This paper presents a comparison study on two design for assembly (DFA) tools, Boothroyd and Dewhurst’s Design for Manufacturing and Assembly software and the Mathieson-Summers connective-complexity algorithm, focusing on the amount of information required from the designer to complete the analysis and the subjectivity of this information. The Boothroyd Dewhurst software requires the user to answer a set of questions about each part and how it is assembled to estimate an assembly time, assembly cost, and to suggest design improvements. The connective-complexity method predicts assembly times based on the physical connectivity between parts within an assembly. The methods are applied to three consumer products and evaluated and compared through five criteria: approximate time to conduct the analysis, predicted assembly time, amount of required input information, amount of subjective information, and number of redesign features provided to the user. The results show that the DFMA software requires the user to go through eight types of information answering a total of forty nine questions per part. Sixteen of these questions are based on subjective information making the analysis nearly a third subjective. The connectivity method requires only two types of information and a total of five questions per part to complete the analysis, none of it being subjective. The predicted assembly times from the connective-complexity DFA method ranged from 13.11% to 49.71% lower than the times predicted by the DFMA software. The results from this comparison can be used to bench mark DFA methods so that their weaknesses can be identified and improved.

The paper presents a tool for selecting appropriate Design for Manufacturing and Design for Assembly rules during product design while considering Design for Disassembly rules and end-of-life recovery conditions. This tool exposes the relations between the various types of design rules and end-of-life recovery parameters. Four different relationship types are developed in this research: recovery conditions and recovery options relationship, Design for Disassembly rules and recovery options relationship, Design for Disassembly rules and recovery conditions relationship, Design for Disassembly rules, and Design for Manufacturing and Design for Assembly rules relationship. The purpose of this research is to build these relations and transform these relationships into a database. The database serves as tool from which design rules can be retrieved by running queries. In addition to design rule retrieval, the tool also shows the relationships with various design rules, recovery options, and recovery conditions. This provides designers with information as to which rules are in conflict and which are complementary for the specific situation under consideration. To illustrate this tool, it is applied to motor-drive assembly and thermal gun sight, which are already design products. Additionally the application of the tool is demonstrated using a hypothetical scenario which involves products like coffee cup, cell phone and stapler.