Parametric Modeling for Globoidal Cam Based and NC Machining

This paper describes a computer-aided design for design of the concave globoidal cam with cylindrical rollers and indexing turret follower. Three models with different modelling methods are made from the same input data. The input data include some basic dimensions of the globoidal cam system and a table of angular input and output displacements of the cam and the follower. The cam model must have no interference with the rollers when their motions are simulated in assembly conditions. In this study, Pro/ENGINEER® Wildfire 2.0 is used for modelling the cam, simulating motions and checking interference and errors of the system.

Study on the geometric characteristics of mating surfaces of globoidal cam mechanisms

CAD/CAM techniques together with NC machining allow to reduce products manufacturing time and costs. The aim of this paper is to present a brief overview of reverse engineering as a necessary phase which provides benefits to the design and production processes in advance. Taking blades as object of study, one method is proposed to improve the design efficiency for blades model reconstruction and NC machining. The process consists of three main components: 3D optical digitizing, model reconstruction and NC machining. First of all, point cloud data acquisition is made through camera type 3D scanner, and the data pre-processing is made by Geomagic software, then it is imported in CATIA software for model reconstruction and generating NC code. Results show that this method can improve the efficiency of blades model reconstruction.

ملخص:- تحتوي نماذج الانحدار على مکونين أحدهما مکون عشوائي يمثل حد الخطأ (Error Term) والأخر مکون غير عشوائي يمثل متغير الاستجابة(Response Variable) وهذا المکون هو محل الاهتمام فيتم تقديره بإحدى الطريقتين هما: الطريقة المعلمية أو الطريقة اللامعلمية أو کلاهما. نموذج الانحدار المعلمي (Parametric Regression Model) هو النموذج الأکثر شيوعا حيث أنه يفترض أن متغير الاستجابة له صيغه دالية محدده مسبقا والتي تم الحصول عليها من معلومات سابقه حول هيکل دالة الانحدار من خلال ذلک يتم تقدير فئة من المعالم. ورغم أن النماذج المعلمية تعد أحد أهم أدوات تحليل البيانات؛ لأنها فعاله ويمکن تفسيرها بسهوله، إلا انها لم تستطع ان تکون کافية في بعض الحالات. أما نموذج الانحدار اللامعلمي (Nonparametric Regression Model) فانه يعتمد على تقدير دالة الانحدار مباشرة من البيانات کما أنه لا يفترض فروضا معينه لتقدير معالم النموذج مثل التي يفترضها النموذج المعلمي وبالتالي فهو يتمتع بمرونة أکثر لاکتشاف البيانات التي قد تکون مفقودة او في الحالات التي لا تتوافر فيها معلومات سابقة. يتم انشاء نموذج الانحدار شبه المعلمي (Semi parametric Regression Model) من خلال مزج الطريقتين السابقتين معا. فغالبا ما يتم استخدام هذا النموذج في المواقف التي تکون فيها الافتراضات المعلمية غير محددة وغير متسقة، أو أن النموذج اللامعلمي لا يعمل بشکل کامل. يشتمل هذا البحث على تطبيق نماذج الانحدار المعلمية وشبه المعلمية بالإضافة إلى النموذج اللامعلمى کحالة خاصة من نموذج الانحدار شبه المعلمى لتقدير الدالة الافتراضية وتحديد شکل العلاقة بين المتغير التابع والمتغيرات المستقلة بالاضافة الى شکل انتشار البيانات مع خط (أو منحني) التقدير وذلک على بيانات واقعية تم الحصول عليها من الإتحاد المصري لألعاب القوى والمعروفة بـبيانات لعبة العشاري . Regression models contain two components, one of which is a random component that represents the Error Term and the other is a non-random component that represents the response variable and this component is of interest and is estimated in one of two methods: the parametric method or the nonparametric method or both. Parametric regression model is the most common model since it assumes that the response variable has a predetermined functional formula which was obtained from previous information about the structure of the regression function by which a class of parameters is estimated. Although parameter models are one of the most important tools for analyzing data; Because it is effective and can be explained easily, but it could not be sufficient in some cases. As for the nonparametric regression model, it relies on estimating the regression function directly from the data, as it does not assume specific assumptions for estimating the model parameters, such as those assumed by the parametric model, and thus it has more flexibility to discover data that may be missing or in cases where previous information is not available. The semi-parametric regression model is constructed by blending the two previous methods together. This model is often used in situations where the parametric assumptions are indeterminate and inconsistent, or the nonparametric model is not fully functional. This research includes the application of parametric and semi-parametric regression models in addition to the nonparametric model as a special case of the semi-parametric regression model for estimating the hypothetical function and determining the form of the relationship between the dependent variable and the independent variables in addition to the data spread form with a line (or curve) estimation on realistic data On it from the Egyptian Athletics Federation, known as Decathlon data.

