Title: An integrated inventory model for single-vendor single-buyer system with freight rate discount and stochastic demand

Authors: Wakhid Ahmad Jauhari; Ayudia Fitriyani; Azizah Aisyati

Addresses: Department of Industrial Engineering, Sebelas Maret University, Jl. Ir Sutami 36 A, Surakarta 57126, Indonesia ' Production System Laboratory, Department of Industrial Engineering, Sebelas Maret University, Jl. Ir Sutami 36 A, Surakarta 57126, Indonesia ' Department of Industrial Engineering, Sebelas Maret University, Jl. Ir Sutami 36 A, Surakarta 57126, Indonesia

Abstract: This paper deals with joint economic lot sizing model (JELS) in the context of two stage supply chain comprising of single-vendor and single-buyer. The shipment from vendor to buyer is conducted in equally sized and the demand in buyer side is assumed to be normally distributed. In this paper, freight cost is explicitly incorporated in the model and formulated by all-weight freight discount model and incremental freight discount model. We provide two procedures to find the optimal shipment size, safety factor, production batch and discount level on both models. Numerical examples are presented to illustrate the benefit of the model. The result shows that incorporating freight discount into inventory model may result in significant saving on total cost. The increase in the number of discount levels will lead to the decrease in buyer cost and total cost. Moreover, it also shows that the changes in ordering cost, purchase cost, setup cost and production rate in incremental freight discount model give significant impacts on shipment size and safety factor.

Keywords: joint economic lot sizing; JELS; freight costs; all-weight freight discount; incremental freight discount; supply chain management; SCM; inventory modelling; inventory management; single-vendor single-buyer systems; stochastic demand; optimal shipment size; safety factor; production batch levels; discount levels; ordering cost; purchase cost; setup cost; production rate.

DOI: 10.1504/IJOR.2016.074757

International Journal of Operational Research, 2016 Vol.25 No.3, pp.327 - 350

Received: 27 Jul 2013
Accepted: 27 Feb 2014
Published online: 17 Feb 2016 *

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