The integrated uncapacitated lot sizing and bin packing problem

¹ Departamento de Tecnologia em Engenharia Civil Computação e Humanidades, Universidade Federal de São João del-Rei, Rodovia MG 443, KM 7, cep: 36420-000, Ouro Branco, MG, Brazil
² Departamento de Ciência da Computação, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, cep: 31270-901, Belo Horizonte, MG, Brazil
³ Departamento de Engenharia de Produção, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, cep: 31270-901, Belo Horizonte, MG, Brazil

^* Corresponding author: prof.mauriciodesouza@gmail.com

Received: 6 August 2020
Accepted: 26 March 2021

Abstract

In the integrated uncapacitated lot sizing and bin packing problem, we have to couple lot sizing decisions of replenishment from single product suppliers with bin packing decisions in the delivery of client orders. A client order is composed of quantities of each product, and the quantities of such an order must be delivered all together no later than a given period. The quantities of an order must all be packed in the same bin, and may be delivered in advance if it is advantageous in terms of costs. We assume a large enough set of homogeneous bins available at each period. The costs involved are setup and inventory holding costs and the cost to use a bin as well. All costs are variable in the planning horizon, and the objective is to minimize the total cost incurred. We propose mixed integer linear programming formulations and a combinatorial relaxation where it is no longer necessary to keep track of the specific bin where each order is packed. An aggregate delivering capacity is computed instead. We also propose heuristics using different strategies to couple the lot sizing and the bin packing subproblems. Computational experiments on instances with different configurations showed that the proposed methods are efficient ways to obtain small optimality gaps in reduced computational times.