The measurement of flexibility in manufacturing systems

This article provides a theoretical basis for measuring the flexibility of manufacturing systems. The concept of multiple levels of measures (necessary, capability, actual, inflexibility, and optimality) for each flexibility type is introduced. Capability and actual measures are then developed for machine, routing, process, product, and volume flexibilities. For each of these flexibility types, a state defining variable is identified. A measure of flexibility is then derived by computing either, (i) the change effort expended in moving between states, (ii) the drop in system performance in moving between states, (iii) a general or physical scale of difference between two successive states, or (iv) a measure combining all three. The use of the developed measures is illustrated via a two-facility example.     

作业车间关键柔性的描述及其度量研究综述

为描述和度量作业制造系统的柔性,在制造系统柔性分类的基础上分析了作业车间的关键柔性,即机器(machine)柔性、工序顺序(operation)柔性和加工路径(routing)柔性,系统地评述了机器柔性、工序顺序柔性和加工路径柔性的描述方法和度量方法,并综述了三种关键柔性对调度的影响,最后讨论了未来可能的研究方向。     

A fuzzy-logic antiswing controller for three-dimensional overhead cranes

In this paper, a new fuzzy antiswing control scheme is proposed for a three-dimensional overhead crane. The proposed control consists of a position servo control and a fuzzy-logic control. The position servo control is used to control crane position and rope length, and the fuzzy-logic control is used to suppress load swing. The proposed control guarantees not only prompt suppression of load swing but also accurate control of crane position and rope length for simultaneous travel, traverse, and hoisting motions of the crane. Furthermore, the proposed control provides practical gain tuning criteria for easy application. The effectiveness of the proposed control is shown by experiments with a three-dimensional prototype overhead crane.     

A cost-tolerance analytical approach for design and manufacturing

Tolerance assignment in mechanical engineering product design and manufacturing is critical both for product quality and performance as well as for its manufacturing cost. Simple design rules, industry available comparative experimental data, tables, charts, and personal expertise are currently used for cost optimum tolerancing. Such a methodology is not very practical, requires considerable time and effort and is not always suitable for a CAD/CAM environment. To face these limitations, a new model for the manufacturing cost-tolerance function has been developed and is presented in the paper. It may well be used for direct-tolerance optimisation applications and it is shown that it produces results that are in satisfactory agreement with existing cost-tolerance data. Its use is further analysed and demonstrated in solving linear manufacturing tolerance transfer problems.     

A rule-based approach to predict forging volume for cost estimation during product design

The cost of manufacturing a part is an important consideration as it is being designed. However, early in the design process, not all of the design details of a part are decided, so the cost must be estimated from a limited amount of data. Raw material typically represents a significant portion of the part’s final cost, especially when parts are formed by forging, which requires a significant amount of additional material to be added to the final part. Therefore, an accurate estimate of the volume of the forging die is needed from limited information about the part geometry. This paper describes a rule-based system to quickly estimate the geometry (and thus, the volume) of the forging die that will be needed for an axisymmetric part based on its geometry. Tests of the methodology on aircraft engine components demonstrate that the methodology produces accurate estimates of the billet weight.     

Analysis of flexibility with rationing for a mix of manufacturing facilities

A major competitive advantage of a flexible manufacturing facility is its ability to cope with uncertainties in demand. At a strategic level, capacity-size decisions for a mix of flexible facilities (each not necessarily producing the same combination of products) are made based on aggregates of product types. Such an approach overlooks possible capacity-devouring by some products, arising at the operational level, when the aggregate demand for the period exceeds the available capacity. A rationing policy is required to ensure that the available aggregate capacity of the facilities is shared equitably. In this article, it is shown that such a rationing policy has an impact on the required capacity size and, therefore, must be integrated with the decisions at the strategic level. Several properties indicating the relative preferences of certain facility strategies are also established.     

