This paper focuses on the problems and potential of one-of-a-kind production, i.e., make-to-order production of non-standard products. The importance of this branch is discussed. The development needs in product design, engineering, and also in production system design is emphasised. Potential and need for interorganisational production management is discussed. The applications of JIT principles also in one-of-a-kind production are addressed. The change of personnel management towards “studio” atmosphere is introduced.
In this paper sufficient conditions for optimality for the single machine job scheduling problem with a linear combination of total flowtime and sum of squared lateness as the objective function are developed. Based on the sufficient conditions a lower bound for the objective function for a given schedule is derived. A branch-and-bound procedure incorporating the lower bound has also been developed. In addition, we also show how to fathom nodes in the branching tree using the a-priori precedence relationships among the jobs that can be determined using the sufficient conditions. Computational experiments for the branch-and-bound and its results are also presented.
When parts are on the shop floor and in manufacture, they are either waiting for or are being attended by a machine or a material handling equipment. When several workstations are required to process a job, the machining and moving of the parts between the workstations can be very time consuming unless it is properly planned. When poorly planned, the processing and handling decision can significantly affect the length of time the job spends in the shop. In this paper, a methodology for planning the machining and the material handling activities for the manufacture of small to medium size batches in a job shop is presented. The model determines the machining rate at each workstation and the unit-load size to use in handling the batch through the production system in order to minimize the total production time. The procedure is easy to implement on a microcomputer for use in planning shop production activities.
This paper considers the development of a general part sequencing methodology which suits flexible systems. A flexible assembly cell configuration is conceptualized. The cell is characterized by a common buffer and a single flexible transfer device for inter-cell transfer activities. Since the time available for decision making on part sequencing is very short, a fast solution is required. A real-time computerized part sequencing system of modular structure is developed. The system comprises three functions: ENTER, ALLOCATE, and TRANSFER SEQUENCE. Each function is provided with various priority options to satisfy different company strategies. Computer simulation is used to compare alternative sequencing structures of the system developed, and to examine its effectiveness under different operating conditions with reference to cell performance and time response.
The objective of this study is to minimize the expected present worth of the production costs incurred over the operational life of a robotic assembly system that is integrated with an Automatic Storage/Retrieval System (AS/RS). Production costs include inventory cost and capital cost of equipment. Inventory cost consists of ordering, holding, and lostproduction costs; and all of these costs depend on the scheduling policy for the assembly robots as well as the inventory policy for the AS/RS. Capital cost of equipment depends on the number of depalletizer robots and the number of assembly robots. To identify the minimum-cost design for a certain automotive assembly operation from a given set of alternative system configurations, we present a simulation experiment in which independent replications of each alternative are controlled by a statistical ranking-and-selection procedure that has been adapted to simulation.
Maintenance in a process industry, such as chemical and oil companies and food processing, needs frequent part replacements to assure continued operations. These parts represent non-repairable items which are best purchased, such as bearings and gaskets. Based on limited information on the time between failures of such systems, one can forecast the need for spare parts for a given planning horizon, which may be from one to several years. In this paper we discuss the methodology to calculate the spare part requirements for non-repairable systems and purchasing strategies for these parts. These strategies are based on a stochastic characterization of the time between failures of the system. The inventory level to be maintained will depend upon the need of such parts in consecutive time intervals or inventory cycles to satisfy the maintenance requirements with an acceptable risk level.
When a company installs flexible manufacturing systems (FMS), the results can be truly startling; e.g. a substantial reduction in the number of machines, number of employees, floor space, inventory level, throughput and lead time and also higher quality products, greater flexibility to respond to the market needs etc. But when one comes to financial analysis through the traditional evaluation approach, the results are really disappointing. This is so because of the inability of traditional modes of financial analysis, like discounted cash flow, to incorporate most of the strategic benefits of FMS in its analysis. FMS investments are strategic investments and their full impact on the firm is not estimable in terms of cash flows. What is required in investment evaluation procedure to truly justify investments in FMS is the combination of both strategic and financial methods. The paper aims at evolving a new investment evaluation procedure which will integrate strategic planning with financial method.
This paper deals with the graphic simulation package developed to simulate mobile robots working in warehousing environments. Paths are planned for each robot that takes care of constraints and possible chances of collision with other robots. Decision making and simulation in real time dynamic environments is studied. Obstacle detection in the paths of the robots could result in bypassing the obstacle or path blockage. The effect on the other robots due to such “dynamic obstacles” is also analyzed.
In practice as well as in literature there is a strong emphasis on developing techniques for the control of production systems. Without attention for the production chain in which such a production system is embedded, this can easily lead to local suboptimization. This paper introduces two analysis tools (the integrated time-function and the integrated costfunction) aimed at preventing such suboptimization.
Bulk conveyor systems often employ bins to segregate flow and to prevent interruptions in material handling. Analytical methods for sizing these bins were explored for the case when they serve multiple loading sources, each discharging a series of individual loads onto the conveyor. These methods included both an exact expression of the probability distribution for the required bin capacity and a normal approximation. The two analytical methods and a simulation model were used to size bins for some real and hypothetical applications. In comparing the modeling results of each method, only minor differences in the bin sizes were seen. For the applications examined, the normal approximation would be preferred as very little computational effort is required.
In this paper, the problem of jointly setting order quantity of fresh items and discount price of one-period old items is modelled as a stochastic dynamic program for commodities that perish in two periods. It is solved using a heuristic procedure that decouples inventory decisions in any two consecutive periods by assuming a salvage value of leftover fresh items that is also the price paid for the entering stock of one-period-old items. For an assumed salvage value, the single period expected profit maximizing ordering - discount policy pair is identified. The m-periods planning problem is then solved by sequentially solving m single period problems. Numerical examples reveal some valuable insights about the inter-dependencies between order quantity and discount price. The percent discount is found to be insensitive to the assumed salvage value.
This paper focuses on the problems of logistics from several viewpoints relevant in practice. Empirical observations are extracted from different branches of industry. Based on these observations we classify a set of approaches. We consider that an appropriate approach in future is the integrated paradigm having a basis on traditional industrial engineering discipline supported by information, communication and calculational technologies. This paper is associated with an ongoing Esprit II project 2277-CMSO (CIM for Multisupplier Operations).
We consider the selection of optimal lead time variability in continuous review inventory models. The variability level is optimized jointly with the lot size and reorder point, where lower variability can be achieved at an extra cost. Low variabilities may correspond to more reliable sources or production processes, and their attainment is one of the implicit goals of JIT logistics. We analyze the resulting tri-variate models, providing sufficient conditions for joint convexity, and hence unique optimum, an algorithm and illustrative examples.
The decision network approach to batch sizing problems presented in this paper arrives at a solution by a technique similar in style to critical path analysis in which much of the information is presented in a network diagram. This allows it to provide a visual representation of the problem and analysis is carried out by forward passes through the network. It is shown that decision networks can be applied to deterministic and stochastic problems.
Determing the number and type of AGVs and the assignment of AGVs to transport parts between workstations is an important problem encountered in the design of an Automated Guided Vehicle System (AGVS). In this paper, an optimization model is proposed to solve this problem. The model minimizes the overall system cost defined as the sum of the annualized cost of operating the AGVs and the cost of transporting parts between workstations. The model is illustrated using a numerical example.
In this paper an algorithm is suggested for determining the economic ordering policy for a product procured centrally by a supplier and distributed from a central warehouse to a number of retailers. The product is subsequently distributed to customers from the retailers. The objective is to minimize the total costs of the supplier resulting from the ordering costs, the distribution costs and the inventory carrying costs of the central warehouse and the retailers. An example is given to illustrate the method.
In this paper, the economic dispatch problem of a power system is formulated mathematically by using a linear load flow model. The generation cost is considered as a quadratic function of the generated active power of the generating nodes of the power system. Thus, the optimum allocation of active power generation, among the generating nodes, can be calculated for minimum generation cost.
Parenco produces high-quality newsprint for several well-known European daily newspapers. To maintain their proud reputation, they must maintain both quality and quantity of production.They use the Bruel and Kjaer Systematic Machine Condition Monitoring concept to monitor the vibration spectrum at 6000 measurement points on their paper machines and power plant. The system features early fault detection, powerful fault diagnosis, and trend analysis to predict the lead time to breakdown.This paper describes the use of this Bruel and Kjaer system at the Parenco paper mill.
Inventory system costs tend to be higher if uncertainty prevails in the supply lead times and consequently in the demand during the lead time because of the possibility of shortages or the need to maintain larger safety stocks. In this paper we explore a dual-sourcing technique in which the replenishment order quantity for the inventoried item with stochastic lead times is split between two sources of supply, and split-orders are placed simultaneously. It is shown that this results in effective lead times with lower variability and hence savings in the inventory holding and shortage costs are possible. If these savings exceed the incremental ordering costs associated with procurement from two sources overall cost economies result. In this paper, the theoretical concepts underlying the dual-sourcing technique and its implications for implementation in procurement management are presented along with an overview of the recent research in the area of dual sourcing.
In this paper a model which explicitly recognizes the relationships between the plant capacity, the lead time for building the plant, and the discount rate used in evaluating the project, is developed. It is shown that the introduction of a discount rate which is a function of capacity, substantially alters the results obtained in a previous study where the discount rate is assumed to be constant. In particular, since the net benefits of an additional unit of capacity is discounted using a higher rate, the NPV is suppressed. An extensive sensitivity analyses on the nonmonetary and monetary parameters and their effect of the optimal plant size vs optimal NPV is provided.
