Joint lot sizing and scheduling of a multi-product multi-period supply chain

The joint lot sizing and scheduling problem can be considered as an evolvement of the joint economic lot size problem which has drawn researchers’ interests for decades. The objective of this paper is to find the effect of a capacitated multi-period supply chain design parameters on joint lot sizing and scheduling decisions for different holding and penalty costs. The supply chain deals with two raw materials suppliers. The production facility produces two products which are shipped to customers through distribution centers. A mathematical model is developed to determine optimum quantities of purchased raw materials, production schedule (MPS), delivered quantities and raw material and products inventory for predetermined number of periods. The model is solved to maximize total supply chain profits. Results showed that at high capacity and low holding cost, the supply chain tends to produce only one product each period, for limited capacity and high value of holding cost, the supply chain may produce the two products together each period

Production planning systems for cellular manufacturing

New product development is one of the most powerful but difficult activities in business. It is also a very important factor affecting final product quality. There are many techniques available for new product development. Experimental design is now regarded as one of the most significant techniques. In this article, we will discuss how to use the technique of experimental design in developing a new product - an extrusion press. In order to provide a better understanding of this specific process, a brief description of the extrusion press is presented. To ensure the successful development of the extrusion press, customer requirements and expectations were obtained by detailed market research. The critical and non-critical factors affecting the performance of the extrusion press were identified in preliminary experiments. Through conducting single factorial experiments, the critical factorial levels were determined. The relationships between the performance indexes of the extrusion press and the four critical factors were determined on the basis of multi-factorial experiments. The mathematical models for the performance of the extrusion press were established according to a central composite rotatable design. The best combination of the four critical factors and the optimum performance indexes were determined by optimum design. The results were verified by conducting a confirmatory experiment. Finally, a number of conclusions became evident.

Demand uncertainty and lot sizing in manufacturing systems: the effects of forecasting errors and mis-specification

This paper proposes a methodology for examining the effect of demand uncertainty and forecast error on lot sizing methods, unit costs and customer service levels in MRP type manufacturing systems. A number of cost structures were considered which depend on the expected time between orders. A simple two-level MRP system where the product is manufactured for stock was then simulated. Stochastic demand for the final product was generated by two commonly occurring processes and with different variances. Various lot sizing rules were then used to determine the amount of product made and the amount of materials bought in. The results confirm earlier research that the behaviour of lot sizing rules is quite different when there is uncertainty in demand compared to the situation of perfect foresight of demand. The best lot sizing rules for the deterministic situation are the worst whenever there is uncertainty in demand. In addition the choice of lot sizing rule between ‘good’ rules such as the EOQ turns out to be relatively less important in reducing unit cost compared to improving forecasting accuracy whatever the cost structure. The effect of demand uncertainty on unit cost for a given service level increases exponentially as the uncertainty in the demand data increases. The paper also shows how the value of improved forecasting can be analysed by examining the effects of different sizes of forecast error in addition to demand uncertainty. In those manufacturing problems with high forecast error variance, improved forecast accuracy should lead to substantial percentage improvements in unit costs

An integrated model for green partner selection and supply chain construction

Stricter governmental regulations and rising public awareness of environmental issues are pressurising firms to make their supply chains greener. Partner selection is a critical activity in constructing a green supply chain because the environmental performance of the whole supply chain is significantly affected by all its constituents. The paper presents a model for green partner selection and supply chain construction by combining analytic network process (ANP) and multi-objective programming (MOP) methodologies. The model offers a new way of solving the green partner selection and supply chain construction problem both effectively and efficiently as it enables decision-makers to simultaneously minimize the negative environmental impact of the supply chain whilst maximizing its business performance. The paper also develops an additional decision-making tool in the form of the environmental difference, the business difference and the eco-efficiency ratio which quantify the trade-offs between environmental and business performance. The applicability and practicability of the model is demonstrated in an illustration of its use in the Chinese electrical appliance and equipment manufacturing industry

Purchasing Functions and MRP in Foodservice Firms

The study examines the purchasing functions and material requirement planning (MRP) in food service and hotel purchasing. Bill of materials (BOM) is one of the three main inputs to the MRP programme (the other two are the master schedule and the inventory record file). Purchasing food and supplies is somewhat unique in that it goes beyond specifying products and placing orders. In foodservice, the functions related to purchasing should be generally done by the same people who do the purchasing. The paper looks at array of purchasing functions in foodservice and offers an effective management of materials approach. It addresses situation where materials planning are established in consultation with other departments, the resources needed and translation of the master plan into specific materials requirement.  A detailed example in the foodservice firm is presented to explain the concept of MRP. Keywords: Bill-of-materials, materials requirement planning, master production schedule, purchasing functio

Models for supply chain negotiation in collaborative relationships

Nowadays, firms are increasingly building collaborative relationships with their partners in order to improve the global performance of the supply chain in which they are involved. Such collaborative relationships require information exchange or share and negotiation. In this paper, we first formalize some practices of collaboration from case studies of the aeronautical area then suggest some models for negotiation, allowing a supply chain member to publish hidden constraints and share risks/costs in order to achieve a win-win situation

The Lean Concept in the Food Industry: A Case Study of Contract a Manufacturer

The paper discusses how the lean concept could be applied to a food-manufacturing company. The paper first presents the lean concept and value-stream mapping tools. The empirical section discusses how a case company, operating as a contract manufacturer in the food industry, has applied the lean production concept and tools. In the case study, three analysis tools are examined and the structures of demand chains of different customers are presented. The delivery times will decrease and more flexibility will be needed from the contract manufacturer. The case study shows that much movement is possible toward the lean supply chain and partnership-based cooperation. By implementing the lean concept, food companies can increase customer value through cost reduction or through provision of additional value-enhanced services.Agribusiness,

Integrated Production and Distribution planning of perishable goods

Tese de doutoramento. Programa Doutoral em Engenharia Industrial e Gestão. Faculdade de Engenharia. Universidade do Porto. 201

A discount ordering strategy in two-level supply chain: A case study of textile industry

Supplier selection, inventory management and optimal lot sizing has been one of the most important issues in many industries especially in production planning issues associated with texture industry. The proposed model of this paper first introduces an algorithm to choose the best supplier and it determines the optimal lot size using discount strategy. The proposed model of this paper considers different influencing factors such as location, quality of materials, cost, and mutual trust for supplier selection, determines their relative importance weights and then a discounting method is used to determine the ordering lot-size. The preliminary results indicate that the proposed model of this paper can be implemented in texture industry, very efficiently since the ordering discount policy is not sensitive to changes on inventory holding and setup expenditures