Short-term Production Scheduling Research Articles

Integrated simulation application design for short-term production scheduling

This paper focuses on the development of an integrated short-term production scheduling simulation model for a complex manufacturing operation. The decision making tool has a front-end user data interface built with Microsoft Access and Visual Basic for Applications software. The model assists production planners to make informed decisions on how best to schedule simultaneously two lanes of daily or weekly production on a unique plastic parts manufacturing line. The advantages and disadvantages (model weaknesses) of using the simulation model, especially as a scheduling tool, are discussed. In this particular application, we find that the advantages far outweigh the disadvantages.

중간저장조의 저장시간과 저장제품의 제약을 고려한 다품종 회분공정의 조업완료시간 알고리듬

The determination of completion time constitutes an important step in developing algorithms for short-term production scheduling. Existing completion time algorithms of multi-product batch processes often assume that intermediate storage tanks are always available when it is needed. In this paper, we consider a serial multi-product batch plants with ZW and NIS policy intermediate storge tank. We limit storage residence time and allocated products in the intermediate storage tank to minimize the quality change of the stored material as well as to reduce the clearing time during product change. A set of recurrence relations is suggested to calculate the completion times for the given batch sequence of products on all processing units. Also analytic solution for the suggested model is solved by a graphical method. The effectiveness of these results is proved by a few illustrative examples.

The influence of deposit uncertainty on mine production scheduling

ABSTRACT A variety of algorithms are available for short-term mine production scheduling. All assume that the key characteristics of the deposit model are smooth and that a unique representation of the orebody exists. Is the current approach to production scheduling valid if these assumptions are violated? Both a stochastic orebody model based on conditional simulation and an estimated model based on kriging are used as input to a math programming-based scheduler. Deviations in resulting schedules are presented in terms of the impact of geologic uncertainty on production, the efficacy of the traditional approach and suggestions for integrating stochastic models into the production scheduling framework.

An integer programming approach to short-term production scheduling in a tobacco plant

An integer programming approach to short-term production scheduling in a tobacco plant

An integer programming approach to short-term production scheduling in a tobacco plant

In this paper, a mathematical model is developed that facilitates daily production scheduling in a tobacco processing plant. The implied objectives are to meet specific horizon production targets (obtained from a master production schedule), to maintain safety stock requirements and to ensure that the demand for labour lies within given limits. The express objective is to minimise the number of machines used in the production process. Additionally, the model incorporates work-in-progress, aspects of the demand for product transportation within the plant and machine capacity (utilisation) reduction effects associated with production sequencing. These aspects are relevant when dealing with time intervals as small as a day but can be averaged out when dealing with monthly time intervals. The developments in this paper represents stage II of the modelling of the tobacco plant, where stage I (already completed) was centred on obtaining a monthly master production schedule for a year ahead and assisting in macro planning activities. This paper also sees the development of a simple user-friendly heuristic which facilitates production sequencing on a daily basis given the master production schedule obtained from Stage I.

An Integer Programming Approach to Short-Term Production Scheduling in a Tobacco Plant

An Integer Programming Approach to Short-Term Production Scheduling in a Tobacco Plant

Optimizing short-term production schedules in surface mining: Integrating mine modeling software with AMPL/CPLEX

Short-term production scheduling is the operational basis for mine production over time spans of days, weeks and months. Short-term schedules concentrate on making long-term mine plans operationally feasible and ensuring a steady flow of product for both meeting gross production targets and blending ore. Mathematical programming techniques have been applied to optimize short- and long-term production schedules, but widespread application of these techniques has been limited by the use of routines that are opaque to the end user or difficult to implement. Several examples are provided to illustrate the advantages of using the math modeling language AMPL in conjunction with Techbase, a popular mine modeling package. The strengths of MIP methods as applied to production scheduling are discussed, as are techniques for coping with the limitations of these algorithms.

A PC-based production scheduling system using a mixed integer programming approach

This study describes the development of a PC-based production scheduling system for a plastic manufacturing company. The complexity associated with the company's scheduling problem arises from the need to address three major scheduling issues simultaneously, namely, lot sizing, machine loading and meeting target due-dates. The resulting system acts as a quantitative planning tool capable of generating short-term production schedules that minimize cost, also a decision-support tool assisting the scheduler in analysing and evaluating user-proposed schedules, provides useful information for short-term planning purposes and uses a user-friendly menu-driven environment allowing the user to specify parameters and to access information on interests.

A simulation-based scheduler for flexible flowlines

Abstract A flexible flowline is a generalized production model employed in a wide variety of manufacturing assembly applications to produce a range of products in small batch quanitites. The MRP systems, which are commonly used in such environments, lack the detail to carry out daily scheduling. Recently, finite capacity planning tools have been suggested as a means of generating short-term production schedules. These tools employ techniques that take a global view of the problem and are based on static ‘snapshots’ of the manufacturing system. However, they ignore any inherent dynamics and therefore are inadequate in managing disruptions that can be very costly in terms of the inability to meet throughput requirements and prior delivery commitments. A simulation-based scheduler, on the contrary, is effective in accommodating the dynamic and/or stochastic nature of the system in arriving at a sheduling solution. In this paper, we introduce a simulation-based scheduler which is used to study a general class...

Flow shop scheduling in serial multi-product processes with transfer and set-up times

Abstract Short-term production scheduling is a widely seen problem in multi-product batch operations. In this paper, an effective heuristic algorithm for scheduling a set of different tasks to be processed on serial processors is presented that provides an approach towards minimizing the entire makespan and improving productivity. Flow shops with an interstage storage policy, non-zero transfer times, and non-zero setup times are considered. The performance of the proposed algorithm was evaluated through numerous simulated problems. Statistical analysis of the output data indicates that in the situation containing up to seven tasks, the algorithm provides optimal or near optimal solutions and needs very short computation time. For a larger number of tasks, it gives up to 20% better solutions than a well-known existing algorithm.

Relevance lost? A critical discussion of different cost accounting principles in connection with decision making for both short and long term production scheduling

Based on principles developed early in this century traditional cost accounting systems still constitute an unchallenged context for both short term and long term product-mix decisions in most manufacturing companies. This is valid in spite of fundamental changes in the structure of manufacturing companies rendering the models increasingly irrelevant. This paper analyses the potential gains of the OPT- and ABC-models as far as they have both claimed to alleviate the short-comings of traditional approaches to product-mix decisions. These analyses lead to the following main conclusions: (1) neither OPT nor ABC have a relevance to all product-mix decisions. Their relevance is highly dependent on the time horizon and the manufacturing environment; (2) OPT represents a major improvement in short term product-mix decisions while taking capacity constraints in bottleneck ressources into consideration. On the other hand using OPT-principles for long-term descisions are potentially dangerous as the total factory costs are distributed undifferentiated to the products according to their consumption of bottleneck time. This may lead to discarding of the products with the best long term profitability; (3) the ABC-philosophy constitutes a necessary basis for long term descisions about product-mix as the complete cost-structures are revealed. However the information derived from ABC-analyses unfortunately is not satifactory for making short term decisions in general; (4) for short term decisions under capacity restrictions the OPT-principles should be practiced; (5) for short term decisions in the absence of capacity contraints traditional variable costing principles should be used, as ABC considers costs as variables that in the short term definately fixed; (6) because most product-mix decisions have both short and long term consequences and difficulties of classifying all costs as either fixed or variable in the decisions context, combinations of different models will produce a bettwen basis for informed descisions; and (7) both the ABC- and OPT-philosophies need to be further elaborated. Some suggestions for further elaborations are developed in the paper.

Optimal short term hydro scheduling including security constraints

A method is presented for short-term production scheduling in a hydro system. The solution technique is based on iterative network linear programming and heuristic techniques. The method handles security constraints due to single branch and specified multiple contingencies. The postcontingency rescheduling capabilities are modeled explicitly in a DC optimal load flow. Using the rescheduling capabilities increases the transmission network utilization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An application of integer programming and simulation to production planning for a stratiform ore body

Planning of underground mines poses considerable difficulties in the areas of safety, environment, ground control and production scheduling. As the industry is faced with more and more marginal reserves, it is becoming imperative to generate mine plans which will provide optimal operating strategies and make the industry more competitive. The problem of production planning in underground mines can be formulated using available operations research techniques and computing power. In this paper a computerized model for short-term production scheduling in a typical block caving mine with a stratiform ore body is presented. By combining simulation with mixed integer programming, it has been possible to model realistically the problem of scheduling draw points for production at the Chingola Mine of Zambia Consolidated Copper Mines Limited. The model is based on a given layout of the mining block which is considered fixed during the planning period. The model is intended for use by planning engineers or mine captains working with personal computers. In comparison with manual scheduling, the computerized model has been found to be faster and generates near-optimal schedules.

A short term production planning and scheduling model

An optimal decision making model is developed to assist the manufacturer to select among the potential customer orders, which orders to reject and which orders to accept and in what quantities such that the net operational profit during the planning time horizon will be maximized. This model is developed based on the group technology concept and assumes that (i) job splitting is allowed, (ii) all the necessary stages of operation of each job (e.g., a batch of identical parts with a specified due date, availability time, required setup time, and required processing time) at each workstation (e.g., assembly cell) is represented by a single aggregated stage of operation, (iii) the time horizon is set to be sufficiently short, and (iv) the processing priorities of the potential customer orders during the planning time horizon is specified. Based on the above model, an operational plan for optimal loading of an integrated manufacturing system consisting of a set of finite capacity workstations linked by a material handling system is obtained.

Completion times in serial mixed-storage multiproduct processes with transfer and set-up times

The determination of completion times constitutes an important step in any algorithm for short-term production scheduling. In this paper, serial multiproduct batch/semicontinuous plants with a mix of interstage storage policies, nonzero transfer times and sequence-dependent set-up times are considered. A set of recurrence relations is presented for calculating the completion times for a given sequence of product batches on all processing units. The relations comprise an optimal, polynomially bounded, single-pass procedure which can be incorporated within any appropriate scheduling algorithm. Simplified expressions for several special cases of interest are deduced from the general results. Finally, important results concerning optimal production sequences for the limiting 2-unit configuration with infinite storage are derived.

Dispatch and Control in the Operation of a Large Hydroelectric Power Supply System

The paper deals with the optimal dispatch and control of the State Power Systems's dominant share of the Norwegian electrical production resources. A description of the different levels in the off-line production scheduling is given. The paper emphasize on the hydro power production scheduling where regional supply/demand analysis and reservoir drawdown analysis are major parts of the weekly production scheduling. The short-term production scheduling is divided into plant predispatch for the coming the week and unit predispatch for the coming day. For on-line control a method is described for active power rescheduling. The rescheduling method is based on a quadratic programming method. The use of the method is demonstrated on an example study in the State Power System. Results from this method are compared with optimal load flow calculations. The quadratic programming method gives fairly accurate results, and the computing time is very low compared to optimal load flow calculations.

Short-term production scheduling of an automated manufacturing facility

We describe a new implementation of the Kimemia-Gershwin hierarchical policy for the real-time scheduling of flexible manufacturing systems. Major improvements result at all three levels of the policy. The algorithm simplification, resulting in substantial reductions of off-line and on-line computation time, is reported, as is the improvement in performance through the elimination of chattering. Simulation results based on a detailed model of a printed circuit card assembly facility are summarized.

Power system operations scheduling using separable programming

The problem of electric power operations scheduling comprises maintenance scheduling, intermediate- and short-term hydro-thermal scheduling, unit commitment and production scheduling. Recognizing the inter-relationship among these subproblems, the effect on one another is analyzed. Computationally efficient formulations and algorithms for maintenance scheduling and intermediate- and short-term hydro-thermal scheduling are presented. A variation of the separable programming technique is presented. This results in a linear programming formulation of the nonlinear scheduling problem. This technique is applied to a hypothetical system containing nuclear, fossil, hydro-electric and pumped-storage units. The large problem of hydro-thermal scheduling due to the inclusion of a nuclear unit is decomposed into two stages. In the first stage, the relatively stable nuclear generation is optimized with respect to the generation from large fossil-steam units. Hourly generation levels for all units in the system are then determined in the second stage.