Validation of an information model for inspection with CMM

Application of Simultaneous Engineering concept can be made at two levels: the first one refers to project work and administration methods, reorganizing teams; the second level refers to the use of computer systems which not only transmits product and process information among them, but also allows them to share it [S. Bloor, J. Owen, Product Data Exchange, UCL Press Limited, London, 1995]. Nowadays, several research groups are working on this second alternative.In this context, the definition of a product information model is very useful: a mechanism able to provide product information to the activities in the production cycle [P. Gu, K. Chang, Product Modelling Using STEP, Computer Aided Design, 27(3) (1995) 163–179; P.R. Wilson, Information Modelling, IEEE Computer Graphics and Applications, 7(12) (1987) 65–67]. This model should satisfy the different points of view that the product lifecycle activities have about the same information [O.J. Canciglieri, R.I.M. Young, A multi-viewpoint reasoning system in design for injection moulding, International Conference on Design and Production of Dies and Molds, Istambul, 19–21 Junio, 1997, pp. 195–205; T. de Martino, B. Falcidieno, S. Habinger, Design and engineering process integration through a multiple view intermediate modeller in a distributed object-oriented system environment, Computer Aided Design, 30(6) (1998) 437–452; Product Data Representation and Exchange. Part 1. Overview and Fundamental Principles, ISO 10303 Part 1, ISO, 1993]: functionality, geometry, manufacturability or inspectionability.STEP standard [Product Data Representation and Exchange. Part 1. Overview and Fundamental Principles, ISO 10303 Part 1, ISO, 1993] provides a way to solve the problem of information integration along the cycle. However, this standard still does not consider the dimensional inspection process integration. This paper shows a solution to integrate the dimensional inspection process in the production cycle using coordinate measuring machines. The integration is achieved by means of an information model implemented in a product central database, accessible to every activity in the cycle. The information model has been defined according to STEP standard philosophy, in such a way that interaction with other information models related to other activities in the cycle is possible.A new framework called IFCIA is presented. Here, the model has been tested taking as reference the information objects included in the previously developed model. This framework was already introduced in Refs. [J. Barreiro, J.E. Labarga, A. Vizán, J. Ríos, Information model for the integration of the inspection activity in a concurrent engineering framework, International Journal of Machine Tools and Manufacture, 43(8) (2003) 797–809; J. Barreiro, J.E. Labarga, A. Vizán, J. Ríos, Functional model for the development of an inspection integration framework, International Journal of Machine Tools and Manufacturing, 43(15) (2003) 1621–1632] but it is explained in detail now. The framework architecture and the difficulties that arise to integrate dimensional measuring equipments in the cycle are shown.     

Information model for the integration of inspection activity in a concurrent engineering framework

The basis of the integration of activities related to the product life cycle is, mainly, the creation of a unique and coherent information model along all the stages in the cycle. Up to date, dimensional inspection activities have not been deeply analysed, possibly due to the fact that, their work influences are smaller than others, such us numerical analysis, materials or numerical control. However, the integration of dimensional inspection is very important for several reasons: the need of specifying the design and planning of the inspection process from the conceptual part design; the increase of use of high speed coordinate measuring machine (CMM) in the production lines; and finally, for the interest of a feedback between data inspection and manufacturing processes. This paper is a detailed proposal of an information model for inspection based on operations for CMM, which represents a consistent structure of the necessary data in an integrated product setting.     

Towards a haptic virtual coordinate measuring machine

In this paper, a novel coordinate measuring machine (CMM) inspection path planning environment, named haptic virtual coordinate measuring machine (HVCMM), is proposed, which makes use of haptic modeling technique for CMM off-line programming. HVCMM is an accurate model of real CMM, simulating a CMM’s operation and its measurement process in a virtual environment with haptic perception. It enables CMM off-line programming to take place exactly as if an operator were in front of a real CMM and moving a real CMM probe. To generate the inspection path of a part, teach pendant programming is made by pointing a probe at the 3D computer-aided design (CAD) model of a part using a haptic device. With the HVCMM system, it is much easier to generate collision-free probe path than using other off-line inspection planning methods. Furthermore, when a contact occurs between the CMM and the object, a force is generated based on a proposed mechanics model besides visually showing the contact in the HVCMM environment. Surface voxel is used for quick collision detection. The HVCMM not only facilitates the inspection path planning, but also speeds it up. The proposed HVCMM can also be used for the training of CMM operation.     

