Experimental push/pull production planning and control system

We introduce an experimental push/ pull production planning and control software system which is designed as an alternative to a MRP-II system for mass manufacturing enterprises in China. It has the following distinguishing features: (1) putting the philosophy of JIT into the master production scheduling of MRP-II via the earliness/ tardiness production planning method; (2) controlling material input by push and processing/ assembly by pull; and (3) adjusting the parameters of the production line by the‘ suggestion for improvement of production line’ module. Simulation results have shown that the proposed system can achieve better planning and control performance than existing systems.     

Development of demand pull type control methods: The design of block action production control methods to reduce throughput time and improve supply chain synchronization

In this paper the implementation of time based manufacturing strategies and pull type control systems in an organization manufacturing electrical switchgear built to customers individual requirements are discussed in detail. The concept of block control to synchronize the production time of all internally and externally sourced components and materials is also introduced in an attempt to simplify production control methods and reduce throughput time. Savings in time and cost are described during a twenty months period of restructuring. Foundations were laid for a second objective which is an attempt to gain some linkage between throughput time reduction and resultant production costs.     

A Production–Inventory Model for a Push–Pull Manufacturing System with Capacity and Service Level Constraints

We study a hybrid push–pull production system with a two‐stage manufacturing process, which builds and stocks tested components for just‐in‐time configuration of the final product when a specific customer order is received. The first production stage (fabrication) is a push process where parts are replenished, tested, and assembled into components according to product‐level build plans. The component inventory is kept in stock ready for the final assembly of the end products. The second production stage (fulfillment) is a pull‐based assemble‐to‐order process where the final assembly process is initiated when a customer order is received and no finished goods inventory is kept for end products. One important planning issue is to find the right trade‐off between capacity utilization and inventory cost reduction that strives to meet the quarter‐end peak demand. We present a nonlinear optimization model to minimize the total inventory cost subject to the service level constraints and the production capacity constraints. This results in a convex program with linear constraints. An efficient algorithm using decomposition is developed for solving the nonlinear optimization problem. Numerical results are presented to show the performance improvements achieved by the optimized solutions along with managerial insights provided.     

Production control for just-in-time tool-and-die manufacturing

The strategy to implement production control varies in different types of manufacturing systems. We address the issue of production control in unit-based manufacturing systems where the production batch size of the final product is one or two, the product is custom designed and is made up of numerous individual components with similar process routeings lor special machine tools, turbines, boilers, tool-and-die, injection moulding equipment, custom fabrication, etc. We have developed algorithms to generate master production schedules in this particular domain of manufacturing systems using the concept of workgroups. We show how a Kanban-based JIT shopfloor control and purchasing system can be implemented in such systems in tandem with an inventory management system by utilizing the concept of demand lists. We also propose a model for practical implementation of production control in this domain. The methodology is illustrated at a tool-and-die plant where a CIM software is used to apply the JIT-based production control. Preliminary results show a significant reduction in lead times. We try to show the relationship between research and industrial applications of productions of production control and how to bridge the gap between them.     

REDUTEX: a hybrid push–pull production system approach for reliable delivery time in knitting SMEs

The textile sector is composed of small and medium enterprises (SMEs) worldwide. Nowadays there is a shortage of technological knowledge in SMEs. Lead time is a critical indicator in any productive company organisation. The aim of this research was to provide an approach, called REDUTEX, based on theoretical concepts of lean and synchronous manufacturing in order to help to understand the behaviour of SMEs and to improve the manufacturing process by reducing the customer lead times. The integration of these philosophies is the basis of REDUTEX; a hybrid push–pull production system approach to knitting SMEs. With this approach, it is possible to obtain a process reliability when the restrictive resource capacity (RRC) is identified, optimised and protected. By synchronising all activities to the rhythm of RRC, through a continuous flow, it is possible to obtain high-impact results through a dual automated system and product quality, through a visual control. REDUTEX uses a push system from the RRC to the location of the supermarket, where accumulated inventory may be distributed in the internal assembly department and external family workshops, making a pull system. Subsequent re-assembly processes use a push system until the end of the product. The stages of REDUTEX are explicitly described and applied to real data, so that the staff of SMEs can easily understand the behaviour of the process and implement it. One of the advantages of REDUTEX is that it does not need highly trained staff. The research methodology was conducted as a case of study in twelve SMEs and validated and implemented in three textile companies of the southern area of the state of Guanajuato in Mexico, obtaining reliable delivery times and very promising results.     

