Utilização de programação linear inteira mista para rebalanceamento de linha multioperada na manufatura de motores diesel

Abstract

The constant ambition for greater productivity in the automotive industry is directly associated with reducing waste and losses. The line balancing problem seeks to optimally balance the resources used in manufacturing, minimizing the idle time of stations and workers. This study is established on solving a real problem for an automotive company in the region of Curitiba, specifically in a production line where diesel engines are manufactured. The need for greater production capacity associated with the increase in the portfolio of products produced in this line were the main factors that drove the search for a feasible rebalancing proposal, given the limitations imposed on the current production system. The factory environment where this work was developed is characterized as a multi-manned assembly line where four main models of products are produced, which can be classified as a Mixed Model Assembly Line Balancing Problem (MALBP). A cyclical methodology was used to solve it, inspired by agile management concepts, where the rebalancing proposal is formulated by a mathematical model in Mixed Integer Linear Programming (MILP). Each version of the results was used to improve the proposed methodology, either through the refinement of restrictions or even in the customization of the mathematical model, incrementally improving the results obtained. As a differential, this work presents itself as an opportunity to approach theoretical solutions to the real problems encountered in most manufacturing companies, where the complexity of a production system is considered, reflecting, for example, the large number of restrictions for repositioning and in the relationship between different product models. Ergonomic limitations that result in idleness were identified in multi-manned workstations, and a synergy indicator was proposed as an additional factor to be optimized to overcome this ergonomic condition, a subject that is little detailed in the literature. The results met the company’s needs, where through the redistribution of 78 activities, out of a total of 212, a new rebalancing proposal is defined, feasible for implementation, validated in a virtual environment, and then practically, with the physical assembly of engines. This proposal also ensures a percentage higher than 98% for the synergy of operators in multi-manned workstations.