hexapod machine available to the authors has been employed for this purpose. The hexapod table with six degrees of freedom is responsible for all shaping motions. This device can be used to produce different motion profiles for complex workpieces. The appropriate profiles are obtained through the inverse kinematics. The maximum force being applied on the hexapod actuators was calculated. Two circular and linear profiles were examined to practically shape cylindrical workpieces, and forming load was compared with conventional forging for producing lead cylindrical workpieces. Ultimately, the forming load ratios in rotary forging with liner profile to conventional forging and rotary forging with circular profile were obtained 0.27 and 0.49 respectively.

The stability analysis of workpiece in fixtures is considered as one of the stages of the fixture verification system. The stability of free-form workpieces in fixtures is affected by different agents including weight, locators, clamps and machining wrenches. In this study, a mathematical model has been presented for part stability analysis based on the minimum norm principle that led to a non-linear quadratic optimization problem. The solution to this problem is the reaction forces at the contact points between workpiece and locators. The study includes the workpiece stability analysis at the loading stages, determination of stability span for workpiece and the investigating the effect of the base locators distances on the workpiece stability through examples. A turbine blade model was incorporated as the case study to evaluate the suggested model capabilities in stability analysis. The loading procedure of this part into the fixture was categorized into sequential stages and its stability was investigated in contact with the locators. The results included the stability span of [15°-58°] for the workpiece on base locators, increased stability by the distanced base locators and the confirmation of the main locating plan through the stability verification at the loading stages. The results showed the model efficiency and accuracy in analyzing the free-form part stability in contact with the fixture elements. The proposed dexterous model can be integrated into the CAFD platform to be used at the early stages of locating and clamping system design applications.

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.

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.

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.

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.

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.

Computer-aided process planning (CAPP) is a bridge for integrating computer-aided design (CAD) and computer-aided manufacturing (CAM). One of the basic computer-aided process planning tasks is sequencing of machining features. Sequencing of machining features is determined based on technical and geometrical rules. In this paper, the technical rules, geometrical rules and sequencing of machining features method were discussed. At first, some of the technical rules were pointed. Then, the geometrical interactions were studied and two new geometrical rules were introduced for sequencing the machining features having geometrical interaction. These rules can yield unique results and they are identified easily by the computer systems. Also, an algorithm was introduced for automated application of these geometrical rules in computer systems. The conflict between the technical and geometrical rules that may occur in some cases was studied. This conflict must be considered in the sequencing of machining features methods. Finally, an algorithm was introduced for sequencing of machining features based on permutation. In this algorithm the technical and geometric rules were applied separately and step by step. If there is any conflict between technical and geometrical rules, this conflict could detect automatically in this algorithm. Algorithms were programmed and verified in PythonOCC.