CAD Database Research Articles

Automated restoration of engineering drawings into a CAD data base

With the increasing use of computers in the area of design and manufacture, a major problem being faced by the industry today is that of getting existing product information in the form of paper drawings into a suitable computer data base. This paper presents techniques for preprocessing and vectorizing scan digitized images of engineering drawings for automatically transferring the resulting data to commercially available CAD/CAM systems. The preprocessing steps include noise removal, void filling, image segmentation, line thinning and contour extraction. Algorithms for raster-to-vector conversion capable of recognizing and fitting straight-line segments, circles, arcs, and conic sections are presented along with results obtained from actual machine drawings.

Automated Group Technology Part Coding From a Three-Dimensional CAD Database

A system of software, named CODER, has been written which can analyze the solid model of a part and generate a group technology part code through the identification of form features. The CODER algorithm is bottom-up in nature, first searching for small form-features and then constructing macro-features from the small elements. The program has been implemented using logic programming techniques and consists of facts, describing the part, which must be searched to satisfy rules defining the form-features. The rules and facts are written in Prolog. The facts are generated automatically in Prolog from the ROMULUS2 solid modeler. Rules can define form-features specific to a particular coding scheme and, therefore, form a code-specific knowledge base. The significance of this research is seen when applied to the many designs which have been generated on wire frame CAD systems in the past and, which, if converted to solid models, could be automatically coded for variant process planning, design retrieval and other applications germane to part coding. The algorithm is written in a combination of Prolog, Lisp and S.I™3.

Computer-aided design of extrusion dies

In this paper, a computer-aided design system of extrusion dies is described. In the development of the CAD system, a hierarchical data structure called locating tree was used to describe extrusion dies and to store the information on how all the components in a die assembly are combined. Based on the data structure, the conceptual design and logical design of the CAD data base system were carried out.

Static grip selection for robot‐based automated assembly systems

AbstractIn this article we present an algorithmic approach to determine the suitable grasp of an object in an automated assembly environment. The algorithm is based on the available object surfaces and the initial and final task constraints and gripper characteristics. If the imposed task and gripper constraints do not allow a possible grasp, intermediate motions may need to be made to reorient the part. Once a set of possible grasps which statisfy task and gripper constraints are found, the stability of each grasp is analyzed using screw theory. An optimal grasp is one which minimizes the grasping forces over the possible set of grasps. Results utilizing our methodology are presented. Our method can be interfaced with CAD database such as a solid modelling system based on boundary representation for automatic selection of grasping configurations.

CAD-Based 3D Object Representation for Robot Vision

This article explains that most existing vision systems rely on models generated in an ad hoc manner and have no explicit relation to the CAD/CAM system originally used to design and manufacture these objects. The authors desire a more unified system that allows vision models to be automatically generated from an existing CAD database. A CAD system contains an interactive design interface, graphic display utilities, model analysis tools, automatic manufacturing interfaces, etc. Although it is a suitable environment for design purposes, its representations and the models it generates do not contain all the features that are important in robot vision applications. In this article, the authors propose a CAD-based approach for building representations and models that can be used in diverse applications involving 3D object recognition and manipulation. There are two main steps in using this approach. First, they design the object's geometry using a CAD system, or extract its CAD model from the existing database if it has already been modeled. Second, they develop representations from the CAD model and construct features possibly by combining multiple representations that are crucial in 3D object recognition and manipulation.

Intelligent reasoning for process planning

Turbo- capp is an intelligent process planning system. The system is able to: (1) interpret geometric data from a 2-1/2D cad system, (2) extract surface features in the cad database, (3) check design consistency of geometric dimensioning and tolerancing, (4) manage an extensive manufacturing knowledge base, (5) update the knowledge base by interacting with experienced planners (learning), and (6) perform intelligent reasoning based on extracted machined surfaces and their relationships with surface finish, geometric dimensions and tolerances, current machine configurations, and available tools in order to generate alternative process plans.

Automated clasification and coding based on extracted surface features in a CAD data base

Group Technology is recognised as one of the best solutions to resolve the problems in a modern manufacturing system. A sound classification and coding system is the basis of successful implementations of GT concept. However, human interpretation of engineering drawings is required during the coding process. In order to eliminate this human interpretation, an algorithm for automatically extracting surface features of symmetrical rotational parts was developed. This algorithm is used as the front-end of an automated classification and coding system. The methodology is detailed and an implementation procedure for generating KK3 GT codes is described along with examples.

An electron beam test system linked with a CAD database

In this paper, the advantages of shorter setup time and ease of operation achieved by linking a CAD system to an electron beam test system are presented. More specifically, by referring to mask pattern data in a CAD database, automatic positioning can be achieved within an accuracy of 0.25 μm to match any designated target position specified on the terminal screen. In addition, automatic generation of a circuit test vector can be realized with a significant decrease in the required setup time.

Expert System for Inspection Planning

An expert inspection task planning system for Coordinate Measuring Machines(CMM) is developed in PROLOG. It is generative in nature and is bused on a feature-oriented computer-aided modelling system which has been developed in association with the planning system. The planning system takes into consideration the CMM characteristics, inspected part function and geometric properties, geometric tolerancing theory as well as the data extracted from the modelling system. New ideas regarding feature accessibility, feature representation in terms of the geometric elements used by CMM, inspection priority of datum features, measurement grouping according to the nature of geometric elements, checking all possible accessible features before changing a probe and/or part orientation, grouping tolerance checking tasks together based on corresponding datums, etc. and associated algorithms are proposed and implemented in this reseach. These concepts were verified and found to be feasible. Syntactic Pattern Recognition technique is used to identify a part directly from a feature-based CAD database from inspection planning point of view. The developed Feature-Oriented Modelling and Planning System, using artificial intelligence techniques, is discussed. Inspection knowledge representation and planning logic are described and illustrated with examples. Sample planning rules and inspection plan are also included. It is believed that this research can provide some useful contributions towards the development of automated inspection task planning, systems especially for coordinate measuring machines.

