Teruhiko Yoshida

Optimal Two-Stage Production Scheduling with Setup Times Separated

Abstract This paper considers the two-machine (-stage) flow-shop problem of minimizing the total elapsed time, where setup times are separated from processing times. A theorem which is an extension of Johnsons for the two-machine flow-shop problem with setup times included is developed for the optimal scheduling with setup times separated. A numerical example is shown in order to clarify the effect of setup time consideration on the reduction of the total elapsed time.

Group production scheduling for minimum total tardiness Part(I)

Abstract This paper considers the problem of group scheduling on a single stage to minimize total tardiness. It is assumed that jobs are classified into several groups on the basis of group technology. Optimal decision as to scheduling sequences will be made as to product group and specific job. This paper proves basic theorems that establish the relative order in which pairs of groups are processed in an optimal schedule. In general, scheduling problems of moderate size may be at least partially ordered so that very few schedules remain to be searched. Two practical algorithms for determining the optimal group schedule and the near optimal group schedule are proposed. Numerical examples are presented in detail.

Layout Planning for Group Technology

Together with the production planning, process planning, production scheduling, and others, an important planning activity in manufacturing firms is to determine a spatial location for a collection of physical production facilities. This is so-called layout planning. The optimal decision about this layout planning leads to the reduction of material handling times and costs, decrease of in-process inventories, the improvement of environmental conditions of workers, shortening of production lead time, increase of machine utilization, and others, thereby resulting in decrease of the total production cost.

Production Scheduling for Group Technology

Product items and their quantities to be produced in the specified periods are determined through production planning. Then an actual implementation plan as to the time schedule for performing required jobs must be established; that is, when, on which machine or work center, and who does what operation. Whether the production activities in a work shop—such as part supply, machining, inspection, and so forth—are performed smoothly or not depends on the time schedule established. When this time schedule is well established, production activities are done smoothly, throughput times of jobs become short, and all the jobs meet their due dates. On the contrary, when badly established, the operations of the jobs may not be performed on the time schedule.

Process Planning for Group Technology

Process planning is the decision making as to the production process through which raw materials are converted into products planned by product design, with a series of operations. This planning is interrelated with product design and layout planning. Information on technical specifications of products established by a product-design function is an important input to process planning. Layout planning requires information on the sequence of operations to manufacture each part or product, which is derived from process planning.

Group Technology and Other Related Topics

Material requirements planning (abbreviated MRP), known as time-phased requirements planning, is a computer-based production planning and control system that is designed to work well for discrete production [1]. Discrete products such as automobile and machine tools are made up of a number of components which often form a hierarchial structure. Hence, whether the discrete products are efficiently produced according to their production schedule or not depends highly on the establishment of an effective production and control system that guarantees that components composing the products are available in necessary quantities when needed.

Production Planning for Group Technology Applications

In order to obtain desirable profit and survive as long as possible, manufacturing firms should make their best efforts to establish various planning activities in different levels of the management hierarchy. Planning activities are usually classified into three levels: strategic, managerial, and operational. Production planning—mostly concerned with managerial and operational planning—is one of the most important functions in production management planning activities.

Group Machine Loading with Variable Processing Times

In most cases in the field of production planning and scheduling, the processing time required to complete a specified operation of a job is set as a constant. In the previous chapter, the machine loading models were constructed under the assumption that the processing time is a constant. In practical situations, however, it is possible to vary the processing times by actively changing manufacturing conditions, especially machining speeds. In these cases, some modifications must be made to the production planning and scheduling models. In order to solve those models, a new type of analysis must be made allowing for variation in processing times and costs. This chapter treats the machine loading models with variable processing times. First, a basic production model with variable processing times is covered, and then it is extended to the machine loading models.

Basic Principles of Group Technology

Group technology (GT) is a manufacturing philosophy that identifies and exploits the underlying sameness of parts and manufacturing processes. In batch-type manufacturing for multi-products and small-lot-sized production, conventionally each part is treated as unique from design through manufacture [1,2,3,4,5]. However, by grouping similar parts into part families based on either their design or processes, it is possible to increase the productivity through more effective design rationalization and data retrieval, and manufacturing standardization and rationalization. The basic concept of group technology has been practiced around the world for many years as part of “good engineering practice” and “scientific management” [6], Applications of group technology concepts are usually identified under different names and in various forms of engineering and manufacturing functions. Traditionally, group technology practices were limited to conventional batch-type manufacturing for productivity improvement, with different degrees of success either in the design or manufacturing areas. For many years, group technology did not receive the formal recognition it deserves and has not been rigorously practiced as a systematic approach to productivity improvements. Recently, however, development and implementation of computer-integrated manufacturing (CIM) led to a renewed interest in group technology since it provides the essential means for higher manufacturing productivity for successful integration of CAD/CAM through the application of the part-family concept [7].

Multi-Stage Group Production Scheduling

Flow-shop scheduling problems are more difficult to solve as compared with sequencing problems, but these problems are relatively tractable as compared with job-shop scheduling problems. Several theoretical analyses have been made to solve the flow-shop scheduling problems.