Simultaneous Lot Sizing and Sequencing for Multistage Production Systems

Inventory and scheduling theory have, in general, been developed independently. This paper presents a model which integrates these two traditionally different aspects of production planning in a multi-stage environment by transforming a lot-sizing problem to an equivalent job-shop scheduling program. The proposed model may improve the effectiveness of existing decision making processes.     

Optimal Lot Sizing in Acyclic Multiperiod Production Systems

This paper addresses the problem of lot sizing within an acyclic hierarchical multiperiod production system. Cost conditions are established for the existence of optimal schedules satisfying the Wagner-Whit in property and a generalized nested schedules property. The method of proof is constructive and based on a network model. Imbedded in the proof are algorithms for adjusting any solution so that it satisfies the properties; thus the algorithms can be used to obtain a locally optimum solution from any trial schedule.     

Multistage Multiattribute Acceptance Sampling in Serial Production Systems

A multistage Bayesian acceptance sampling model for a serial production process, which incorporates multiple-type defects that may occur in each stage of the process is proposed. A subproblem heuristic to solve for near optimal multistage multiattribute acceptance sampling plans is also developed. The performance and sampling characteristics of the multistage model and the solution heuristic are illustrated and compared to a set of independent single stage plans and a final stage composite plan, showing considerable differences.     

The Maximum Value of Inventory and Shortages in Production Lot Size Systems

This paper proposes methods of finding the maximum value of the inventory (MVI), the maximum storage space (MSS), and the maximum value of shortages (MVS) in the production lot size system, where several products are being made on a single facility with repetitive common cycle length. Noting the fact that the MVI, MSS and MVS depend on the slack (idle) times between the production runs of two consecutive products, linear programming formulations are presented to determine the minimum MVI, the minimum MSS and the minimum MVS. In addition, when there are restrictions or upper limits on some or all of these measures, linear programming formulations are developed to obtain the constrained optimal lot sizes.     

A Parallel Heuristic Algorithm for Lot-Sizing in Multistage Production Systems

Existing studies on heuristic lot-sizing techniques for multistage production systems concentrate on optimizing the production operations of the individual stages. This approach induces a family of heuristics, in which the production plans for the individual stages are computed sequentially starting from the final stage. In this paper we introduce a parallel heuristic for the problem. The method, which may be considered as the generalization of the single stage Wagner-Whitin algorithm, attempts to optimize over all stages simultaneously, while building the production plans in a forward manner. In computational experiments the new algorithm performed extremely well.     

对系统提前期/等待时间敏感的批量排队优化模型

过长的制造提前期和过高的在制品库存等问题造成Job shop的生产系统瓶颈,传统的批量策略没有考虑到这些因素.分析了产能、WIP、平均等待时间、系统制造提前期等参数对批量决策的影响,提出了两种不同批量优化策略,分别是减少平均等待时间的最优批量策略和缩短制造提前期的最优批量策略.参数敏感性分析表明,产能约束下,这两种批量...     

Optimum Investment Policies for Diagnostic Equipment under a Limited Budget in Multistage Production Systems

1IntroductionAcommonrequirementofcompaniesfromtheirmaintenanceprogramsistohavethemaximumavailabilityoftheirproductionprocesses.ManufacturersnowhavediagnosticequipmentthatenablesthemtOmonitortheirpreductionprocessesatalltimes.Maintenanceplanning,there...     

When Is The Economic Lot Scheduling Problem Easy?

The Economic Lot Scheduling Problem, common in industry and the literature as well, is NP-hard and remains unsolved in general. We show 'that the very simple Rotation Cycle scheduling rule produces optimal or nearly optimal schedules in very many realistic situations and we give upper bounds for the maximum percentage deviation of the Rotation Cycle's schedule fro m optimality. An implication for Group Technology is discussed.     

Economic Lot Scheduling for Two-Product Problem

In this paper we propose an algorithm for the two-product single machine Economic Lot Scheduling Problem (ELSP). Past research on this problem has relied heavily on the assumption that both products are produced cyclically. In particular Boctor's algorithm provides optimal solution to the two-product problem under such assumption. We first simplify Boctor's algorithm and then propose an algorithm which allows for the unequal cycle time for the more frequently manufactured product. We show that the cost corresponding to our solution is either less than 1.015 times the cost obtained from the Independent Solution, which is a lower bound of the optimal solution, or is better than that obtained by Boctor's algorithm. An example is used to show that the difference in cost can be as much as 24%.     

A Heuristic Production Lot Scheduling Model

This article describes a model which seeks to schedule the production of m products over the next n production planning periods in a manner which minimizes total setup, production, and inventory costs while observing all constraints imposed by the capacities of the productive resources. The model formulates this problem as a fixed charge problem, and then uses a modified version of the simplex method to locate optimal or near optimal solutions of this nonlinear programming problem. A discrete optimizing approach is used to estimate the effectiveness of the model.     

The Effects of Learning on Optimal Lot Sizes: Further Developments on the Single Product Case

This paper reviews the previous research on the problem of determining optimal lot sizes when production costs decrease on a log-linear function. Problems due to simplifying assumptions of the previous work are discussed and modifications of previous models are presented to address more realistic conditions. Using a dynamic programming approach, the new results for two cases of learning, total transmission of learning (from lot to lot) and partial transmission, indicate that optimal lot sizes are increasing in the long-run and long transient states exist, contrary to conclusions of prior papers. The effect of forgetting indicates that operations managers should consider longer production runs for many processes.

The revised model formulation presented in this study is also capable of handling demand characteristics of variance, growth and seasonality, significantly extending the application possibilities of the previous models which were limited to a continuous, deterministic demand pattern.     

The Effect of Restricting Cycle Times in the Economic Lot Scheduling Problem

The economic lot scheduling problem (ELSP) involves specifying economic cycle times for each of several products produced by a set of machines. The extensive, usually experimentally based, literature on the ELSP indicates that it may be desirable to restrict the possible choice of cycle times for each product to a small and very structured set of possible cycle times. In this paper we examine the economic impacts of such a restriction and give evidence that is highly supportive of this type of restriction; in particular, the “powers of 2” sets of possible cycle times used in practice appear to be very desirable from an economic viewpoint.     

Decomposition of Converging Branch Multistage Systems

This article considers an alternate dynamic-programming technique for analysis of converging branch systems. This technique, like superposition, is based on decomposition of the system considered. However, it is not restricted to linear systems. The validity of the approach is shown, and an example problem is presented.     

The Application of Marginal Analysis to the Economic Lot Scheduling Problem

Application of marginal analysis to the Economic Lot Scheduling Problem reduces the solution search to a simple systematic calculation and feasibility check. Compared with mathematical programming methods and heuristic approaches advocated previously, marginal analysis results in lower optimum cost solution with shorter optimum basic period lengths. For comparative purposes, data are included which allow evaluation of marginal analysis results with dynamic programming results of previous researchers.     

Production Lot Sizing Under A Learning Effect

Models are developed for determining optimal production lot sizes under a learning effect. These models consider situations in which both bounded and unbounded learning is assumed to occur. Bounded learning occurs when some nonzero lower limit is set on the time allowed to produce one unit of product.     

Economic Design And Control of Monitoring Mechanisms in Automated Production Systems

Monitoring production processes to assure product quality has been a major managerial and control problem. These processes are subject to shifts to “out-of-control” states, resulting in the production of defective items. Inspection as well as restoration capabilities are necessary to provide early detection and correction of these shifts in the process. This paper considers the costs of different policies for providing these detection and restoration capabilities. These policies amount to periodic or continuous inspection of the production process with perfect information, and continuous or periodic availability of maintenance facilities. The optimal operation of each policy is studied. Comparative analyses are conducted with different specifications of key parameters such as the rate of shift of the process and the cost of producing defective items. These analyses enable the derivation of the optimal policy when only ranges of the values of these parameters are known.     

Priority Scheduling and Inventory Control in Job Lot Manufacturing Systems

This paper examines the relationship between the problems of priority scheduling and inventory control and describes several priority scheduling rules that use inventory information in making machine scheduling decisions. These rules include: Minimum Slack Time Per Remaining Operation? Critical Ratio, and a modification of the Shortest Processing Time Rule. Simulation experiments evaluate the gain in shop and inventory performance resulting from the inclusion of inventory data in scheduling rules. The results indicate that an increase in the timeliness of inventory information for scheduling purposes may not lead to improved performance.     

Economic Design of Quality Monitoring Efforts for Multi-Stage Production Systems

A model is developed for locating quality monitoring stations in a multi-stage production system and determining the parameters of the np-chart (sample size, acceptance number and sampling interval) used at each quality monitoring station. Each production stage can shift to an out-of-control state associated with an assignable cause. Various cost, profit and time elements are included in the derivation of the net profit per unit function. Dynamic programming and direct search techniques are used to maximize this expected net profit per unit function across the production system. Numerical examples and sensitivity analysis of the model are presented.     

经济批量与运送排产问题中的协调机制研究

针对现有研究采用集中决策的局限,研究了分散决策情形下经济批量与运送排产问题的最优决策。分析表明在无协调机制作用时,分散决策无法实现供应链系统的最优绩效,进一步提出一种利润共享和成本分担协议（PCS）,并证明在PCS协议作用下,采用分散决策可以实现供应链协调,同时供应链利润可以在供需双方任意分配,具有很好的柔性。     

单件小批条件下的动态生产函数模型

基于微观投入产出理论，本文总结了几种动态生产函数，并对其在单件小批订货生产类型企业的生产决策中的应用条件进行了研究。提出了改进基本模型的具体方案。