STEP/XML based macro data representation for parametric CAD model exchange

Most CAD tools currently do not have advanced capability built in for directly analyzing the feasibility of product assembly during the design stage. As a result, the feasibility of product assembly has to be analyzed using external assembly analysis tools. To integrate external assembly analysis tools with CAD tools, geometrical data from the CAD models must be extracted from CAD files and imported into the assembly analysis tools. To transfer geometrical data between CAD tools and assembly analysis tools, a neutral file format is needed. STEP (standard for the exchange of product model data) is a neutral file format for convenient and reliable data exchange between different design and manufacturing systems. Therefore, STEP is considered as one of the most popular formats for saving designs. As a result, to evaluate designs, extracting geometrical data from CAD-STEP file is important. Comparing with some other currently available methods, first translating STEP file into XML and then using Java DOM to get geometrical information from XML file is much better. This paper explores the process of extracting geometrical data from a CAD-STEP file for assembly sequence planning. A STEPXML translator, Java-XML parser and DTD (document type definition) generator are used on the JDK 1.4 platform. In this project, DOM (document object model) is applied as the API (Application Programming Interface) for XML.

Assemblability analysis and evaluation play a key role in assembly design, assembly operation analysis and assembly planning. This paper proposes an integrated approach to assemblability analysis and evaluation for STEP (STandard for the Exchange of Product model data, officially ISO 10303) based electro-mechanical products. In the paper, two assembly representation models are first brought up and elaborated: the EXPRESS/XML schema based model and the NIST object-oriented UML-based Open Assembly Model (OAM). These two models are then integrated together; the OAM incorporates the EXPRESS/XML schema based assembly model to completely capture the detailed geometric information. Based on STEP, the proposed assembly evaluation approach uses the EXPRESS/XML schema based model as the information source, and the evaluation structure covers not only the assembly parts’ geometric and physical characteristics but also takes into account the assembly operation data necessary to assemble the parts. The feature of this approach is the linkage of the STEP product definition to the fuzzy analytic hierarchy process (AHP) for assembly evaluation. The proposed approach has the flexibility to be used in various assembly methods and different environments. The case study shows that the proposed approach is feasible.

Draft STEP (Standard for the Exchange of Product Model Data) application protocols, developed by the Navy Industry Digital Data Exchange Standards Committee (NIDDESC), have been issued to define the information content of a product model for a ship. The work reported in this paper combines the existing CAD models of the DDG51 Class design with a newly developed non-graphic database so that the overall information content complies with the STEP protocols. This work represents the first-time implementation of the application protocols and is a significant step in the Navy's plan to do the design of variants of the DDG51 Class totally in computer-aided design (CAD). The combined graphic/non-graphic database is referred to as the DDG51 engineering product model. Emphasis has been placed on populating the non-graphic database with the information necessary to perform all required engineering analyses. The basic schema described in this paper may be extended to support other areas of interest, such as logistics support.

ISO10303 STEP (STandard for the Exchange of Product model data) released a suite of application protocols covering the most important product life-cycle activities. The maturity in the development and usage of these standard models was conducted to the redesign of the classical architecture of STEP application protocols to a more agile architecture in order to better fit the emergent technologies and facilitate the understanding, development, reuse, and implementation of normalized reference product data models. This paper introduces the new modular architecture of ISO10303, comparing it with the classic architecture of STEP. Then, it describes the structure of the new modular AP236, concluding with a proposal for a graphical framework for the design and development of normalized modules and new modular application protocols.

Various studies have focused on developing an interface system that could integrate the machining process with CNC (Computer Numerical Control) machine tools by producing tool paths using STEP (Standard for the Exchange of Product model data) file as an input function. Studies to recognize features in STEP file by encoding the data of geometric entities of a CAD (Computer-Aided Design) design has been done by many researchers. However, they only focus on Cutter Location (CL) which eventually describes the machining profile in the x and y planes without considering the depth of the machining feature in the z-axis. Identifying and recognizing machining features in the STEP file is important since STEP is a platform for converting industry-standard CAD systems and software data models. The aim of this paper is to identify profiles of geometric machining features for rectangular fillet blind pockets using the Geometric Data Extraction (GDE) approach. Three cases have been carried out namely single rectangular fillet blind pocket, double rectangular fillet blind pocket and triple rectangular fillet blind pocket. The results were verified by manual graph plotting and automatic graph plotting using CPM 3D Plotter.

Implementing ISO standard 10303 application protocol 224 for automated process planning

Standards are increasingly important for ECAD frameworks. The emerging international standard for the exchange of product model data (CAD data, CAM data,...) is ISO 10303 “Industrial automation systems and integration — Product data representation and exchange”, better known as STEP (STandard for Exchange of Product data). This paper addresses the STEP technology for ECAD databases.

Insufficient technologies made good integration between the die components in design, process planning, and manufacturing impossible in the past few years. Nowadays, the advanced technologies based on Standard for the Exchange of Product model data are making it possible. This article discusses the three main steps for achieving the complete process planning for prismatic parts of the die components. These three steps are data extraction, feature recognition, and process planning. The proposed computer-aided process planning system works as part of an integrated system to cover the process planning of any prismatic part die component. The system is built using Visual Basic with EWDraw system for visualizing the Standard for the Exchange of Product model data file. The system works successfully and can cover any type of sheet metal die components. The case study discussed in this article is taken from a large design of progressive die.