A game-theory approach for job scheduling in networked manufacturing

This paper presents a new kind of scheduling solution for jobs in networked manufacturing environments. The main contributions of this study can be focused on three points: The first is to distinguish the concepts and requirements of job scheduling in the networked manufacturing environment form those in the traditional manufacturing environment. The second is to construct a game-theory mathematical model to deal with this new job scheduling problem. In this presented mathematical model, this new job scheduling problem is formulated as an N-person non-cooperative game with complete information. The players correspond to the jobs submitted, respectively, by related customers and the payoff of each job is defined as its makespan. Each player has a set of strategies which correspond to the feasible geographical distributive machines. Therefore, obtaining the optimal scheduling results is determined by the Nash equilibrium (NE) point of this game. In order to find the NE point, the last point is to design and develop a genetic algorithm (GA)-based solution algorithm to effectively solve this mathematical model. Finally, a numerical example is presented to demonstrate the feasibility of the approach.     

A systematic approach for the sequence controller design in manufacturing systems

This paper presents a systematic approach for the design and implementation of the sequence controller in manufacturing systems. By employing the IDEF0, we construct the simplified Petri net controller (SPNC) through the material flow diagram and the information flow diagram. Then, the ladder logic diagram (LLD) can be transformed from the SPNC through the token passing logic (TPL). The proposed approach, including the IDEF0, SPNC, and TPL tools, leads to the standard IEC1131-3 LLD for PLC implementation. Finally, an application of a stamping process is provided to illustrate the design procedure of the developed approach .     

A methodology for investigating effects of cell size on operational flexibility in flexible manufacturing systems

There are two aspects to cell formation in flexible manufacturing systems, cell sizing or deciding on the optimum number of machines to be allocated to each cell, and then allocation of specific machines to each cell. Although the latter problem has been investigated extensively there is a paucity of published work on the former. This paper discusses the effects of cell sizing on operational flexibility.Operational flexibility is that aspect of flexibility that enables manufacturing systems to respond with speed and efficiency to changes in the manufacturing environment while maintaining an effective level of control.     

制造系统柔性评价方法研究

深入分析评价制造系统柔性的基本要求,并介绍柔性熵的概念,建立评价系统柔性的数学模型。通过实例分析,证明该模型对评价制造系统柔性有一定的价值。     

软件柔性的概念和度量

为解决用户需求不断变化的问题,将柔性引人软件工程领域。讨论了软件柔性的相关概念,分析了软件的脆性、刚性、弹性、塑性、韧性和动物性等形态变化特征,提出了柔点、柔力、柔度、柔距及柔量等软件柔性的度量要素,给出它们的计算公式和计算实例;将面向用户的软件柔性划分为潜在柔性、可利用的柔性、已利用的柔性、当前柔性及需求柔性;将软件柔性的层次划分为自柔性、面向低级用户的柔性、面向高级用户的柔性和面向开发人员的柔性。针对信息系统中报表功能的问题,提出了柔性报表系统的思想,并以柔性报表系统为例,对软件的柔性、柔性软件系统及其应用进行了说明。     

Forming part-machine families for cellular manufacturing: A neural-network approach

This paper presents a new approach to forming group-technology part families for cellular manufacturing. The approach is based on neural-network technology, which mimics the way biological brain neurons perform to generate intelligent decisions. A procedure of forming part families using parallel and simple artificial neurons is described with examples. The implications and advantages of using neural networks in group technology are discussed.     

A systematic approach to manufacturing packaging logistics

Packaging is one of the most important activities in the distribution systems and supply chains. Nevertheless, it attracts little attention of people, especially in the manufacturing sector because packaging has been intensively used as a protective agent only. One of the prime factors that inhibit manufacturing efficiency and productivity is treating packaging activities as an individual task. In other words, traditional packaging is usually considered as a cost driven center rather than a value added component throughout the manufacturing and distribution processes. If we reconsider the packaging design in a systematic approach, it is easy to develop more cost effective solutions for manufacturing processing that can support handling and distribution as well as providing protection of the product. By the same token, it will bring additional values to a company because of the improvement in manufacturing and distribution efficiency. The aim of the paper is to review and reorganize the major functions and roles of the packaging played in the manufacturing and logistics system and suggest a methodology for a systematic approach to packaging logistics. The proposed approach is demonstrated through a case study. How to transform an existing packaging system to the proposed one is also suggested.     

