摘要:

Some quality control schemes have been developed when several related quality characteristics are to be monitored: simultaneous X¯ charts, Hotelling's T2chart, multivariate CUSUM and multivariate EWMA. Hotelling's T2control chart has the advantage of its simplicity but it is slow in detecting small process shifts. The latest developments in variable sample sizes for univariate control charts are applied in this paper to define an adaptive sample sizes T2control chart. As occurs in the univariate case the ARL improvements are very important particularly for small process shifts. An example is given to illustrate the use of the proposed scheme.

ISSN:0020-7543    

DOI:10.1080/00207549608905062

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper includes the results of a sample survey of the reorder point system (ROP) in airline operator (hereafter AO) and maintenance service (MS) organizations. The presentation provides, at an executive level, an overview of the use of the traditional ROP system by companies to control their spare parts inventory. The survey shows that many companies, unsatisfied with their existing system, were looking for alternative concepts along the lines of the material requirements planning system (MRP).

ISSN:0020-7543    

DOI:10.1080/00207549608905063

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents the results of a simulation study of a just–in–time (JIT) production control system and its performance under different operational conditions. In particular, the effects of two different kanban withdrawal policies on such performance measures as throughput rate, station utilizations and total work in process levels are investigated. Also, simulation experiments are carried out to determine the effects of processing time variability, number of different types of kanbans allowed at each station and production line length on the mentioned performance measures of JIT production control method. The simulation experiments were carried out for production lines in which processing times of stations were assumed to follow gamma and Erlang distributions.

ISSN:0020-7543    

DOI:10.1080/00207549608905064

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper, we investigate cell formation problems in a manufacturing system with flexible processing and routeing capabilities. Flexible processing means that a part can be manufactured by any one of several process combinations. Flexible routeing means that even when the processes are fixed, the part can traverse any one of several routes—each offering the same processes. The cell formation problems for these types of manufacturing systems are different from traditional problems. Traditional cell formation problems are for manufacturing systems with fixed processes and routes where one knows what machines will be used for manufacturing the parts. However, this information will not be available in the flexible systems discussed here, since a part can be completed by any one of the many different combinations of machines. In other words, it is possible to manufacture two identical parts using different sets of machines. Traditional cell formation techniques rely on knowing the specific machine usage information of parts, therefore cannot be applied to the cell formation problems defined here. We propose a solution procedure that can overcome this difficulty and allow us to solve the cell forming problems in this flexible processing and routeing manufacturing environment.

ISSN:0020-7543    

DOI:10.1080/00207549608905065

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Most of the literature dealing with the determination of cyclic part input sequences in a flexible flow system is restricted in that it only searches for input sequences that are permutations of the minimal part set (MPS). This study is unique in that it investigates input sequences generated by integer programming (IP) formulations that balance or unbalance machine workloads to help maximize overall machine utilization (Stecke 1992). Also, this study integrates the input sequence determination decision with the part mix ratio determination, within the overall framework of a flexible approach to FMS operation over time. A simulation model of a flexible flow system was designed to study the effects on overall machine utilizations caused by utilizing alternative part mix ratios to help determine input sequences. The procedures used to determine the part mix ratios include IP formulations and those that are generated randomly, including the MPS mix ratios. Three different experimental settings are used to test these effects as well as (I) the robustness of the part input sequences that can be derived from the IP generated mix ratios, and (2) the relative importance of the part mix ratio decision in relation to the part input sequence determination. A new FMS physical design that can also be easily modelled to capturelook-ahead capabilityproved to be simple and effective. Several significant conclusions regarding part mix ratios, pan input sequences, and look-ahead capability are revealed. These include: (1) the determination of the part mix ratios proved to be more significant in improving FMS performance than the determination of part input sequences; (2) the robust nature of the IP formulations was demonstrated; and (3) look-ahead capability provides equally high overall machine utilizations at lower levels of work-in-process. Future research areas are presented that would help validate and extend the observations found in this study.

ISSN:0020-7543    

DOI:10.1080/00207549608905066

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Automated storage and retrieval systems (AS/RS) have made a dramatic impact on material handling and inventory control in warehouses and product systems. A unit-load AS/RS is generic and other AS/RS represent its variations. In this paper, we study a problem of sequencing retrieval requests in a unit-load AS/RS. In a unit-load AS/RS, there are usually multiple openings and a unit-load can be stored in any opening. Given a list of retrieval requests and the locations of openings, this problem seeks a sequence of dual cycles that minimizes total travel time taken by a storage/retrieval machine. Previous researchers believed that this problem is computationally intractable and provided greedy-style heuristic algorithms. In this paper, we present an algorithm that combines the Hungarian method and the ranking algorithm for the assignment problem with tour-checking and tour-breaking algorithms. We show that this algorithm finds either a verified optimal or near-optimal solution quickly for moderate size problems. Using this algorithm, we also evaluate the effectiveness of the existing simple heuristics. Computational results are reported.

ISSN:0020-7543    

DOI:10.1080/00207549608905067

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

TESSA is a facility layout heuristic for obtaining a maximal planar adjacency graph (MPG) from relationship chart data. Computational experiments performed by Boswell (1992b) have shown that the algorithm produces good quality solutions, almost all of which are above 90% of the often unattainable upper bound. In this paper we show that the heuristic displays arbitrarily bad theoretical worst case performance.

ISSN:0020-7543    

DOI:10.1080/00207549608905068

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608905069

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608905070

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608928094

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor