QFD-Based TOPSIS Methodology for Material Selection

Introduction

The successful design and development of an engineering component is highly dependent on appropriate selection of material to manufacture the component. It is essential to focus on material selection during the conceptual stage of mechanical design process instead of embodiment stage leads to achieve more optimal design solutions. The initial stage of product development process is known as conceptual design stage in which design solution concepts are generated to meet the design requirements of a product (Prasad et al., 2014).The conceptual design stage is more important and critical stage compared to the other design stages in product development process as it involves complex decision making activities such as the selection of design concepts, materials selection and manufacturing process selection. The conceptual design stage plays a vital role in the overall success of the product as once the conceptual design process has been completed, the majority of product cost and quality has been fixed by selecting particular concepts (Rehman and Yan, 2003). It is reported in the literature that 70-80% of a product cost is committed during the conceptual phase of product development process (Rush and Roy, 2000). Material cost is one of the main cost components while determining the total cost of a product. In the conceptual stage, the designers are usually planned for selecting a material to satisfy design requirements of the product and available at minimum cost. If the material selection issues are not properly addressed in conceptual stage, there is no scope for product designers in detailed design stage to make any modifications for consciously considered material issues. Therefore, design team has to take astute decision on selection of materials which leads to a lot of time saving in product development and minimizing the probability of late detection of materials related critical characteristics.

The objective of material selection process is the transformation of product design requirements into a list of required material properties so as to find an appropriate material for manufacturing a product. Usually product design team considers various parameters such as functional requirements, manufacturability, environmental and economic considerations, mechanical properties, physical and chemical properties etc. In addition to these parameters, product designers need to consider user requirements during material selection so as to achieve competitive advantage in the present market scenario. The improper material selection may lead not only to failure in achieving manufacturer requirements but also users’ expectations. Therefore, it is necessary to capture users’ needs and then deploy them into material selection process. The users of a product are generally expressing their requirements in the form of unclear and non-measurable statements as they may not have sufficient technical knowledge. Therefore, in a conceptual design stage, it is required to translate their need statements into appropriate design requirements and then it is possible to identify necessary criteria for material selection in accordance with the design requirements. To deal with this issue Quality Function Deployment (QFD) technique is adopted in the proposed methodology.