摘要:

Cell formation (CF) consists of identifying machine groups (MGs) and part families (PFs). Many CF procedures use a part machine matrix as an input and attempt to obtain a block diagonal form. A perfect diagonalization of the part machine matrix to form exclusive PFs and MGs is not possible in many instances. Considering alternate routeings (i.e. alternate plans for the parts and additional copies of machines) improves this diagnonalization. This aspect has not been adequately dealt with in literature. Moreover, existing CF procedures consider indirect measures such as similarity indices, rank order, bond energy etc., that may not obtain a good block diagonalization of the part machine matrix. Also these procedures decouple cell formation and cell evaluation procedures. In this paper a non-linear integer programming model is developed for CF to identify PFs and MGs simultaneously considering alternative routeings. The model combines the evaluation procedure by considering the minimization of a weighted sum of the voids and the exceptional elements in the objective. This leads to better identification of groupings in the existing data, Also, in the model, changing weights for void and exceptional elements gives the designer the flexibility of forming large loose cells (more voids but less exceptional elements) or small tight cells (less voids and more exceptional elements). The model has been illustrated with numerical examples. The optimal solutions for these examples are obtained by solving the linearized version of the model. For efficient solution of larger problems a simulated annealing algorithm is developed.

ISSN:0020-7543    

DOI:10.1080/00207549608904970

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In an increasingly automated environment, the control of material handling tasks in a goods distribution centre (DC) is a complex activity. It is necessary to control not only scheduling and routing of goods, but also material handling equipment, which is becoming increasingly autonomous and ‘intelligent’. The problem of devising a control system so that (1) material flow and (2) material handling equipment are both controlled is addressed in this paper. A discrete event modelling formalism is employed, and the concept of fuzzy logic is applied for controlling an automated goods transporting device. This approach is a significant departure from currently used techniques of modelling control in a distribution centre.

ISSN:0020-7543    

DOI:10.1080/00207549608904971

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We consider the scheduling of two-stage flexible flowshops. This manufacturing environment involves two machine centres representing two consecutive stages of production. Each machine centre is composed of multiple parallel machines. Each job has to be processed serially through the two machine centres. In each machine centre, a job may be processed on any of the machines. There arenindependent jobs to be scheduled without preemption. The jobs can wait in between the two machine centres and the intermediate storage is unlimited. Our objective will be to minimize the maximum completion time of the jobs. We formulate the problem as a mixed integer program. Given this problem class is NP-hard in the strong sense, we present three lower bounds to estimate the optimal solution. We then propose a sequence-first, allocate-second heuristic approach for its solution. We heuristically decompose the problem by first creating a priority list to order the jobs and then assign the jobs to the available machines in each machine centre based on this order. We describe seven rules for the sequencing phase. The assignment phase consists of a heuristic which attempts to minimize each partial schedule length while looking ahead at the future assignment of the currently unscheduled jobs. The computational performance of the heuristic approach was evaluated by comparing the value of each heuristic variant to the best among the three lower bounds. Its effectiveness was tested on scenarios pertinent to flexible flowshop environments, such as cellular manufacturing, by conducting a computational study of over 3400 problems. Our computational results indicate that the most effective approach used Johnson's rule to provide the priority list for job assignment. This provided integrality gaps which on the average were less than 0·73%.

ISSN:0020-7543    

DOI:10.1080/00207549608904972

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The ceramic silicon nitride was machined with a short pulsed Nd:YAG laser. The cuts made were crack free and exhibited promising characteristics for precision laser machining of such materials. The cut kerf geometry was analysed and modelled as a function of energy density. This model proved fairly accurate for lower level energy densities, but the amount of material removed increased with energy density up to a maximum point and then began to decrease. This work shows that laser machining silicon nitride can be accomplished with no crack formation and that the kerf characteristics can be modelled using an energy density formulation.

ISSN:0020-7543    

DOI:10.1080/00207549608904973

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper explores the sales productivity of manufacturing companies in four countries. Specifically, data envelopment analysis (DEA) is used to compare the use of labour and equipment to produce domestic and export sales in the People's Republic of China, Hungary, the USSR (before the break-up of the republic) and the United States. Firms from the machine tool industry were evaluated using data gathered by the Global Manufacturing Research Group. When labour hours and equipment are considered, the United States’ firms are the most efficient at producing sales output and China's firms the least. When labour dollars instead of labour hours are considered, surprisingly, China's firms remain least efficient while those from the USSR and Hungary fare quite well when compared with those from the United States. Several important differences in manufacturing practices help explain the differences in sales productivity and point out areas where care must be taken in creating joint ventures between firms in these countries.

ISSN:0020-7543    

DOI:10.1080/00207549608904974

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Unlike the traditional cell formation problem with machine-part incidence matrix, this paper deals with the formation of cells for jobs with operation times on different machines. The cell formation procedure in this paper consists of two distinct phases. The first phase analyses the relationship between the number of cells and the maximum number of operations that can be performed without duplicating the machines and develops a closed form expression for the optimal number of cells that minimizes the total associated cost. The second phase proposes a methodology for clustering the machines and the parts into a prespecified optimal number of cells given an upper limit on the total processing time of the jobs in a cell. Finally an attempt has been made to balance the system with an objective of reducing the degree of workload deviation in the cells.

ISSN:0020-7543    

DOI:10.1080/00207549608904975

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608937002

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608928090

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0020-7543    

DOI:10.1080/00207549608937000

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor