Kenji Yura

Multiobjective Design Optimization of Machine-Tool Spindles

A method of multiobjective design optimization is presented in order to evaluate conflicting objectives in designing machine-tool spindles. A Pareto optimum set which shows a trade-off relationship between two objectives minimizing the total weight of the spindle and the static torsional or bending compliance, is derived using the Kuhn-Tucker necessary conditions for optimality, and through analyses of objective and constraint functions. Weighting factors between the two objectives are obtained on the Pareto optimum set. Expanded problems and numerical examples are given.

Cyclic scheduling for re-entrant manufacturing systems

A scheduling method is elucidated for the re-entrant manufacturing systems, where the process route of a job passes production facilities one or more times. The objectives of the scheduling problem are maximization of the production rate as a primary one and minimization of the throughput time as a secondary one. The method makes the cyclic schedule, where an adequate number of jobs are treated as a lot and the lot is cyclically released into the system. The lot size is determined to maximize the production rate, and a sequencing method of the lots is developed to minimize the throughput time.

Parts-mix analysis in recycling-oriented manufacturing systems for multiple-item production

One solution to environmental problems is to construct a recycling-oriented manufacturing system, in which waste products after consumption are collected, and reusable parts in the collected products are employed to produce new products. A parts-mix in the manufacturing system for multiple-item production is analysed by taking into consideration the merits and demerits of the usage of common parts over multiple products and special parts utilized for individual products. The parts-mix problem is formulated to minimize the life-cycle cost, which consists of production costs and recycling costs. The property of the optimal parts-mix is clarified, and a decision procedure to solve the parts-mix is developed. The procedure decides whether the common parts are effective or not.

Cyclic schedules in production and operations management

The peculiar feature of cyclic schedules is the repetitive occurrence of a pattern in the schedule. Such schedules often appear in manufacturing environments and the scheduling problems have attracted considerable attention. In this article, after explaining the typical analytical methods, some important features and planning procedures are explained for cyclic scheduling of flow-shop type manufacturing systems, job-shop-type manufacturing systems, and other related problems in manufacturing activities.

Foreign Direct Investment in the Case of Time-Dependent Manufacturing Costs.

This paper describes a strategy for foreign direct investment (FDI) of multinational enterprises when manufacturing costs change with time. This FDI planning problem is formulated in order to determine how many manufacturing facilities are needed in each country when they are needed, and how many products should be manufactured to meet the product demand in each country. It is assumed that both product demand and manufacturing costs in each country change with time. Finally, an algorithm for finding an optimal solution of the FDI planning problem is developed and an example is demonstrated.

Production Planning for a Firm in Diversification.

One of the strategies for achieving continuous growth in firms is the diversification of products. In diversification, manufacturing resources for a product whose market is matured are moved to the manufacturing of a product whose market is growing. The diversification has risks in that the firm may fail to get a return, because competition in a growing market is fierce. In this research, a production planning problem for a firm was analyzed to maximize the expected return and to minimize the risk on the return. An optimization method was developed to determine production quantity and allocation of production capacity, and a numerical example was demonstrated.

Multi-Job Cyclic Scheduling for an Automated Job-Shop-Type Manufacturing System : Relationship between Job Output Interval and Buffer Capacity

A multi-job cyclic scheduling problem for an automated job-shop-type manufacturing system was analyzed. In the cyclic scheduling problem, an optimum schedule is a non-idle schedule, where a bottleneck machine produces jobs without idle time in the steady state. A dividing method of the jobs was introduced and the job output interval in the steady state was clarified. A lower bound on the buffer capacity was obtained to construct a non-idle schedule.

Multi-job cyclic scheduling for a network with complicated processes (A case of process network having some loops)

A multi-job cyclic scheduling problem, in which production processes of the jobs are various, was analyzed. In particular, a case of a process network having some loops was investigated. It was found that jobs output interval between some cycles is constant at the steady state. This number of cycles was obtained. It was also shown that the branch-and-bound method is applicable to solving a job sequencing problem minimizing the jobs output interval. A numerical example was demonstrated to clarify analytical results.