Assembly Sequence Generation from 3D CAD Models
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Solution Overview
Problem
Existing methods for generating assembly sequences from CAD data of assemblable products face challenges such as incorrect allocation of annotation items, omission of standard parts in large models, and inefficient disassembly path calculation, leading to increased design time and CAD operation response deterioration.
Innovation Solution
An apparatus and method that detect adjacency and connection precedence relationships between parts in a 3D CAD model, automatically identify unconnected parts, and generate assembly sequences by creating directed and assembly graphs, thereby deducing assembly steps and reducing the need for manual correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If standard parts are omitted in large-sized 3D CAD models to improve response speed, then CAD operation response is improved, but assembly sequence generation becomes inaccurate due to missing fastening parts
Solution Approach 1:
The system performs preliminary detection of characteristic shapes (holes, grooves) and their spatial relationships during the CAD modeling phase, even before standard parts are added. This preliminary analysis creates a framework that can later be populated with standard parts automatically, maintaining both fast initial response and accurate final assembly sequences
Solution Approach 2:
The system uses the geometric features already present in the CAD model (holes, grooves, adjacent surfaces) to self-identify where standard parts should be placed. The characteristic shape detection and adjacency relationship analysis enable the system to infer fastening part locations without manual input, allowing accurate assembly sequence generation even when standard parts are initially omitted
2Measurement precision
If interference calculation is performed during disassembly to search for disassembly path, then disassembly path accuracy is improved, but calculation time and complexity increase
Solution Approach 1:
The disassembly path search is segmented into two phases: first, a preliminary phase that identifies disassembly candidates based on connection precedence relationships and adjacency relationships without complex interference calculations; second, a refinement phase that performs interference calculations only for the limited set of identified candidates. This segmentation reduces overall calculation complexity while maintaining accuracy
Solution Approach 2:
The system performs preliminary analysis of connection precedence relationships and adjacency relationships to identify potential disassembly candidates before conducting interference calculations. This preliminary filtering reduces the search space significantly, allowing accurate disassembly path determination with reduced computational complexity
3Quantity of substance
If annotation information and part relationship information are searched to create work contents, then work manual completeness is improved, but information allocation accuracy deteriorates due to shape combination issues
Solution Approach 1:
The system transitions from two-dimensional annotation item allocation to three-dimensional spatial relationship analysis by detecting characteristic shapes and their adjacency relationships in 3D space. This dimensional enhancement enables accurate matching of annotation items to specific geometric features and their spatial contexts, resolving allocation accuracy issues
Solution Approach 2:
The system applies local quality analysis by examining the specific geometric characteristics (cylindrical holes, grooves, adjacent surfaces) and their local spatial relationships rather than applying generic annotation rules. This localized geometric analysis ensures that annotation items are allocated to the correct parts and features with high precision
4Extent of automation
If adjacency relationship and connection precedence relationship are calculated to automatically detect unconnected parts, then assembly sequence automation is improved, but processing time increases
Solution Approach 1:
The automated assembly sequence generation is segmented into distinct processing stages: characteristic shape detection, adjacency relationship calculation, connection precedence relationship calculation, unconnected part detection, and assembly sequence generation. Each stage processes specific information independently, improving automation efficiency and reducing overall processing time through modular computation
Data Source
AI summary
An apparatus for generating assembly steps and an assembly sequence for sequentially assembling a product is provided with: a part detecting section for detecting designated characteristic shapes from the 3D CAD model, detecting a part present in a radial direction of each characteristic shape, and detecting a part present in an axial direction of the detected part; a section for generating a directed graph where a node denotes a part and a directed edge denotes a connection precedence relationship between parts; an assembly graph generating section for generating, an assembly graph where a node denotes a part and an edge denotes an adjacency relationship; a work order adding section for adding work contents and work orders to a list of the detected unconnected parts; and a generating section for generating the assembly sequence and an assembly direction by generating and reversely converting a disassemblable direction and a disassembly sequence.