Evaluation of value stream mapping in manufacturing system redesign

The value stream mapping (VSM) technique, developed within the lean production paradigm, was presented as an innovative graphic technique to help practitioners redesign production systems. This paper presents the results of a project whose main purpose is to evaluate the real applicability of VSM to redesign disconnected flow lines based on manufacturing environments with a diversity of logistical problems. The research was developed using multiple case study methodology in six industrial companies. The experiences have served to highlight the following results: (1) the validity of VSM as a redesign tool is confirmed; (2) resources required for the application process are established; and (3) the differences between theoretical concepts proposed by VSM and their real-world practical applications are indicated and analyzed. These results have led to conclusions relating to: (1) communication solutions for practitioners to obtain maximum efficiency when using VSM; and (2) definitions of theoretical development points for VSM to become a reference among redesign techniques.     

延迟制造技术条件下单螺杆式压缩机生产改进研究

基于延迟制造技术的基本理论,主要研究单螺杆式压缩机的生产方法。分析运用延迟制造技术后。生产管理方面的变化情况,重点研究采用延迟制造技术后有关单螺杆式压缩机生产计划编制和工艺方法。最后对于延迟制造技术和大规模定制的广泛应用进行分析、总结。     

Use of the manufacturing system design decomposition for comparative analysis and effective design of production systems

The focus of this paper is on the use of the Manufacturing System Design Decomposition (MSDD) to make effective cost and production system design decisions. A comparative study is conducted to illustrate how and why the total cost is reduced when the functional requirements defined by the MSDD are achieved. The ultimate goal of this research was to advance manufacturing and production system development to being guided by engineering science and design rather than the common practice of duplicating another person’s or entity’s notion of the best physical implementation.     

On postponement strategies for product families with multiple points of differentiation

Several researchers have studied the benefits of product and process design that calls for delaying the differentiation of products. Previous research has focused on products having only one point of differentiation. However, in reality most product families have several points of differentiation. In this paper, we develop two models to study products with more than one point of differentiation. In each model, we examine the benefits of delayed differentiation at each of these points, and derive the necessary conditions when one type of delayed differentiation is more beneficial than the other. Our analysis indicates that demand variabilities, correlations and the relative magnitudes of the lead times play an important role in determining which point of differentiation should be delayed.     

Delayed reconfigurable manufacturing system

Reconfigurable manufacturing systems (RMS) is a new manufacturing paradigm aiming at providing exactly functionality and capacity needed and exactly when needed. Reconfiguration is the main method to achieve this goal. But, the reconfiguration is an interruption to production activities causing production loss and system ramp-up problem and the ‘exact functionality’ may increase the reconfiguration efforts and aggravate the production loss and the ramp-up time. Therefore, a special RMS – delayed reconfigurable manufacturing system (D-RMS) is proposed to promote the practicality of RMS. Starting from the RMS built around part family with the characteristic of delayed differentiation, whose reconfiguration activities mainly occur in the latter stages of manufacturing system and the former stages have the potential to maintain partial production activities to reduce production loss during reconfiguration. Inspired from this, the basic structure of RMS is divided into two subsystems, subsystem 1 is capable of maintain partial production with a certain more functionality than needed, subsystem 2 reconfigure to provide exactly functionality and capacity of a specific part exactly when needed. And then, the benefits of D-RMS are analysed from inventory and ramp-up time aspects. Finally, a case study is presented to show the implementation process of D-RMS and validates the practicability of D-RMS.     

Two-level hedging point control of a manufacturing system with multiple product-types and uncertain demands

This research is motivated by the co-operative production process of networked manufacturing systems (NMS). Manufacturing resource sharing and flexible production scheduling are two features of NMS. For an individual manufacturing system in an NMS, ‘flexible production scheduling’ means that it can produce multiple product-types and the switching of products is quick enough to respond to the demand fluctuation. ‘Manufacturing resource sharing’ means the utilisation of extra production capacity from other manufacturing systems in the NMS. Of course, that will bring extra cost. This paper focuses on the optimal production control problem of such a situation: one manufacturing system, multiple product-types, and uncertain demands. Here, it is assumed that there are two demand-levels for each product-type: the lower one and the higher one. The total normal production capacity is larger than the total lower demands and smaller than the total higher demands. If the total demands cannot be satisfied and the work-in-process (WIP) of all product-types decrease to a certain level, e.g. zero WIP, the extra production capacity may be utilised. For such a system, a new two-level hedging point policy is proposed, in which two hedging points (a higher one and a lower one) are given for each product-type. Different from the prioritised hedging point (PHP) policy which is usually applied to one-machine and multiple part-type systems, our control policy considers all part-types at the same prioritised level and keeps the work-in-process states of all product-types on a straight line in the state space. Thus, the total costs for WIP inventory and the occupation of extra capacity can be obtained in a closed form, which is a function with respect to the hedging points. Then the method for optimising the hedging points is proposed and the special structure of the optimal hedging point is obtained. Numerical experiments verify the optimality and the special structure of the hedging point obtained by our method.     

