Modelling and Simulation of a Bakery Production Line Using Hierarchical Timed Coloured Petri Nets

Abstract

Numerous efforts are being made yearly by researchers to improve the production flow, planning and scheduling of food manufacturing systems through the use of modelling to meet both current and future market demands. In this paper, a Hierarchical Timed Coloured Petri Nets (HTCPN) model was developed for bakery production system using Ladoke Akintola University of Technology (LAUTECH) Bakery, Ogbomoso, Nigeria, as a case study. The HTCPN model was developed consisting of main module and five sub modules. The sub-modules named mixing, fermenting, rolling, cutting and baking modules modelled the sequential processes of converting flour into bread. The model was simulated using Coloured Petri Nets Tools to determine the average production processing times for processing of 50, 100, 150 and 200 kg of flour into bread. The simulation was also extended to determine the utilization rates required at varying units (manual mixing process, the rolling machine, manual cutting process and baking) for processing of 50 and 100kg bags of flour. The model was validated by comparing the simulated and the actual processing times at 5% significance level using statistical t-Test. The simulation results revealed that the production processing times for processing of 50, 100, 150 and 200 kg of flour starting from the mixing process till baking process were 217, 314, 411 and 508 minutes respectively. The utilization rates required at the mixing process unit, the rolling machine unit, the cutting process unit and baking unit were 0.138; 0.115; 0.046; 0.147 respectively for processing of 50kg bags of flour and 0.191; 0.159; 0.064; 0.203 respectively for processing of 100kg bags of flour. Statistically, there were no significant differences between the simulated and the real processing times. This model could be employed to study worker and machine utilization rates as well as production time required to produce bread from a given quantity of flour in the considered bakery production system or other related ones.