Sampling strategy design for dimensional measurement of geometric features using coordinate measuring machine

Dimensional measurement using a coordinate measuring machine (CMM) has been commonly adapted in advanced manufacturing environments to ensure that manufacturing products have high quality and reliability. To conduct dimensional inspection effectively in a computer-integrated manufacturing (CIM) environment, there is an urgent need to derive a sampling strategy which can be used to specify a set of measuring points that lead to accurate sampling while minimizing the sampling time and cost. Owing to the variations in characteristics of geometric features and manufacturing processes, different feature surfaces on a workpiece usually have different variations in their dimensional accuracy and surface finish. The variations may differ considerably from one surface to another, even though those surfaces may share the same feature. Therefore, the variation in dimensional accuracy and surface finish should be considered in determining the proper sampling size for each geometric feature generated by various processes with different production parameters. In this paper, a feature-based methodology which integrates the Hammersley sequence and a stratified sampling method are developed to derive the sampling strategy for various geometric features which have specified measuring points. Case studies are used to compare the effectiveness of Hammersley sequence sampling, uniform (systematic) sampling and random sampling. The results show that the derived sampling strategy based on the Hammersley sequence leads to a nearly quadratic reduction in the number of samples compared with the uniform sampling method, and hence units of time and cost, while maintaining the same level of accuracy. The derived sampling strategy also shows a better performance when compared with the random sampling method.     

Parametric process optimization to improve the accuracy of rapid prototyped stereolithography parts

The functional requirements of a rapid prototyping system are speed and accuracy, and they are both functions of vendor defaulted and user selected manufacturing parameters. Accuracy is evaluated by dimensional errors, form errors and surface roughness of manufactured parts. A specially designed specimen with 20 dimensional, geometrical, and surface roughness features has been used in the inspection of RP manufacturing processes. In terms of Taguchi experimental design techniques, an orthogonal array of experiments has been developed which has the least number of experimental runs and desired process parameter settings. Using a 3-D coordinate measuring machine and surface profilometer, a series of measurements in evaluating the SLA parts quality has been conducted to find the functional relationships between the output part quality and input manufacturing process parameters. Two analysis tools, response surface methodology and Analysis of Variance (ANOVA), have been used to evaluate the SLA RP process and to perform the product optimization. The optimal setups of SLA manufacturing parameters for both individual features and a general part with various features have been concluded from this study.     

曲面类飞机产品激光跟踪测量工艺规划研究

为了提高通用航空飞机产品的加工质量,数字化定义模型和光学测量定位技术在产品质量检测体系中得到逐步应用。利用激光跟踪仪及其配套测量软件Polyworks对通飞曲面产品的测量过程进行工艺规划和测量路径可视化过程仿真,为曲面类产品的现场测量提供理论及工艺指导。为了提高测量拟合精度提出自由度定位基准点坐标对齐与最近点迭代算法对齐点数据相结合的方法,将产品测量坐标映射到设计坐标系下,完成数字化测量坐标系的统一,并实例验证。利用CATIA的开发接口采用CAA C++技术作为二次开发手段完成信息获取,并在计算机三维软件中与激光跟踪仪测量软件Polyworks完成测量点通信,利用宏脚本编辑语(MSCL)编辑程序将坐标转换之后的测量点进行路径仿真从而生成可视化的数字化测量工艺规划过程。     

铸造3D喷墨打印砂型尺寸精度测量评定方法研究

随着铸造行业的转型发展,3D打印技术已经成熟的应用于制造铸造砂型,所制作的砂型不再单单作为铸造过程中的半成品,而是可以作为产品面向各铸造厂进行销售。但是目前对于砂型的检验标准存在缺失,对于砂型质量的把控和评定缺少依据。针对铸造砂型的尺寸精度,通过设计制作测量试块,给出了一种3D喷墨打印砂型的测量方法及评定标准,填补了目前铸造行业中这一领域在标准上的空白,对推动3D打印技术在铸造行业的应用以及砂型的产品化有着重要的意义。     

结构光三维扫描测量在逆向建模中的应用研究

介绍了在产品逆向建模时使用的两种测量方法,即触测式三坐标测量机与结构光三维扫描测量,举例对比两种测量方法的测量原理、测量过程、实体拟合结果的优缺点,为类似产品实际生产需要选择更符合产品测量及逆向的方式,提供了一种使产品的测量及拟合质量提高,产品扫描检测速度提升,产品不良率降低的测量参考方向。     

Metrological solutions for an adapted inspection of parts and tools of a sheet-bulk metal forming process

