A flexible inspection cell for machined parts

This paper describes the development of a computer-aided vision system, in a flexible inspection cell, for checking the dimensional accuracy of machined parts. Most vision systems identify parts for which models are already reside in the database, whereas this particular system allows parts for which models are not available in the database to be checked. Also described in the paper is a feature-based approach which this system adopts for identifying the parts.     

Inspection of the machined surfaces using manufacturing data

Accuracy of complex machined parts is usually estimated using coordinate measurement machines. The inspection results can be used to control or monitor a production system. Traditional inspection process of a machined surface commonly compares the resulting manufactured surface with the CAD-model or the nominal designed surface. Although, the result of this CAD-based inspection can be used to accept or reject the machined part, it does not provide the correct information required to study the machining errors and their behaviour. This paper presents a methodology to inspect a machined surface directly based on its actual CAM geometric model. The presented CAM-based inspection methodology can be used to model and understand the real machining errors, which can be utilized for process control, design for manufacturing or closed-loop machining.     

Machining feature-based similarity assessment algorithms for prismatic machined parts

This paper presents algorithms for identifying machined parts in a database that are similar to a given query part based on machining features. In this paper we only consider parts that are machined on 3-axis machining centers. We utilize reduced feature vectors consisting of machining feature access directions, feature types, feature volumes, feature dimensional tolerances and feature group cardinality as a basis for assessing shape similarity. We have defined a distance function between two sets of reduced feature vectors to assess the similarity between them from the machining effort point of view. To assess the similarity between the two parts, one set of reduced feature vectors is transformed in space using rigid body transformations with respect to the other set such that the distance between them is minimized. The distance between the two sets of aligned reduced feature vectors is used as a measure of similarity between the two parts. The existing machined parts are rank ordered based on the value of the distance with respect to the query part. The cost of previously machined parts that have a very small distance from the query part can be used as a basis for estimating the cost of machining the new part.     

A : A tool for identifying and repairing un-machinable shapes in designs

Providing early feedback on the manufacturability of a part design can greatly improve the quality of the product while reducing the time and cost of production. However, the necessary manufacturing knowledge is not always available. Computer tools that can provide this manufacturing knowledge by analyzing a design suggesting changes to improve its manufacturability would be a valuable asset to a designer. To this end, we present an approach to automatically generate redesign suggestions to improve the manufacturability of machined parts. Novel aspects of this approach include the ability to identify un-machinable shapes in a part and transform them into machinable features and to automatically identify the possible shape transformations based on properties of the machining equipment. This increases the scope of redesign generation tools by allowing them to be applied to parts that are not already machinable. We have developed a system called automated redesign for machined parts ( ) that assists users in repairing parts that contain un-machinable shapes.     

CM,RE和CAD/CAM系统集成环境的研究

对三坐标测量系统、联系实际向工程、CAD/CAM系统信息集成中存在的问题进行分析，提出了面向快速逆向设计和制造集成环境的功能模型、关键技术和处理方法。通过建立CM，RE，CAD/CAM系统的集成平台，对样件、模型进行快速测量，并对测量数据进行数据处理、特征重建、几何造型和数控加工处理，以实现对产品样件或模型的快速逆向设计与制造。     

Local enhancement of compressed images

We develop a simple focusing technique for wavelet decompositions. This allows us to single out interesting parts of an image and obtain variable compression rates over the image. We also study similar techniques for image enhancement.Partially supported by U.S. Air Force Office of Scientific Research grant 89-0455 and Defense Advanced Research Projects Agency grant AFOSR 89-0455.     

Structural optimization of as-built parts using reverse engineering and evolution strategies

In industry, some parts are prone to failures or their design is simply sub-optimal. In those critical situations, one would like to be able to make changes to the part, making it lighter or improving its mechanical resistance. The problem of as-built parts is that the original computer-aided design (CAD) model is not available or is lost. To optimize them, a reverse engineering process is necessary to capture the shape and topology of the original design. This paper describes how to capture the original design geometry using a semi-automated reverse engineering process based on measurement provided by an optical 3D sensor. Following this reverse engineering process, a Fixed Grid Finite Element method and evolutionary algorithms are used to find the optimum shape that will minimize stress and weight. Several examples of industrial parts are presented. These examples show the advantages and disadvantages of the proposed method in an industrial scenario. Presented at the 7th World Congress on Computational Mechanics, Los Angeles 2006.     