A simulation testing and analysis of aggregate production planning strategies

In this study, a hybrid discrete event simulation (DES) and system dynamics (SD) methodology is applied to model and simulate aggregate production planning (APP) problem for the first time. DES is used to simulate operational-level and shop-floor activities incorporated into APP and estimate critical time-based control parameters used in SD model of APP and SD is used to simulate APP as a collection of aggregate-level strategic decisions. The main objective of this study is to determine and analyse the effectiveness of APP strategies regarding the Total Profit criterion by developing a hybrid DES–SD simulation model for APP in a real-world manufacturing company. The simulation results demonstrated that the priority of APP strategies with regards to Total Profit criterion is: (1) the pure chase strategy, (2) the modified chase strategy, (3) the pure level strategy, (4) the modified level strategy, (5) the mixed strategy and (6) the demand management strategy, respectively. The APP system is first simulated under mixed strategy (basic scenario) conditions to include all APP capacity and demand options in constructed SD simulation model to show a comprehensive view of APP components and their interdependent interactions. Then, the obtained results will be used as Total Profit measure to compare with system's performance under some experimental scenarios applying different APP strategies.     

A Simulation Study of Work-in-Process Inventory Drive Systems and their Effect on Operational Measurements

This simulation study compares three operational measures of performance through the exploration of three work-in-process (WIP) inventory drive systems and their associated inventory buffer characteristics. The three drive systems under study are a push, a pull and a hybrid push-pull system. While these systems have many aspects in common, their buffer management systems do not. The data analysis was based on information gathered from three computer-simulated flow shop assembly lines all operating in the same environment. Hypotheses concerning the operational performance measurements were established, independent variables were controlled and manipulated and a conclusion was drawn as to which system would afford the operation optimum results. While inventory has traditionally been considered and is currently being shown as an asset from an accounting point of view, it is obvious from the findings of this study, that excess WIP inventory, above the minimal requirements for production, may have a negative effect on the operational measurements evaluated.     

Delayed Differentiation for Multiple Lifecycle Products

Modular design allows several generations of products to co‐exist in the installed base as product designs change to take advantage of improved performance via modular upgrades. Use of a common base platform and modular design approach allows a firm to offer updates for improved performance and flexibility via remanufacturing when products have multiple lifecycles. However, as the product evolves through multiple lifecycles, the large pool of product variants leads to the curse of product proliferation. In practice, product proliferation causes high levels of line congestion and results in longer lead times, higher inventory levels, and lower levels of customer service. To offer insights into the product proliferation problem, the authors employ a delayed differentiation model in a multiple lifecycle context. The delayed differentiation model gives flexibility to balance trade‐offs between disassembly and reassembly costs by adaptively changing the push‐pull boundary. An adaptive, evolving push‐pull boundary provides flexibility for a remanufacturing firm to meet changing customer demands. The delayed differentiation model includes both a mixed‐integer linear program and an analytical investigation of the evolutionary nature of the push‐pull boundary. Both field observations and experimental results show that the nature of product proliferation and changing demand structures play significant roles in the cost and flexibility of the evolving delayed differentiation system.     

Push and Pull Contracts in a Local Supply Chain with an Outside Market*

Wholesale price contracts are widely studied in a single supplier‐single retailer supply chain, but without considering an outside market where the supplier may sell if he gets a high enough price and the retailer may buy if the price is low enough. We fill this gap in the literature by studying push and pull contracts in a local supplier–retailer supply chain with the presence of an outside market. Taking the local supplier's maximum production capacity and the outside market barriers into account, we identify the Pareto set of the push and/or pull contracts and draw managerial implications. The main results include the following. First, the most inefficient point of the pull Pareto set cannot always be removed by considering both the push and pull contracts. Second, the supplier's production capacity plays a significant role in the presence of an outside market; it affects the supplier's negotiating power with the retailer and the coordination of the supply chain can be accomplished only with a large enough capacity. Third, the import and export barriers influence the supply chain significantly: (i) an export barrier in the local market and the supplier's production capacity influence the supplier's export strategy; (ii) a low import (resp., export) barrier in the local market can improve the local supply chain's efficiency by use of a push (resp., pull) contract; and (iii) a high import (resp., export) barrier in the local market encourages the supplier (resp., retailer) to bear more inventory risk.     

The introduction of Kanban principles to material management in EWSD production

Kanban systems combine two distinct and important functions. They control the flow of material through the manufacturing plant and they act as identifiers for deficiencies in the logistics of the production chain. This paper describes a Kanban system recently introduced to a Siemens manufacturing plant for telecommunication switching equipment in Florida, USA. Almost all stages of the formerly push-based manufacturing process were linked to each other through various types of pull systems. Ultimately, the system was extended to include suppliers of material. Emphasis is given to the importance of the planning and implementation processes since they have proven to be crucial to the success of the system.     