Processes of the new production technology sheet-bulk metal forming allow a fast and efficient near-net-shape forming of highly complex parts. Thus the need of energy and raw material as well as the production cycle time can be reduced. In order to guarantee these advantages by avoiding scrap and moreover to ensure the parts’ geometrical requirements, production-related metrological solutions for an adapted inspection of parts and tools of sheet-bulk forming processes have to be developed. To fulfill the demands of the differing measuring tasks two prototypical measurement solutions are under development: a multi-scale multi-sensor fringe projection system allows for holistic inspections in feature adapted resolutions, whereas a fiberscopic fringe projection system captures the forming tool partly between forming steps. For the purpose of evaluating the metrological solutions’ capabilities of capturing the geometry of filigree structures a comparison of both systems is presented in this work. To guarantee realistic results, the performed measuring tasks have to be comparable to the areas of applications both systems were designed for. During the development of the measuring systems the emphasis was put on the inspection of small complex geometries. These are most challenging for fast and reliable optical inspection under production-related conditions. By considering measurements of calibrated standards on the one side as well as of measuring tasks resulting out of real sheet-bulk metal forming processes on the other side a realistic comparison is assured. Next to the measuring systems’ performances also an approach for combining the measurement data of both metrological solutions is shown. By combining the advantages of both measuring systems, highly detailed information for further interpretations of the forming processes can be provided.     

三坐标测量机在超硬材料制品检测领域的应用

三坐标测量机是一种高精度的自动化测量设备,检测范围广泛。不仅适用于常规产品的尺寸公差、形位公差检验,而且也适用于复杂工件以及复杂尺寸的测量,同时也可应用于产品的逆向开发,为我们在日常的产品设计和制造过程中提供了重要的技术资料。我们通过列举在实际工作中的几个测量事例,说明三坐标测量机在超硬材料行业中已经发挥着重要作用,为我们的科研生产和产品开发提供技术支持。      

面向锻件产品开发的知识建模方法及应用

针对日前锻件产品开发的特点及存在的问题,规划了基于知识的锻件产品开发流程,并根据开发流程,结合开发知识的特点将知识划分为领域知识、实例知识和设计历史知识,提出了面向锻件产品开发的知识建模方法.本文采用规则/框架的综合表达方法对3种锻件产品开发知识进行组织建模,并利用面向对象方法将这3类知识模型集成构建了锻件产品开发知识集成模型.基于该建模方法和ASP.NET平台,采用面向对象语言C#,结合ORACLE数据库技术开发了锻件产品开发系统并得到了有效应用.     

A new algorithm for determining a collision-free path for a CMM probe

Recent developments in computer integrated manufacturing (CIM) systems have made the speed and accuracy of the traditional approaches in dimensional inspection bottlenecks of the production line. To overcome these bottlenecks, computer integrated dimensional inspection was proposed with the coordinate measuring machine (CMM) being the key device. In this investigation, a framework for integrating the CMM into the computer-aided design/computer-aided manufacturing (CAD/CAM) environment is developed to automate the process of design, manufacturing and inspection. An algorithm to generate an optimum collision-free CMM probe path is proposed. This algorithm uses the ray tracing technique to locate the collision of the possible paths, between the initial probe point and the target point, with the workpiece to be inspected. If there is a collision, the algorithm works through the topological structure of the part and selects the midpoint of the edge, shared by the face with which the path collides and the adjacent face nearest to the target point, as the next probe point. This procedure is followed till the target point is reached. The first half of the proposed algorithm is implemented using Mechanical Desktop as the CAD system and AutoCAD Runtime Extension (ARX) as the application programming interface, running on a Windows NT 4.0 platform. The effectiveness of the proposed algorithm is verified by the results of the implementation demonstrating optimum collision-free dimensional inspection path generation for three prismatic parts.     

Geometric error measurement of spiral bevel gears using a virtual gear model for STEP-NC

Geometric error measurement is required to evaluate the grade of the manufactured gears. Due to the complexity of the spiral bevel gear, direct measurement with the physical part has been conducted in a very limited way. In this paper, we present an indirect measurement based on the virtual gears model (VGM), obtained by NUBS fitting of the surface points measured by CMM (coordinate measuring machine). By comparing the VGM with CAD model (soft-master model), various errors such as tooth profile error and tooth trace error can be automatically measured. The developed method is simple and robust without requiring a special measuring device, and hence it can be applied for the industrial practice as a means for measuring the tooth profile and tooth trace errors which cannot be measured by the conventional method. Further, the model-based method can be incorporated on the advanced CNC controller based on the new CAM–CNC interface scheme of STEP-NC [STEP (standard for transfer and exchange of product model data) based data model for CAM and CNC interface] as an on-line inspection module. Algorithmic details together with experimental validation results are given.     

