Shun Takai

A lifecycle-cost model of concept testing

This paper presents a lifecycle-cost model of concept testing, with and without learning. In the lifecycle-cost model, product lifecycle is divided into four stages: marketing, concept generation, prototyping, and product lifecycle after prototyping. Engineers minimize the expected lifecycle cost to find the optimum number of prototypes that engineers develop to test concepts. The optimum number of prototypes is a function of unit costs in these stages. The optimum number of prototypes depends not on the absolute cost of prototyping one concept, but on prototyping cost relative to the other stage costs. In the lifecycle-cost model with learning, engineers can more accurately choose good concepts that they test as prototypes once they gain experience in developing similar products or as they learn more effectively from their experiences. As engineers gain more experience or improve their learning capability, the optimum number of prototypes decreases.Copyright

Effects of Non-Geometric Features and Incentive Schemes on Manual Assembly of System Variants: An Experimental Study

Although numerous firms have been shifting toward automated assembly, most still rely on manual assembly when complex assembly operation is required for large-scaled systems. Furthermore, because firms design variants of a system to satisfy diverse customer needs, they may manufacture these system variants in the same assembly line. This type of operation, called mixed model assembly, may improve the utilization of existing manufacturing facilities; however, it may also increase assembly errors due to interchanging geometrically similar parts between system variants. Design for Assembly (DFA) is a design guideline that assists engineers in designing systems that are easier to assemble. However, because DFA guidelines group geometrically similar parts in the same part category, it may be impossible to distinguish geometrically similar but functionally different parts (modules) used in different systems. This paper proposes experimenting how cognitive effects of non-geometric part features influence the productivity and quality in mixed model assembly operations. Furthermore, because the productivity and quality of manual assembly may be influenced by the motivation of operators, this paper examines how productivity and quality may be influenced by different incentive schemes.Copyright

The role of modularized QFD in an interdisciplinary approach for system concept selection

This paper discusses a role of modularized Quality Function Deployment (QFD) matrices in an interdisciplinary approach for system concepts selection. The approach uses a set of interdisciplinary tools that consists of marketing, accounting, value engineering and design engineering. When using modularized QFD matrices in the interdisciplinary approach, engineers specify target requirements before assessing how each output design requirements (e.g., system requirements) contributes to the achievement of input design requirements (e.g., customer requirements). Then engineers use their value of each output design requirement in QFD relationship matrices. By setting target requirements for each system module, engineers can freeze interactions between modules when modularizing QFD matrices. By using engineers’ value in QFD relationship matrices, engineer can allocate worth of system (for the customers) to system modules based on engineers’ value. The target cost of modules calculated from the allocated worth reflect both customers’ and engineers’ value.Copyright

An Approach Toward Estimating Cost of a New System in the Conceptual Design Stage Using Knowledge-Base

To estimate profitability of a new system in the conceptual design stage, engineers need to estimate the cost of concept (the cost of the final system developed from each system concept). If engineers have abundant experiences developing similar systems, they can construct a knowledge-base consisting of historical cost data and use it to estimate the cost of concept. However, if the firm is entering a new market, engineers do not have historical cost data to accurately estimate the cost of concept. In this case, engineers need to benchmark similar systems in the marketplace and construct a knowledge-base with the benchmarked information. This paper proposes an approach toward developing a distribution (belief) about the cost of concept using a knowledge-base. The proposed approach retrieves a subset of information from the knowledge-base relevant to estimating the cost of concept, constructs a histogram about the cost of concept, and develops a distribution of the cost of concept. This paper demonstrates the proposed approach by using printers as an illustrative example.Copyright

Simulation-based and experimental studies of subjective clustering and bootstrap application to subjective clustering

The success of any product in today’s competitive market is dictated by its ability to satisfy the needs of the customers. In this effort, it is important to group similar needs to recognize representative needs, and then identify product requirements that can fulfill these representative needs. One approach to this is to apply Subjective Clustering (SC) to sample data (grouping of customer needs by a sample of customers); however, clusters obtained by SC give only a point estimate of the primary clusters of customer needs by the entire population of customers (population primary clusters). Applying Bootstrap to SC (BS-SC) helps engineers to make inferences on the population primary clusters. In this paper, we randomly pulled out samples of different sizes from both the simulation approach using simulation-generated population data and the empirical approach using experimental population data, and compared the accuracies of SC and BS-SC. Regardless of population sizes, when the sample size was small, BS-SC was more accurate than SC in estimating the population primary clusters. Also, the BS-SC and SC estimates were similar for both simulation and empirical approaches.Copyright

