Reorganizing CAD Assembly Models (as-Designed) for Manufacturing Simulations and Planning (as-Built)

2004 ◽  
Vol 4 (2) ◽  
pp. 98-108 ◽  
Author(s):  
Uma Jayaram ◽  
YoungJun Kim ◽  
Sankar Jayaram ◽  
Venkata K. Jandhyala ◽  
Tatsuki Mitsui
Keyword(s):  
Hybrid Method ◽  
Assembly Planning ◽  
Cad Model ◽  
Assembly Model ◽  
Assembly Sequence ◽  
Cad Systems ◽  
Cad System ◽  
Planning Tools ◽  
Assembly Constraints ◽  
Assembly Models

A CAD assembly model is a collection of components, comprised recursively of various levels of individual parts and sub-assembly models. Although the overall geometry in the CAD assembly model accurately represents the final finished product, this model is often meaningless from a manufacturing planning and simulation point of view. The grouping of the components into sub-assemblies and the assembly sequence implied by the CAD model does not accurately represent the manufacturing/assembly sequence or process. Reordering, regrouping, and modifying existing sub-assemblies, or creating new sub-assemblies in the CAD model may be needed to ensure this correspondence for simulation or assembly planning tools that derive the manufacturing sequence directly from the CAD system. Although this task can be performed using the existing functionality of the CAD system, it quickly becomes unwieldy for large industry-grade models due to the assembly constraints and relationships in place during the model creation. In industry today, there are several digital mockup and assembly planning tools that greatly outstrip the ability of CAD systems in loading complete models and creating assembly plans. Methods to organize the CAD model assembly quickly and easily for use in these systems, and to record the “as manufactured” assembly in the CAD data format are needed to close the loop and ease the transfer, storage, and maintenance of model data between the CAD systems, PDM systems, and these new age planning and mockup systems. In this paper, a new hybrid method is proposed to provide this functionality. Of key significance is the fact that using this approach, polygonal representations of any new or modified sub-assemblies designated in the reorganized hierarchy can be produced and that the original constraints used in the original assembly are transformed in a consistent manner to the new components. In addition, corresponding property files for the new components can be created for use in the assembly planning tool. In order to validate this hybrid approach, the time required to rearrange the assembly hierarchy and output the required information using both methods are compared–1) the traditional method using the CAD system alone, and 2) the new hybrid system. A statistical analysis using three treatment factors indicates that if the number of components is more than 15, then it is far more efficient to use the hybrid method over the CAD system by itself. This hybrid method implementation has now been used very successfully in virtual assembly simulations of many industry models, some with several hundred components, provided by various industry partners.

CAD Model Assembly Hierarchy Reorganization for Application in Virtual Assembly: A Hybrid Approach Using the CAD System and a Visualization Tool

2003 ◽  
Author(s):  
YoungJun Kim ◽  
Uma Jayaram ◽  
Sankar Jayaram ◽  
Venkata K. Jandhyala ◽  
Tatsuki Mitsui
Keyword(s):  
Hybrid Method ◽  
Hybrid Approach ◽  
Virtual Assembly ◽  
Assembly Planning ◽  
Visualization Tool ◽  
Assembly Model ◽  
Cad System ◽  
Assembly Sequences ◽  
Component Assembly ◽  
Time Required

The hierarchy of assembly components in a CAD assembly model is rarely a true representation of the sequence of assembly of these components during manufacturing. Thus, any assembly planning or evaluation software system needs to re-order and re-group the various components of the CAD assembly model to reflect the sequence of component assembly. Although all parametric CAD systems allow reorganization of the assembly tree, it is a difficult and timeconsuming process due to the relationships and constraints between the various components. We propose an alternative hybrid method that couples the CAD system and a visualization tool that supports reorganization, while preserving data, to allow fast and easy rearranging of the assembly hierarchy. Also, after the reorganization, polygonal representations of the new sub-assemblies are created and the original constraints are also transformed in a consistent manner. As a next logical step, we compare the time required to rearrange the assembly hierarchy using both methods — the CAD system alone and the hybrid system. A statistical analysis using three treatment factors indicates that if the number of components is more than 15, then it is more efficient to use the hybrid method over the CAD system. The overarching goal was to allow fast and efficient creation of different assembly hierarchies to allow the corresponding assembly sequences to be verified in a virtual assembly application that derives its models and constraints from the assembly hierarchy in the CAD system. We have implemented the method to allow the successful reorganization and virtual assembly verification of many industry models, some with several hundred components, provided by various industry partners.

Computer Aided Generation the Assembly Process Files for Virtual Assembly

2012 ◽  
Vol 201-202 ◽  
pp. 1008-1012
Author(s):  
Xiang Hua Zhang ◽  
Guo Hong Dai ◽  
Feng Xie ◽  
Xiao Ying Dong
Keyword(s):  
Virtual Assembly ◽  
Assembly Planning ◽  
Cad Model ◽  
Assembly Process ◽  
Assembly Model ◽  
Assembly Sequence ◽  
Generation System ◽  
Computer Aided ◽  
Speed Reducer ◽  
Set Up

Computer Aided Assembly Process Planning is a method of automatically generating assembly process files with computer. This paper describes an integrated assembly process files generation system for virtual assembly. The objectives of this study are to integrate assembly planning of a product with its CAD model, generate a correct and practical assembly sequence and establish a software system to generate the assembly process files. The method of generating assembly process charts for virtual assmbly is researched. The system framework of generating assembly process charts is been set up. The assembly model information that needed for the assembly process charts generation is analyzed. The expression method of assembly sequence and arithmetic of generating assembly process charts is put forward. A speed reducer is used as an example to check the system.

Functional Interface-Based Assembly Modeling

2005 ◽  
Author(s):  
James R. Stoddard ◽  
Marvin Law
Keyword(s):  
Full Range ◽  
Tolerance Analysis ◽  
Assembly Model ◽  
Assembly Modeling ◽  
Cad System ◽  
Kinematic Theory ◽  
Analysis Application ◽  
Functional Interface ◽  
Assembly Constraints ◽  
Geometric Variation

Current CAD system approaches to assembly representation do not support the full range of needs for an assembly model. They cannot account for the natural manufacturing and assembly variability that occurs in the assembled interfaces. The current solvers work well for idealized assembly design behaviors at nominal conditions, but in order to make accurate predictions about assembly performance and product quality the variability of the assembled interfaces must be comprehended in the assembly model. This paper will outline two key issues to support a robust approach to assembly modeling based on characterizing the true mating surface contact between parts in the assembly. These assembly interface definitions are adaptable enough to achieve an exact constraint design to ensure a stable analysis. These approaches are based in kinematic theory and support the efficient solution of the assembly constraints in the presence of geometric variation. An example of this approach within the context of a tolerance analysis application will be presented.

scholarly journals A multi-user selective undo/redo approach for collaborative CAD systems

2014 ◽  
Vol 1 (2) ◽  
pp. 103-115 ◽  
Author(s):  
Yuan Cheng ◽  
Fazhi He ◽  
Bin Xu ◽  
Soonhung Han ◽  
Xiantao Cai ◽  
...  
Keyword(s):  
Cad Model ◽  
Feature Combination ◽  
Collaborative Systems ◽  
Cad Systems ◽  
Cad System ◽  
Design Error ◽  
Engineering Design Process ◽  
Dependency Relationship ◽  
Cad Models ◽  
Remote Sites

Abstract The engineering design process is a creative process, and the designers must repeatedly apply Undo/Redo operations to modify CAD models to explore new solutions. Undo/Redo has become one of most important functions in interactive graphics and CAD systems. Undo/Redo in a collaborative CAD system is also very helpful for collaborative awareness among a group of cooperative designers to eliminate misunderstanding and to recover from design error. However, Undo/Redo in a collaborative CAD system is much more complicated. This is because a single erroneous operation is propagated to other remote sites, and operations are interleaved at different sites. This paper presents a multi-user selective Undo/Redo approach in full distributed collaborative CAD systems. We use site ID and State Vectors to locate the Undo/Redo target at each site. By analyzing the composition of the complex CAD model, a tree-like structure called Feature Combination Hierarchy is presented to describe the decomposition of a CAD model. Based on this structure, the dependency relationship among features is clarified. B-Rep re-evaluation is simplified with the assistance of the Feature Combination Hierarchy. It can be proven that the proposed Undo/Redo approach satisfies the intention preservation and consistency maintenance correctness criteria for collaborative systems.