Tool-integrated spring back measuring system for automotive press shops

The spring back on car body parts defines their dimensional accuracy. Throughout the production process in press shops the conformity with the geometrical specification is inspected by tactile or optical measuring devices offside the production line in no particular order. To enable an efficient control of dimensional accuracy during production processes, this study deals with the investigation of a tool-integrated measuring system, which generates specific geometrical information for every produced part. On a pilot basis, eddy current sensors for distance measurement are integrated into the tool-support of an inner door panel. The system shows that it is able to detect process variations such as different material batches or variations in blank holder forces and their effect on the forming process, resulting in changes of the car body geometry.     

Selection of an optimum sample size for flatness error estimation while using coordinate measuring machine

In the present day manufacturing environments it is becoming increasingly important to be able to deliver quality products at the right time to the market at competitive costs. The quality, cost and time to market depend not only on the design and manufacturing but also on the inspection process adopted. Design specifications rely on extensive usage of form tolerances to ensure that the functionality of surfaces and features of the product are maximized. The use of the coordinate measuring machines (CMM) has greatly improved the efficacy of form tolerance measurement and is also used as the key device in this work. The focus of this work is to deal with the method and strategies for measurement of flatness error so as to be able to predict the flatness error accurately at reduced sample sizes in batch and mass production setups. Accurate evaluation of flatness will require large sample sizes which increase the cost and time of inspection and hence a need to reduce the sample sizes without compromising on the accuracy. In the absence of robust models that can predict the errors due to manufacturing processes, an alternative technique has been devised to arrive at a reduced sample size. The procedure involves using large sample data inspected on the first component as the basis for evolving smaller sample sizes for subsequent components.Experimental verification of the developed algorithm shows that flatness error can be predicted with sufficient accuracy at small sample sizes.     

基于UG软件的变速箱顶盖重力铸造模具设计

金属型重力铸造相比于砂型铸造来说,铸件的力学性能和尺寸精度更好,生产成本更低,有利于批量化生产。本设计过程全部运用UG7.5软件,利用砂芯来成型产品的内腔和侧孔部分,虽然在制造过程中需要制造两副模具,但是从批量化的生产当中看,还是切实可行的,而且在设计上也更直观,避免了侧抽芯等复杂的模具结构设计,提高了模具精度。     

钛合金环形管成形工艺设计数据库系统的研究

为解决传统环形管成形工艺设计中耗时、费力且设计不精准的难题,避免设计人员进行重复性工作,以Access 2000作为后台管理系统,应用面向对象的Visual Basic 6.0界而开发软件,开发了一套钛合金环形管成形工艺设计数据库系统.该系统集环形管成形工艺、强度校核、弯曲模具以及缺陷知识查询为一体,能快速的进行环形管工艺的确定,实现环形管模具的设计制造,提高了设计精度、缩短了制造周期,同时用户可以不断的更新材料信息,对工程实践具有重要的指导意义.     

板坯库信息化管理系统

板坯库信息化管理系统主要利用现代信息化技术实现对板坯的跟踪控制与管理。硬件上采用L2级（服务器）与L1级（触摸式计算机、PLC）两级计算机控制结构和多传感器检测技术及高稳定的通讯技术;软件中采用大型数据库存储方式和高信息化管理技术、增量编码坐标定位方式。系统稳定可靠,具有较高的管理水平,生产和管理效率得到了极大提高。     

一种简便快捷的发动机排气管位置精度综合检具

采用三坐标测量机抽检发动机排气管位置精度，不能满足生产及质量要求。分析排气管装配技术要求的基础上，运用逆向抽象思维及化繁为简的方法，构想将3套不同定位尺寸的一面两销定位装置集合于一体，设计出能分别检测3种不同规格排气管位置精度的综合检具，并介绍了该检具的制造工艺及使用方法。新检具的全面使用，完全替代了操作复杂的三坐标测量机，将复杂费时的终端抽检变为简便快捷的在线检测；统一了各协作制造厂的检测工具，使排气管的位置精度得到精确控制，极大地提高了检测效率。     

Applications of 3-D solid modelling to coordinate measuring inspection

This paper describes a set of algorithms for the automation of component inspection using coordinate measuring machines. Solid modelling techniques are used to describe the component, and this model is then used to generate a set of inspection points and a collision-free probe path. The model is also used in the analysis of the resulting measurements. The algorithms have been implemented in a system that will handle the range of form, location and attitude tolerances, as defined by BS 308, for planar, cylindrical, conical and spherical features.