Data envelopment analysis with multiple modes of functioning. Application to reconfigurable manufacturing systems

In principle, data envelopment analysis (DEA) does not consider the possibility, which can occur in practice, of a production system being able to operate in different modes of functioning. In this paper, a new DEA modelling approach is proposed in which the different modes of functioning are taken into account and included in the analysis. The observed input consumption and output production in each mode of functioning is used to derive a mode-specific technology. The overall DEA technology aggregates these mode-specific technologies according to their respective time allocations. The proposed model computes a target operating point for each mode of functioning so that the operation of the overall system is efficient. The proposed approach is applied to assess the technical, cost and allocative efficiency of a reconfigurable manufacturing system. The inputs considered are modules/tools usage, labour and energy consumption. The outputs are the number of units produced of each part type. The production possibility set is determined by previous observations of the system functioning, from which the best practices can be identified. Technical, cost and allocative efficiency scores can be computed. The proposed approach not only generates input cost savings but also lead time reductions.     

异地协同设计制造关键技术及系统实现

 在分析制造业面临的新挑战以及网络化制造特点的基础上，提出了基于Web的异地协同设计制造系统的体系结构并开发了一个实际系统eCWS(e—cooperative work system )．详细介绍了该系统的功能和关键技术的实现，包括协同系统管理、协同工作管理、协同应用、约束管理和冲突消解、协同工具、安全控制、分布式产品数据管理等技术． 最后介绍了应用实例．     

Performance evaluation for a footwear manufacturing system with multiple production lines and different station failure rates

This paper develops a three-phase procedure to measure the performance of a highly value-added footwear manufacturing system taking reworking actions into account, in which the system consists of multiple production lines. We mainly address the system reliability as a performance indicator to evaluate the possibility of demand satisfaction. First, we construct the manufacturing system as a manufacturing network by graphical transformation and decomposition. Second, capability analysis is implemented to determine the input flow of each station based on the manufacturing network. Third, a simple algorithm is proposed to generate all minimal capacity vectors that stations should provide to satisfy the given demand. We evaluate the system reliability in terms of the minimal capacity vectors. A further decision making issue is discussed to decide a reliable production strategy. Whenever the system state changes, the proposed performance evaluation procedure can be implemented easily and flexibly.     

Modelling and analysis of a multiple product manufacturing system with split and merge

To satisfy a rapidly changing market and various requirements of customer demand, many automotive assembly systems are designed to increase flexibility. One way to achieve this is to have a system making multiple products through split and merge. This paper presents an iterative approach to model such a kind of flexible manufacturing system with common lines and dedicated branches to process different products. The mathematical procedures, associated with the justification of convergence and accuracy, are provided. A case study is presented to illustrate the applicability of the method.     

Stochastic economic lot sizing and scheduling problem with pitch interval,reorder points and flexible sequence

This paper presents a solution for a class of the stochastic economic lot sizing scheduling problem that is typical of the replenishment pull system proposed by the lean manufacturing approach. In this class, lots of any product are produced in fixed intervals called pitch. The proposed solution uses flexible production sequences and reorder points that are compatible with the concepts of supermarket and level production. It adopts the queuing discipline obtained from a fluid model that approximates the stochastic process of arrival and production orders. Given the queuing discipline, an iterative algorithm returns a near-optimal solution for the system. The proposed approach allows us possible to differentiate inventory cost and service levels by product, and the stock required is lower than that required by the discipline ‘first stock out, first out’. The algorithm is fast and stable, allowing its frequent use in real-world instances.     

双重资源约束条件下制造系统的调度

 根据近年来关于制造系统优化调度问题的研究状况，阐述了具有计算智能的方法，特别是遗传算法在调度问题研究中的应用． 指出同时考虑设备和工人两种资源限制的双重资源约束条件是很重要的，提出了一种混合调度原理和方法．     

Two-step approach to robust deadlock control in automated manufacturing systems with multiple resource failures

ABSTRACT

In an automated manufacturing system (AMS), resource failures are inevitable, which renders the existing deadlock control policies for AMSs without considering resource failures ineffective. For the AMSs with multiple unreliable resources, in this paper, a method is developed for robust deadlock resolution using the framework of Petri nets (PNs). The considered AMSs are modeled with PN models called system of simple sequential process with resources (S³PR). An unreliable S³PR (U-S³PR) is obtained by adding recovery subnets that model the resource failures and recovery procedures of the places where resource failures may happen. Based on the model, a two-step approach is developed to design a robust controller. At Step 1, we use a siphon-based deadlock control method to analyze the behavior with resource failures and propose an incomplete robust deadlock controller for a U-S³PR. At Step 2, a reachability-graph-analysis-based method is utilized to consummate the robust deadlock controller. Then, a robust liveness-enforcing supervisor is derived to make an unreliable S³PR live even if multiple types of resources break down. Finally, the proposed method is illustrated by using an example.     