Preserving Design Intent in Data Integration Between Virtual Prototyping and CAD Systems

1998 ◽  
Author(s):  
Sankar Jayaram ◽  
Uma Jayaram ◽  
Robert Kreitzer
Keyword(s):  
Information Needs ◽  
Virtual Prototyping ◽  
Typical Feature ◽  
Test Case ◽  
Cad Model ◽  
Original Design ◽  
Design Intent ◽  
Cad System ◽  
Cad Models ◽  
Assembly Constraints

Abstract State of the art CAD/CAM technology enables the capture of user design intent through the use of assembly constraints, features, parameters, etc. However, due to the large size of the CAD models, engineers are using other virtual prototyping methods for visualization and complete assembly analysis. Constraint and parameter information is lost in the transfer of models from the CAD system to the virtual prototyping systems. In virtual prototyping systems, users typically have tools to modify the location of an assembly component. In order to maintain model validity, procedures need to be developed to transfer these modifications back to the CAD system while maintaining the design intent of the original CAD user. In other words, how do we take information about changes to absolute or relative location and orientation of a component and transform this to updated constraint and parametric information in the original CAD model? In this paper, we address this need to update the constraints and parametric information of a CAD model based on location and orientation changes communicated from a virtual prototyping system. After analyzing and categorizing the assembly constraints in a typical feature-based CAD system, we propose a methodology to decide what information needs to be updated, and a procedure to update the information — all based on the original design intent captured in the constraints. The results of a test case to validate the methodology are also presented.

Exchange of parametric assembly models based on neutral assembly constraints

2019 ◽  
Vol 27 (4) ◽  
pp. 285-294 ◽  
Author(s):  
Youngki Kim ◽  
Hanra Lee ◽  
Mutahar Safdar ◽  
Tahir Abbas Jauhar ◽  
Soonhung Han
Keyword(s):  
Computer Aided Design ◽  
Boundary Representation ◽  
Assembly Model ◽  
Parametric Approach ◽  
Model Data ◽  
Computer Aided ◽  
Design Systems ◽  
Aided Design ◽  
Assembly Constraints ◽  
Assembly Models

It is difficult to exchange parametric assembly models using conventional neutral formats such as the standard for the exchange of product model data or the initial graphics exchange specification. These formats only support the boundary representation information that leads to the inability to perform parametric re-evaluation, once a model is exchanged. In order to exchange parametric information along with the design intent, a design history-based macro-parametric approach was proposed. Our method is macro-parametrics approach, however, supported only the exchange of individual part models. As most of the products are manufactured in assemblies, where several components are connected with multiple constraints, it is necessary to exchange the assembly model data. To overcome the issue of post-exchange editability, a collection of neutral assembly commands was introduced to extend the capabilities of the macro-parametric approach. A set of neutral assembly constraints was defined and a system for exchanging the parametric assembly models was implemented. An assembly model consisting of coaxial and incidence constraints was successfully exchanged between two commercial computer-aided design systems: CATIA and NX. It was possible to re-evaluate the assembly model parametrically after the exchange. The method can be further extended to exchange the remaining constraint types in different commercial computer-aided design systems.

Analysing Mechanical Systems in Domestic and Foreign CAD Systems

2018 ◽  
pp. 10-17
Author(s):  
V. A. Martynyuk ◽  
V. A. Trudonoshin ◽  
V. G. Fedoruk
Keyword(s):  
Sheet Material ◽  
The Finite Element Method ◽  
Cad Systems ◽  
Cad System ◽  
Software Products ◽  
Foreign Products ◽  
Nonlinear Algebraic Systems ◽  
Software Product ◽  
Pipeline Design ◽  
The Mathematical Model

