产品公差的并行优化设计

在分析产品公差设计现状的基础上，提出了公差并行优化设计的数学模型；给出了一个份真实例。     

An inspection advisor for form error in cylindrical features

Due to inherent variability in even the so-called “high-precision” machines, the need for accurate, quick and economical inspection of tolerances of machined features has become very important. Coordinate measuring machines (CMMs) are very popular in industry for inspection of components. In addition to hardware capabilities, some of the critical factors that affect the accuracy and precision of inspection using CMMs have been identified as sample size, sampling technique and form evaluation method. Selecting an optimal inspection plan for the CMM is vital to improve the quality of measurements while simultaneously minimizing inspection costs and time. The motivation behind this paper is to provide the user flexibility and control in choosing an optimal inspection plan for evaluation of form error in cylindrical features according to his/her specific needs in a practical manufacturing scenario. In view of this objective, a two-way relationship between the inspection strategy used and inspection performance metrics achieved has been established using multiple regression. The forward model is a plan evaluator that computes numerical estimates of the expected accuracy and precision for different inspection plans. The reverse model is a strategy designer that recommends the most economical inspection plan that can meet the acceptable quality criteria considering the user’s constraints and available resources. Both the models have been incorporated into a user-friendly inspection advisor with a graphical interface.     

A tolerance method for industrial image-based inspection

Although image-based inspection has been applied to a wide range of industrial applications, inspection accuracy remains a challenging issue due to the complexity involved in industrial inspection. The common method adopted in industry is to use a qualified image as a template image to inspect each live image on a pixel-by-pixel basis. In this paper, a tolerance method is presented to replace the template image method. The said tolerance is formed by two indices computed from a sample image, instead of using the whole image for inspection. To ensure an accurate tolerance zone, a neural networks method is used to take the noise and uncertainties in the images under inspection into consideration. To improve neural networks training speed, the Taguchi method is adopted to select a minimum number of the sample images needed for training. Once a tolerance zone is obtained, live images are inspected against it. If the indices of a live image fall inside the tolerance zone, the part is regarded as good, otherwise defective. Three examples are given: one for auto part inspection, one for label inspection, and one for machining part inspection. The inspection accuracy achieved is above 94%.     

无铅焊点检测光源的分析与优化设计

为了提高自动光学检查(AOI)系统的性能,对AOI光源进行了研究.介绍了AOI光源的结构设计方法.光源由红、绿、蓝3种不同颜色,不同照射角度的LED阵列组成.然后.建立了光源的照度模型以及焊点的反射模型.最后,根据简化的照度模型对光源的几何参数进行优化.仿真和实验结果表明,所设计的光源在检测无铅焊点时同样有效.并能使不同类焊点间的特征距离更大.最大为半球形光源照射下的11.88倍.从而提高了特征在无铅焊点缺陷检测的分辨能力.验证了光源设计的有效性.     

A new strategy for circularity problems

The evaluation of circularity based on the minimum zone criterion as a non-linear and non-convex problem, which requires a substantial amount of computational effort in general, is investigated. A new strategy for improving the computational efficiency by collecting data points at the farthest and nearest locations from current minimum radial separation center until all collected data points meet the optimum criterion is proposed. A number of mathematical models developed in this paper indicate that the minimum circularity can be determined by using a small number of critical data points. The validated results show that the proposed strategy offers an effective way to identify the critical data points at the early stage of computation and gives an efficient approach to solve the circularity problems, especially when the number of data point is large.     

主梁截面设计的一种优化方法

以主梁腹板面积和截面总面积比作为变量，在定量面积和腹板高厚比条件下对惯性矩和抗弯模量进行优化，用最简单、实用的方法求主梁截面理想的强度和刚度。     

A comparison of different algorithms for circularity evaluation

The measurement and evaluation of circularity of cylindrical components is very important for the majority of cylindrical workpieces used in precision engineering. Further, since the measurement and evaluation of cylindricity is more complex and time consuming, only circularity is evaluated for most applications.The evaluation of circularity from a circularity graph and/or from digital data requires a suitable algorithm. The most commonly used criterion for this has been the least squares criterion, though it is known that this does not necessarily give the best solution. Hence, an attempt has been made in this paper to propose different algorithms and compare them. The algorithms considered are based on the methods of least squares, intuition, general second-degree equation for a circle, best-fit ellipse and simplex search. A comparison of these methods is presented.     

