Production, Manufacturing and LogisticsAn economic order quantity model with partial backordering and a special sale price
Highlights
► We combine two of the extensions of the basic EOQ found in the literature. ► Partial backordering of demand during a stockout period and responding to a short-term one-time opportunity for a discount. ► We develop and prove optimality of the solution.
Section snippets
Introduction and literature review
Since the basic economic order quantity model (EOQ) was introduced by Harris (1913), there have been many extensions that have relaxed one or more of its assumptions or added additional features. In this paper we combine two of those extensions: (1) determining whether to place a special order if there is an opportunity to buy at a temporary sale price and, if so, the order quantity and (2) partial backordering at a constant backordering rate.
A constant unit purchase cost is one of the main
Problem definition and assumptions
Consider a situation in which a company stocks a particular item which, since the demand rate is constant and the other usual conditions for doing so are met, it orders regularly using an EOQ model. Assume that it is discovered that a temporary discount is available for a short time, during which the regular price of the item, C, is reduced to CS = C − C′. After the temporary sale the price of the item will return to C. The logical reaction to finding an item on sale at the time of a regular
Model development
We introduce the parameters and the variables of the model in Section 3.1. We next review some of the previous work on the two basic components of our model: the special sale problem without backordering (Section 3.2) and the EOQ with partial backordering (Section 3.3). Our models for the problem under different assumptions about when the sale price is available are developed in Sections 3.4.1 Scenario 1: The sale price coincides with the normal time to place an order, 3.4.2 Scenario 2: The
Solution method
To justify ordering a special quantity during the sale period, the profit from ordering the optimal special quantity must be more than the profit from using regular EOQ order quantities for the same amount of time TS (CTPS > CTPn). Another way of saying this is to say that the optimal value of G1, G2, or G3, whichever is relevant for the particular scenario being faced, must be positive to justify placing a special order at the sale price.
We noted above that the coefficients of the variable terms
Numerical examples
To illustrate the application of the solution procedure given above, we will use the numerical example from Pentico and Drake (2009), adding the new parameters which are used in this paper. The fixed parameters in all examples are D = 200 units/year, A = $50/order, h = $3/unit/year, π = $1/unit/year, π′ = $2/unit lost, C = $11/unit, C′ = $3/unit, P = $11/unit, and i = 0.3. Following we introduce four examples based on those parameter values.
Conclusion
We have developed EOQ models for three scenarios with a special sale price and partial backordering: the sale price is available at the normal time to place an order, it is available only when there is still existing inventory, or it is available only when there is a stockout. We consider that the purchaser either orders a special quantity Qs to take advantage of the discount price or sticks to the regular EOQ model and orders Q. Since ordering a special quantity during the sale period requires
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