Production Quantity Model For Items Research Articles

An economic production quantity model for items with time proportional deterioration under permissible delay in payments

In traditional economic order quantity (EOQ) models, the items are replenished instantaneously and payments for the purchased items are made whenever the items are received. But, sometimes, the supplier may offer the retailer a trade credit period for the purchased goods. The retailer can pay the amount of purchased goods within this stipulated credit period. Beyond this period, some interest may be charged for the purchased items. The supplier offers to the retailer this permissible delay in payments to attract the new customers. These new customers can increase their sells by reducing the price of the items or by increasing the amount of stock displayed to attract the customers. Therefore, within the trade credit period, the retailers can trade without using their capitals. The purpose of this paper is to investigate the optimal production time and optimal cycle time in an economic production quantity model for items with time-proportional deterioration. The model is solved analytically to obtain the op...

Economic production quantity model for items with continuous quality characteristic, rework and reject

The economic production quantity (EPQ) model is a well-known and commonly used inventory control technique. However, the model is built on an unrealistic assumption that all the produced items need to be of perfect quality. Having relaxed this assumption, some researchers have studied the effects of the imperfect products on the inventory control techniques. This article, thus, attempts to develop an EPQ model with continuous quality characteristic and rework. To this end, this study assumes that a produced item follows a general distribution pattern, with its quality being perfect, imperfect or defective. The analysis of the model developed indicates that there is an optimal lot size, which generates minimum total cost. Moreover, the results show that the optimal lot size of the model equals that of the classical EPQ model in case imperfect quality percentage is zero or even close to zero.

Economic order quantity model for items with imperfect quality with learning in inspection

The economic order quantity (EOQ) model is the simplest and earliest inventory model in the literature. Its simple mathematics is attributed to its assumptions, which are rarely met. Salameh and Jaber [2000. Economic production quantity model for items with imperfect quality. Int. J. Prod. Econ. 64, 59–64] addressed one of these assumptions that items received or produced are not of perfect quality. This paper extends Salameh and Jaber's work for the case where there is learning in inspection. The model is realistic in that it considers situations of lost sales and backorders. Mathematical models are developed with numerical examples provided and results discussed for the cases of (i) partial transfer of learning, (ii) total transfer of learning, and (iii) no transfer of learning.

Economic order quantity model for items with imperfect quality, different holding costs, and learning effects: A note

In this note, we present the optimal lot sizes for an item with imperfect quality based on Salameh and Jaber [Salameh, M. K., & Jaber, M. Y. (2000). Economic production quantity model for items with imperfect quality. International Journal of Production Economics, 64, 59–64], Maddah and Jaber [Maddah, B., & Jaber, M. Y. (2008). Economic order quantity for items with imperfect quality: Revisited. International Journal of Production Economics, 112, 808–815], and Jaber et al. [Jaber, M. Y., Goyal, S. K., & Imran, M. (2008). Economic production quantity for items with imperfect quality subjected to learning effects. International Journal of Production Economics, 115, 143–150] when different holding costs for the good and defective items are considered. When there is no learning effects, the results show that the lot size with different holding costs for good and defective items increases when the percentage of defective increases, as one would expect in the real manufacturing environment. When there is learning effects, the lot size with different holding costs for the good and defective items is more than the one with same holding costs for the good and defective items. However, as the learning takes place in the system, the difference between the lot sizes with and without different holding costs for the good and defective items disappears.

Economic production quantity model for items with imperfect quality subject to learning effects

Salameh and Jaber [2000. International Journal of Production Economics 64, 59–64] developed an inventory situation where items received are not of perfect quality (defective), and after 100% screening, imperfect quality items are withdrawn from inventory and sold at a discounted price. This paper extends the work of Salameh and Jaber by assuming the percentage defective per lot reduces according to a learning curve, which was empirically validated by data from the automotive industry. Mathematical models are developed with numerical examples provided and discussed. The developed model was compared with the model of Salameh and Jaber to emphasize the importance of learning.

A two-warehouse inventory model with imperfect quality production processes

One of the weaknesses of some production-inventory models is the unrealistic assumption that all items produced are of good quality. But production of defective units is a natural phenomenon in a production process. Defective items should be treated as a result of imperfect quality production. On the other hand, the classical inventory models usually assume the available warehouse has unlimited capacity. In many practical situations, there exist many factors like temporary price discounts making retailers buy a capacity of goods exceeding their own warehouse. In this case, retailers may rent other warehouses for the need of business. A lot of researchers studied inventory models with two warehouses and inventory models with imperfect quality separately. Compared with previous models, based on Salameh and Jaber [Salameh, M. K., Jaber, M. Y. (2000). Economic production quantity model for items with imperfect quality. International Journal of Production Economics, 64, 59–64.], this paper tries to incorporate the above concepts to establish a new inventory model with two warehouses and imperfect quality simultaneously. The mathematical model by maximizing the annual total profit and the solution procedure are developed and numerical examples are provided to illustrate them.

Economic order quantity for items with imperfect quality: Revisited

We rectify a flaw in an economic order quantity (EOQ) model with unreliable supply, characterized by a random fraction of imperfect quality items and a screening process, developed by Salameh and Jaber [2000. Economic production quantity model for items with imperfect quality. International Journal of Production Economics 64(1–3), 59–64]. This leads to simple expressions of the optimal order quantity and expected profit per unit time. We then analyze the effect of screening speed and variability of the supply process on the order quantity, and show that the order quantity in our model is larger than that of the classical EOQ model when the variability of the yield rate is reasonably low. In addition, we extend the model by allowing for several batches of imperfect quality items to be consolidated and shipped in one lot. This is likely to be useful when there are economies of scale in shipping of imperfect quality items. Finally, we present numerical results to illustrate the application of the model and draw insights.

Note on: Economic production quantity model for items with imperfect quality – a practical approach

In this note we present a simple approach for determining the economic production quantity for an item with imperfect quality. We compare the results based on the simple approach with the optimal method for determining the lot size and show that almost optimal results are obtained using the simple approach.

Economic production quantity model for items with imperfect quality

The assumptions necessary to justify the use of economic production quantity (EPQ/EOQ) models are rarely met. To provide mathematical models that more closely conform to actual inventories and respond to the factors that contribute to inventory costs, the models must be extended or altered. This paper hypothesizes a production/inventory situation where items, received or produced, are not of perfect quality. Items of imperfect quality; not necessarily defective; could be used in another production/inventory situation, that is, less restrictive process and acceptance control. The electronics industry gives good examples of such situations. This paper extends the traditional EPQ/EOQ model by accounting for imperfect quality items when using the EPQ/EOQ formulae. This paper also considers the issue that poor-quality items are sold as a single batch by the end of the 100% screening process. A mathematical model is developed and numerical examples are provided to illustrate the solution procedure.