Adapting EWMA Control Charts for Batch-Correlated Data

Batch production is common in the chemical and process industries. This article demonstrates how EWMA charts should be modified to account for substantial batch-to-batch variation. A batch-correlation model is considered, and methods of estimation and hypothesis testing for the batch-correlation coefficient are developed. This discussion is most appealing for production processes in which items are processed in batches but are related within batch.     

A service-level-oriented heuristic approach to production planning in a robotized spinning-mill

This paper presents a heuristic approach to production planning and inventory control. The heuristic was developed for scheduling the production of N-products on many machines when both production and demand rates are stochastic. The key for scheduling production is a target inventory level to be maintained at the beginning of each period; hysteresis factors within the heuristic make the production plan more or less sensitive to transient conditions in both demand and production. Experimental results of its application in a production environment are provided.     

基于Witness的汽车零部件生产物流系统仿真研究

在分析某企业汽车零部件生产物流系统基础上,采用Witness仿真软件对汽车零件的制造流程进行仿真研究。通过仿真发现该企业汽车零件生产物流系统存在的问题,进而提出改进方案。结果对比,设备利用率提高幅度91.43%;生产周期缩短幅度43.43%;生产率提高幅度67.80%。应用本论文研究结论可有效提高该企业的生产效率和效益,同时本论文也为其他制造企业的生产物流系统分析与改善提供了理论依据和方法。     

Optimising lot sizing and order scheduling with non-linear production rates

This research focuses on developing an optimum production schedule in a process with a non-linear production rate. Non-linear production processes may exhibit an increasing production rate as the lot size increases, which results in increasing efficiency in per-unit production. The degree to which this learning is carried forward into the next lot varies by process. Sometimes the learning effect experiences a 100% carryover into the next lot, but other times some learning is forgotten and there is less than a 100% carryover. We consider processes in which the learning effect is completely forgotten from lot to lot. In practice non-linear processes are often treated as linear. That is, the production data are collected and aggregated over time and an average production rate is calculated which leads to inaccuracies in the production schedule. Here we use a discretised linear model to approximate the non-linear process. Production occurs in discrete time periods within which the amount produced is known. This enables a production schedule to be determined that minimises production and holding costs. A dynamic programming model that starts with the latest demand and progresses towards the earliest demand is used to solve the single-product single-machine problem. The model is tested using the production function from the PR#2 grinding process at CTS Reeves, a manufacturing firm in Carlisle, Pa. Solution times are determined for 50, 100, 200, 500, 1500, and 3000 periods.     

Optimal cycle time and production rate in a family production context with shelf life considerations

This paper considers the problem of determining the optimal production rate for each item and the optimalcycle time for the family of items in a family production context with restrictions on the shelf life of the various items in the family. An algorithm that determines the optimal production rate for all the items as well as the optimal cycle time is proposed. This is an improvement over the existing method by Silver (1995) that can determine the optimal production rate only for one item for which the shelf life constraint is binding. Examples are provided to illustrate the proposed method.     

Estimating the output of a series production system

This paper presents methodology which can be used to estimate the output of a production line with surge (in-process inventory or buffer stocks). This methodology is of use to those concerned with designing new production lines and modifying existing ones. The approach is specifically developed for unbalanced production lines but is applicable to the balanced line as well. A balanced production line is one where all machines operate at an identical rate. It is assumed that uptimes are exponentially distributed; however, the development is valid for general downtime distributions.     

Setup tasks scheduling during production resettings

Production waste reduction during production resettings is critical in the industry as it is the key point of flexibility increase. One way to improve production waste is to assign setup tasks efficiently to operators. This article describes a possible model of this problem adapted to a real-life application. This model is based on an unrelated parallel machines problem that takes into consideration the skills of the operators and the production line structure. The nature of the data and some industrial constraints help us simplifying this problem into an assignment problem. As often in the industry, the objective is to maximise production. Because most production lines are complex series parallel lines, it is often possible to maintain production even if not all machines are running. This particularity makes the criterion hard to express as it depends on the line structure. In this article we describe three heuristics to solve this problem: a hill climbing algorithm, a genetic algorithm and a memetic algorithm that combines the advantages of the two previous algorithms. The neighbourhood used for these algorithms is based on multiple exchanges of tasks between operators.     