This article studies the application of nonparametric modeling approach to model magnetorheological (MR) dampers. For comparison purposes, another typical parametric modeling method for electrorheological (ER) and MR dampers is reviewed. The existing parametric MR damper model includes a stiff Bouc-Wen model that is not friendly for simulation study and real time implementation of model-based advanced control algorithms. In order to avoid the difficulties by using the existing parametric model, the test data from a commercialized MR damper is employed to develop nonparametric models, which can consist of a series of numerically efficient mathematic functions. In addition, the selected functions are required to be continuous and differentiable for potential model-based control algorithms. The results of the nonparametric models show that such different models are comparable. Furthermore, one nonparametric model is selected to be compared with a parametric model and the test data to illustrate the accuracy of the model. The comparison shows that the proposed nonparametric models are able to accurately predict the damper force characteristics, damper bilinear behavior, hysteresis, and electromagnetic saturation. It is further shown that the nonparametric models can be numerically solved with an integration step size of the order of 10 2 s, much faster than the parametric models of the order of 10 5 s, which clearly shows that the proposed nonparametric models are feasible even for real time model-based control algorithms.

Simplified models are widely applied in finite element computations regarding mechanical and structural problems. However, the simplified model sometimes causes many deviations in the finite element analysis (FEA) of structures, especially in the non-designed structures which have undergone unknowable deformation features. Hence, a novel FEA methodology based on the parametric model by approximating three-dimensional (3D) feature data is proposed to solve this problem in the present manuscript. Many significant and effective technologies have been developed to detect 3D feature information accurately, e.g., terrestrial laser scanning (TLS), digital photogrammetry, and radar technology. In this manuscript, the parametric FEA model combines 3D point clouds from TLS and the parametric surface approximation method to generate 3D surfaces and models accurately. TLS is a popular measurement method for reliable 3D point clouds acquisition and monitoring deformations of structures with high accuracy and precision. The B-spline method is applied to approximate the measured point clouds data automatically and generate a parametric description of the structure accurately. The final target is to reduce the effects of the model description and deviations of the FEA. Both static and dynamic computations regarding a composite structure are carried out by comparing the parametric and general simplified models. The comparison of the deformation and equivalent stress of future behaviors are reflected by different models. Results indicate that the parametric model based on the TLS data is superior in the finite element computation. Therefore, it is of great significance to apply the parametric model in the FEA to compute and predict the future behavior of the structures with unknowable deformations in engineering accurately.

The technology of NC machining simulation is a reflection in virtual environment. Machining simulation may effectively reduce the invalid feeding and probability of interference or collision between cutter and fixture due to unreasonable machining parameters. Researches on machining simulation of multi-axis NC machining are complex and representativeness. This paper took a process of surface under NX CAM environment on a non-orthogonal five axis machine tool—DMU50eVolution as the object for machining simulation, by inputting the proper engagement for the cutter, using the method of coordinate transformation to create a post processor with UG post-builder and integrated into the library of post-processing. The NC codes created have been verified in the simulation system with VERICUT. And it has been shown that the preparation time of NC machining has been reduced, the efficiency of NC machining improved and the phenomenon of collision and interference effectively prevented.

Based on the analysis of the disadvantages of shoe last making with 3-axis shoe last NC machine, this paper presents a novel solution for last making with 5-axis shoe last NC machine, introduces the working principles, motions, components and implementation of 5-axis shoe last NC machine in detail. A key feature of the machine is that it can produce complete lasts in one working process, avoiding milling the toe and heel with final manual finishing operations. This paper proposes an algorithm of the tool path generation of the machine. By the grid data of the last surfaces and spiral interpolation, we can obtain the cutter contact points and cutter location points and then deduce the formula of solving each component motion in the machining. A model machine developed by the presented solution demonstrates the improved machining efficiency and high quality of shoe last.

With the use of Visual C++ 6.0 programming development tools as the secondary development of Unigraphics NX (UG), dynamic link library DLL plug-ins were created. This paper takes fixed pedestal which is a standard part with assembly level of mold as an example, describing the parametric assembly modeling technology and implementation method of automatic virtual assembly process. The method can improve the design efficiency greatly by changing the related parameters of the parts to regenerate model fast and complete the design as well as assemble of fixed pedestal. It is proved that this method can meet the mould design requirements, and can be expanded and used for parameterized modeling and assembling of other standard parts with assembly level of mold in the practice.

Standard, nonparametric statistical methods estimate only the impact of therapy on survival rate up to a selected follow-up interval. In contrast, parametric methods can estimate the impact of treatment on the two cardinal parameters of malignancy: likelihood of cure and recurrence free survival time among uncured patients. The authors screened a total of six parametric survival models. Three of these, including the log normal model, were applied to survival data from five clinical trials of adjuvant therapy for Stage II breast cancer. For comparison, the log rank test, a standard nonparametric method, was also applied to the same data. Both parametric and nonparametric methods identified a significant therapeutic in three of the five trials. In only one of these three trials, however, did parametric analysis identify a significant difference in the likelihood of cure between treatment groups. In the remaining two trials, a significant difference was found in recurrence free survival time among uncured patients. The three parametric survival models gave similar results. These findings suggest that parametric analysis may warrant further study as a method for measuring the long term clinical impact of adjuvant therapy on Stage II breast cancer.

High-Efficient parametric aeroelastic modeling and experimental validation for a morphing aircraft testbed

Cam mechanism is the most difficult part in the design and manufacture of stamping dies of automobile panels. The same series of cam products need to meet the needs of different working angles. Each specification needs to design and prepare a three-dimensional model, which brings great challenges to the design, editing, and management of the models. Therefore, a new design system of full parametric association modeling based on geometric features for standard cam was proposed, which is seamlessly integrated in NX software platform. The models of different work angles of the same series of cam are integrated into a fully parametric model. The specification and assembly location of standard parts, activation and suppression of detail features will automatically change with work angle based on parametric feature and association constraint technique. By modifying the work angle, the system can automatically instantiate different specification models of cam. Furthermore, the optimized design of cam structural is easier to achieve by motion simulation and finite element analysis based on the parametric model and geometric features. The system can also output the BOM table, when the model is instantiated. The cam of KMACG 600 demonstrates that the newly developed system shows an excellent performance on the model simplification, data management, and optimization design of cam, which can generate high quality design and reduce cost and designing time significantly.

Contaminated surgical instruments and variant Creutzfeldt-Jakob disease

Response to ‘Letter to the editor about “Comparing the usefulness of a fluoroscopic navigation system in femoral trochanteric fracture for orthopaedic residents with the conventional method”

The parametric model of product is the foundation of implementation product series design. In order to solve the data conflict problem of product series design in the process of parametric modeling, a parametric modeling method of product was proposed based on the directed graph. Product, components and parts was expressed by vertex, and the driven relationship of parameter for model was expressed by directed edge. The process of product parametric design was analyzed and reconfigured by the structure directed graph of product parametric model. The structure directed graph of product parametric model was divided into a number of sub-graphs, and those sub-graphs were combined to directed trees of the parametric model of product. The parametric model of product was achieved to support product series design. So product parameters was droved from top-down so as to improve the efficiency of modified and reuse of parametric model of product and convenient to operate within the model. As an example, the series design of the Gatling gun proved the applicability and effectiveness of the method, and the method can meet with product series rapid design