A fuzzy-neural approach for estimating the monthly output of a semiconductor manufacturing factory

The customer order scheduling problem (COSP) is defined as to determine the sequence of tasks to satisfy the demand of customers who order several types of products produced on a single machine. A setup is required whenever a product type is launched. The objective of the scheduling problem is to minimize the average customer order flow time. Since the customer order scheduling problem is known to be strongly NP-hard, we solve it using four major metaheuristics and compare the performance of these heuristics, namely, simulated annealing, genetic algorithms, tabu search, and ant colony optimization. These are selected to represent various characteristics of metaheuristics: nature-inspired vs. artificially created, population-based vs. local search, etc. A set of problems is generated to compare the solution quality and computational efforts of these heuristics. Results of the experimentation show that tabu search and ant colony perform better for large problems whereas simulated annealing performs best in small-size problems. Some conclusions are also drawn on the interactions between various problem parameters and the performance of the heuristics.     

A holistic approach for the problem of storage space allocation in cellular manufacturing

Storage spaces are vital resources that must be allocated strategically in the design of cellular manufacturing systems. In this paper, a new storage space allocation approach was developed. A linear programming model was used to allocate available storage spaces among manufacturing cells, and an algorithm was used later to adjust the allocation levels based on the storage space availability. A simulation analysis aimed at determining the long-term effects of the space allocation on system performance was also performed. A sample problem was used to illustrate the allocation process. The results indicate that the developed model and the adjustment provided by the algorithm decrease the number of unsuccessful load transfer attempts by the intercell handling system.     

A decision-making approach to the operation of flexible manufacturing systems

This paper introduces a generic decision-making framework for assigning resources of a manufacturing system to production tasks. Resources are broadly defined production units, such as machines, human operators, or material handling vehicles; and tasks are activities performed by resources. In the specific context of FMS, resources correspond to individual machines; tasks correspond to operations to be performed on parts. The framework assumes a hierarchical structure of the system and calls for the execution of four consecutive steps to make a decision for the assignment of a resource to a task. These steps are 1) establishment of decision-making criteria, 2) formation of alternative assignments, 3) estimation of the consequences of the assignments, and 4) selection of the best alternative assignment. This framework has been applied to an existing FMS as an operational policy that decides what task will be executed on which resource of this FMS. Simulation runs provide some initial results of the application of this policy. It is shown that the policy provides flexibility in terms of system performance and computational effort.     

A novel particle swarm optimization approach for product design and manufacturing

This paper presents a novel optimization approach that is a new hybrid optimization approach based on the particle swarm optimization algorithm and receptor editing property of immune system. The aim of the present research is to develop a new optimization approach and then to apply it in the solution of optimization problems in both the design and manufacturing areas. A single-objective test problem, tension spring problem, pressure vessel design optimization problem taken from the literature and two case studies for multi-pass turning operations are solved by the proposed new hybrid approach to evaluate performance of the approach. The results obtained by the proposed approach for the case studies are compared with a hybrid genetic algorithm, scatter search algorithm, genetic algorithm, and integration of simulated annealing and Hooke-Jeeves pattern search.     

Effects of routing flexibility, sequencing flexibility and scheduling decision rules on the performance of a flexible manufacturing system

This paper focuses on a simulation-based experimental study of the interaction among routing flexibility, sequencing flexibility and part sequencing rules in a typical flexible manufacturing system (FMS). Two scenarios are considered for experimentation. Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using various measures related to flow time and tardiness of parts. The simulation results are subjected to statistical analysis. The analysis of results reveals that deterioration in system performance can be minimized substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. Part sequencing rules such as earliest due date and earliest operation due date provide better performance for all the measures at higher flexibility levels.     

Comparative influence of three flexibility types on manufacturing lead-time performance

This paper presents the results of a conceptual study and simulation experimentation aimed at understanding the impact of three important types of flexibility on the lead-time performance of a manufacturing system. The three flexibility types, viz. transformation flexibility, sequencing flexibility and product flexibility have been identified based on a new conceptual model for flexibility in manufacturing systems and supply chains. The influence of these three flexibility types has been studied using simulation models. The studies indicated that among the three, product flexibility has the greatest influence followed by transformation flexibility and the sequencing flexibility. The reasons for the inferior performance of sequencing flexibility is found to be reduction of dynamic flexibility levels as compared to its static flexibility levels and the reasons for superior performance of product flexibility is found to be the lower movement of products within the manufacturing system.