A new perspective on Workload Control by measuring operating performances through an economic valorization

Abstract

Workload Control (WLC) is a production planning and control system conceived to reduce queuing times of job-shop systems, and to offer a solution to the lead time syndrome; a critical issue that often bewilders make-to-order manufacturers. Nowadays, advantages of WLC are unanimously acknowledged, but real successful stories are still limited. This paper starts from the lack of a consistent way to assess performance of WLC, an important burden for its acceptance in the industry. As researchers often put more focus on the performance measures that better confirm their hypotheses, many measures, related to different WLC features, have emerged over years. However, this excess of measures may even mislead practitioners, in the evaluation of alternative production planning and control systems. To close this gap, we propose quantifying the main benefit of WLC in economic terms, as this is the easiest, and probably only way, to compare different and even conflicting performance measures. Costs and incomes are identified and used to develop an overall economic measure that can be used to evaluate, or even to fine tune, the operating features of WLC. The quality of our approach is finally demonstrated via simulation, considering the 6-machines job-shop scenario typically adopted as benchmark in technical literature.

Shop floor dispatching with variable urgent operations based on Workload Control: An assessment by simulation

“…[14]) and allow us to obtain stable results while keeping the simulation run time at a reasonable level. The four principal performance measures considered in this study are as follows, such as most of the previous literature [31,[36][37][38]: (i) the gross throughput time (GTT), that is, the completion of the job minus its entry time; (ii) the shop floor throughput time (SFTT), that is, the gross throughput time minus the queueing time in the pre-shop pool; (iii) the mean tardiness time (MTT), where T j = max (0, L j ) indicates the tardiness of job j, with L j being the lateness of job j (i.e. the actual delivery date minus the due date of job j); (iv) the percentage tardy (PT), that is, the percentage of jobs delivered after the customer due date.…”