Designing, Prototyping and Testing of the Digital Twin of a 3D Printer to Meet Industry 4.0 Requirements

This thesis aims to explain the structure and operation of a multifunctional digital twin for a material extrusion 3D printer. Among its functionalities, the digital twin includes an advanced remote control and monitoring of the printing process, the ability to collect and sort job data, run simulations, react to errors and identify their cause, evaluate the geometric accuracy of the printed piece, monitor machine wear, and self-calibrate. The structure of the twin is modular, it has been built entirely with open-source software and does not rely on proprietary solutions so that it is easily replicable and extendable to different systems. The printer used for testing is a Cartesian material extrusion printer equipped with encoders, accelerometers, additional thermometers, and a machine vision system. The data collected by the sensors during printing is sent to a data interface that sorts it into the twin core, and a remote storage system. The digital twin core houses the simulation of the printer's physics and control logic and performs simulation, monitoring, and diagnostic functions. This module is also capable of generating a detailed representation of the printed model in real-time from data collected during processing. This representation can be used to evaluate the geometric conformity of the obtained piece compared to an ideal printing model, all carried out through an automatic procedure. An additional part of the digital twin is a GUI, that is intended to allow the user to remotely interact with the system, view collected data, and perform post-processing operations. Both the core and the GUI are able to communicate with the printer through a print host software, so that the system can secure the printer automatically, if an error occurs, and guide the user in a procedure to recover the interrupted job; moreover, the digital twin can perform an auto-calibration procedure, where error situations are created in a controlled way with the aim of identifying the working limits. The functionalities of the digital twin are verified with a series of tests carried out at different printing speeds, both in simulation and in real prints. The simulations are able to predict the impact of the settings used on the duration of the print, on the axes load, on the wear of the components, and on the dimensions of the piece; on the other hand, from the real prints it is possible to obtain the actual data, the evaluation of the geometric conformity of the pieces, and the virtual model of the printed parts. Through the analysis of the latter, it is possible to investigate the influence of the chosen settings and of the printer structure on the geometric characteristics of the parts.