A note on Toyota's goal of sequencing mixed models on an assembly line

Toyota's goal of sequencing mixed models on an assembly line is to keep the constant usage of every part used in the assembly line. This goal is a good way of fitting the just-in-time concept in Toyota's production system. In all of Toyota's goal oriented studies a consideration which has not been explained explicitly in the literature is that all the parts of a given product are assumed to be used at the epoch of just this unit into the assembly line. This treatment is equivalent to an assumption of a single workstation assembly line with zero length. For an assembly line with multiple workstations, however, it is clear that the parts of a given product are used at different epochs subsequent to originally feeding this unit into it. This note discusses Toyota's goal of sequencing mixed models on an assembly line with multiple workstations. The sequencing problem is formulated based on defining the ideal usage rate of a part as the requirement for the part per time period. A modified goal chasing algorithm is proposed for solving this sequencing problem. An example is given to illustrate the methodology.