The control of a quick turnaround cell — An integrated CAD and CAM system

Quick turnaround Cell (QTC) is an integrated software/hardware system for rapid product prototyping. A QTC consists of some engineering workstations, one of a few machine tools, and a vision inspection system. The major objective of the project is to study the integration of CAD, process planning, cell control, and vision inspection. Currently a prototype QTC has been implemented at Purdue Uniersity. It is capable of producing prismatic parts. After a part is designed, it can be machined and inspected automatically. There is no human decision necessary for the planning, part programming, and cell control. The cell controller plays an extremely important role on coordinating all the system functions and providing user and machine interfaces. In this paper we will address the issues encountered in designing the cell control. The structure and the functionality of the specific design will be discussed.     

Automated system for machine tool capacity and utilization

An automated system based on Symphony spreadsheet software has been developed to monitor machine tool utilization and capacity in a small- to medium-sized machine shop. This application compiles reports on annual machine tool requirements and use from production routing data for a shop producing over 100 different small machined parts with batch sizes ranging from 100 to 1000 parts and up to 25,000 parts per year. The operational routings for approximately 30 parts are currently stored in the system. Levels of utilization are analyzed, which aids in determining the need for addition equipment or multiple workshifts, and thereby helps balance the workload and product flow. Valuable information was compiled in a special report for layout of a new shop facility. Group technology cell arrangements of equipment were analyzed for capacity and utilization. Many Symphony spreadsheet and data base management features were used to produce this program. The final system incorporated menu systems for users unfamiliar with this spreadsheet software.     

Signature analysis and defect detection in layered manufacturing of ceramic sensors and actuators

This paper presents the concept of a process signature for the use of online signature analysis and defect detection in the layered manufacturing (LM) of ceramic sensors and actuators. To achieve the high quality of parts built by the fused deposition of ceramics (FDC), an online process-monitoring system is implemented to detect the processing defects. Using a process signature extracted from the image of a layer captured by the monitoring system, an ideal image is created that is then compared to the original image to detect and identify the defects. Some results of signature analysis and defect detection for single-material and multi-material parts are also presented.Received: 22 July 1999, Accepted: 21 October 2001, Published online: 29 October 2003 Correspondence to: Mohsen A. JafariThis work was supported by the Office of Naval Research under grant # N-0014-96-1-1175. Ref. US Patent # S-5738817, April 14, 1998.     

A process control system for cryogenic CNC elastomer machining

The application of cryogenics in manufacturing has previously received significant attention in supporting manufacturing processes. This paper explores the continued application of cryogenic manufacturing for producing personalised products. This paper presents the novel concept of cryogenic CNC machining of elastomers and the development of a process control system for cryogenic CNC machining. The control process is illustrated alongside material dependent machining data and example soft elastomer machined parts. An enhancement to the process is also detailed within a closed loop thermally monitored cryogenic CNC machining facility.     

Web系统维护中的逆向工程研究

分析了软件维护当中的问题,提出了一种针对Web系统的逆向工程方法.该方法以Web站点为输入分析页面的源码,从页面链接和交互进行逆向,构建出站点的部署和任务模型,从而直观地表示出对维护人员有帮助的系统信息,同时介绍了笔者自行开发的逆向工程辅助工具.通过该方法,维护人员能够直接得到系统信息, 而不必去分析源代码,克服了缺乏设计文档的困难.通过一个Web站点的逆向实例,演示了这种方法.     

Optimization of machine setup and tooling using the principles of group technology

A number of the problems which arise in batch manufacturer are a result of the high variety of components produced. One of the basic features of group technology is to reduce this variety by effectively sorting components requiring similar processes into families to increase efficiency and productivity.This paper presents a research project to study and optimize the choice of toolings, tooling setups and scheduling of component parts to be machined on different kinds of turning machines. A computer program called OPSSP (OPtimization of Setup and Scheduling of Parts) was developed to achieve this goal. Furthermore, as a step toward the completion of automated process planning of parts, the system is designed to select appropriate holders for cutting tools and prepare detailed work instructions containing the clamping device and a list of required tooling for parts.The verification studies indicated that the system is capable of producing realistic practical results and can be effectively be used to achieve effective tooling, setup, and processing of parts.     

