Hung Da Wan

An ant based simulation optimization for vehicle routing problem with stochastic demands

The Vehicle Routing Problem (VRP) is of considerable economic significance in logistic systems as it manages the distribution of goods to make an efficient transportation system. Considering a practical application, this paper solves a vehicle routing problem with stochastic demand (VRPSD) in which the customer demand has been modeled as a stochastic variable as opposed to conventional VRP. To deal with the additional computational complexity, this paper uses a simulation optimization approach to solve the VRPSD. To enhance the algorithm performance, a neighborhood-search embedded Adaptive Ant Algorithm (ns-AAA), an improved Ant Colony Optimization approach, is proposed. The performance of the proposed methodology is benchmarked against a set of test instances generated using Design of Experiment (DOE) techniques. The results verified the robustness of the proposed algorithm against Ant Colony Optimization and Genetic Algorithm, over which it always demonstrated better results, thereby proving its supremacy on the concerned problem.

A Web-Based Lean Simulation Game for Office Operations: Training the Other Side of a Lean Enterprise

This research proposes a Web-based version of a lean office simulation game (WeBLOG). The game is designed to be used to train lean concepts to office and administrative personnel. This group belongs to the frequently forgotten side of a lean enterprise. Over four phases, the game presents the following seven lean tools: one-piece flow, error-proofing, elimination of overprocessing, balanced workload, multifunctional workforce, pull, and total quality. The concept of continuous improvement is also covered. Participants can play the game from remote and separate locations by logging into a specified Internet site. Additionally, the game can be played with a combination of real and virtual (simulated) players. Several performance metrics are automatically calculated and displayed at the conclusion of each phase. The results of the current phase can then be compared to the results from all previous phases to better illustrate the impact of newly introduced lean tools.

Beyond Partnerships: The Power of Lean Supply Chains

Managing an integrated supply chain has become a necessary capability for competing in the global market. Cooperating with business partners prevents duplicating efforts and allows a company to focus on its core competencies. Hence, collaborating companies together have the potential to form a strong supply chain. At the individual company level, practitioners of lean concepts have demonstrated dramatic improvements in productivity within their manufacturing facilities. However, the potential benefits of lean implementation are limited to four walls of companies when business partners are excluded from integrating into a leaner overall value stream. The flow from a lean supplier to a lean customer may not be lean if the two parties are not synchronized. As a result, the supply chain formed within lean companies may not be lean after all, due to lack of cooperation and synchronization among participating companies. Extending the value stream from a lean company to its partners allows the company to widen the pursuit for perfection to the whole supply network. Furthermore, applying lean concepts to a supply chain opens new windows of opportunity for supply chain participants to collectively achieve higher levels of competitiveness. Thus, the integration of supply chain management and lean thinking covers both local and overall leanness, which leads to a truly lean supply chain. This chapter provides an overview of the lean supply chain, the including concepts, approaches, challenges, and future development. In the first part of the chapter, basic concepts and impacts of lean thinking will be introduced, followed by the issues of applying lean thinking in supply chain management. Then, an integrated framework of a lean supply chain will be presented. The second part of the chapter covers the building blocks of lean supply chains, including lean logistics, information technology, performance measurement and improvement, and collaboration beyond partnerships. Subsequently, the challenges for building or maintaining a sustainable lean supply chain will be discussed. Finally, discussions of potential developments that can further improve lean supply chains will be summarized in the concluding section.

Enhancing lean training for the office environment through simulation and gaming

Modern training methods call for active engagement of the trainees in the training process. Simulation games are among the most effective methods of training. As waste elimination concepts become more popular, numerous lean training packages have been developed. Most of these packages include simulation games as a hands-on training tool. So far, lean simulation games have largely focused on manufacturing. However, administrative or office processes also contain a great deal of waste and could benefit from a game aimed at their processes. This paper proposes a lean office simulation game to demonstrate the effect of lean implementation on office processes. The game uses four phases to simulate the impact of several lean tools. Various performance metrics are recorded during the game to capture the impact of these tools. A case study of the game played by administrative personnel is included along with an analysis of the results.

Simulation Studies of Hybrid Pull Systems of Kanban and CONWIP in an Assembly Line

Pull system is an important component of lean manufacturing that can effectively reduce typical wastes associated with push production systems, such as overproduction. Using Toyota’s Kanban system, a production line can be configured as a pull system to avoid unnecessary accumulation of Work in Process (WIP). Another common method to carry out a pull concept is the CONWIP line, which maintains a constant WIP level within a segment of production line. Both methods have proven effective, but they may have different characteristics. The objective of this paper is to explore the potential to combine Kanban and CONWIP methods into a robust hybrid pull system that preserves the advantages of both methods while minimizing the disadvantages of each individual method. A simulation study has been carried out based on a real-world assembly line. Various pull system configurations of the assembly line have been evaluated and compared in terms of WIP level, number of Kanban cards in system, and throughput. The study shows that the productivity of CONWIP configuration outperforms Kanban configuration in majority of scenarios; and the performance of a well designed hybrid system can be more robust to various scenarios, compared to Kanban and CONWIP system.

Impact of lean tools selection: a simulation study of two assessment approaches

As lean becomes more popular in various industries, the amount of available lean tools also increases. Selecting appropriate tools to be implemented to the right place at the right time becomes a challenge. Several methods have been developed to help, including some assessment-based approaches and value stream mapping. Creating a good ‘future state’ map requires solid knowledge and experiences. While assessment tools are available for inexperienced users, they often rely on static models or roadmaps that may not suit a variety of systems. This paper investigates the impact of using different selection methods of lean tools in improvement projects. A simulation study based on a real manufacturing system has been conducted for the comparison of effectiveness of two assessment-based approaches. The results show that when lean tools are selected by an adaptive assessment approach, the improvement progresses better than using a static roadmap approach.