A neural network approach to determining optimal inspection sampling size for CMM

This paper reports a neural network approach to determining the optimal inspection sampling size of ‘hole’ features using the Coordinate Measuring Machine (CMM). Factors which could affect sample size due to design, manufacturing, and measurement related factors, i.e. size, dimensional and geometrical tolerances, machining processes, and confidence levels, have been studied. Machining process type, size, and tolerance band have been identified as the known factors which may affect the sample size required. Experiments have been carried out to collect sampling size data versus the variation of these factors for different ‘hole’ features. The implicit correlation between the sample size and these factors, has been achieved by training a back-propagation neural network using the collected data. The neural network architecture is described, and the test of the trained neural network on a few new ‘hole’ features is presented to highlight the applicability of this approach.     

Optimal inspection strategy planning for geometric tolerance verification

Two features characterize a good inspection system: it is accurate, and compared to the manufacturing cost, it is not expensive. Unfortunately, few measuring systems posses both these characteristics, i.e. low uncertainty comes with a cost. But also high uncertainty comes with a cost, because measuring systems with high uncertainty tend to generate more inspection errors, which come with a cost.     

A Web-based interactive advisor for assembly line balancing

Assembly line balancing (ALB) aims at distributing those work required to assemble a product in mass or series production among a set of workstations in an assembly line. Heuristics approaches, in corporation with computer simulation, have demonstrated a number of advantages in practice. Recognizing the importance of interactions between production planners and the scheduling system, this paper discusses the design and implementation of a Web-based ALB advisor for scheduling hard disk drive assembly involving multiple criteria. With the assistance of such an ALB advisor, production engineers, who may have difficulties in understanding those sophisticated ALB heuristics, can remotely present and specify their particular ALB problems. Based on the user input, the advisor will compose a schedule based on various heuristic algorithms embedded in its library. The schedule can be manipulated directly via a graphical user interface. The advisor also generates simulation models for the user-specified ALB problems and presents the user with performance evaluation of the suggested ALB solutions.     

Automated optical inspection for the runout tolerance of circular saw blades

Additive manufacturing allows close-to unrestrained geometrical freedom in part design. The ability to manufacture geometries of such complexity is however limited by the difficulty of verifying the tolerances of these parts. Tolerances of features that are inaccessible with traditional measuring equipment such as coordinate measuring machines cannot be verified easily. This problem is addressed by developing an in-line reverse engineering and 3D reconstruction method that allows a true-to-scale reconstruction of a part being additively manufactured. In earlier works (Pedersen et al. 2010; Hansen et al. 2011), this method has shown its potential with 3D printing (3DP) and selective laser sintering additive manufacturing processes, where it is possible to directly capture the geometrical features of each individual layer during a build job using a digital camera. When considering the process of direct light projection (DLP), the possibility of directly capturing the geometrical features of the object during a build job is limited by the specific machine design and the fact that photoactivated monomers often do not change optical characteristics in the polymerization process. Therefore, a variant of the previously tested and verified method has been implemented on DLP machine, where instead of capturing the geometrical features of the produced objects during the build job directly, these features are captured indirectly by capturing the reflection of the projected light projected during the build job. Test series were made, and a reconstruction of two octave spheres were produced and compared with the input CAD file and scans of the produced objects. The comparison showed a good correlation between the reconstructions and the scans considering the resolution of the images used for the reconstruction, and it was thereby concluded that the method has a promising potential as a verification method for DLP machines.     