An Approach Toward Target Warranty Costing in the Conceptual Design Stage

The importance of system quality has been increasingly emphasized in the past several decades. In 1987, Malcolm Baldrige National Quality Award (MBNQA) was established to promote quality awareness. Since then, more than 1,100 organizations have applied to the award. One way to measure system quality is by warranty cost. In the automobile industry, for example, warranty costs account for 3–4% of revenue. This paper proposes a framework for managing the warranty cost by setting a target warranty cost for the system and then allocating it to system modules in the conceptual design stage. In the proposed framework, engineers begin by constructing a knowledge-base of past warranty costs. Then regression analysis is used to set the target warranty cost of the new system, and Quality Function Deployment to allocate the target warranty cost to system modules. If detailed design becomes available, engineers can then compare estimated warranty cost with the target and decide whether to further improve reliability or reduce risk of system failure. This paper demonstrates the proposed methodology by using printers as an illustrative example.© 2007 ASME

Sensitivity of Relative Worth in QFD Matrices to Rating Scales and Worth Calculation Schemes: An Empirical Study

In the past several decades, Quality Function Deployment (QFD) has gained its popularity among engineers as a tool to relate (map) customer requirements (inputs) to system requirements or system components (outputs), and to calculate relative worth of these requirements and components. The benefits of QFD in system development include cost reduction, fewer design changes after the start of production, and improved communication among engineers. Despite the observed benefits, the needs for QFD research have been addressed by researchers. These research needs include decision-making process in QFD, rating scales used in QFD matrices, and calculation schemes for calculating the worth of outputs (e.g., system requirements) from the importance of inputs (e.g., customer requirements). The purpose of this paper is to empirically study sensitivity of the relative worth and rank of outputs in QFD matrices to rating scales and worth calculation schemes. We collected QFD matrices from journal articles and textbooks; then calculated the changes of relative worth and the rank of outputs when one type of rating scale and/or worth calculation scheme was changed to the other. The results suggest that the relative worth and rank of outputs are relatively insensitive to rating scales and worth calculation schemes in the QFD matrices studied in this paper.Copyright

Effects of individual and team competitive rewards on collaboration and productivity of team

In the modern system development approach, engineers with diverse discipline form teams and work together in engineering projects. An example is a cross functional team in concurrent engineering. It is important to design incentive systems that maximize team achievements; however, there is a tradeoff between rewarding individual vs. team achievements. Rewarding solely on individual achievements may hinder the overall team achievements, while rewarding solely on team achievements may lead to the phenomenon called social loafing or free riding in which individuals tend to perform worse or contribute less in group. This paper studied the effects of competitive rewards based on individual and team’s achievements by conducting experiments using prisoner’s dilemma game (PDG) in which participants face tradeoff between working more or less in hypothetical individual and team assignments. The unique approach in this paper is to decompose the overall PDG payoff matrix into payoff matrix for individual achievements and that for team achievements to test the effects of individual and team competitive rewards. The experiment results suggested that introduction of team competitive rewards resulted in higher cooperation among team members and overall productivity, compared to when individual competitive rewards were introduced.Copyright

Sensitivity Analysis in Perceptual Evaluation of System Module Concepts

Selecting optimum concepts for a system and its subsystems in the conceptual design stage involves uncertainties due to imperfect information about customer preferences (market shares), cost of the system developed from each concept, and feasibility of new technology used in the new system. When analytical relationships between system performance and system inputs or parameters are unknown in the early system development stage, one approach to quantify the goodness of a concept is to use rating scales. This paper studies the effects of variations (precisions) in rating scales and in cost estimation for evaluating the goodness of system module concepts (e.g., sub-systems, assemblies, subassemblies, and parts). This paper presents a global sensitivity analysis (GSA) in perceptual concept evaluation, three probability measures for evaluating and selecting optimum concepts in GSA, and one-set-of-factors-at-a-time GSA to identify the sets of factors that cause significant variations in concept evaluation outcomes.© 2007 ASME

Influence of Individual and Team Rewards on Collaboration and Productivity of Team

Due to an increased globalization in modern system development, there is a growing need for engineers to collaborate with other engineers in distant locations, in different organizations, and across different disciplines. An effective collaboration among engineers is the key to successful system development and engineering projects. A cross-functional team is an example. The need for collaboration in real engineering environment has resulted in increasing numbers of team-based projects in undergraduate and graduate programs. This paper uses an economic prisoners dilemma game to investigate how students decide to collaborate in hypothetical team projects under different individual and team reward schemes. Experiment results suggest that individual rewards may significantly reduce students intention to collaborate with their teammates. Lack of collaboration resulted in lower productivity in the prisoners dilemma framework.Copyright