A LOWER BOUND FOR THE SINGLE-LEVEL DYNAMIC HORIZON LOT-SIZING PROBLEM

Conventional production planning methods assume the existence of a medium- or longrange demand horizon. However, demand usually is known over a much shorter range; scheduling decisions must be made within this “decision window,” which rolls forward in time. This paper presents a new lower bound for lot-sizing heuristics in a rolling-horizon framework and compares it to the well-known Wagner-Whitin bound. The new bound indicates heuristic schedules that have costs close to the optimum. Rolling-horizon schedule costs are compared to corresponding static-horizon schedule costs (assuming the whole horizon is known in advance), using the ratio of decision-window size to the natural order cycle as a parameter. For values below unity, the rolling-horizon policy is significantly more costly. For values above one, the two policies have similar costs and actually converge as the parameter value increases.     

A DISCRETE DYNAMIC OPTIMIZATION MODEL FOR MADE-TO-ORDER COST ANALYSIS

A model is presented that yields optimal production rates for a firm producing a contracted order. The model is unique in that it considers the influence of production rate and learning on total program cost. An application to the specific characteristics of two military production programs is presented. As demonstrated by the application, models of this type may be used as decision-making tools when negotiating the cost impact of contract modifications.     

Presence Through Absence: Phylloxera and the Viticultural Imagination in McLaren Vale,South Australia

Grape phylloxera is an insect pest that has destroyed vineyards and brought ruin to winegrowing regions worldwide. In South Australia, however, strong biosecurity regulations have ensured it has remained absent. In this absence phylloxera takes on powerful symbolic value, and regional viticultural identities may be imagined in relation to the presence of phylloxera elsewhere. This paper draws from ethnographic research with grape growers and wine producers in McLaren Vale, a region whose vineyards are understood through this ‘phylloxera-free’ paradigm. The article specifically explores controversies around modification of South Australian biosecurity regulations in a way that favoured large winegrowing corporations’ need to more easily move material between regions, to the perceived detriment of vineyard security. The phylloxera risk has economic, social and symbolic dimensions in McLaren Vale, where the insect has become symbolically aligned with the most impersonal, pervasive and destructive aspects of globalised wine capitalism.     

Some implementation experiences with just-in-time manufacturing

A case study on the implementation of a just-in-time (JIT) production system by a Canadian manufacturer in the heavy machinery industry is presented. Many hurdles and difficulties were encountered during implementation and the way in which these problems were resolved is reported. While the successful implementation of a JIT system depends on a host of technical and human factors, this study suggests that the people involvement factor is the most crucial. It is seen that the key elements to securing people involvement are institution leadership, company-wide education and training and mutual understanding, trust and respect among employees. The moral of this study is that without employee involvement nothing will happen and no result will be achieved.     

Shop floor control system for tool rooms

A shop floor control system (SFCS), which is the most important component of any production control system, ff has a direct e ect on the productivity of a tool room. The SFCS presented in this paper aims at streamlining various tool room activities, such as process planning, operations scheduling, loading, progress monitoring, and performance monitoring. The system discussed in this paper is characterized by simplicity and is user friendly. Basic information, consisting of three types of information (order details, process details, and part details), is input through interactive dialogue sessions. On-line updating of the process information is carried out, again through interactive dialogue sessions. The basic input to the system along with the on-line updating enables a number of useful and important reports and documents to be generated ff by the system for e ective control of the shop floor. The reports generated include operations scheduling, process sheet, part list, ffi job card, load pending report, e ciency report, etc. This SFCS is developed for a medium sized tool room in an automotive company and its successful implemention reduced paperwork and improved resource management and has resulted in productivity. It can be said that this system offers a first venture into computer integrated manufacturing (CIM) for a tool room.     

Development of an integrated information management model: A case of textile industry

For past two decades many organisations have tried to implement integrated information management systems for better production management based on co-ordination of information and therefore activities of different departments. Although Enterprise Resource Planning systems have been in the market for the past decade, many industries find it difficult to implement such systems due to the amount of work involved in streamlining the documentation, customisation and of high costs reported in implementation. An attempt is made through this paper to propose an integrated model, which can be easily understood by production personnel, with specific emphasis on the textile sector.     

Trade-off between quoted lead time and price

In a make-to-order environment, lead time and price can play a crucial role in determining the financial success of a firm. Their importance increases when demand is sensitive to the quoted lead time and price. A model is presented which uses the quoted lead time and price as a mechanism to determine the optimal demand level. The relationships between the model parameters and their impacts on the firm's profit is also analysed. In addition, the effect of the number of job requests, and the mean processing time are examined. Based on the results presented in this paper, there is clear indication that the firm's profit is sensitive to the inventory holding rate, and that the inventory holding cost component is redundant in the presence of a tardiness cost component.     

A modified hierarchical production planning system integrated with MRP: A case study

In this paper, a hierarchical planning system is proposed which integrates aggregate capacity planning with MRP. This system is to be implemented in a metal box manufacturing company which multi-user MRP system covering manufacturing activities as well as procurement sales order processing and accounting systems. The hierarchical planning system includes a medium-range aggregate planning model adapted to the firm's requirements and strategies. The model consists of a mathematical formulation which covers labour capacity has already installed a constraints and includes certain cost estimations in the objective function. The planning horizon of the medium range planning is taken as twelve months in order to cover sales seasonality. The aggregate production quantities resulting from the optimized medium-range planning model are disaggregated according to procedures already found in the literature. Furthermore, the theoretical infeasibilities pertaining to the disaggregation procedures are also resolved in an heuristic manner. Using the latter modified disaggregation procedure, a feasible disaggregated plan is generated for the whole planning horizon. The proposed plan is compared with the current production policy of the firm and it is observed that the proposed plan leads to backorder reduction.     

Toward a Feminist Political Economics

Feminist critiques of globalization have received insufficient attention in public discourse.Spike Peterson's RVP framework integrates feminist scholarship in a way that adds punch to such critiques. Its main contribution consists in bringing into view women's labor in the 'reproductive' economy. A shortcoming is that it retains the opposition between production and reproduction. The RVP framework is built on a constructivist ontology that allows for the integration of discursive and institutionalist approaches and provides grounds for further theoretical elaboration.