The article considers applications of foreign CAD-systems in creating the challenging projects at domestic enterprises and design bureaus. As stated in the article "... presently, there is no domestic CAD-system that could completely replace such foreign products as NX, CATIA, Credo". Besides, due to international cooperation in creating the challenging projects (for example, the project to create a modern wide-body aircraft, proposed jointly with China), it makes sense to use the worldwide known and popular CAD systems (the aforementioned NX, CATIA, Credo). Therefore, in the foreseeable future, we will still have to use foreign software products. Of course, there always remains a question of the reliability of the results obtained. Actually, this question is always open regardless of what software product is used - domestic or foreign. This question has been haunting both developers and users of CAD systems for the last 30 to 40 years. But with using domestic systems, it is much easier to identify the cause of inaccurate results and correct the mathematical models used, the methods of numerical integration applied, and the solution of systems of nonlinear algebraic systems. Everything is much more complicated if we use a foreign software product. All advertising conversations that there is a tool to make the detected errors available to the developers, remain only conversations in the real world. It is easily understandable to domestic users, and, especially, to domestic developers of similar software products. The existing development rates and competition for potential buyers dictate a rigid framework of deadlines for releasing all new versions of the product and introducing the latest developments into commercial product, etc. As a result, the known errors migrate from version to version, and many users have accepted it long ago. Especially, this concerns the less popular tools rather than the most popular applications (modules) of a CAD system. For example, in CAD systems, the "Modeling" module where geometric models of designed parts and assembly units are created has been repeatedly crosschecked. But most of the errors are hidden in applications related to the design of parts from sheet material and to the pipeline design, as well as in applications related to the analysis of moving mechanisms and to the strength or gas dynamic analysis by the finite element method.The article gives a concrete example of a moving mechanism in the analysis of which an error was detected using the mathematical model of external influence (a source of speed) in the NX 10.0 system of Siemens.

Applications of Mating Conditions in Assembly Sequence Planning Task

1998 ◽  
Author(s):  
Pongsak Dulyapraphant ◽  
Tulga Ozsoy
Keyword(s):  
Degrees Of Freedom ◽  
Tolerance Analysis ◽  
Assembly Sequence Planning ◽  
Assembly Model ◽  
Assembly Sequence ◽  
Kinematics Analysis ◽  
Sequence Planning ◽  
Planning Task ◽  
Intuitive Interface ◽  
Mating Conditions

Abstract Because of their intuitive interface, mating conditions have been prevalently used in assembly modelling. Besides their use for modelling purposes, other type of information, such as spatial relationships between parts and local degrees of freedom, can be directly derived from mating conditions. This information in turn can be used in various engineering analysis applications, such as kinematics analysis or automatic tolerance chain generation for tolerance analysis. In this paper, application of mating conditions in an assembly sequence-planning task is investigated. The proposed approach mainly engages the mating information represented in the CAD assembly model to automatically generate sequence plans based on the minimization of the number of assembly directions.

Assembly Modeling for 3D Component Based on Polychromatic Sets

2011 ◽  
Vol 411 ◽  
pp. 388-392 ◽  
Author(s):  
Yun Long Li ◽  
Jian Min Gao ◽  
Lei Shi ◽  
Song Wang
Keyword(s):  
Information Matrix ◽  
Spatial Location ◽  
Assembly Sequence Planning ◽  
Assembly Model ◽  
Assembly Sequence ◽  
Assembly Modeling ◽  
Sequence Planning ◽  
Location Modeling ◽  
Dynamic Interference

In order to improve the efficiency of assembly modeling and provide a complete assembly model for assembly sequence planning (ASP), a method of assembly modeling based on polychromatic sets (PS) is proposed. Firstly, the assembly information of 3D Component is obtained by API function in SolidWorks. In addition, assembly incident matrix, information matrix and mapping matrix are built. On the basis of these matrixes, a method of location modeling is explored. The interference relation matrix is developed by judging the spatial location and analyzing dynamic interference relation among parts. Finally, a case study is given to verify the method.

Micro-Assembly Sequence and Path Planning Using Subassemblies

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Vinoth Venkatesan ◽  
Joseph Seymour ◽  
David J. Cappelleri
Keyword(s):  
Path Planning ◽  
Search Algorithm ◽  
Assembly Sequence Planning ◽  
Assembly Sequence ◽  
Micro Assembly ◽  
Final Assembly ◽  
Custom Made ◽  
Planning Algorithm ◽  
Path Planning Algorithm ◽  
Assembly Constraints

This paper presents a novel assembly sequence planning (ASP) procedure utilizing a subassembly based search algorithm (SABLS) for micro-assembly applications involving geometric and other assembly constraints. The breakout local search (BLS) algorithm is adapted to provide sequencing solutions in assemblies with no coherent solutions by converting the final assembly into subassemblies which can be assembled together. This is implemented using custom-made microparts which fit together only in a predefined fashion. Once the ASP is done, the parts are manipulated from a cluttered space to their final positions in the subassemblies using a path-planning algorithm based on rapidly exploring random tree (RRT*), a random-sampling based execution, and micromanipulation motion primitives. The entire system is demonstrated by assembling LEGO® inspired microparts into various configurations which involve subassemblies, showing the versatility of the system.

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