Usporedna analiza modela dva tipa elemenata za stezanje u dinamičkim uvjetima (original) (raw)
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This paper studies the compliance of the fixture-workpiece system. Workpiece clamping case with two types of clamping elements is considered. The first type of clamping element is standard, with flat top, while the second one is specially designed, with round cutting insert. Analyzed was the case of workpiece clamping using small forces, whereby the deformations in the workpiece/clamping element interface are predominantly on the order of magnitude of roughness height. A comparative analysis of dynamic behaviour of both types of clamping elements is also presented. In comparison with its standard counterpart, the specially designed clamping element with round cutting insert has superior clamping performance regarding both tangential load capacity and compliance.
Finite Element Modelling and Analysis of Workpiece-Fixture System
International Journal of Applied Research in Mechanical Engineering
The fixture design and analysis lead-time is always a major influencing factor for the bottleneck between product design and manufacturing. With advent analysis and simulation tools, there is a lot of potential to expand the scope of optimization of fixture elements to achieve the objectives such as ‘maximizing rigidity’ and ‘minimizing weight’ of a fixture assembly. There are many sources which affect the rigidity of fixture assembly. The rigidity of fixture assembly mainly depends upon various factors such as material properties, geometry of individual components, stability against thermal distortions, clearances or plays on fixture elements (to facilitate loading and unloading of workpiece), contact deformations at contacting surfaces, etc. Among these, contact deformations at contact interface are one of the important sources of errors in precision fixture design. These contact deformations are measure of contact stiffness and therefore needed to be studied in accordance with wo...
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In this paper is described the design methodology of clamping fixture with the foolproofing capability. This capability eliminates the wrong work piece inserting and positioning in the clamping fixture. This methodology includes the work piece classification by its symmetry. To work piece symmetry evaluation are used the rotational and mirroring transformations. In the explored area of symmetrical transformations interactions we put the foolproofing pins, or switches.
Stability analysis of free-form workpieces in fixtures ARTICLE INFORMATION ABSTRACT
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, and 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 investigating the effect of the base locator's 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 ...
Comprehensive Approach for Mathematical Modeling of Mechanical Systems: Fixture Design Case Study
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Present work is devoted to locating and clamping of prismatic parts in fixtures during the machining on drilling-milling-boring machines. The special feature of locating schemes of parts of the present type is that one of the flat surfaces is used as a datum (3 contact points) ensuring stability, convenience of locating and vibration elimination during the machining process. Within the scope of the presented work, the comprehensive mathematical model of the system “fixture – workpiece” has been developed taking into account technological features of locating and clamping processes of workpiece in fixture. The methodology of determination of the rigidity of the cutting tool and functional elements has been proposed. As a result, the static and dynamic analysis of the workpiece in the fixture under the effect of spatial system of cutting and clamping forces is being determined. In addition, the free frequencies of the system “fixture-workpiece” and forms of the free and forced vibrati...
A Review on Design of Fixtures.pdf
In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain the machining accuracy. The various methodology used for clamping operation used in different application byvarious authors are reviewed in this paper. Fixture is required in various industries according to their application. This can be achieved by selecting the optimal location of fixturing elements such as locators and clamps. The fixture set up for component is done manually. For that more cycle time required for loading and unloading the material. So, there is need to develop system which can help in improving productivity and time.Fixtures reduce operation time and increases productivity and high quality of operation is possible.
Force and Deformation Analysis for Determination of Optimum Fixture Configuration
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An important aspect in the design of a good fixture is that of imparting sufficient rigidity to the entire work piece surface that are to be machined. Rigidity refers to the ability of the system to withstand applied loads with minimal deformation. A good fixture must able to completely restrain the work piece to counter any possible cutting forces and couples in machining stages. The present study aims at implementing finite element analysis and finite element optimization techniques to determine the optimum fixture configuration for drilling through a deformable work piece. The 3-2-1 locating principle has been used and in order to simulate real time conditions contact elements have been used at the interfaces of the work piece and the fixturing elements. The desired fixturing characteristics are optimized with respect to the objective function. Excessive clamp forces and improper location may cause large elastic deformations in the work piece. Hence the lateral deflection of the ...
A Review on Design of Fixtures
In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain the machining accuracy. The various methodology used for clamping operation used in different application by various authors are reviewed in this paper. Fixture is required in various industries according to their application. This can be achieved by selecting the optimal location of fixturing elements such as locators and clamps. The fixture set up for component is done manually. For that more cycle time required for loading and unloading the material. So, there is need to develop system which can help in improving productivity and time. Fixtures reduce operation time and increases productivity and high quality of operation is possible.
Development of computer aided clamping system design for workpieces with freeform surfaces
Computer-Aided Design, 2018
The development of computer aided fixture design has already encountered numerous mathematical and technical challenges having hampered realization of automated design of fixturing system consisting of locating and clamping systems. This is more critical for workpieces of freeform surfaces compared with those of polyhedral geometry. In the present study, the mathematical foundation of clamping system design has been developed by using the concept of screw theory and the minimum norm principle. An algorithm has been proposed to realize the developed theory. In this algorithm, three criteria have been taken into consideration to be respected when designing the clamping system. These are minimum number of clamps, maximum contrariety of clamping force components with respect to the twists tending to break contact between the workpiece and the locators, and maintenance of workpiece's static stability under different wrenches. The suggested theory and algorithm have been incorporated into a platform already developed by the authors in Python-OCC for computer aided fixture design. The fixturing of three different machining workpieces have been examined for evaluating the capabilities of the suggested theory and algorithm. These workpieces had freeform surfaces which were defined by NURBS formulation.
The International Journal of Advanced Manufacturing Technology, 2008
Contact forces between workpiece and fixture define fixture stability during clamping and influence workpiece accuracy during machining. In particular, forces acting in the contact region are important for understanding deformation of the workpiece at the contact region. This paper presents a model that combines contact elasticity with finite element methods to predict the contact load and pressure distribution at the contact region in a workpiecefixture system. The objective is to determine how much clamp forces can be applied to generate adequate contact forces to keep the workpiece in position during machining. The model is able to predict the normal and tangential contact forces as well as the pressure distribution at each workpiece-fixture contact in the fixturing system. Model prediction is shown to be in good agreement with known industry practice on clamp force determination. The presented method has no limits on the types of materials that can be analyzed.