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In any industrial assembly process, there are a number of sources of variation. Variation in the manufacturing process leads to component variation, which, together with fixture variation and variation stemming from the joining process, propagates to the final product. In order to analyze and diminish the effect of variation, it is important to identify and be able to simulate the phenomena contributing to final variation. In this paper, the focus is variation in welding distortion arising from non-nominal components that are joined. In the welding process, it has been shown that variation in components and in fixtures influences the size and distribution of weld-induced distortion. Hence, in order to accurately simulate geometric variation of an assembly joined by weld joints, variation simulation and welding simulation need to be performed in combination. Previous research that focused on the combination of variation simulation and welding simulation has not considered components that are clamped. Instead the components were treated as rigid bodies at non-nominal positions prior to welding. In many industrial applications, clamps are used when assemblies are welded, and it is therefore important to quantify the influence that clamping has on welding of non-nominal components. In this paper, we simulate the combination of variation in components and fixtures with welding, considering that the components are clamped prior to welding. Although clamps will force the components closer to their nominal positions along the weld joint, they also introduce a stress field in the structure, which together with the welding process may cause additional distortion. Two case studies are performed and analyzed: a T-weld joint and a butt-weld joint. The results show that welding distortion depends on fixture error even in the presence of clamps. [ABSTRACT FROM AUTHOR]

This paper is focused on a combined deep drawing and extrusion process dedicated to the new process class of sheet bulk metal forming (SBMF). Exemplified by the forming of gearings, combined sheet and bulk forming operations are applied to sheet metal in order to form local functional features through an intended and controlled change of the sheet thickness. For investigations on the form filling and the identification of significant influencing factors on the material flow, a FE simulation model has been built. The FE model is validated by the results of manufacturing experiments using DC04 with a thickness of 2.0 mm as blank material. Due to the fact that the workpiece is in extensive contact to the tool surface and that the pressure reaches locally up to 2500 MPa, the tribological conditions are a determining factor of the process. Thus, their influence is discussed in detail in this paper. In the first instance, different fictional zones having a distinct effect on the resulting material flow are identified and their effect on improved form filling is demonstrated. Subsequently, a more comprehensive methodology is developed to define tribological zones of forming tools. For this, a system analysis of the digital mock-up of the forming process is performed. Besides friction, other relevant aspects of forming tool tri-bology like contact pressure, sliding velocity, and surface magnification are considered. The gathered information is employed to partition the tools into tribological zones. This is done by systematically intersecting and re-merging zones identified for each of the criterion. The so-called load-scanning test allows the investigation of the friction coefficient in dependence of the contact pressure and possible loading limits of tribological pairings. It provides an appropriate tribological model test to evaluate tribological measures like coatings, surface textures and lubricants with respect to their targeted application in particular zones. The obtained results can be employed in the layout of further forming processes to reach the desired process behavior. This can be, for example, an improved form filling, less abrasive wear and adhesive damage or lower forming forces, respectively tool load for an improved durability of the die. [ABSTRACT FROM AUTHOR]

Finish milling with a ball end mill is a key process in manufacturing high-precision and complex workpieces, such as dies and molds. Because of the complexity of the milling process, it is difficult to evaluate the microcharacteristics of machined surfaces real time, which necessitates the simulation of the process. In this area, the existing related simulation researches mainly focus on scallop height evaluation, but few have presented a whole picture of the microcharacteristics of milled surfaces. This paper develops a comprehensive simulation system based on a Z-map model for predicting surface topographic features and roughness formed in the finish milling process and studies the effect of machining parameters. The adoption of the discretization concept of the tool's cutting motion makes it possible to dynamically track the cutting tool-workpiece interaction with the tool movement and to describe the cutting edges-workpiece discrete cutting interaction more realistically and, therefore, the microcharacteristics of the machined surfaces more accurately. Also, the effects of the cutting tool run-out and wear are incorporated into the developed model through modifying the tool center motion and the cutting-edge shape, respectively. As a fundamental study, the tool-swept envelope has been simulated. The developed simulation system is applied to thoroughly study the surface features formed by the 2.5-axis finish milling process. The application for general three-axis machining is discussed. Additionally, this paper studies the effect of the tool inclination, which is the most common characteristic in 3+2- or five-axis milling processes, on the machined surface features. Experiments are carried out to study the milling process and to verify the simulation results. The difference between the simulated and experimental results is discussed, and the reason behind the difference is explored. [ABSTRACT FROM AUTHOR]

