Relationship matrix based automatic assembly sequence generation from a CAD model

Abstract

Currently in industry, design and communication of a product assembly is through the use of computer-aided design (CAD) systems. However, there are no commercial systems that can automatically generate feasible assembly sequence plans. There is past and current academic research in methods to provide automatic assembly sequence planning. Assembly sequence planning using a commercial system often relies on an expert assembly sequence planner, and it is predominantly done manually. This requires a great amount of time and expert knowledge; assembly sequence plans generated may not even be the most efficient. The ability to automatically generate assembly sequence plans will lead to the reduction of planning time, less reliance on the amount of knowledge required, and better plans at earlier stages of the design process. CAD models are based on feature constraints to create and define an assembly. The challenges to automatically generate assembly sequences using CAD models lie in intelligent reasoning and analysis of the modelled assembly data. Based on past research findings, there is a reason to believe that assembly constraints used in CAD assembly models can provide essential information related to the assembly process. This paper presents a system that can analyse and utilize assembly data available from a CAD model to generate assembly sequences. The system also considers a user input as a type of assembly constraint. The system is capable of producing a set of ranked feasible assembly sequence plans for an operator to evaluate. A matrix approach has been adopted to process the information retained from a CAD model. Interference and stability studies are carried out during the creation of assembly sequence plans. The outputs are ranked based on the ease of assembly and the stability of the generated assembly sequence plans. Case studies are used to evaluate the system and the feasibility of the output. A case study using a two stroke engine is presented, which demonstrates how the system generates assembly sequence plans.