Web系统维护中的逆向工程研究

分析丁软件维护当中的问题,提出了一种针对Web系统的逆向工程方法。该方法以Web站点为输入分析页面的源码,从页面链接和交互进行逆向,构建出站点的部署和任务模型,从而直观地表示出对维护人员有帮助的系统信息,同时介绍了笔者自行开发的逆向工程辅助工具。通过该方法．维护人员能够直接得到系统信息,而不必去分析源代码,克服了缺乏设计文档的困难。通过一个web站点的逆向实例,演示了这种方法。     

Extracting and Sharing Knowledge from Medical Texts

In recent years,we have been developing a new framework for acquiring medical knowledge from Encyclopedic texts.This framework consists of three major parts.The first part is an extended high-level conceptual language (called HLCL 1.1)for use by knowledge engineers to formalize knowledge texts in an encyclopedia.The other part is an HLCL 1.1 compiler for parsing and analyzing the formalized texts into knowledge models. The third part is a set of domain-specific ontologies for sharing knowledge.     

Descriptive databases in some design manufacturing environments

A comprehensive set of software development tools - BOS Infrastructure Software - is introduced. This system enables purpose built datastructures to be constructed for a range of engineering disciplines. The development of BOS Building Design Systems containing three dimensional assembly datastructures and comprehensive parts databases, and Engineering Management Systems describing product assemblies are introduced.     

Granularity issues for solving polynomial systems via globally convergent algorithms on a hypercube

Polynomial systems of equations frequently arise in many applications such as solid modelling, robotics, computer vision, chemistry, chemical engineering, and mechanical engineering. Locally convergent iterative methods such as quasi-Newton methods may diverge or fail to find all meaningful solutions of a polynomial system. Recently a homotopy algorithm has been proposed for polynomial systems that is guaranteed globally convergent (always converges from an arbitrary starting point) with probability one, finds all solutions to the polynomial system, and has a large amount of inherent parallelism. There are several ways the homotopy algorithms can be decomposed to run on a hypercube. The granularity of a decomposition has a profound effect on the performance of the algorithm. The results of decompositions with two different granularities are presented. The experiments were conducted on an iPSC-16 hypercube using actual industrial problems.This work was supported in part by AFOSR grant 85-0250.     

Three-dimensional optical measurements and reverse engineering for automotive applications

The paper describes a very special and suggestive example of optical three-dimensional (3D) acquisition, reverse engineering and rapid prototyping of a historic automobile, a Ferrari 250 Mille Miglia, performed primarily using an optical 3D whole-field digitiser based on the projection of incoherent light (OPL-3D, developed in our laboratory). The entire process consists in the acquisition, the point cloud alignment, the triangle model definition, the NURBS creation, the production of the STL file, and finally the generation of a scaled replica of the car.The process, apart from the importance of the application to a unique, prestigious historic racing car, demonstrates the ease of application of the optical system to the gauging and the reverse engineering of large surfaces, as automobile body press parts and full-size clays, with high accuracy and reduced processing time, for design and restyling applications.     

Analysis of Sensing Errors for Manufacturing Geometric Objects from Sensed Data

In this work we address the problem of manufacturing machine parts from sensed data. Constructing geometric models for objects from sensed data is the intermediate step in a reverse engineering manufacturing system. Sensors are usually inaccurate, providing uncertain sensed information. We construct geometric entities with uncertainty models from noisy measurements for the objects under consideration, and proceed to do reasoning on the uncertain geometries, thus, adding robustness to the construction of geometries from sensed data.     

Adaptive restoration of complex geometry parts through reverse engineering application

After a certain number of hours of running, no two mechanical components are completely the same due to normal wear or foreign object damage. A nominal CAD model from a component designer is different from its corresponding worn one and therefore cannot be directly used for tool path generation for build up and machining repair processes. This is the main reason that most repair process used for complex geometry parts, such as gas turbine blades, is currently carried out manually and is called the “Black Art”.This paper proposes a defects-free model-based repair strategy to generate correct tool paths for build up process and machining process adaptive to each worn component through the reverse engineering application. Based on 3D scanning data, a polygonal modelling approach is introduced in this paper to rapidly restore worn parts for direct use of welding, machining and inspection processes. With this nominal model, this paper presents the procedure to accurately define and extract repair error, repair volume and repair patch geometry for the tool path generation, which is adaptive to each individual part. The tool paths are transferred to a CNC machine for the repairing trials. Further research work is performed on repair geometry extraction algorithm and repair module development within the reverse engineering environment.