This paper proposes a comprehensive quality prediction framework for multistage ma- chining processes, connecting engineering design with the activities of quality modeling, variation propagation modeling and calculation, dimensional variation evaluation, dimensional variation analysis, and quality feedback. Presented is an integrated information model utilizing a hybrid (feature/point-based) dimensional accuracy and variation quality modeling approach that incorporates Monte Carlo simulation, variation propagation, and regression modeling algorithms. Two important variations (kinematic and static) for the workpiece, machine tool, fixture, and machining processes are considered. The objective of the framework is to support the development of a quality prediction and analysis software tool that is efficient in predicting part dimensional quality in a multistage machining system (serial, parallel, or hybrid) from station level to system level. [ABSTRACT FROM AUTHOR]

This paper describes the modeling and simulation of the Z axis of a five axis machining center for high-speed milling. The axis consists of a mechanical structure: machine head and electro-mandrel, a CNC system interfaced with the feed drive, and a pneumatic system to compensate for the weight of the vertical machine head. These subsystems were studied and modeled by means of: (1) finite element method modeling of the mechanical structure; (2) a concentrated parameter model of the kinematics of the axis; (3) a set of algebraic and logical relations to represent the loop CNC-Z feed drive; (4) an equation set to represent the functioning of the pneumatic system; and (5) a specific analytical model of the friction phenomena occurring between sliding and rotating mechanical components. These modeled subsystems were integrated to represent the dynamic behavior of the entire Z axis. The model was translated in a computer simulation package and the validation of the model was made possible by comparing the outputs of simulation runs with the records of experimental tests on the machining center. The firm which promoted and financed the research now has a virtual tool to design improved machine-tool versions with respect to present models, designed by traditional tools. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive time domain model that simulates end milling processes under general cutting conditions. Over an extensive range of axial depths of cut, the model can accurately predict regenerative forces and dynamic responses by considering varying dynamics along the cutting depth, three-dimensional forces, and cutting tool geometries. The prediction of stability limit is validated under cutting conditions of both large depths and very small radial immersions, hi addition, three-dimensional surface profiles under both stable and chatter conditions are predicted and compared with measured ones. A new method to extract cutting pressure coefficients is also introduced and applied to the experimental validations. [ABSTRACT FROM AUTHOR]

The productivity of a manufacturing system is greatly influenced by the configuration of the manufacturing system. This paper examines the importance of configuration on productivity, and the improvements that can be obtained by bufferless parallel-serial configurations, i.e. multiple machining lines in parallel, both with and without crossover between the operations. Combinatorial algebraic models are developed to quantify the productivity of parallel-serial configurations. It is shown that significant improvements to productivity can be obtained by placing operations in parallel, and that there is a synergistic improvement to productivity from having crossover between the operations. [ABSTRACT FROM AUTHOR]

This paper proposes a method of the preliminary geometric design for gear tooth profiles based on given sliding coefficients. A design procedure is developed and a simplified derivation of the mathematical model of tooth profiles is presented. The characteristics of the gear drive designed by the proposed method are analyzed. A comparison study on the sliding coefficient with the involute gear drive is also carried out in this work. The effects of parameters, including tooth number and modulus, on the characteristics of the gear drives are studied. The contact and bending stresses of this new drive are also analyzed. A manufacturing method of the proposed gear is studied, and a simulation of the machining process demonstrates its feasibility. The results show that the designers can design tooth profiles according to required sliding coefficients by the proposed method. [ABSTRACT FROM AUTHOR]

In the lapping process of hypoid gears, a gear set is run at varying operating positions and under a light load in order to lap the complete tooth surface. Because of the rolling and sliding motion inherent to hypoid gears, the lapping compound acts as an abrasive and refines the tooth surface to achieve smoothness in rolling action and produce high quality gear sets. In this paper, the lapping process is reproduced using advanced modeling tools such as gear tooth vectorial simulation for the tooth surfaces and reverse engineering to analyze the tooth contact pattern of existing gear sets. Test gear sets are measured using a coordinate measurement machine prior to a special lapping cycle where the position of the gear sets on the lapper does not change, and then are remeasured after lapping in order to establish how much and where material was removed. A wear constant named “wear coefficient” specific to the lapping compound is then calculated. Based on the obtained wear coefficient value, an algorithm for simulating the lapping process is presented. Gear sets lapped on the production line at AAM are used for simulation case studies. Initial results show significant scattering of tooth distortion from tooth to tooth and from gear set to gear set, which makes the simulation process difficult. However, it is possible to predict a confidence range within which actual lapping should fall, thereby opening the door to the optimization of the lapping process. [ABSTRACT FROM AUTHOR]