Evaluating the unfastening effort in design for disassembly and serviceability

Disassembly is the process of physically separating a product into its parts or subassemblies. Recently, product designers are being challenged to address the concept of 'ease of disassembly' while configuring new designs. This is driven by the need for new products to undergo a design for disassembly and serviceability (DfDS) analysis. DfDS promotes design features and attributes, which reduce the subsequent disassembly costs. The disassembly process commonly involves an unfastening action. In this paper we present the unfastening effort analysis (U-effort) model, which helps designers to evaluate and select their fastener options. The U-effort model was developed from an experimental investigation of the most common fastener types used in industry. For each fastener type, the U-effort model identifies several causal attributes, and uses these to derive the U-effort index for a given case. From our experiments, we found that the most significant causal attributes are usually related to fastener size, shape or operational characteristics. The U-effort model is easily integrated into DfDS analysis schemes. The disassembly times generated from the U-effort model can be used to perform economic analysis of product service and/or end-of-life disassembly operations.