ISSN:0020-7543    

DOI:10.1080/00207549508930224

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper deals with the development of an intelligent algorithm for nesting of irregular shaped sheet metal blanks with varying blank geometries. A nesting algorithm has been developed by incorporating a new sliding technique in order to find all the feasible arrangements in such a manner that two arbitrary blanks do not overlap or intersect. The algorithm considers the constraints of sheet metal stamping operation like bridge width and grain orientation and also satisfies the design requirements such as maximizing the strength of the blank when bending is involved as a subsequent operation. The algorithm is designed in such a way that it automatically stops a search for the optimal cluster and also minimizes the computation time based on heuristics incorporated.

ISSN:0020-7543    

DOI:10.1080/00207549508930225

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper examines the role that both the planning and shop floor control systems play in the operation and performance of a dual resource constrained (DRC) job shop. Using causal analysis, the results show an effective planning system, as it accounts for the largest gain in shop performance. Generating and releasing smoothed schedules (work loads) allows the use of simplified shop floor control procedures such as Order Review/Release (ORR), job dispatching and labour assignment rules without adversely affecting performance. This study uses the results to resolve the current paradox surrounding ORR systems and shows that the ORR rules' performance is strongly dependent on the planning system, and that ORR rules can be considered moderating variables. Further, the study develops a variance control framework that indicates the necessary managerial actions to improve shop performance. This paper demonstrates that the planning system, not the shop floor control system, is the major determinant of shop performance. By making improvements to the planning system, the shop can use simple ORR rules, job dispatching and labour assignment procedures to control the flow of work without adversely impacting shop performance. These findings will help guide managerial investments in planning and shop floor control systems.

ISSN:0020-7543    

DOI:10.1080/00207549508930226

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Recently, some stochastic neural network models have been presented for the purpose of overcoming the defect that the deterministic neural network models do not have the ability to escape from a local optimal solution. However, the specification of the values of various parameters and weights in these stochastic neural network models is more complicated than that in the deterministic neural network models. In this paper, a new stochastic neural network model is proposed in order to reduce the complication of specifying the values of parameters and weights. For a practical purpose, the proposed model is applied to the problem of grouping parts and tools in flexible manufacturing systems (FMSs).

ISSN:0020-7543    

DOI:10.1080/00207549508930227

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Most of the past research on job shop scheduling has assumed the shop environment where the load-smoothing function in the production planning and control system is ignored and consequently no visibility is provided to the shop. In practice, some kind of load-smoothing is used to smooth the work load level of the shop across the periods, by pulling jobs forward or pushing jobs back. In this study, three load-smoothing approaches with two levels of control for each approach are proposed and tested with two order review/release decisions in a bottleneck job shop. No smoothing becomes a benchmark. Also, the effectiveness of a feedback loop between load-smoothing and the shop floor is investigated. Experiments were conducted in a six-machine job shop simulation model. Results showed that the employment of load-smoothing is important, and pulling jobs forward in a valley period is better than pushing back jobs in a peak period. Controlling the release of jobs to the shop floor in the order review/release phase, given the amount of jobs to be processed during the planning period, is not effective. Also, the feedback system between the planning phase and shop floor to maintain the minimum shop load becomes much more important than simply controlling job release time.

ISSN:0020-7543    

DOI:10.1080/00207549508930228

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper reports a system which employs string based syntactic pattern recognition techniques for feature extraction. A B-rep based solid model of the component is used for processing the face boundaries (loops) to derive boundary strings which are syntactically analysed to detect feature signatures. The detected signatures are geometrically verified, and the positional and dimensional parameters of the features are calculated. The system is capable of detecting features with complex cross sections; compound features which include nested and intersecting features; and various types of holes and pockets. These capabilities of the system make it an effective interface between a geometric solid modeller and various application programs.

ISSN:0020-7543    

DOI:10.1080/00207549508930229

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The researchers conducted an indepth field project to study the planning and scheduling process in the printed circuit board industry. The formal versus informal scheduling practices are compared, and several aspects of the scheduling situation discussed. Heuristics and techniques used to address instability in the manufacturing system are presented. Instability refers to the manufacturing state when expected or unexpected changes are encountered—e.g. changes in policies, procedures, or a machine fails. The ability to encode the heuristics as a formal model or computer program and have the heuristics mechanically applied is also discussed. The study also provides insights regarding the existence and nature of scheduler expertise.

ISSN:0020-7543    

DOI:10.1080/00207549508930230

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Cumulative Sum Chart for process control is designed to detect relatively small shifts in the mean of the process variable. In this paper, we show that by using samples of two different sizes, rather than a fixed sample, improvements in the chart's ability to detect small shifts are possible. These improvements are obtained without increasing the likelihood of a false alarm when the process mean is on target. The average run length values for the adaptive sample scheme are compared to those for a fixed sample scheme for different magnitudes of shifts in the process mean. A fast initial response scheme is presented. An example from a manufacturing process is used to illustrate the advantages of the adaptive sampling scheme.

ISSN:0020-7543    

DOI:10.1080/00207549508930231

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A comprehensive analysis of the static stability in self-piloting drilling is made in order to define the optimal location 7lpar;based upon the criteria of the equal pad normal reactions and equal stability coefficients) of the drill's supporting pads (relative to the drill's cutters). The optimal location is achieved under unsyrnmetrical location of the supporting pad relative to direction of the resultant cutting force in a plain perpendicular to the drill axis. Significant attention is paid to the drill entrance stability and three methods to reduce the bell mouth (the increase of the bore diameter and worse surface finish at the entrance) are introduced. By the detailed consideration of the drill static force system in the plain which contains the drill axis and vectors of the radial and tangential forces, a new design concept is proposed. The essence of this concept is to design the self-piloting drills with minimum offsets of the pad faces relative to the bottom of the hole being drilled. The experimental study of the newly designed drill shows that the use of the proposed design concept provides better hole quality, reduction of the bell mouth (diameter error and length), and reduction of the drill sensitivity to the value of the clearance between tool and pilot bush.

ISSN:0020-7543    

DOI:10.1080/00207549508930232

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper we propose approximate dynamic models, based on continuous material flows, in order to overcome the difficulties usually faced by classical machine scheduling methods, such as computational complexity, limited ability to model all the features of real manufacturing environments and to cope with unpredictable events. The continuous flow approach, which has been often proposed for repetitive manufacturing environments, is exploited here for a batch manufacturing environment; a multi-stage case is used to illustrate the methodology. Both discrete and continuous time dynamic models are considered. Some computational complexity results are given for the resulting optimization problems. Based on these models, a two-level hierarchical approach is proposed: the task of the upper hierarchical level is to solve the continuous flow scheduling problem, yielding a reference production trajectory; the task of the lower level is detail scheduling, aimed at meeting the production targets set by the upper level. Constraints may be added to the continuous flow model in order to cope with unfeasibilities detected by the lower level, resulting in a two-way hierarchical scheme.

ISSN:0020-7543    

DOI:10.1080/00207549508930233

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor