Efficient scheduling to reduce setup times and increase utilization in a multiple-part manufacturing system

Abstract

Two scheduling procedures were developed to reduce the total setup time and increase utilization in a multiple-part-type manufacturing system with sequence-dependent setups. These scheduling systems focus on reducing setup time by taking advantage of part family setups. A part family is a set of parts that have similar geometries or use the same fixturing or tooling in a flexible machine, thus the labor involved in transitioning between two parts in a family is simpler, and therefore quicker, compared to the average machine setup. One of the scheduling procedures, the setup matrix methodology, was tested through implementation in an actual manufacturing system. The setup matrix is a data-set that contains the setup time between any two parts that are fabricated on a machine. By knowing either the exact or relative values for the setup times between all parts, the setup matrix can be used to schedule a set of production orders to minimize the total setup time. The setup matrix methodology demonstrated significant reductions in total setup time, with little to no adverse effects in systems with large setup time to production time ratios (of 1:5 or larger). In systems with low setup time to production time ratios (of 1:10 or smaller), the cost of having particular orders fall behind due to this scheduling procedure is non-negligible compared to the saving generated from the removed setup time. These two values must be compared to determine whether or not it is beneficial to implement this scheduling system in those particular areas. The other scheduling procedure, QPR Scheduling, was tested through simulation. The QPR Scheduling procedure is a derivative of the standard (Q,R) ordering policy used in supply chain design, which includes an additional reorder point to take advantage of part family setups on a machine. In the simulation, the QPR Scheduling procedure also generated considerable reductions in total setup time, without producing backorders or significant increases in inventory.