Digital-Twin-Driven Design and Financial Validation of a Collaborative Robotic Cell for Automated Chocolate-Bar Unwrapping in a Small-Scale Confectionery Plant

Abstract

Manual unwrapping of chocolate bars in a family-owned confectionery in Monterrey, Mexico, is a labor-intensive process that produces inconsistent cycle times, high product damage, and elevated payroll costs. This paper presents the design, discrete-event and kinematic simulation, and financial validation of a collaborative robotic cell that automates the gripping, unwrapping, and placement of chocolate bars using a Digital Twin methodology. A macroscopic process model was built in Tecnomatix Plant Simulation to quantify throughput, utilization, and bottlenecks, while a microscopic three-dimensional model was built in Tecnomatix Process Simulate to validate robot reachability, collision-free trajectories, and kinematics for a 6-degree-of-freedom UFACTORY xArm 6 cobot fitted with a custom compliant gripper. A Siemens/Schneider PLC layer, a Node-RED edge gateway, a Firebase database, and a large-language-model-based analytics loop were integrated to provide SCADA 4.0 supervision and closed-loop setpoint correction. Simulation results show that the automated cell increases throughput from 356 to 576 successfully unwrapped units per 30 minutes (a 61.8% improvement) while sustaining a 96% quality rate and eliminates the 100% input-side blockage observed in the manual process. The financial analysis indicates a total capital investment of approximately $425,766 MXN, an annual net benefit of $179,890 MXN, a projected Internal Rate of Return of 31.2%, and a payback period of 2.3 years. These results indicate that a compact, food-grade collaborative robotic cell is a technically feasible and financially attractive solution for small and medium-sized confectionery producers seeking to automate deformable-product handling.