Modelling and analysis for sequentially optimising production,maintenance and delivery activities taking into account product returns

This paper develops and analyses a stochastic optimisation problem with a service level constraint for generating a sequentially optimal plan of production, maintenance and delivery activities in a deteriorating manufacturing system. Stochastic demand along with product returns are both assumed the latter of which allows for restocking products returned by the customer which are still new and thus in saleable condition. A constrained production/maintenance/delivery problem with service level, stochastic demand, delivery time, failure rate and product returned is formulated based on quadratic model. This quadratic formulation is adapted to provide an inventory, delivery, production and maintenance policies. The objective of this paper is to study the delivery time influence on the planning of the production, maintenance and delivery activities. Finally, we present simulation results to illustrate the exploitation of the proposed approach.     

Regional Innovation Measured by Patent Data—Does Quality Matter?

This paper devises a new way of measuring the geographical scope of innovation based on patent data and compares its geographical distribution with that of patents granted and production. Indicators of patent quality are used to form an index of regional innovation, which is argued to be an improvement over patent counts, which are seen as indicators of inventions. Innovations are more concentrated than inventions, which in turn are more concentrated than production, gauged by employment levels. Innovations are, moreover, concentrated to regions with already high production and invention levels. This indicates that the concentration of innovation is understated, as raw patent counts are used to proxy for innovation rather than quality patents. The results further point to the need for revaluing effect of R&D on local innovative activity.     

应用工业工程的方法提高生产效率:案例研究

介绍了某种型号滤波器的生产工艺改善.在运用工业工程的技术和方法对生产工艺加以分析后,一些工位被重新编排,而一些手动操作则实现了自动化.通过工作再设计,生产线的平衡得到改善,生产率也因此得到很大的提高,同时生产成本也降低了近1/3.     

基于柔性生产的生产物流平衡策略研究

柔性生产的有效开展需要保持生产物流始终处于平衡状态。研究了柔性生产下如何保持生产物流平衡的策略问题。首先分析了柔性生产下生产物流平衡的内容,然后就如何平衡生产物流进行了深入探讨。研究结果表明,提高生产的负荷率、均衡率和合同的完成率,这是柔性生产下平衡物流的目的,也是物流平衡的主要内容;而保持生产线平衡、识别瓶颈资源、编制好生产作业计划、设置缓冲环节则是平衡生产物流行之有效的关键手段和策略。     

Product quality inspection in Bernoulli lines: analysis,bottlenecks, and design

This paper is devoted to serial production lines consisting of producing and inspection machines that obey the Bernoulli reliability and Bernoulli quality models. Such production lines are encountered in automotive assembly and painting operations where the downtime is relatively short and the defects are due to uncorrelated random events. For these systems, this paper develops analytical methods for performance analysis, bottleneck identification, and design. In addition, insights into the nature of bottlenecks in such systems are provided, and an empirical rule for placing an inspection machine that maximises the production rate of non-defectives is formulated.     

Optimal policies for aggregate production and capacity planning under rapidly changing demand conditions

This paper presents an optimal control approach to continuous-time aggregate production planning problems. The proposed approach describes the production and capacity expansion processes in the form of differential equations with regular production, overtime and capacity expansion rates controllable on one hierarchical level. In this way, the traditional disadvantages of the two-level problem consideration (one level for strategic capacity planning and the other for production smoothing) are avoided and optimal control policies can be obtained. This approach is of special importance when taking into account highly changing demand profiles and nonlinear cost functions. Study of the maximum principle results in analytical properties for the optimal production and capacity expansion policies and conditions for their changeover. Based on these results, insight into the optimal behaviour of the production system is gained and a fast numeral method is developed to identify and sequence the optimal policies for arbitrary demand profiles. A computational example illustrates the effectiveness of the approach.     

An integrated preventive maintenance and production planning model with sequence‐dependent setup costs and times

This paper considers the integration of preventive maintenance and tactical production planning in a multiproduct production system, where setup costs and times are sequence dependent. A set of products needs to be produced in lots during a finite planning horizon, where preventive maintenance is conducted periodically at the end of some production periods and corrective maintenance is always performed when there is a failure. The system downtime—as caused by maintenance and setup—affects the system's available production capacity. We use a sequence‐oriented method to search for the optimal setup sequence and develop some steps to prune the searching tree. Our objective is to find the optimal preventive maintenance interval, production lot size, and production sequence in every period, by minimizing the sum of maintenance, production, inventory, and setup costs within the planning horizon. Numerical examples are presented to illustrate our model.     

