Even-Flow, A Scheduling Method for Reducing Lateness in Job Shops

The development of the Even-Flow system was initiated by Mr. Gregory M. Boni, who observed that the elapsed time to complete a job in job shops was often a function of the number of operations performed rather than the time spent actually performing the operations, and that the time between operations was relatively constant. When this is true, the job shop can be thought of as an assembly line in which the machines are the stations, and the work to be done at each station consists of all of the operations which must be performed if the jobs are to flow evenly from machine to machine through the shop. The existence of a predictable time between the successive operations of each job gives one the ability to schedule the completion of parts at desired due-dates with reasonable assurance. This ability is crucial in the production of parts for assembly lines; the shortage of one part could result in shut-down of the line or expensive out-of-station work. The Even-Flow system described below is an attempt to maximize the number of on-time completions by integrating the scheduling, loading, and dispatching functions in a manner which capitalizes on the "natural" movement of work through the shop. The simulation of this system in comparison with other scheduling rules, described below, was conducted by Professors Conway and Maxwell on the Cornell University Simulator, a program written for the IBM-650. "Management Technology", ISSN 0542-4917, was published as a separate journal from 1960 to 1964. In 1965 it was merged into Management Science.