Dynamic performance of a hybrid inventory system with a Kanban policy in remanufacturing process

In this paper we study a hybrid system with both manufacturing and remanufacturing. The inventory control strategy we use in the manufacturing loop is an automatic pipeline, inventory and order based production control system (APIOBPCS). In the remanufacturing loop we employ a Kanban policy to represent a typical pull system. The methodology adopted uses control theory and simulation. The aim of the research is to analyse the dynamic (as distinct from the static) performance of the specified hybrid system. Dynamics have implications on total costs in terms of inventory holding, capacity utilisation and customer service failures. We analyse the parameter settings to find preferred “nominal”, “fast” and “slow” values in terms of system dynamics performance criteria such as rise time, settling time and overshoot. Based on these parameter settings, we investigate the robustness of the system to changes in return yield and the manufacturing/remanufacturing lead time. Our results clearly show that the system is robust with respect to the system dynamics performance and the remanufacturing process can help to improve system dynamics performance. Thus, the perceived benefits of remanufacturing of products, both environmentally and economically, as quoted in the literature are found not to be detrimental to system dynamics performance when a Kanban policy is used to control the remanufacturing process.     

Supply Chain Management of Fresh Products with Producer Transportation*

This article considers a class of fresh‐product supply chains in which products need to be transported by the upstream producer from a production base to a distant retail market. Due to high perishablility a portion of the products being shipped may decay during transportation, and therefore, become unsaleable. We consider a supply chain consisting of a single producer and a single distributor, and investigate two commonly adopted business models: (i) In the “pull” model, the distributor places an order, then the producer determines the shipping quantity, taking into account potential product decay during transportation, and transports the products to the destination market of the distributor; (ii) In the “push” model, the producer ships a batch of products to a distant wholesale market, and then the distributor purchases and resells to end customers. By considering a price‐sensitive end‐customer demand, we investigate the optimal decisions for supply chain members, including order quantity, shipping quantity, and retail price. Our research shows that both the producer and distributor (and thus the supply chain) will perform better if the pull model is adopted. To improve the supply chain performance, we propose a fixed inventory‐plus factor (FIPF) strategy, in which the producer announces a pre‐determined inventory‐plus factor and the distributor compensates the producer for any surplus inventory that would otherwise be wasted. We show that this strategy is a Pareto improvement over the pull and push models for both parties. Finally, numerical experiments are conducted, which reveal some interesting managerial insights on the comparison between different business models.     

Decentralized WIP-oriented manufacturing control (DEWIP)

DEWIP is a manufacturing control system for job shop environments aiming at achieving short and reliable lead times by establishing WIP control loops between the manufacturing work centres. The paper describes the mode of function, the setting of parameters and simulation results of the new manufacturing control system. The setting of parameters is done with the aid of the funnel model and the theory of logistic operating curves, both developed at the Institute of Production Systems at the University of Hanover. The simulation is conducted using industrial data and makes it possible to assess DEWIP with regard to lead times, WIP level, performance and schedule reliability. DEWIP is compared both with an uncontrolled process and with the manufacturing control systems Load oriented order release (LOOR), Conwip and Polca. The results suggest that DEWIP and the models employed for the setting of parameters are suitable for job shop production and therefore offer a valuable alternative to prevailing centralized manufacturing control systems.     

Information-Processing Alternatives for Coping with Manufacturing Environment Complexity

Investment in information systems and technology is often justified as a necessary strategy for coping with the increased complexity and information needs of today/s manufacturing environments. However, the world class manufacturing paradigm suggests that increased complexity is not always necessary to meet the needs of markets and customers. Galbraith/s (1973, 1977) seminal information-processing model is applied to a manufacturing environment, supported by the world class manufacturing paradigm, to test the role of various information-processing alternatives for coping with increased environmental complexity. Moderated regression and multiple discriminant analysis are used to test hypotheses in a sample of 164 manufacturing plants. Environmental complexity was found to be related to manufacturing performance for each of the five dependent variables. This relationship was moderated by at least one information-processing alternative for each dependent variable, including self-contained tasks, lateral relations, and environmental management strategies for reducing manufacturing, supplier, and goal diversity. Investments in information systems and reduction of labor and customer diversity did not moderate this relationship. Practices that were found to be particularly effective in moderating this relationship included the use of multifunctional employees, communication of manufacturing strategy, coordination of decision making, product design simplicity, reduction of parts counts, supervisory interaction facilitation, recruiting and selection for flexible employees, JIT practices, blanket purchase orders, and strong customer relationships.     

Applying Process Knowledge for Yield Variation Reduction: A Longitudinal Field Study*

The widespread recognition of the detrimental effects of high yield variation in advanced manufacturing technology settings, both in terms of cost and management of production processes, underscores the need to develop effective strategies for reducing yield variation. In this article, we report the findings of a longitudinal field study in an electromechanical motor assembly plant where we examined how the application of process knowledge by production work teams can reduce yield variation. We propose and provide an operationalizion of a strategy to identify the sequence of particular types of actions—actions to control the mean followed by actions to control the variance—that work teams should pursue over time to apply process knowledge for reducing yield variation. The results of our empirical analysis show that yield variation was significantly reduced on three of the four production lines at the manufacturing plant that served as our research site. Differences in strategies for applying process knowledge help explain the different results on each of the production lines.     

