Abstract

In today’s global marketplace, companies have become aware of the need for agility in the development of new products to survive or in the best case to continue the endless competition. In order to stay competitive, companies are adopting various approaches to maintain a high level of performance in all enterprise domains and deliver value to their customers. With much success in production environments, lean principles have also been found to be applicable in other areas of the enterprise, including product development (PD).
The research reported in this thesis addresses the goal of continuous improvement of flow in PD. While the lean philosophy has been implemented successfully in manufacturing, the context of PD lacks application of such concepts.To tackle the information flow problem, practitioners of lean in manufacturing have established the “one piece flow” logic where the size of the lot of goods moving from one process to the next is intented to be closer to one. However, information as the moving piece in PD is not as visible as in manufacturing. Therefore, the “one piece flow” concept is difficult, if not impossible, to achieve in PD.
A smooth and steady flow of value delivery among processes results in several improvements, such as a reduction in lead time, intellectual work in process (IWIP), rework, and so on. The current research is mainly focused on achieving flow in PD by making a bridge among lean principles, queueing theory and operations research. Information flow is translated into entities of a simple priority queuing system that monitors the flow rate of jobs among servers, or PD team members. The reverse flow of jobs from downstream processes represents rework which due to its nature has a higher priority than those of regular tasks. Since rework flow updates information and assumptions within a process, preemptive queuing policies are studied. Two types of waste through the value stream, namely queue waiting time and outdated information processing time (lost effort), have been quantified accordingly. The wastes, along with the throughput, have been optimized using a multi-objective non-linear model regarding the flow rates among engineers.
Results show higher rework generation in downstream processes increases the congestion (the main barrier to flow) in the system, which leads to increase in the overall lead time. Finally, in addition to a plausible approach to maintain flow, a criterion to improve decision making for value stream managers has been presented.