一种面向热膨胀性能的公差设计方法

双材料点阵是实现热膨胀设计最有效的途径之一,然而制造误差会对热膨胀性能造成影响,传统公差理论无法保证产品性能的精确实现。提出了一种能保证双材料点阵等效热膨胀系数精确实现的功能性公差设计方法。首先,分析尺寸的热膨胀效应,根据结构热膨胀性能的极限情况进行变量分组;然后,分析尺寸敏感度,分别采用逐步降低敏感尺寸的公差等级和优先降低非敏感尺寸的公差等级两种方法对尺寸偏差优化模型进行改进;最后,通过对三种热膨胀性能的胞元进行公差设计,验证了方法的正确性。本文首次考虑了双材料结构的公差设计,建立了公差设计和结构热膨胀性能之间的关系,对双材料点阵的制造与应用具有很大的理论和实际意义。     

基于价值分析的公差优化设计及计算程序

本文用价值分析的方法对公差优化设计进行讨论，得出了使成本最低的公差设计公式，并给出了相应的计算程序。     

A note on optimal design of columns

To illustrate characteristic aspects of optimal design of columns, a discrete model of an elastically clamped column is used, which consists of rigid segments that are joined by elastic hinges to each other and to the supports. It is shown that the optimum is analytical when the elastic clamping is weak, but nonanalytical when it is strong.     

A hybridized approach to optimal tolerance synthesis of clutch assembly

Specifying proper tolerances for manufactured goods results in greater savings and improved performance, which may ultimately determine whether a product succeeds or fails in the marketplace. In the past, tolerance specification has been more an art than a science, and is largely dependent upon experiences. A more scientific and reliable approach is presented in this paper. A hybrid of Nelder-Mead simplex method and particle swarm optimization (NM-PSO) is introduced for the design of tolerance of the machine elements of an overrunning clutch assembly. The objective is to obtain tolerances of the individual components so that the cost of manufacturing and quality loss is minimized. Experimental results demonstrate that hybrid NM-PSO is extremely effective and efficient in locating best-practice optimal solutions compared to geometric programming (GP), genetic algorithm (GA), and particle swarm optimization (PSO) methods.     

A manufacturability advisor for spun and rollformed sheet metal components

In today’s manufacturing scenario, accounting for manufacturability considerations at the product design stage is not an option but a necessity. When CAD/CAM tools are used to reduce design lead times, accounting for manufacturing process related considerations implicitly is often difficult. Availability of manufacturability advisor systems that analyze part geometry and other product related information for ease of manufacturing could be a solution to this problem. The purpose of a manufacturability assessment is to give feedback to the designer in order to make the product/process more effective. Present research is concerned with the development of an automated manufacturability advisor for sheet metal components. Unlike most of the work done in the past that concentrated on bending and other forming processes, present work deals with sheet metal components manufactured by two different processes, namely “spinning” and “rollforming”. Effectiveness of the proposed manufacturability advisor is demonstrated by taking the number of industrial parts as examples.     

A revised design of circular hydrostatic bearings for optimal pumping power

A modification of the circular flat externally pressurized thrust bearing is presented in this paper. This involves the addition of a central step in the bottom of the rotating pad for the purpose of restricting the lubricant flow and minimizing the pumping power required for continuous operation. The performance of such a bearing configuration under static loads is analysed and the key design parameters are discussed, grouped and presented in a design chart. In addition to the minimization of pumping power, the proposed configuration provides higher thrust loads and enables the bearing to withstand radial loads, an advantage which could not be achieved in other hydrostatic thrust bearing configurations. The bearing is also able to restore concentricity due to the lateral damping provided by the squeezed lubricant film in the clearance between the step and the recess.     

转轴的抗疲劳稳健优化设计研究

结合转轴的失效模式,建立了转轴的抗疲劳稳健优化设计模型,利用Visual C＋＋、SQL开发完成其原型系统。整个设计过程充分考虑了不确定因素对疲劳强度的影响,以提高转轴质量的抗干扰能力,保证了质量的稳健性。     

Generalised design for optimal product configuration

Design of configurable product family or design for configuration has emerged as an efficient tool to deal with the new challenges of a continuous dynamic and volatile market. Design for configuration provides an efficient and effective mean to realise the product variety. This paper tackles the optimal product configuration. The introduction of fuzziness to capture the subjective nature of the design for configuration process, the building of multiple fuzzy models, which correspond to the multiple views of a configurable product, permits to propose the possible physical solutions to configure a product. It corresponds to the consensus problem of design for configuration. The extended problem formulation is the proposition of an optimal product configuration. The optimal solution is searched using p median problem formulation. The proposed approach is validated by the design case study of a configurable product.