The standard for the exchange of product model data (STEP) is an effort geared towards facilitating the computer-readable exchange of the total information used to define an industrial product. STEP is being released as a set of inter-related parts. Application protocols, the 200-series parts, describe the use of integrated resources satisfying the scope and information requirements for a specific application context. A proposal exists to develop an application protocol for the casting industry. This proposal is currently in abeyance and the effort required to complete it should be enormous. This paper attempts to make an analysis of the expected effort by studying a casting process. The steps required to develop a prototype information model that will capture all product data about one costing process are attempted. The problems related to product data representation and exchange are introduced with an overview of STEP. The casting industry is briefly addressed. The proposed approach in independent development of an application protocol is thoroughly analyzed, including development of a DBMS using NIAM methodology, an interface language to link DBMS to different computer systems via a neutral file exchange format, and EXPRESS. Problems and contributions of the approach are discussed. >

Relationship Between Students’ Spatial Visualization Ability and their Ability to Create 3D Constraint- Based Models from Various Types of DrawingsEngineering graphics educators have been studying the constraint-based modeling strategies ofstudents for approximately 20 years. These studies include students’ modeling strategies,methods of evaluating models, and conceptual framework research. A recent series of studiesinvestigated students’ ability to model parts when given assembly drawing information. Theseinvestigations revealed that the developed modeling test had mixed results when examiningrelationships with measures in the course (e.g., final project and final exam). These studies alsoexamined whether students’ modeling ability was related to their spatial visualization ability.There were positive correlations between the PSVT:R and the modeling test (not all weresignificant) and significant positive correlations between the MCT and the modeling test.Recommendations included repeating the study using a shorter modeling activity, examining amore efficient way of evaluating the models, and conducting qualitative methods for evaluatingstudent modeling strategies.During the fall of 2013, a study was conducted where students completed the PSVT:R and theMCT and then were asked to complete three different modeling tasks. These tasks includedmodeling a part when given an isometric pictorial of the object, modeling a part when given theobject in the context of an assembly drawing, and finally modeling a part when given a detaildrawing of the object. Research questions for this study include the following: Does a simplerrubric provide similar scores as the previous rubric? Is there a relationship between a student’sspatial visualization ability and their ability to model a part from a pictorial, assembly drawing ordetail drawing? Is the MCT still a better predictor of a student’s modeling success than thePSVT:R? This paper will report the results of this study as well as give recommendations forfuture research.

For rapid modelling of ship structure and sharing of product data for a computer-integrated manufacturing system in shipbuilding, this research proposes a data exchange method between two-dimensional drawings and three-dimensional finite element models. The report of the research is followed by appropriately planning the structure of the extracted data based on the Standard for the Exchange of Product Model Data. A set of rules for two-dimensional feature recognition is established, and then the method for the extraction of graphic and non-graphic design information from two-dimensional drawings of transverse sections is presented. An algorithm for rapid modelling of the longitudinal hull structure is proposed, based on data extracted from the transverse sections. This algorithm bypasses the geometric modelling stage required in traditional manual modelling, exclusively making use of the extracted information. The proposal also enriches data exchange, greatly reduces human error in modelling and consequently improves the accuracy of the finite element modelling for the shipbuilding industry.

An approach to accessing product data across system and software revisions

Data Probes are software tools built using the emerging international Standard for the Exchange of Product Model Data -commonly referred to as STEP. A Data Probe is easily created from any information model written in the Express specification language. It is used to view information from the information model for which it was created and is also used to create, edit, or view data that conforms to that information model.

Fixture design and planning is one of the most important manufacturing activities, playing a pivotal role in deciding the lead time for product development. Fixture design, which affects the part-quality in terms of geometric accuracy and surface finish, can be enhanced by using the product manufacturing information (PMI) stored in the neutral standard for the exchange of product model data (STEP) file, thereby integrating design and manufacturing. The present paper proposes a unique fixture design approach, to extract the geometry information from STEP application protocol (AP) 242 files of computer aided design (CAD) models, for providing automatic suggestions of locator positions and clamping surfaces. Automatic feature extraction software “FiXplan”, developed using the programming language C#, is used to extract the part feature, dimension and geometry information. The information from the STEP AP242 file is deduced using geometric reasoning techniques, which in turn is utilized for fixture planning. The developed software is observed to be adept in identifying the primary, secondary, and tertiary locating faces and locator position configurations of prismatic components. Structural analysis of the prismatic part under different locator positions was performed using commercial finite element method software, ABAQUS, and the optimized locator position was identified on the basis of minimum deformation of the workpiece. The area-ratio (base locator enclosed area (%)/work piece base area (%)) for the ideal locator configuration was observed as 33%. Experiments were conducted on a prismatic workpiece using a specially designed fixture, for different locator configurations. The surface roughness and waviness of the machined surfaces were analysed using an Alicona non-contact optical profilometer. The best surface characteristics were obtained for the surface machined under the ideal locator positions having an area-ratio of 33%, thus validating the predicted numerical results. The efficiency, capability and applicability of the developed software is demonstrated for the finishing operation of a sensor cover – a typical prismatic component having applications in the naval industry, under different locator configurations. The best results were obtained under the proposed ideal locator configuration of area-ratio 33%.

Enriching standards-based digital thread by fusing as-designed and as-inspected data using knowledge graphs