OPTIMAL PRODUCTION PLANNING AND INVENTORY CONTROL*

This paper is concerned with the optimal production planning and inventory control. The first problem is a multiperiod production scheduling problem in which the objective is to minimize the operating cost for a planning period. This cost is composed principally of the sum of the production cost and inventory carrying cost. The second problem considers an inventory system with two decision variables in each planning period. These are the production schedule and work force which are to be determined so as to minimize the operating cost which includes the costs of changing the production rate, of changing the work force and of carrying the inventory. The maximum principle in the discrete form is used to reduce both the first problem which has N decision variables and the second problem which has 2N decision variables respectively to a series of two decision variables problems. The so-called sequential simplex pattern search technique is used to determine the optimal values of these two decision variables. Numerical examples are given to demonstrate the method.     

灵捷生产系统

我国企业面临变化和不确定的市场环境，要求建立具有快速性、多品种适应性和可重组性三层特性的灵捷生产系统，以抓住市场机遇。本文针对某小型企业的具体情况，设计了一种基于自治单元的混合生产系统。这个方案交少的层次，统一管理生产部门和生产后勤部门；综合动用拉式与推式方法进行生产计划与控制。论文讨论了单元内部的组织机制和可重组性的实现要素。本文对我国中小企业生产重构有一定参考价值。     

Parallel-machine,multiple-product-type,continuous-time scheduling: decomposable cases

This paper considers a manufacturing system where multiple-product-types are produced on a set of parallel machines. The production quantity for each product-type in a planning horizon is predetermined. However, the planning horizon is not fixed, and a cost must be paid for each unit of time in the horizon. Inventory holding costs are incurred due to storing products in the buffer placed after each machine. In addition, a production cost is incurred if a machine is not idle. Our objective is to schedule the production so that inventory, production, and planning horizon costs are minimized. With the aid of the maximum principle, this continuous-time scheduling problem is studied, and the conditions such that the problem can be decomposed into a set of well-structured, discrete-time sub-problems are derived. Consequently, several solvable cases are identified, and their corresponding polynomial-time algorithms are suggested.     

Economic order quantities and variations in production load

When production orders are initiated by an inventory control system the production load daring a given time period can be looked upon as a random variable. When order quantities are large the variations in production load can be a severe problem. One way to smooth the variations in the load is to use smaller order quantities than those given by traditional lot sizing techniques. This is in practice done with the aid of simple rules of thumb. In this paper we describe a model for determining order quantities when the cost of a varying production load is recognized. The required production capacity is defined by a small given probability for overload during the time period regarded.     

Quality control by the optimal control of a discrete-state stochastic process

This paper provides a stochastic control approach to quality control. Results and numerical examples are used to assess the mutual effects of the costs of inspection sampling and the failure of units that have been sold. The approach is an extension of classical statistical quality-control procedures. Firstly, the time dimension in production is explicitly considered and secondly, non-constants, such as variations in production output, production reliability, etc., with lines, are used in formulating the problems. These problems are then resolved analytically for linear inspection and failure costs and numerically for non-linear costs.     

Manufacturing batch size and ordering policy for products with shelf lives

This paper determines an optimum production schedule and raw material ordering policy for a family of products that share a common piece of production facility, and the inventory operates under a shelf life constraint. The problem of manufacturing a family of products under shelf life is addressed here mainly under three major issues: adjusted production rate, adjusted cycle time, and simultaneous adjustment of production rate and cycle time. This research addressed the issues in two major parts: the first part comprises planning an optimum production schedule and material ordering policy for a family of products with a constant production cost for operating the machines. The second part of the research considers a generalized production cost of operation where the cost of operation may increase or decrease depending on the production system. Results are demonstrated to show the computational mechanics and incremental advantages over the other models. A sensitivity analysis is performed to study the effect of variability of some parameters that play important roles in the models. An empirical test has also been conducted to show the relative performance of the models.