Performance analysis of re-entrant manufacturing networks under surplus-based production control

Motivated by the problem of planning and scheduling in large semiconductor manufacturing facilities we study the performance of re-entrant production networks. In such networks, each product has to go multiple times through the entire manufacturing line before it is ready. Each machine in a re-entrant network can receive products from different routings, but the products from only one of the routings can be served at a time. This complicated network structure makes it difficult, and at the same time important, to estimate in advance the performance of such a network under a demand-driven control policy. In this paper we present results on the influence of perturbations, buffer inventory levels and the number of manufacturing stages on the production tracking error of each machine in the re-entrant network operated under a surplus-based production control policy. The results are provided in the form of so-called ‘worst case scenario’ bounds on the steady-state production demand tracking accuracy of each stage as well as bounds on the content of each intermediate inventory level. By means of simulation examples we show that the results obtained have an important meaning and can be used as a practical reference tool.     

Formation of independent manufacturing cells with the consideration of multiple identical machines

Cellular manufacturing is a manufacturing philosophy with the goal to produce low-medium volume products with high variety, while maintaining the high productivity of large-scale production. It is recognised as one of the most powerful management innovations in job-shop and batch production. Among the problems of designing a cellular manufacturing system, cell formation is the central and foremost issue. In the present paper, we investigate the formation of independent manufacturing cells with the consideration of multiple identical machines, in which inter-cell movements are completely eliminated by allocating identical machines in different manufacturing cells. Incorporating many real-life production factors including processing time, set-up time, alternative processing routes, machine capacity, batch size and cell size, we formulate a bi-objective mathematical model to minimise workload imbalance among manufacturing cells. Then, a genetic algorithm based on non-dominated sorting genetic algorithm II is developed to solve it. The computational results of numerical examples and the comparison analysis validated the performance of the proposed algorithm.     

Balancing of manufacturing systems with complex configurations for delayed product differentiation

In response to increasing product variety, manufacturing systems with complex asymmetric configurations have often been used for delayed product differentiation. Balancing these types of manufacturing systems, however, is a challenge, since existing line balancing methods usually have been developed for symmetric configurations, such as serial lines with parallel machines at some stages. This paper proposes a novel binary integer programming (BIP) model for task-machine assignment and workload balancing in complex asymmetric configurations for mixed-model production. The new model includes (1) mathematical representations of task relations and system configurations, (2) constraint equations for task precedence relations in asymmetric configurations, and (3) constraint equations for parallel/serial relations among tasks. This study extends the area of line balancing and task-machine assignment problems to asymmetric system configurations, and helps to select a configuration from alternatives.     

Measuring machine and product mix flexibilities of a manufacturing system

This paper provides a brief discussion on flexibility concepts in manufacturing. It emphasizes that flexibility measurements in a manufacturing system should be studied under dynamically changing environments rather than static ones. The approaches for assessing two major flexibility types, machine flexibility and product mix flexibility response, are presented. The machine flexibility model is based on machine-operation efficiency. The product mix flexibility response model is based on the difference between products in terms of tooling requirements, the number of operations that a machine can perform and the efficiency of different machines.     

Fuzzy-based system reliability of a labour-intensive manufacturing network with repair

This paper presents a fuzzy-based assessment model to evaluate system reliability of a labour-intensive manufacturing system with repair actions. Due to the uncertainty in human performance, labour-intensive manufacturing systems must determine the capacity of each labourer in order to accurately characterise the performance of the systems. Therefore, we model such a manufacturing system as a fuzzy multi-state network in order to characterise the labourers’ influence on workstation performance. First, the workstation reliability is defined according to the loading state by three fuzzy membership functions, namely ‘under loading’, ‘normal loading’ and ‘over loading’, respectively. The system reliability is subsequently evaluated with fuzzy intersection operations in terms of these workstation reliabilities. Thus, the system reliability is defined as a fuzzy membership function to assess whether the manufacturing system performance is sufficient to satisfy the demand reliably. A case study of a footwear manufacturing system is illustrated to explain the proposed model. Furthermore, we apply the proposed model to a non-labour-intensive manufacturing network in order to validate the applicability to this class of systems.     

基于成组编码的零件制造成本评价

根据敏捷制造的特点，在分析现有零件制造成本评价方法的基础上，提出了基于成组编码的零件制造成本评价方法，并以冲压件为例，制定了基于成本特征的零件成组编码系统，实现了敏捷制造模式下零件制造成本的快速评价。     

The elementary flux modes of a manufacturing system: a novel approach to explore the relationship of network structure and function

Elementary flux modes (EFMs) are a concept from Systems Biology, where they serve as an indicator of component relevance in metabolic networks. An elementary flux mode is a functionally relevant, non-decomposable path through a given network. In this paper, we apply elementary flux mode analysis to manufacturing systems, with the aim of using the number of EFMs as a predictor for resource significance in the manufacturing system. For this, we formulate a network representation of a manufacturing process, which allows us to define the manufacturing equivalent of a stoichiometric matrix to draw an analogy between metabolic and manufacturing systems. This, in turn, allows the computation of EFMs, which we conduct in a case-study for a real manufacturing system. We further show that the change of EFMs under resource breakdown is a good indicator of the average order lateness in the manufacturing system. In this way, EFMs provide insight into the relationship of network structure and function in manufacturing.