مدل برنامه ریزی خطی صحنه سازی زمان برای مشکلات بارگذاری تولید با محدودیت فضای واردات در یک زنجیره عرضه جهانی

Globalization has ushered in a new era when more and more companies are expanding their manufacturing operations on a global scale. This poses some special challenges and raises certain issues. This paper examines production loading problems that involve import quota limits in the global supply chain network. Import quota, which is imposed by importing countries (mostly in North America and Europe), requires that certain types of products imported into these countries are against valid quotas held by the exporters. Globally loading of production, therefore, requires new methods and techniques, which are different from those used in domestic loading of production. This paper presents a time staged linear programming model for production loading problems with import limits to minimize the total cost, consisting of raw materials cost, machine cost, labour cost, overtime cost, inventory cost, outsourcing cost and quota related costs. To enhance the practical implications of the proposed model, different managerial production loading plans are evaluated according to expected changes in future production policies and situations. A series of computational results demonstrate the effectiveness of the proposed model.

Today’s business has inevitably set in a global environment in which materials and products can be bought, manufactured and sold anywhere in the world. Managing supply chains in such an environment has become an important factor for gaining competitive advantages for business organizations. A vast majority of manufacturers have some form of global presence through exports, strategic alliances, joint ventures, or as part of a committed strategy to sell in foreign markets or locate production abroad (Dornier, Ernst, Fender, & Kouvelis, 1998). Although global supply chains have many of the same fundamental functions and concepts as domestic supply chains, the differences are quite substantial and require different managerial approaches and techniques. This study is motivated by the production loading problems faced by multinational manufacturing companies that participate in global supply chain activities. In the global supply chain, the multinational companies have their headquarters at one place, somewhere in the world. Product sales, R&D and customer service are typically centred in different markets, mainly North America and Europe. However, companies would like to establish production facilities in low-cost countries. Investment destinations have been diverse with production networks now extending to practically all over the world. China (mainland) is so far one of the favourite places for companies because of its low production and labour costs. This kind of global supply chain network plays an important role in today’s business. In the global supply chain systems, one of the most important decisions is loading production among plants, which are typically located in different regions and/or countries. While loading production, companies not only consider cost and capacity in terms of raw materials, machine, workforce, inventory and market demand, but also the import quota limits allowed to the country of manufacture. Import quotas are assigned by importing countries. Quotas control the quantity or volume of certain merchandise that can be imported into North American and European countries. The importing countries allocate a certain quantity of quota to each exporting country. Any products that belong to quota restriction categories have to have the corresponding quotas for the exporting countries. Many developing countries, including China, face restraints on textile and clothing exports to their trading partners that maintain import quotas, including the US, Canada, and European Union. For example, clothing and textile products are divided into 147 categories by the US and 143 categories by the European Union. Dickson (2005) states that not all the exporting countries face the same quota limitations for products. For example, China faces the US’s quota limitation in 81 of 147 categories, while for India the figure is 30. At the same time, China faces quota limitation in 61 of 143 categories assigned by the EU, while for India it is 17. Therefore, global manufacturing companies have to consider quota limitations when they distribute manufacturing tasks among different plants, which are typically located in different cities and countries. If the quota for a certain category or product is used up in a country or quota price for that product/category is very high, companies may need to find alternatives in other countries that own quotas with reasonable price for the same product. Quota prices fluctuate because of many factors, like changing market demand and government policies. In this study, we will look at a multinational garment manufacturing company, whose headquarters is in Hong Kong, and product sales, R&D, customer service and consumer markets are spread across North America and Europe. The Hong Kong headquarters collects customer information through its American and European branch offices. Then the headquarters commissions the plants, which are located in Mainland China, Sri Lanka, the Philippines, etc., to undertake the processing work. The finished products are then shipped to Hong Kong for onward shipping to overseas markets. Thus loading production among different plants is a critical managerial task for the company. The aim of this paper is to present a decision-making framework for modelling the production loading problems involving import quota limitation in the global supply chain. The rest of the paper is organized as follows. Section 2 is literature review part. Section 3 describes production loading process in the global supply chain. Section 4 presents a time staged linear programming model for the production loading problems with import quota limits. In Section 5, a set of data from the company is used to test the effectiveness of the proposed model. Different production loading strategies are provided to match different production requirements so that decision-makers can handle complicated changes under the global supply chain management environment. The final section gives the conclusions of the paper and the recommendations for future research.

Today’s business has been set in the global supply chain management environment. More and more companies have realized the importance of global supply chain management by seeking suitable locations and facilities anywhere in the world for manufacturing, marketing and distributing. This paper studies the production loading problems in the global supply chain network, in which the import quota limit is applied for companies, which distribute production task among different plants in China aiming at satisfying North American and European market demand while attempting to minimize the total production cost. This type of production loading problem becomes more and more important in today’s highly competitive global markets. Therefore, effective production loading strategies can provide a competitive advantage by reducing production cost. In this paper, a time staged linear programming model is presented for modelling production loading problems with import quota limits. Decisions include the quantities of used resources, including machine, labour and initial quotas, as well as inventory levels, outsourcing levels, purchased quotas from local markets and unused quotas. A series of experiments, whose data is from a multinational garment company, are designed to test the effectiveness of the proposed model in solving practical production loading problems. Different production loading strategies are provided so that production managers can handle complicated future changes for the production loading problems in the global manufacturing environment. The computational results also show that import quota is a significant factor in loading production in terms of availability and cost in importing–exporting trade. Production managers have to adopt new approaches and techniques to handle production loading problems with import quota limit in the global supply chain environment. The methods used in global manufacturing are different from those in the domestic production loading process. Failure to consider the international factors, such as quota limits discussed in this paper, may lead to higher production costs and even disastrous consequences. For example, the finished products are not permitted to be exported to demand locations because of the lack of the corresponding quotas for the specific products. Future research will consider uncertainties in production loading process, such as dynamic and changing market demand and quota price; dynamic programming, stochastic programming and fuzzy programming techniques can be applied to these problems. As these models would substantially increase the computational time, artificial intelligence algorithms like genetic algorithm, tabu search and simulated annealing may be considered to solve the large scale of problems.