Push or Pull? Design of Content Delivery Systems

Advances in information technology, especially the expansion of cellular and WiFi networks, are dramatically changing how people consume digital content. These changes in user access behavior present a challenge of delivering content to a diversified consumer base. This article addresses this challenge by identifying the key factors for the design of content delivery systems (gross value of content, delivery delay, sensitivity to delivery delay, accessing cost, and processing cost) and explicitly modeling their interactions. We investigate two content delivery systems—push and pull systems, and solve for the content provider's optimal push frequency decision and consumers’ push versus pull decisions. We show that the content provider's selection of push frequency plays a critical role determining the segmentation of the consumer market into the push group and the pull group. Our findings suggest that firms should set a relatively high push frequency to cater to high‐type consumers, which leads to two consumer groups with low‐type consumers belonging to the pull group and high‐type consumers belonging to the push group.     

基于改进策略的混合型制造/再制造系统分析

在制造和再制造并存的混合型系统中,制造商需要同时协调新产品生产过程和旧产品再制造过程,这种双向物流的集成运作使得传统的生产规划和库存管理方式不再适用,如何构建一种有效的控制策略来协调生产过程和再制造过程就显得十分关键。本文在优化库存信息的基础上提出了一种适用于混合系统的改进策略,同时考虑到系统复杂性,主要采用控制理论中的传递函数技术构建了系统模型。仿真结果表明,本文提出的改进策略不仅可以有效协调新产品生产过程和旧产品再制造过程,而且还可以显著改善系统性能。     

Performance Impacts of Strategy,Information Technology Applications,and Business Process Outsourcing in U.S. Manufacturing Plants

This paper develops a conceptual model to study the role of outsourcing strategies and plant‐level information technology (IT) application infrastructure in the outsourcing of production and support business processes, as well as their subsequent impact on overall plant performance. We validate this model empirically using cross‐sectional survey data from U.S. manufacturing plants. We find that some IT applications are more effective at enabling the outsourcing of business processes than others. For example, the implementation of enterprise management systems is associated with the outsourcing of both production and support processes, whereas operations management systems are not associated with the outsourcing of plant processes. Plants with a low‐cost outsourcing strategy are more likely to outsource support processes than plants with a competency‐focused outsourcing strategy. However, both cost‐ and competency‐based strategies have a positive and similar impact on the outsourcing of production processes. In terms of implications for plant performance, our findings indicate that the outsourcing of production and support processes is associated with higher gross margins. Although plant IT infrastructure is positively associated with favorable on‐time delivery rates, there is no positive association between the incidence of plant outsourcing and on‐time delivery rates. These results have implications for crafting plant‐level outsourcing strategies and for investments in IT systems to facilitate the outsourcing of business processes for enhanced plant performance.     

The Comparison of Two Vertical Outsourcing Structures under Push and Pull Contracts

In a three‐tier supply chain comprising an original equipment manufacturer (OEM), a contract manufacturer (CM), and a supplier, there exist two typical outsourcing structures: control and delegation. Under the control structure, the OEM contracts with the CM and the supplier respectively. Under the delegation structure, the OEM contracts with the CM only and the CM subcontracts with the supplier. We compare the two outsourcing structures under a push contract (whereby orders are placed before demand is realized) and a pull contract (whereby orders are placed after demand is realized). For all combinations of outsourcing structures and contracts, we derive the corresponding equilibrium wholesale prices, order quantities, and capacities. We find that the equilibrium production quantity is higher under control than under delegation for the push contract whereas the reverse holds for the pull contract. Both the OEM and the CM prefer control over delegation under the push contract. However, under the pull contract, the OEM prefers control over delegation whereas the CM and the supplier prefer delegation over control. We also show that for a given outsourcing structure, the OEM prefers the pull contract over the push contract. In extending our settings to a general two‐wholesale‐price (TWP) contract, we find that when wholesale prices are endogenized decision variables, the TWP contract under our setting degenerates to either a push or a pull contract.     

基于网络外部性的绿色制造策略研究

根据消费者的绿色偏好以及产品的网络外部性特征构建消费者效用函数,在此基础上,对供应链的制造策略进行分析。首先,利用逆向归纳法获得了Stackelberg均衡,并证明了产品的网络外部性对供应链成员收益存在正向影响。其次,利用比较分析法给出了制造商实施绿色制造策略的条件。然后,对信息不对称模型进行研究发现,当制造商对绿色产品网络外部性的估计满足一定条件时,零售商的信息共享策略对制造商和零售商都有利。最后,将模型拓展到混合制造策略下,并通过数值方法,讨论了各种参数变化带来的影响。所得结论对企业绿色制造决策具有重要的参考价值。