CAE application for the preparation of structural dynamic models

The manual activities involved in the preparation of large dynamic structural models can be substantially eliminated by using CAE methods. Additionally, the possibility of errors is reduced. All information relating to geometry or design loads can be extracted from the CAD data base, and is visualized on the screen. It can be forwarded with the corresponding software for the preparation of the model. The control of the model preparation process is supported by the standard software of the operating system. The prepared input data is written on a file to be transferred for execution. However, if different operating systems are used for the CAD part and for the FE-analysis part, a suitable interface is requested. An interface procedure is outlined for the preparation of a lumped-mass-beam model.

Functional specification for CAD databases

Techniques for handling CAD data, and the development of a comprehensive programme for integrating engineering software tools, which are to share CAD data, remain open issues in CAD research. The importance of addressing database problems in such endeavours is well known. However, before problems can be solved they must be clearly defined, and a clear definition of the CAD database problem has yet to be provided. In fact, the CAD database literature bemoans the lack of even a comprehensive functional specification for CAD databases. In this paper, results of research into the problems of CAD databases are reported in the form of a twenty point functional specification for CAD databases.

Costing the benefits of CAD-based ATE

Many manufacturers have already invested in computer-aided design equipment for the layout of printed circuit boards. The CAD database can be used to generate information for automated test and computer-aided repair, resulting in further dramatic savings in time and labour costs.

Costing the benefits of CAD-based ATE

Many manufacturers have already invested in computer-aided design equipment for the layout of printed circuit boards. The CAD database can be used to generate information for automated test and computer-aided repair, resulting in further dramatic savings in time and labour costs.

A model and its implentation in a practical CAD/CAM database

A practical CAC/CAM database system concept and a CAD specialized database are discussed. For conforming to practical design environments, the CAD/CAM database system is organized with three-layered databases, global, local and working databases. In this database organization, the working database which si a CAD specialized database id characterized by: - The information of a CAD data model based on the relational model, mixed with the network model to represent production-part structures;- Variable-length data manipulation to process non-structured data colection of unfixed number elements;- A vie mechanism to improve data independency;- FAst processing for designer-system interactions.From its comparison with the conventional relational and or CODASYL database systems, it has been seen that this system can manipulate a CAD database three to ten times as fast as these systems.

Integrating CAD and CAM through automated process planning

Computer-aided process planning is an important function in the integration of CAD and CAM. There are two approaches in computer-aided process planning— variant and generative. The generative is more suitable to CAD/CAM integration because it can synthesize a process plan. The success of developing a generative process planning system is dependent on the CAD interface and process capability analysis, The direct interface with CAD eliminates the tedious data preparation for a process planning system (i.e., it eliminates coding). The process capability analysis provides an information base for process and sequence selection. This paper presents a generative process planning system—TTPPS (Totally Integrated Process Planning System). TIPPS uses a boundary representation from a CAD database for a part. A user applies the crosshair cursor on a graphics terminal and a menu display to specify surfaces to be machined. The system then utilizes the information stored in a process knowledge base to determine manufacturing processes, sequence, cutting parameters and time estimation. The geometric modelling, process modelling, decision mechanism and a planning example are discussed.

Semi Autonomous Systems for Automatic Assembly

The users of programmable machines are constantly increasing the demands on the ‘teach’ facility provided by the operating systems. There are practical limits to the extent to which such a ‘teach’ facility can fulfill these requirements. This is even more so in the case of the off-line ‘teach’, which is becoming more common and often utilises the CAD data base. The author will explain his dual approach in complementing the ‘teach’ facility by autonomous adaptable systems, which will allow the ‘teach’ to be carried out in a coarse manner, thus reducing the ‘teach’ effort and also relaxing the precision specification of the hardware. These systems will allow for the variations in the immediate manufacturing environment (component variation, inaccuracy of components' placement, etc). Units described in the paper are of integral design equipped with sensors, local processing power and local actuation. The units are developed to be placed on the machinery used for automatic assembly, which may have either hard automation or robotic form.

Educational requirements for CAD in industry

The number of CAD-systems installed in industry is growing at a rapid rate in terms of volume and in terms of variety of applications. In order to increase productive CAD-applications in an appropriate manner various measures have to be taken. The most important one concerns the human aspect in general and educational measures in particular, since these mandate the longest lead times. Computer science and the designers knowledge, i.e. mechanical engineering, are the subjects of prime importance considered in this article. To some varying degree, knowledge of both is a must for all concerned. Graduates of universities have so far been offered few opportunities during their formal education. Too much is presently left to industry with respect to CAD education. At the same time the range of CAD-application in terms of model-complexity, data structures and communications is growing from drafting oriented single work stations towards company wide integrated approaches. This will eventually change the corporate data structure. Integration will then foster some kind of CAD data base administrator among other additional jobs descriptions. As a consequence the variety of job descriptions will grow wider as CAD becomes the standard mechanism to support all activities of design.

Data definition and manipulation languages for a CAD database

In this paper the main features of ARDBID (A Relational Database for Interactive Design) have been described. An overview of the organization of the database has been presented and a detailed description of the data definition and manipulation languages has been given. These have been implemented on a DEC 1090 system.